5/13/2011

Team Four Senior Design Project

Liz Kladder | Jay Prins | Zach Talen | Tim Bangma| Jon Mulder

CALVIN COLLEGE ENGINEERING

HYDRAULIC HYBRID FINAL REPORT

Team 4 – I

Abstract

This report describes team Hydraulic Hybrid’s senior design project and presents the work conducted towards achieving the project goals over the course of the year. The goal of this project was to use a hydraulic hybrid system to increase the fuel efficiency of a vehicle in stop and go operating conditions by 40%. Currently, several companies are developing similar systems for delivery truck applications; however, none of these systems use only hydraulics to power the vehicle. The prototype described in this report is a golf cart equipped with a gasoline engine and a series hydraulic system, consisting of a hydraulic pump, high pressure accumulator, flow control valves and a hydraulic drive motor. The report includes a description of the prototype vehicle and the technologies incorporated to achieve this goal. The testing conducted at the end of the project resulted in a 52% increase in stop and go fuel efficiency.

Team 4 – II

Table of Contents 1. Introduction .......................................................................................................................................... 1

1.1 Team Hydraulic Hybrid .................................................................................................................. 1

1.2 Problem Statement ....................................................................................................................... 2

1.3 Project Objectives ......................................................................................................................... 2

2. Design Functionality .............................................................................................................................. 2

2.1 Design Norms ................................................................................................................................ 2

2.1.1 Transparency ......................................................................................................................... 2

2.1.2 Stewardship .......................................................................................................................... 3

2.1.3 Caring .................................................................................................................................... 3

2.2 Project Scope ................................................................................................................................ 3

2.3 Hybrid Background ........................................................................................................................ 3

2.3.1 Types of Hybrids .................................................................................................................... 3

2.3.2 Benefits of Hydraulic Hybrids ................................................................................................ 3

2.3.2.1 Less Energy Conversions ................................................................................................... 3

2.3.2.2 Regenerative Braking ........................................................................................................ 4

2.3.2.3 Optimal Engine Speed ....................................................................................................... 4

2.4 Project Hydraulic System .............................................................................................................. 8

3. Base Case Cart ..................................................................................................................................... 12

3.1 Beginning Cart ............................................................................................................................. 12

3.2 Frame Modifications ................................................................................................................... 12

3.3 Drive Train ................................................................................................................................... 14

3.3.1 Engine .................................................................................................................................. 15

3.3.2 Chain and Tensioner ........................................................................................................... 15

3.3.3 Jackshaft .............................................................................................................................. 15

3.3.4 Axle ...................................................................................................................................... 15

3.4 Vehicle Control ............................................................................................................................ 15

3.4.1 Throttle ............................................................................................................................... 15

3.4.2 Brakes .................................................................................................................................. 16

4. Hydraulic Hybrid.................................................................................................................................. 17

Team 4 – III

4.1 Frame Modifications ................................................................................................................... 17

4.1.1 Engine Mounting ................................................................................................................. 17

4.1.2 Accumulator Mounting ....................................................................................................... 17

4.1.3 Reservoir Mounting ............................................................................................................ 18

4.2 Hydraulic Drive train ................................................................................................................... 19

4.2.1 Engine .................................................................................................................................. 19

4.2.2 Pump ................................................................................................................................... 19

4.2.2.1 Type ................................................................................................................................. 19

4.2.2.2 Mounting ......................................................................................................................... 19

4.2.3 Hydraulic Motor .................................................................................................................. 20

4.2.3.1 Type ................................................................................................................................. 20

4.2.3.2 Mounting ......................................................................................................................... 20

4.2.4 Jackshaft .............................................................................................................................. 21

4.2.5 Axle ...................................................................................................................................... 21

4.3 Hydraulic Vehicle Control ........................................................................................................... 21

4.3.1 Engine Control ..................................................................................................................... 21

4.3.1.1 Electronic Control............................................................................................................ 22

4.3.1.2 Hydraulic Cylinder ........................................................................................................... 22

4.3.1.3 Manual Control ............................................................................................................... 23

4.3.2 Acceleration Control ........................................................................................................... 23

4.3.2.1 Valve Type ....................................................................................................................... 23

4.3.2.2 Mounting ......................................................................................................................... 24

4.3.2.3 Linkage ............................................................................................................................ 24

4.3.3 Brake Valve ......................................................................................................................... 25

4.3.3.1 Valve Type ....................................................................................................................... 26

4.3.3.2 Mounting ......................................................................................................................... 26

4.3.3.3 Linkage ............................................................................................................................ 27

4.3.3.4 Redundant Bakes ............................................................................................................ 28

4.3.4 Directional Selector Valve ................................................................................................... 29

4.3.4.1 Valve Type ....................................................................................................................... 29

4.3.4.2 Mounting ......................................................................................................................... 29

4.3.4.3 Purpose ........................................................................................................................... 30

Team 4 – IV

4.3.5 High Pressure Relief Valve .................................................................................................. 30

4.3.5.1 Valve Type ....................................................................................................................... 30

4.3.5.2 Purpose/Use .................................................................................................................... 31

4.3.6 Check Valves ....................................................................................................................... 31

4.3.6.1 Types ............................................................................................................................... 31

4.3.6.2 Purpose ........................................................................................................................... 31

4.4 Other Hydraulic Components ..................................................................................................... 32

4.4.1 Accumulators ...................................................................................................................... 32

4.4.1.1 Type ................................................................................................................................. 32

4.4.1.2 Purpose ........................................................................................................................... 32

4.4.1.3 Plumbing ......................................................................................................................... 32

4.4.1.4 Mounting ......................................................................................................................... 33

4.4.2 Gages ................................................................................................................................... 33

4.4.3 Reservoir ............................................................................................................................. 33

4.4.4 Filter .................................................................................................................................... 33

4.5 Retrofit Hydraulic Hybrid System Costs ...................................................................................... 34

5. Testing and Results ............................................................................................................................. 34

5.1 Test Procedure ............................................................................................................................ 34

5.2 Base Case Cart Results ................................................................................................................ 35

5.3 Hydraulic Hybrid Cart Results ..................................................................................................... 36

5.4 Discussion .................................................................................................................................... 36

6. Project Schedule ................................................................................................................................. 36

7. Project Budget..................................................................................................................................... 37

7.1 Prototype Cost ............................................................................................................................ 37

7.2 Bill of Materials ........................................................................................................................... 37

8. Business Plan ....................................................................................................................................... 37

8.1 Financial Analysis ........................................................................................................................ 37

8.2 Payback Period ............................................................................................................................ 37

9. Conclusion ........................................................................................................................................... 38

Team 4 – V

List of Figures Figure 1: Engine power data ......................................................................................................................... 4Figure 2: Engine torque data ........................................................................................................................ 4Figure 3: Engine fuel consumption data ....................................................................................................... 5Figure 4: Graph of torque per fuel flow rate versus engine speed ............................................................... 6Figure 5: Graph of power per fuel flow rate versus engine speed ............................................................... 7Figure 6: Hydraulic system schematic ........................................................................................................... 9Figure 7: Flow route for major driving scenarios ........................................................................................ 10Figure 8: Picture of original cart .................................................................................................................. 12Figure 9: CAD image of engine frame ......................................................................................................... 13Figure 10: Photo of engine frame in cart .................................................................................................... 13Figure 11: Schematic of engine mount ....................................................................................................... 14Figure 12: Photo of base case drive train ................................................................................................... 14Figure 13: CAD model of throttle control lever .......................................................................................... 16Figure 14: Throttle control lever ................................................................................................................. 16Figure 15: CAD image of accumulator mounting assembly ........................................................................ 17Figure 16: Photo of accumulators mounted on cart ................................................................................... 17Figure 17: CAD image of reservoir mount .................................................................................................. 18Figure 18: Photo of mounted reservoir ...................................................................................................... 18Figure 19: Photo of Eaton Series 26 pump ................................................................................................. 19Figure 20: CAD image of pump mounting assembly ................................................................................... 20Figure 21: Photo of mounted pump ........................................................................................................... 20Figure 22: Electric motor was modified to support hydraulic components ............................................... 21Figure 23: Throttle lever in idle position .................................................................................................... 22Figure 24: Throttle lever in charging position ............................................................................................ 23Figure 25: Acceleration control: restrictive flow control valve ................................................................... 24Figure 26: CAD model of accelerator valve mounting bracket ................................................................... 24Figure 27: CAD model of accelerator valve linkage .................................................................................... 25Figure 28: Accelerator valve linkage picture ............................................................................................... 25Figure 29: Braking control: restrictive flow control valve ........................................................................... 26Figure 30: CAD model for brake valve mounting bracket ........................................................................... 27Figure 31: CAD model of brake pedal linkage ............................................................................................. 27Figure 32: Brake valve linkage picture ........................................................................................................ 28Figure 33: Redundant brake’s linkage picture ............................................................................................ 28Figure 34: Metro machine six port - two position selector valve ............................................................... 29Figure 35: Positions of the directional selector valve ................................................................................. 29Figure 36: Location and mounting of the directional selector valve .......................................................... 30Figure 37: High pressure relief valve .......................................................................................................... 31Figure 38: Mounted Stucci check valve ...................................................................................................... 32

Team 4 – VI

Figure 39: City driving course, five laps ...................................................................................................... 35Figure 40: Payback period (lifetime of vehicle) dependednt on gasoline price ......................................... 38

Team 4 – VII

List of Tables Table 1: Retrofit system costs ..................................................................................................................... 34Table 2: Base case cart fuel efficiency results ............................................................................................. 35Table 3: Hydraulic hybrid cart fuel efficiency results .................................................................................. 36

Team 4 – Page 1

1. Introduction Calvin College is a four-year, liberal arts college in Grand Rapids, Michigan that offers a variety of undergraduate degrees. The Calvin engineering program is accredited by the Accreditation Board of Engineering and Technology (ABET) to provide Bachelor of Science in Engineering degrees in Chemical, Civil & Environmental, Electrical & Computer, and Mechanical concentrations. As a part of the engineering program, seniors partake in a design project that is part of a two semester long capstone course, ENGR 339 and ENGR 340. The main objectives of the first semester of the course are identifying a project for the team and performing a feasibility study of the project. In the second semester, teams focus on designing and implementing the project. The following report presents the details of the hydraulic hybrid prototype design, evaluation procedures, and test results.

1.1 Team Hydraulic Hybrid Tim Bangma is a senior engineering student with a mechanical concentration at Calvin College. Tim grew up in Whitinsville, Massachusetts, attended Whitinsville Christian School, and spent his summers working at a local fruit and vegetable farm stand. Ever since he was young, he had a passion for designing, building, and working on mechanical things from Legos, to dirt bikes, to cars. Tim has interned part-time with Innotec Group in Zeeland, Michigan, and full-time during the summer of 2010 as a machine designer with Extol Inc., also in Zeeland, Michigan. Tim has accepted a job at Gentex in Zeeland, Michigan as a Process Support Engineer and will start after graduation in May of 2011.

Liz Kladder is a senior engineering student with a mechanical concentration who is also receiving a minor in business. Originally from Holland, Michigan, she began her college career at Willamette University in Salem, Oregon. She now lives in Grand Rapids with her husband, Jon, and her dog, Bosun. She loves to be outdoors, whether hiking, biking, snowboarding, or sailing on beautiful Lake Michigan. During her time at Calvin, Liz has had the valuable opportunities to work at both Profile Industrial Packaging in Wyoming, Michigan and at Gentex Corporation in Zeeland, Michigan. After graduating in May of 2011, she will continue her work full-time at Profile Industrial Packaging.

Jon Mulder is a senior engineering student with a mechanical concentration at Calvin College. He grew up in Jenison, Michigan and attended Jenison Christian School and Unity Christian High School. He loves to spend his free time with friends and family and enjoys golfing, singing, listening to music and watching the Detroit Tigers. Jon has gained engineering knowledge and experience while working as a Quality Intern at Stanley InnerSpace in Kentwood, Michigan. Upon obtaining his degree in May of 2011, Jon will start working full-time at Dematic in Grand Rapids, Michigan as a Mechanical Systems Engineer.

Jay Prins is a senior engineering student with a mechanical concentration at Calvin College. Originally from Loveland, Colorado, he enjoys running in road races, snowboarding, and fishing in his spare time. Jay spent the summer of 2010 working at General Motors Component Holdings in Grand Rapids, Michigan as a test engineer intern. After graduation in May 2011, Jay will be working for Egemin Automation as a Site Technician.

Team 4 – Page 2

Zach Talen was born in Bakersfield, California, but moved Grand Rapids, Michigan at the age of five. He is now a senior at Calvin College majoring in engineering with a mechanical concentration. He enjoys living a life of adventure, which includes spending time outdoors and on the water. Zach enjoys sailing, water skiing and snowboarding. He has worked around engineers since he was in high school, but recently acquired an internship at Gentex Corporation working within the prototype and applied materials areas. He works with engineers who are responsible for being the last line of defense in problem solving as well doing continual improvement projects on the machines. Post graduation, Zach will be leaving for a five month adventure to sail from Michigan to the Caribbean. Once he returns, he will be getting married and looking for a job that utilizes his degree and his passions within the engineering field.

1.2 Problem Statement Inefficient fuel usage is often unavoidable for many vehicles. Most specifically, vehicles that operate under frequent stop and go conditions, such as delivery vehicles, are most affected by these inefficiencies. With increasing fuel prices and inefficient fuel use, there is an obvious need for a more resourceful solution. The solution that this team investigated was a hydraulic hybrid system.

1.3 Project Objectives The primary objective of this project was to validate that a hydraulic hybrid system can increase the stop and go fuel efficiency of a vehicle by 40%. The testing of the hydraulic system was conducted by prototyping the system on a golf cart. Furthermore, sub-goals were also considered which helped to keep the performance of the hybrid vehicle consistent with a non hybrid. These goals included a top speed of at least 20 miles per hour, adequate acceleration and braking capabilities, and necessary safety precautions, such as a high pressure relief valve and mechanical brakes for redundancy, should the hydraulic system fail.

2. Design Functionality

2.1 Design Norms Christians are called to live lives that are “holy and pleasing to God” (Romans 12:1). As followers of Christ, the team holds certain moral standards and guidelines in everything they do. Similarly, the senior design project will have specific moral guidelines that will be followed. These moral guidelines, as associated with engineering design, are called design norms. The design norms that have been selected for this project are: stewardship, trust, and transparency. Colossians 3:23-24 helped guide the team when choosing these design norms to govern the project. The passage explains that “whatever you do, work at it with all your heart, as working for the Lord, not for men… It is the Lord Christ you are serving.”

2.1.1 Transparency The design is transparent so that the control of this system functions as intuitively as possible. It was designed to be controlled by gas and brake pedals so that any new user will be familiar with its control.

Team 4 – Page 3

The design of the hydraulic system was created so it in no way hinders the performance or integrity of the vehicle. Not only will the system be predictable in use, it will be reliable and consistent.

2.1.2 Stewardship Christians strive to be conscious of the gifts God has given them, not only the physical things, but also the less tangible gifts of time and talent. It is not necessarily a Christian ideal to make a product that is more efficient; however, the team believes they should use the resources given by God to the best of their abilities.

2.1.3 Caring The design was created to be safe and trustworthy. The hydraulic system, was designed to be dependable, reliable, and consistent so that a customer will be able to trust it. This was achieved by implementing safety measures such as a redundant braking system in the event of a hydraulic component failure and a high pressure relief valve.

2.2 Project Scope The scope of the project was to test hydraulic hybrid technology, rather than designing a marketable system. Much of the time was spent on better understanding and implementing the knowledge and design aspect of the project, with less effort placed on making the product marketable and profitable on a large scale.

2.3 Hybrid Background

2.3.1 Types of Hybrids Hybrid vehicles are becoming more and more common in the auto industry. A hybrid vehicle is simply a vehicle that operates using a primary engine and secondary energy storage device. While electric hybrid vehicles are the most familiar and have been commercially produced, hydraulic hybrid technology is being investigated as a better hybrid option. Hydraulic hybrid vehicles are being introduced into the industry by companies such as Parker Hannifin Corporation and Eaton Corporation. Hydraulic hybrid systems can be divided into two different system types: parallel and series.

In a parallel hydraulic hybrid, the hydraulic components are connected to the conventional transmission and driveshaft. While the engine is always running and consuming fuel, the hydraulic system is able to assist in acceleration when the engine is working its hardest, thus increasing fuel efficiency. Series hydraulic hybrid systems use the same basic principles as parallel systems, but do not utilize the conventional transmission or driveshaft. The hydraulic system transmits all power directly to the wheels.

2.3.2 Benefits of Hydraulic Hybrids

2.3.2.1 Less Energy Conversions A hydraulic hybrid offers a number of advantages over electric hybrids. The largest of these advantages is that the system employs less energy conversions, leading to higher efficiencies. An electric hybrid converts kinetic energy to electrical energy and then to chemical energy that is stored in a battery. A hydraulic hybrid converts kinetic energy to fluid pressure energy and this is how the energy is stored.

Team 4 – Page 4

This results in one less energy form conversion to help the hydraulic hybrid achieve higher efficiency than other types of hybrids.

2.3.2.2 Regenerative Braking Regenerative braking is a large advantage to a hybrid system, especially when the vehicle is subject to frequent stops. Normally, in a conventional vehicle, all of the kinetic energy is lost to heat, an irreversible process. A hybrid however captures some of this energy through regenerative braking to be reused the next time the vehicle accelerates. Through simulations, it was estimated that 40% of the kinetic energy of the vehicle would be recycled through a regenerative braking event with the hydraulic hybrid system.

2.3.2.3 Optimal Engine Speed Operating the engine of a hybrid vehicle at its optimal operating point is of value because the engine can generate the most power per flow rate of fuel. To find this point for the engine used in this project, the following data was obtained from the manufacturer: engine power versus engine speed, engine torque versus engine speed, and engine fuel consumption rate versus engine speed. These data graphs are presented below in Figure 1, Figure 2, and Figure 3. The engine used in this project is represented by the orange line in all three figures. From this, a ratio was calculated at each engine speed of engine power or torque per volumetric flow rate of fuel. This was then graphed to find the optimum operation point.

Figure 1: Engine power data

Figure 2: Engine torque data

Team 4 – Page 5

Figure 3: Engine fuel consumption data

Team 4 – Page 6

Figure 4: Graph of torque per fuel flow rate versus engine speed

Team 4 – Page 7

Figure 5: Graph of power per fuel flow rate versus engine speed

Team 4 – Page 8

From Figure 4 and Figure 5, it was determined that the slower the engine runs, the better the torque per fuel consumption rate. However, the power graph shows a speed at which the engine maximized the amount of power obtained per fuel flow rate. From this data, the engine would be tuned to run at about 2200 rpm when pumping hydraulic fluid. This speed is close to the optimal operating speed for our engine, thus providing the best use of the fuel consumed by the engine.

2.4 Project Hydraulic System A hydraulic system schematic was created for a series hydraulic hybrid vehicle. This schematic was designed to include acceleration and braking control using hydraulic flow control valves, regenerative braking using check valves, and forewords and reverse directions using a directional selector valve. An important safety feature of the hydraulic schematic is the high pressure relief valve, which ensures that the pressure in the system never reaches an unsafe level. A copy of this schematic can be found in Figure 6.

Team 4 – Page 9

Figure 6: Hydraulic system schematic

A simplified hydraulic system schematic is shown in Figure 7 for the three major driving scenarios: accelerating, braking, and coasting. The diagrams trace the fluids route through the system during each of the scenarios.

Team 4 – Page 10

Accelerating

During acceleration, high pressure fluid is throttled through a flow control valve and sent to the hydraulic motor. The hydraulic motor uses the high pressure fluid to power the wheels, and outputs low pressure fluid back to the reservoir.

Braking During braking, wheels turn the shaft of the hydraulic motor, which opens a check valve and draws fluid into the motor. Fluid is then blocked from returning to the reservoir by closing the flow control valve and is re-directed through a check valve and stored in a high pressure accumulator.

Figure 7: Flow route for major driving scenarios

Team 4 – Page 11

Coasting When coasting, wheels turn the shaft of the hydraulic motor, which opens a check valve and draws fluid into the motor. The motor then pushes fluid through an open flow control valve back to the reservoir.

Figure 7, Continued: Flow route for major driving scenarios

Team 4 – Page 12

3. Base Case Cart Obtaining a baseline value of fuel efficiency was the first part of the project so that the team could compare the effectiveness and performance of the hydraulic hybrid system. A base case cart was created to simulate the performance a non-hybrid vehicle.

3.1 Beginning Cart The base of the vehicle was a three wheeled EZ-Go golf cart that was donated to the team. The cart, shown in Figure 8, was originally an electric golf cart in marginal condition. It provided a sufficient starting point for future modifications and improvements.

Figure 8: Picture of original cart

3.2 Frame Modifications The first step in the base case cart preparation was to modify the frame to mount the gasoline engine. A frame was designed to fit under the seat of the cart to which the engine would be mounted. The frame was constructed out of 1” x 1” x 0.125” thick steel tubing. Figure 9 and Figure 10 show a CAD image and a picture of the frame that was welded into the existing cart. Appendix B - 1 shows a dimensioned drawing of the engine frame weldment.

Team 4 – Page 13

Figure 9: CAD image of engine frame

Figure 10: Photo of engine frame in cart

Another important feature of the engine mounting was the motor mounts. These served to isolate the engine vibration from the rest of the cart. The isolation was achieved by sandwiching rubber pieces between the metal mounts and bolts of the engine. This allowed the engine to vibrate while running, without shaking the rest of the frame. A schematic of a motor mount is shown in Figure 11. The frame design also allowed for adjustment in engine position from side to side, as well as front to back. This ensured proper alignment of the drive train.

Team 4 – Page 14

Bolt

Nut

Rubber Isolators

Steel Mounts

Figure 11: Schematic of engine mount

3.3 Drive Train The drive train of the base case cart consisted of the following major components: engine, clutch, chain and tensioner, jackshaft, and axle. A photo of this drive train is shown in Figure 12. The drive train was designed to achieve a top cart speed of approximately 20 mph, to simulate normal golf cart operation. The engine had a maximum operating speed of 3600 rpm and the rear axle of the cart had a reduction ratio of 12:1. From these constants, a 14-tooth driving sprocket and 10-tooth driven sprocket were chosen to obtain the correct drive ratio for the desired speeds.

Figure 12: Photo of base case drive train

Tensioner

Chain

Engine

Clutch

Jackshaft

Axle

Team 4 – Page 15

3.3.1 Engine The engine used for the cart was a Kohler Command Pro 15 gasoline engine. This is a four stroke, 15 horsepower, single cylinder, overhead cam, air cooled engine. The engine was obtained through donation. Additional engine specifications are listed in Appendix D - 1.

3.3.2 Chain and Tensioner A size 40 chain was obtained from the spare parts room at Calvin. The tensioner was designed to take up the slack in the chain and allow for the chain length to vary as the rear suspension compressed, changing the distance between the driving and driven sprockets. The components for the tensioner were all obtained from Calvin including the hinge, bracket, spring, and idler sprocket.

3.3.3 Jackshaft The jackshaft was created by stripping the rotor from the original electric motor of its magnets and copper coils. The shaft was then machined to accept a ¾” bore, 10-tooth sprocket with a keyway. The shaft housing was machined to allow for the chain to pass through. The housing also contained the electric motor’s original bearings to ensure proper support, alignment, and free rotation of the jackshaft.

3.3.4 Axle The final component of the base case drive train was the axle that originally came with the cart. This axle had a gear ratio of 12:1 from the input to the output. The horizontal input of the axle was ideal for lining up the components of the drive train into a workable system.

3.4 Vehicle Control

3.4.1 Throttle The acceleration of the vehicle was controlled by adjusting the throttle. A throttle cable was used to attach the engine throttle to a linkage which was attached to the accelerator pedal. In order to open the throttle completely, the throttle cable needed to be pulled 0.5 inches. The existing accelerator linkage had 1.5 inches of travel; therefore, a lever was added to reduce the distance. The lever was mounted with a bracket that bolted onto the modified golf cart frame. A bushing was threaded onto the throttle control mounting bracket. The lever arm was bolted to the bracket through the bushing, allowing it to rotate freely. The lever attached to the existing throttle control linkage with the ball joint and stud. A picture of the CAD model of the throttle control lever can be seen in Figure 13.

Team 4 – Page 16

Figure 13: CAD model of throttle control lever

The throttle cable was attached to the bottom of the lever and the cable housing was mounted to a bracket bolted onto the frame. Figure 14, below, is a picture of the assembled throttle control lever installed onto the golf cart frame. A complete set of drawings used to machine the throttle control lever can be found in Appendix B - 2.

Figure 14: Throttle control lever

3.4.2 Brakes The drum brakes from the electric golf cart were used to control the deceleration of the gas-driven cart. Before the gas cart was driven, the brakes were disassembled, cleaned, re-assembled, and adjusted.

Bracket/ Bushing

Lever Arm

Cable Housing Bracket

Ball and Socket Joint

Team 4 – Page 17

4. Hydraulic Hybrid

4.1 Frame Modifications After testing of the base case cart was complete, the frame of the base case vehicle was further modified to allow mounting of the necessary components. Frames were welded in to support the accumulators, reservoir, and hydraulic motor.

4.1.1 Engine Mounting The engine mounted the same way in the hybrid cart as it did in the base case cart. The exhaust was slightly modified to move the hot exhaust pipe away from critical hydraulic components. A new exhaust flange was made and welded to a pipe. This moved the muffler away from the engine. The muffler was mounted to an angle iron bracket that was welded to one of the chassis rails.

4.1.2 Accumulator Mounting The accumulators allow for regenerative braking and energy storage in a hydraulic hybrid. Accumulators work best when mounted vertically. For this reason, a rack was welded into the frame, behind the seat rests, on which the accumulators would rest. A CAD image and picture of the mounting frame and brackets are shown below in Figure 15 and Figure 16. Drawings for these parts can be found in Appendices B - 3 and B - 4. The accumulators rest in the large hole in the accumulator mounting bracket with a piece of rubber cushioning this interface. A strap holds the top of the accumulator to the vertical piece of the black rack that is welded into the frame. The brackets were welded together and bolt onto the black part of the frame. Each accumulator weighs 118 pounds so this is significant structure.

Figure 15: CAD image of accumulator

mounting assembly

Figure 16: Photo of accumulators mounted on cart

Team 4 – Page 18

4.1.3 Reservoir Mounting The reservoir holding the excess hydraulic oil also needed to be mounted to the cart. A frame was made that welded on the back of the cart in place of the back bumper. This would provide a mounting surface for the reservoir. A CAD image and photo of his frame are shown in Figure 17 and Figure 18. A dimensioned drawing of this weldment is shown in Appendix B - 5.

Figure 17: CAD image of reservoir mount

Figure 18: Photo of mounted reservoir

Team 4 – Page 19

4.2 Hydraulic Drive train The hydraulic drive train converts the power of the engine to motion of the cart. It works through a pump and motor attached to the engine and axle, respectively.

4.2.1 Engine The engine used for the hydraulic drive train was the same as the base case cart.

4.2.2 Pump The pump was used to move fluid from the low pressure reservoir to the high pressure manifold and accumulators, and ultimately through the hydraulic motor.

4.2.2.1 Type The specific pump used was an Eaton Series 26 pump, shown in Figure 19. The model number is 26002-LZF. It is a fixed displacement gear pump with a 0.50 in3 per revolution displacement. This was originally a left hand rotation pump; however the team converted it to a right hand rotation pump. The pump has a maximum continuous pressure rating of 3000 psi and was rated for 3600 rpms. The manufacturer specification sheet for the hydraulic pump can be found in Appendix D - 2.

Figure 19: Photo of Eaton Series 26 pump

4.2.2.2 Mounting The pump was attached directly to the motor with a custom mounting bracket. A CAD model and photograph of the pump mounting assembly are shown in Figure 20 and Figure 21. The engine’s output shaft was coupled to the pumps input shaft with a LoveJoy coupler. Dimensioned drawings of the bracket components are shown in Appendix B - 6.

Team 4 – Page 20

Figure 20: CAD image of pump mounting assembly

Figure 21: Photo of mounted pump

4.2.3 Hydraulic Motor A hydraulic motor was used to propel the vehicle in both the forward and reverse directions. It was also utilized to pump fluid back into the accumulators when using the regenerative braking system.

4.2.3.1 Type The type of hydraulic motor chosen was a Haldex GC series bidirectional gear motor. It is a high speed, low torque motor that will spin up to 5000 rpm at 2500 PSI. This motor uses a set of internal check valves to properly direct the flow of the fluid without then need to utilize a drainage port back to the low pressure reservoir. It uses a set of gears to either pressurize fluid to a high pressure, or uses a high pressure to rotate the shaft. Further manufacturer specifications for the hydraulic motor are listed in Appendix D - 3.

4.2.3.2 Mounting The hydraulic motor was attached to the back of the old electric motor housing. The electric motor was stripped of its components, and the shaft and housing were used. The housing was useful since it connected directly to the transaxle, and the center of rotation was already located. The electric motor housing was cut down and the back side was modified to have the face of the hydraulic motor coincident with the back of the casing. The hydraulic motor was then bolted to the back of the old electric motor housing. A comparison of the old electric motor to the modified housing that supports the hydraulic components can be seen in Figure 22.

Team 4 – Page 21

Figure 22: Electric motor was modified to support hydraulic components

4.2.4 Jackshaft The jackshaft came from the original electric motor that was installed on the golf cart. Since it already had one end properly machined for a gear that connected to the transaxle, it was a convenient piece to use. The shaft was originally to long, and to big in diameter. It was cut in length and the diameter of the last inch of the shaft was turned down to a one inch diameter. A keyway was then put in to allow for the use of a spider couple. The hydraulic motor could then connect to the jack shaft through the use of a spider coupler on each shaft.

4.2.5 Axle The axle utilized was the same axle that was on the cart originally. The gear ratio of the transaxle, around 12:1, was convenient to use with a high speed, low torque hydraulic motor. Since the axle was originally intended for an electric motor that ran at speeds up to 7000 RPM, it was determined that the use of this axle would be a good fit for a high speed hydraulic motor. Calculations were done to make sure that the speed of our hydraulic motor and the top speed of our cart would match up.

4.3 Hydraulic Vehicle Control

4.3.1 Engine Control To regulate the pressure in the accumulators, the gas engine throttle needed to be adjusted accordingly to charge the accumulators to the required maximum pressure. This ensures the accumulators neither fully discharge, suffocating the hydraulic system of necessary pressure to run, nor exceed the maximum operating pressure of the hydraulic system, risking a potentially dangerous failure. It will increase the throttle of the engine when the accumulators reach a low pressure of 800 psi and automatically throttle down the engine to idle when the accumulators’ pressure reaches 2200 psi. This ensures the hydraulic system is transparent and caring, as the control of the engine speed is completely automated and will prevent potentially harmful failures.

Team 4 – Page 22

4.3.1.1 Electronic Control Initially, the team wanted to use electronics to monitor the accumulator pressure and control a stepper motor to vary the throttle accordingly. Due to the team's limited experience and knowledge of complex logic design, the potential complexity of debugging, the potential modes of failure of such a system, and the expensive nature of electronic hydraulic pressure sensors, the team decided that an electronic control system was not the best option for the hydraulic hybrid prototype.

4.3.1.2 Hydraulic Cylinder After eliminating the electronic control option, the team moved on to looking into a mechanical means of controlling the engine throttle. Hydraulic cylinders allow for variation in piston position as it is related to the system pressure. Therefore, a single action, spring returned hydraulic cylinder acts similar to a pressure sensor because an increase in hydraulic pressure causes the piston to extend further out of its housing. This movement is used to shift a mechanical linkage that controls the position of the engine throttle. This linkage is seen below in Figure 23 and Figure 24: Throttle lever in charging position.

As the pressure in the accumulators decreases, the piston retracts until it reaches the engine throttle bar. It pulls the throttle until it is locked into position by the horizontal catch bar. This ensures the engine is held at its optimal rpm until the accumulators are full charged. As the engine charges the accumulators, the piston begins to extend, leaving the throttle in its charging position. When the accumulators reach their maximum pressure of 2200 psi, the hydraulic piston is in its fully extended position. Here, it bumps the release pin which allows the tension in the throttle cable to pull the throttle bar back to its idle position. The movement of the catch bar and pin are assisted by an extension spring and a compressions spring, respectively.

Figure 23: Throttle lever in idle position

Team 4 – Page 23

Figure 24: Throttle lever in charging position

Due to the constraints of budget and time, this solution was not implemented on the prototype. The goal of this project was to prove the feasibility of the hydraulic system. As this aspect of the project only aims to automate the control of the system pressure for the driver, it was not a critical feature that was necessary for the project to be deemed successful.

4.3.1.3 Manual Control If the constraints of time and budget were not present, the addition of an automated pressure regulation system would allow a single person to operate the vehicle. As this was only a secondary goal of the project, the team decided that the engine was to be manually controlled. This involved a passenger to ride with the driver to physically monitor the accumulator pressure gauges and throttle the engine up and down as necessary with a basic lever.

4.3.2 Acceleration Control Acceleration of the hydraulic hybrid vehicle was controlled using a restrictive flow control valve. The restrictive flow control valve varies the flow rate through the valve from 0 to maximum flow as the handle is turned. This valve was placed between the high-pressure manifold and the hydraulic motor. During acceleration, the valve is opened, allowing oil to flow to the hydraulic motor. During coasting and braking, the valve is fully closed.

4.3.2.1 Valve Type A RD – 175-30 Prince Adjustable Flow Control Valve with the excess flow port plugged was used as the flow restrictor valve. This valve is rated up to 3000 psi, and controls flow between 0 and 30 gallons per minute. A picture of the acceleration control valve can be seen below Figure 25. Appendix D - 3 contains the specification sheet from the manufacturer.

Team 4 – Page 24

Figure 25: Acceleration control: restrictive flow control valve

4.3.2.2 Mounting The acceleration control valve was mounted to the vehicle using a bracket that bolted on to the modified frame. The valve was mounted in line with the accelerator pedal so simple modifications could be made to the existing accelerator linkage. The valve was mounted at 45˚ tilt so that the travel range of the valve handle could be adjusted without any binding of the linkage. Figure 26 below is a picture of the bracket designed to mount the accelerator control valve. The drawing created to machine the bracket can be found in Appendix B - 7.

Figure 26: CAD model of accelerator valve mounting bracket

4.3.2.3 Linkage The acceleration control linkage from the original electric golf cart was modified to control the flow control valve. The existing accelerator linkage was lengthened roughly 3 inches using threaded steel rod and a post. The threaded ball joint was threaded onto the extended steel rod. The ball stud was

Team 4 – Page 25

threaded into the accelerator control valve handle. The length of the flow control valve was adjusted so that the valve was fully open when the accelerator pedal was fully engaged. Figure 27 is a screen shot of the CAD model used to design the accelerator linkage. Figure 28 below is a picture of the accelerator valve linkage.

Figure 27: CAD model of accelerator valve linkage

Figure 28: Accelerator valve linkage picture

4.3.3 Brake Valve Braking of the hydraulic hybrid vehicle was controlled using a restrictive flow control valve, the same type of valve as used for the acceleration control. The restrictive flow control valve varies the flow rate

Ball /Socket Joint

Accelerator Valve

Coupler

Team 4 – Page 26

through the valve from 0 to maximum flow as the handle is turned. This valve was placed between the low-pressure manifold and the hydraulic motor. During acceleration and coasting, the valve is fully open. When braking, the valve is fully closed, blocking the fluid from reaching the low-pressure reservoir. Instead, the oil is pushed through a check valve to a high pressure.

4.3.3.1 Valve Type A RD – 175-30 Prince Adjustable Flow Control Valve with the excess flow port plugged was used as the flow restrictor valve. This valve is rated up to 3000 psi, and controls flow between 0 and 30 gallons per minute. A picture of the brake control valve can be seen below. Appendix D - 3 contains the specification sheet from the manufacturer.

Figure 29: Braking control: restrictive flow control valve

4.3.3.2 Mounting The brake control valve was mounted to the vehicle using a bracket that bolted on to the modified frame. The valve was mounted left of the main frame on the driver’s side. The valve was mounted here so that the hoses going to the valve did not interfere with the pump. The valve was mounted at 45̊ tilt so that the travel range of the valve handle could be adjusted without any binding of the linkage. Figure 30 is an image of the CAD model illustrating the brake valve mounting bracket. A drawing for the mounting bracket for the brake valve can be found in Appendix B - 8

Team 4 – Page 27

Figure 30: CAD model for brake valve mounting bracket

4.3.3.3 Linkage The brake control valve was linked to the brake pedal using a threaded steel rod and clevis joints. A 2-inch plate was welded to the bottom of the brake pedal to connect the linkage rod to the brake pedal. The linkage rod was long enough to close the valve completely. Figure 31 below contains a picture of the CAD model of the brake valve linkage. Figure 32 is a picture of the brake valve linkage.

Figure 31: CAD model of brake pedal linkage

Team 4 – Page 28

Figure 32: Brake valve linkage picture

4.3.3.4 Redundant Bakes The drum brakes used from the original electric golf cart were adjusted to ensure the vehicle could always come to a complete stop in panic situations. The brakes were adjusted to fully engage in half of the brake pedal’s travel. This was accomplished by adding a lever between the brake pedal and the brake cables. The brake cables were attached to the lever with a threaded rod. The engaging point of the redundant brakes is adjusted by setting a nut and washer on the threaded rod attached to the brake cables. A picture of the redundant brake linkage is shown below in Figure 33.

Figure 33: Redundant brake’s linkage picture

Team 4 – Page 29

4.3.4 Directional Selector Valve A directional selector valve was included in the hydraulic schematic. The directional selector valve allows fluid flow to easily be re-directed by simply switching the position of the spool. Two junctions in the hydraulic schematic required a directional selector valve. A single, six port selector valve was used to combine these two junctions into the same valve.

4.3.4.1 Valve Type The directional selector valve used in the hydraulic hybrid vehicle was a Metro Machine MDS-08-20 six port - two position double selector valve. A picture of directional selector valve can be seen in Figure 34.

(www.northerntool.com)

Figure 34: Metro machine six port - two position selector valve

This valve is rated up to 3000 psi, has a 30 GPM flow capacity, and has standard open crossover porting, which simply switches the outlet port for a given inlet. Figure 35 below is a diagram showing the two possible spool positions for the valve.

Figure 35: Positions of the directional selector valve

4.3.4.2 Mounting The directional selector valve was mounted so that the knob could easily be reached by the driver of the vehicle. The valve was bolted onto the frame with a bracket, mounted to the face of the valve. The valve was mounted below the seat on the driver’s side. A spacer for the valve knob was constructed so that the knob could easily be pulled. Figure 36 shows a picture of the position of the mounted double selector valve.

Team 4 – Page 30

Figure 36: Location and mounting of the directional selector valve

4.3.4.3 Purpose This valve was used to easily switch the cart’s driving direction by switching the high pressure fluid to the opposite port of the motor.

4.3.5 High Pressure Relief Valve The high pressure relief valve was implemented in the system to control the amount of pressure that could build up within the system. Once the pressure reached a specified limit, the valve allowed fluid to flow to low pressure, thus decreasing the risk of component failure. Once pressure is low enough, the valve will close, allowing pressure to build up again when necessary. This valve is adjustable to allow for a specific maximum operating pressure to be obtained and may be used to purge the system of remaining high pressure if a failure occurs.

4.3.5.1 Valve Type The valve used in the Hydraulic Hybrid prototype was a HydraForce RV10-26 relief valve. A picture of the valve is shown in Figure 37. The specification sheet for the valve is shown in Appendix D - 5.

Team 4 – Page 31

Figure 37: High pressure relief valve

4.3.5.2 Purpose/Use The purpose of the high pressure relief valve was to ensure the safety of the driver, passenger, and hydraulic components.

4.3.6 Check Valves A check valve is a type of passive flow control valve that only allows fluid to flow one direction through a part of the hydraulic circuit. Five check valves were incorporated into the hydraulic schematic to prevent fluid back flow into the hydraulic pump and to instantaneously direct flow during braking and costing scenarios.

4.3.6.1 Types Four Stucci VU-100-NPT-21 PSI check valves were used between the motor and the high and low pressure manifolds to direct flow during braking and costing. A Metro Machine FC- 50 check valve was installed between the high pressure port of the pump and the high pressure manifold to prevent fluid from flowing back into the pump. The manufacturer specification sheet for the Stucci check valves can be found Appendix D - 6.

4.3.6.2 Purpose During coasting, the check valve between the inlet side of the motor and the low pressure reservoir is cracked open by the back pressure created by the motor. This draws fluid from the low pressure reservoir, cycles it through the hydraulic motor, and returns to the low pressure reservoir through the brake valve. During braking, the brake valve blocks fluid from returning to low pressure. Instead, the hydraulic motor pressurizes the fluid and pushes the fluid through the check valve between the high

Team 4 – Page 32

pressure manifold and the outlet of the motor. Figure 38 is a picture of the four Stucci check valves mounted between the high and low pressure manifolds.

Figure 38: Mounted Stucci check valve

4.4 Other Hydraulic Components

4.4.1 Accumulators Accumulators were needed in order to store hydraulic fluid at a high pressure in a safe and efficient manner.

4.4.1.1 Type The type of accumulator chosen was a bottom repairable bladder accumulator rated to 3000 PSI. Of the many types of accumulators in the market, bladder accumulators are the most maintenance and leak free. The necessary accumulator volume calculated for the system was approximately five gallons. This calculation also took into consideration the size constraint that may come with large accumulators. Two 2.5 gallon, 6000 PSI bottom repairable bladder accumulators were obtained through a donation.

4.4.1.2 Purpose The purpose of the accumulators is to store fluid at a high pressure. The fluid can then be used to not only propel the vehicle, but it also provided the back pressure necessary to utilize regenerative braking. The accumulators store nitrogen in a bladder a high pressure, known as a pre charge. Fluid is then pushed into the accumulators, which compresses the nitrogen, raising the pressure in the accumulators.

4.4.1.3 Plumbing The design for the plumbing out of the bottom accumulator would have been a 1 7/8 inch SAE straight thread, and then reduced down to the nominal fitting size of the system. As accumulators were donated, the optimal choice of plumbing was not available. The donated accumulators came with a 2

Team 4 – Page 33

inch SAE split flange mount. To properly attach to this flange, a four bolt SAE flat flange with a 90 degree bend, an o-ring and two captive flanges were needed.

Four bolt SAE flanges are valued at $200 each, and another $30 for the captive flanges. Due to budget constraints, the purchasing of these components was not feasible. Instead, the components were machined using stock material from the shop at Calvin College. The four bolt flanges were machined out of a block of 7075-T6 aluminum. These flanges were designed around the rough dimensions from a distributor’s website. After the final design of the four bolt flanges, hand calculations and finite element analysis were done in order to make sure the stresses were below yield and the deflections would not cause a leak. The stresses fell three times below the yield stress of the aluminum, and the deflections were small enough to cause no issues. The captive flanges were made from steel, and also designed off dimensions from a distributor’s website. Final dimensions of the four bolt flanges and captive flanges can be found in Appendix B - 9 and Appendix B - 10, respectively.

4.4.1.4 Mounting Since each accumulator weighed 118 pounds without fluid, it was necessary to ensure that they were properly mounted and supported. It was decided to mount the accumulators vertically, since they are most efficient in that position. Accumulator mounting stands and U-bolts with a rubber coating could have been used to properly secure the accumulators. Because purchasing accumulator stands would cost 180 dollars each as well as 60 dollars for each of the U-bolts, it was decided that the accumulator mounts would be fabricated. The dimensions of the mounting stands were taken of the website of the manufacture, and the stands were manufactured by the team. They were then mounted to a frame welded to the back of the cart. Heavy duty nylon strap, similar to that used in packaging and shipping, was used to properly secure the accumulators in an upright and safe position.

4.4.2 Gages In order to properly monitor the pressure in the accumulators, gauges would need to be attached to the top of the accumulators. Permanent mount gauge blocks, which include a valve for filling the nitrogen, a bleeder valve and a port for a gauge, were mounted to the tops of the accumulators. Optimally, the gauges would have been digital so readout of the pressures could be brought to the dashboard of the vehicle. Due to budget constraints, analog gauges were purchased and mounted to the gauge blocks.

4.4.3 Reservoir The reservoir was chosen to hold the proper amount of fluid for the entire system without it running dry. Since 5 gallons could be stored in the accumulators, a reservoir was chosen to store that much fluid, plus a safety amount. A seven gallon reservoir was chosen and mounted to the back of the vehicle. The reservoir was sized to hold excess fluid so that there was time for the fluid to cool before being cycled back into the hydraulic system.

4.4.4 Filter A filter was needed in order to prevent particles from getting into the pump and the rest of the system. A 25 micron, 15 GPM spin on filter was chosen. It was installed in between the reservoir and the pump’s inlet port. There is easy access to the filter so it can be changed periodically.

Team 4 – Page 34

4.5 Retrofit Hydraulic Hybrid System Costs Table 1, below, shows a list of all of the hydraulic components. The total cost of the hydraulic retrofit system was about $6300. Hydraulic components are expensive in nature and therefore must drastically improve the performance of the vehicle in order to be financially advantageous.

Table 1: Retrofit system costs

Component Cost

Eaton Hydraulic Pump $246.50

Accumulators Inc. Accumulators $3286.00

7 gal. Reservoir $100.00

Haldex Hydraulic Motor $200.25

Misc. Hydraulic Valves $843.00

Misc. Hoses and Fittings $550.00

Mechanical Couplers $60.00

Pressure Fixtures $1000.00

Total $6285.75

5. Testing and Results

5.1 Test Procedure To best determine the benefits of the hydraulic hybrid system, the golf cart was driven both before and after the hydraulic retrofitting in three different driving scenarios. A city driving test, a top speed test, and a mid-level speed test.

In the city driving scenario, the cart was driven and came to a complete stop multiple times around a track for five laps, shown in Figure 39.

Team 4 – Page 35

Figure 39: City driving course, five laps

The cart was driven on the course to simulate commuting approximately half a mile (five course laps) incorporating numerous stops and starts. Cones were set up around the course allowed for repeatability as the driver could accelerate toward and stop at each set of cones. In the top and mid-level speed test, the cart was driven around the same track for five laps, without stopping. In order to determine fuel efficiencies, the initial amount of fuel was measured using a graduated cylinder. The difference in the volume of fuel in the cylinder before and after the test provided the amount of fuel consumed during the test. The cylinder was re-filled as necessary, and each test was run at least three times to obtain a consistent data set.

5.2 Base Case Cart Results The results from testing the base case cart are displayed in Table 2, below. As expected, the stop and go test produced the worst fuel efficiency, and the sustained speed results were better. This data provided a baseline for improvements to be calculated from for the hydraulic hybrid system.

Table 2: Base case cart fuel efficiency results

Test:Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal):

0.551 0.042 0.551 0.038 0.551 0.039 0.551 0.041 0.551 0.040MPG: 13.039 MPG: 14.692 MPG: 14.192 MPG: 13.547 MPG: 13.868

Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal):0.551 0.023 0.551 0.022 0.551 0.022 n/a n/a 0.551 0.022MPG: 23.980 MPG: 25.442 MPG: 24.544 MPG: n/a MPG: 24.656

Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal): Distance (mi): Fuel (gal):0.551 0.018 0.551 0.019 0.551 0.018 n/a n/a 0.551 0.018MPG: 30.236 MPG: 29.384 MPG: 29.804 MPG: n/a MPG: 29.808

Reduced Speed

Top Speed

Trial 3 Trial 4 Average

Stop and Go

Trial 1 Trial 2

Team 4 – Page 36

5.3 Hydraulic Hybrid Cart Results Due to some technical difficulties of the prototype hybrid cart, complete testing was not able to be conducted, however complete data for the stop and go performance of the hybrid cart and preliminary data for the reduced speed test were gathered. These results are displayed in Table 3. Since this project focused on improving the stop and go fuel efficiency of the vehicle, this data was of most importance. The results, shown below, indicate a 52% increase in stop and go fuel efficiency from the base case cart. These results surpassed the goal of 40% that was set at the beginning of the project.

Table 3: Hydraulic hybrid cart fuel efficiency results

It is important to note the preliminary results from the reduced speed test. The hybrid cart actually performed at 50% worse fuel efficiency than the base case cart. These results are not finalized, but are explainable because the hybrid uses a less efficient drive train compared to a mechanical connection. A hybrid’s two main benefits, regenerative braking and optimal engine operation, are not effectively used in this highway driving scenario, thus emphasizing the importance of how the hydraulic hybrid is used.

5.4 Discussion The prototype system was not optimized for all driving scenarios and more work could be done to improve the sustained speed test results. Different combinations of pump and motor sizes could help to improve the efficiency in a highway driving scenario. Also, the use of a variable displacement motor could help by adding some variability in the torque applied and fluid required to move the cart at different speeds. The system could also be optimized to reduce minor losses in the fluid flow by using less bends and elbows and valves that allow less obstructed flow.

6. Project Schedule To complete the project on-time, a detailed and rigorous project schedule was created and maintained throughout the project. This project schedule included a scheduled work breakdown structure and Gantt chart that were instrumental in keeping the team on schedule. The project was able to successfully follow the timetable to create and test the gas powered base case cart as well as build and test the hydraulically driven prototype by the Senior Design Banquet held on May 7, 2011. The chart followed during the fabrication and testing of the prototypes can be found in Appendix F.

Test:Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal)

0.551 0.029 0.551 0.024 0.551 0.026 0.551 0.026 0.551 0.026MPG: 18.966 MPG: 23.181 MPG: 20.863 MPG: 21.508 MPG: 21.129

Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal) Distance (mi): Fuel: (gal)0.551 0.037 n/a n/a n/a n/a n/a n/a 0.551 0.037MPG: 14.902 MPG: n/a MPG: n/a MPG: n/a MPG: 14.902

Stop and Go

Reduced Speed

Trial 1 Trial 2 Trial 3 Trial 4 Average

Team 4 – Page 37

7. Project Budget

7.1 Prototype Cost The prototype cost proposed in the Project Proposal and Feasibility Study was estimated at $1,658. Because of the expensive nature of the project and the team’s limited budget, this was based on an optimistic pricing of the smallest components that would be able to work in the proposed hydraulic system. Due to the high cost of the hydraulic components used, the team saw the need to look for a donor to alleviate some of the budget restrictions. The Vermeer Corporation assisted the team by donating a significant amount of the primary components used in the hydraulic system.

The total cost of the Hydraulic Hybrid project (including components for the base case cart) is estimated to be $9,133.14, based on the retail value of the purchased and donated parts. The total cost of the donated parts amounted to $7,899.01 and the cost of the purchases made using Calvin’s given budget totaled $1,234.53. A detailed outline of the prototype budget is included in the BOM, found in Appendix C.

7.2 Bill of Materials A bill of materials (BOM) was constructed to highlight the individual components, fasteners, and other materials used in the completion of the hydraulic hybrid prototype. The details of the method of acquisition, donor/vendor, unit price, value, and cost to the team can all be found in the BOM, located in Appendix C.

8. Business Plan There are two main options when looking to incorporate this product into a business. The first option is a retrofit kit. Current vehicles would arrive and be modified to run using a hydraulic hybrid drive train. This would allow the product to get into the market faster, but would be considerably expensive for the lifetime of the vehicle. The second option is to incorporate the product with the original equipment manufacturer (OEM). This would provide a less expensive route for the customer, but it would take longer to get product to the market.

8.1 Financial Analysis With the prototype cart, the total expenses for hydraulic components were approximately $6,300. Taking in labor costs, product design and all other variable and fixed costs with a 100% mark-up, the system would cost $26,780. The financial forecasting can be seen in Appendix E - 1.

8.2 Payback Period At the current gasoline price of $4.17 per gallon (May, 2011), the payback period on a system would be twenty-two years. Figure 40, below, shows how long the vehicle would have to last at a selected gasoline price in order to payback the investment. To get a payback of 10-15 years, the reasonable lifetime of a vehicle, gasoline prices would only have to rise between $5.50/gallon and $7.00/gallon. All assumptions and variables for the payback period of a fleet can be seen in Appendix E - 2.

Team 4 – Page 38

Figure 40: Payback period (lifetime of vehicle) dependednt on gasoline price

9. Conclusion To conclude, the project was a success. First off, the team met and surpassed the fuel efficiency savings expectations of 40% by obtaining an average stop and go fuel efficiency of 52%. The team also proved that the hydraulic hybrid system is functional in an intuitive manner. The primary downside of a hydraulic hybrid system is the very expensive cost of necessary components. Due to this, it is unlikely to anticipate a small company to start up with this technology. Finally, the entire team not only learned a significant amount about the design and function of hydraulic systems, but also gained valuable experience when it comes to working as a team to solve engineering problems.

Team 4 – Page 39

Appendices Appendix A. Acknowledgements ............................................................................................................. 40

Appendix B. Part Drawings ...................................................................................................................... 41

B - 1. Engine Racking ........................................................................................................................ 41

B - 2. Engine Throttle Lever Assembly .............................................................................................. 42

B - 3. Accumulator Mount ................................................................................................................ 46

B - 4. Accumulator Frame ................................................................................................................. 47

B - 5. Reservoir Mounting ................................................................................................................ 48

B - 6. Pump Mount ........................................................................................................................... 49

B - 7. Accelerator Control Valve Mount ........................................................................................... 50

B - 8. Brake Control Valve Mount ..................................................................................................... 51

B - 9. SAE 4 Bolt Flange ..................................................................................................................... 52

B - 10. Captive Flange ......................................................................................................................... 53

Appendix C. Bill Of Materials ................................................................................................................... 54

Appendix D. Part Specification Sheets ..................................................................................................... 57

D - 1. Kohler Engine .......................................................................................................................... 57

D - 2. Pump ....................................................................................................................................... 59

D - 3. Hydraulic Motor ...................................................................................................................... 64

D - 4. Restrictive Flow Control Valves ............................................................................................... 65

D - 5. Relief Valve .............................................................................................................................. 67

D - 6. Check Valves ........................................................................................................................... 69

Appendix E. Business Financials .............................................................................................................. 71

E - 1. Financial Forecasting ............................................................................................................... 71

E - 2. Payback Period Analysis .......................................................................................................... 73

Appendix F. Scheduling Documents ........................................................................................................ 74

Team 4 – Page 40

Appendix A. Acknowledgements

The team would like to extend its gratitude to the Vermeer Corporation for providing both purchasing and technical support, as well as the Vermeer Charitable Foundation for its financial support. We would also like to thank Mary Andringa, President and CEO of Vermeer Corporation, as well as Bob Vermeer, Chairman of the Board, for their willing support of our Senior Design project. Additionally, the team would like to acknowledge Lois Vermeer for her financial collaboration on the project and Kelly Dawley for facilitating the success of the project. The team would also like to thank Matt Mills for his key role in helping the team acquire key information and components; we greatly appreciate all of his time and effort and many supportive emails! The team would like to show appreciation to Michael Harris, Executive Director of the Enterprise Center, for his instrumental role in helping us with patent research and the acquisition of our sponsor and donor.

The team would also like to thank the following individuals and companies for their indispensible support which allowed this project to be a success:

• Phil Jasperse – Calvin Shop Supervisor, for his problem-solving expertise • Professor Ned Nielsen – Team Advisor • Ren Tubergen – Industrial Consultant • Bond Fluidaire – Hydraulic lines and fittings • Jim Kuipers – Donation of the golf cart frame that was used for the project • Drew Griffioen - Donation of the initial golf cart that ended up being scrapped • Rex Shemer – Printing of the decals • Great Lakes Fluid Power – Accumulator pre-charging

Last, but certainly not the least, the team would like to thank its family and friends for their love and unconditional support. Whether lending a willing ear or giving a reaffirming word of encouragement, these past four years would not have been the same without you. Thank you!

Team 4 – Page 41

Appendix B. Part Drawings

B - 1. Engine Racking

Team 4 – Page 42

B - 2. Engine Throttle Lever Assembly

Team 4 – Page 43

Team 4 – Page 44

Team 4 – Page 45

Team 4 – Page 46

B - 3. Accumulator Mount

Team 4 – Page 47

B - 4. Accumulator Frame

Team 4 – Page 48

B - 5. Reservoir Mounting

Team 4 – Page 49

B - 6. Pump Mount

Team 4 – Page 50

B - 7. Accelerator Control Valve Mount

Team 4 – Page 51

B - 8. Brake Control Valve Mount

Team 4 – Page 52

B - 9. SAE 4 Bolt Flange

Team 4 – Page 53

B - 10. Captive Flange

Team 4 – Page 54

Appendix C. Bill Of Materials

Team 4 Hydraulic Hybrid Bill of Materials 500 Work Hours (second semester)

Purchased Components

Qty Item Description Method of Acquisition

Donor/ Vendor

Unit Price

Value Cost To Team

1 3 Wheeled Golf Cart Donation Jim Kuipers $200.00 $200.00 $0.00 1 Kohler 15 hp Engine Donation Vermeer $1,175.00 $1,175.00 $0.00

1 Eaton Hydraulic Pump (26002-LZF) Donation Vermeer $246.50 $246.50 $0.00

1 Hydraforce Relief Valve Donation Vermeer $50.00 $50.00 $0.00

1 14 T, 1in bore Clutch Purchased Northern Tool $119.99 $119.99 $119.99

1 10 tooth sprocket Salvage Calvin $12.00 $12.00 $0.00 1 #40 Chain Salvage Calvin $20.00 $20.00 $0.00 2 Quarts Gear Oil Purchased Autozone $4.00 $8.00 $8.00 3 Quarts 10W-30 Motor Oil Purchased Autozone $3.29 $9.87 $9.87 4 Check Valves Donation Vermeer $80.00 $320.00 $0.00

1

Hytrel Spider for 2-7/64" Outside Diameter Flexible Spider Shaft Coupling Hub

Purchased McMaster-Carr $14.38 $14.38 $14.38

1 Flexible Spider Shaft Coupling Hub 1" Bore, 2-7/64" OD, with Keyway

Purchased McMaster-Carr $9.86 $9.86 $9.86

1 Spider Shaft Coupling Hub SAE A Splined, 1.00" Length, 2-7/64" OD

Purchased McMaster-Carr $19.50 $19.50 $19.50

2 2.5 Gal Hydraulic Accumulators Donation Vermeer $1,643.00 $3,286.00 $0.00 1 6 port selector valve Donation Vermeer $89.99 $89.99 $0.00

2 Prince Adjustable Flow Control Valve — 3/4in. Donation Vermeer $179.98 $359.96 $0.00

1 HALDEX BARNES Motor, Fluid, 3.1 GPM Purchased Grainger $200.25 $200.25 $200.25

1 Nortrac Steel Hydraulic Oil Tank — 7 Gallon Purchased Northern

Tool $99.99 $99.99 $99.99

7 Run Tee Purchased Bond FluidAire $8.680 $60.76 $60.76

8 BUSHING Purchased Bond $3.070 $24.56 $24.56

Team 4 – Page 55

FluidAire

2 90degsteel steel Purchased Bond FluidAire $5.560 $11.12 $11.12

12 1/2"ID -1/2MPS Purchased Bond FluidAire $10.650 $127.80 $85.20

8 1/2 MPT-1/2 HOSE END Purchased Bond FluidAire $3.400 $27.20 $27.20

9 1/2" ID-8 JICFS 90 EL Purchased Bond FluidAire $9.670 $87.03 $87.03

8 -8 x 1/2mpt Strt Purchased Bond FluidAire $1.910 $15.28 $15.28

1 -8 x 1/2fpt Strt Purchased Bond FluidAire $3.190 $3.19 $3.19

2 1/2" ID-6FS HE Purchased Bond FluidAire $9.440 $18.88 $18.88

2 MJIC X MOR STRT (Steel fitting) Purchased Bond FluidAire $1.250 $2.50 $2.50

1 MORXFTP STRT Purchased Bond FluidAire $4.610 $4.61 $4.61

1 BUSHING Purchased Bond FluidAire $40.410 $40.41 $40.41

1 BUSHING Purchased Bond FluidAire $9.910 $9.91 $9.91

3 1/2ID-10M.O-RING Purchased Bond FluidAire $6.870 $20.61 $20.61

36 3000WP TOUGH COVER Purchased Bond FluidAire $2.950 $106.20 $106.20

1 Spin-on Filter, 25 Micron, 15 GPM, 3/4 In Purchased Grainger $31.25 $31.25 $31.25

1 Flexible Spider Shaft Coupling Hub 1/2" Bore, 2-7/64" OD, with Keyway

Purchased McMaster-Carr $9.86 $9.86 $9.86

1 Metro Machine Check Valve, 3/4in. Purchased Northern

Tool $22.99 $22.99 $22.99

2 Accumulator Pre-Charge: 800 PSI Purchased Great Lakes Fluid Power $35.00 $70.00 $70.00

1 ENERPAC hydraulic cylinder Donation Vermeer $342.00 $342.00 $0.00

2 Permanent mount pressure monitors Donation Vermeer $500.00 $1,000.00 $0.00

2 5 Gallon Tractor and Hydraulic Oil Purchased Sam's Club $35.00 $70.00 $70.00

2 0-3000 PSI Pressure Gauges Purchased McMaster-Carr $8.52 $17.04 $17.04

1 NTN Radial Ball Bearing Purchased Grainger $14.09 $14.09 $14.09

Team 4 – Page 56

Machined Details

Qty Item Description Method of Acquisition

Donor/ Vendor

Unit Price Value Cost To

Team 2 Spring Shop Stock Calvin $1.20 $2.40 $ -

17.5 1x1 Frame Pieces Shop Stock Calvin $2.50 $43.75 $ - 2.5 1/4 steel plates Shop Stock Calvin $3.15 $7.88 $ - 11 2"x.125 angle iron Shop Stock Calvin $2.00 $22.00 $ - 5 1"x.125 angle iron Shop Stock Calvin $1.04 $5.20 $ - 2 .700 plate Shop Stock Calvin $8.58 $17.16 $ - 3 Aluminum Angle Brackets Shop Stock Calvin $5.00 $15.00 $ -

13 .105 Stainless pipe Shop Stock Calvin $5.00 $65.00 $ - 4 Rubber motor mounts Shop Stock Calvin $3.00 $12.00 $ -

0.5 2x2 aluminum tube Shop Stock Calvin $5.15 $2.58 $ - 4 Steel brackets Shop Stock Calvin $8.00 $32.00 $ - 1 Jack Shaft Donation Jim Kuipers $10.00 $10.00 $ - 2 Throttle Linkage Shop Stock Calvin $20.00 $40.00 $ - 2 SAE 4 bolt flat flange mount Shop Stock Calvin $200.00 $400.00 $ - 2 SAE Captive Flanges (pair) Shop Stock Calvin $40.00 $80.00 $ -

Totals

Value Cost To Team

$9,133.54 $1,234.53

Team 4 – Page 57

Appendix D. Part Specification Sheets D - 1. Kohler Engine

Team 4 – Page 58

Team 4 – Page 59

D - 2. Pump

Team 4 – Page 60

Team 4 – Page 61

Team 4 – Page 62

Team 4 – Page 63

Team 4 – Page 64

D - 3. Hydraulic Motor

Team 4 – Page 65

D - 4. Restrictive Flow Control Valves

Team 4 – Page 66

Team 4 – Page 67

D - 5. Relief Valve

Team 4 – Page 68

Team 4 – Page 69

D - 6. Check Valves

Team 4 – Page 70

Team 4 – Page 71

Appendix E. Business Financials E - 1. Financial Forecasting

Year 1 Year 2 Year 3

Sales Goals 65 75 100

Year 1 Year 2 Year 3

Sales revenue 1,740,700 2,008,500 2,678,000 Variable Cost of Goods Sold 669,500 772,500 1,030,000 Fixed Cost of Goods Sold 88,500 38,500 38,500 Depreciation 21,435 47,453 55,320 Gross Margin 961,265 1,150,048 1,554,180 Variable Operating Costs 200,850 231,750 309,000 Fixed Operating Costs 200,000 250,000 300,000 Operating Income 560,415 668,298 945,180 Interest Expense 30,018 59,975 59,765 Income Before Tax 530,397 608,322 885,415 Income tax (40%) 212,159 243,329 354,166 Net Income After Tax 318,238 364,993 531,249

Year 1 Year 2 Year 3

Beginning Cash Balance - 1,190,263 1,525,709 Net Income After Tax 318,238 364,993 531,249 Depreciation expense 21,435 47,453 55,320 Invested Capital (Equity) - - Increase (decrease) in borrowed funds 1,000,590 (2,000) (5,000) Equipment Purchases (150,000) (75,000) (75,000) Ending Cash Balance 1,190,263 1,525,709 2,032,278

Hydraulic Hybrid Soulutions Corp.Pro-Forma Statement of Income

Hydraulic Hybrid Soulutions Corp.Pro-Forma Statement of Cash Flows

* Assume no change in Accounts Receivable, Inventory or other current assets other than cash; Accounts Payable or other current Liabilities other than Notes Payable; Fixed Assets other than equipment; or Equity Accounts other than Retained Earnings

Team 4 – Page 72

Sales revenue 1,740,700 2,008,500 2,678,000 Less: Variable Costs: Variable Cost of Goods Sold 669,500 772,500 1,030,000 Variable Operating Costs 200,850 231,750 309,000 Total Variable Costs 870,350 1,004,250 1,339,000 Contribution Margin 870,350 1,004,250 1,339,000 Less: Fixed Costs Fixed Cost of Goods Sold 88,500 38,500 38,500 Fixed Operating Costs 200,000 250,000 300,000 Depreciation 21,435 47,453 55,320 Interest Expense 30,018 59,975 59,765 Total Fixed Costs 339,953 395,928 453,585 Income Before Tax 530,397 608,322 885,415

Year 1 Year 2 Year 3

Total Fixed Costs 339,953 395,928 453,585 Contribution Margin 870,350 1,004,250 1,339,000

Break Even Sales Volume 0 0 0 0.390593095

EquipmentPurchases Year 1 Year 2 Year 3

Equipment Purchases Year 1 150,000 21,435 36,735 26,235 Equipment Purchases Year 2 75,000 10,718 18,368 Equipment Purchases Year 3 75,000 10,718

21,435 47,453 55,320

MACRS Rates (7-year recovery period) 0.1429 0.2449 0.1749

Interest Expense:Annual interest rate on debt 6%

Year 1 Year 2 Year 3Average debt balance 500,295 999,590 996,090 Interest expense 30,018 59,975 59,765

Depreciation

Hydraulic Hybrid Soulutions Corp.Break - Even Analysis

Year 1 Year 2 Year 3

Team 4 – Page 73

E - 2. Payback Period Analysis

Lifetime of the Vehicle 22 years Miles to replace brakes 18,000 miles12 mpg ($250) $/vehicle

12,000 miles/year 0.6667 Times/year($4.17) $/gal 1 replacements/yr

25 Vehicles/fleet 5 Gallons3% ($35) $/5 Gal6%

Increased Energy Efficiency 50%($26,780)

2010 2011 2012 2013 2014 2015 2016 2017 2018(4.17) (4.30) (4.42) (4.56) (4.69) (4.83) (4.98) (5.13) (5.28)

(104,250) (107,378) (110,599) (113,917) (117,334) (120,854) (124,480) (128,214) (132,061)52,125 53,689 55,299 56,958 58,667 60,427 62,240 64,107 66,03052,125 50,650 49,216 47,823 46,470 45,155 43,877 42,635 41,428

(55,599) (55,599) (55,599) (55,599) (55,599) (55,599) (55,599) (55,599) (55,599)

(55,599) (53,980) (52,407) (50,881) (49,399) (47,960) (46,563) (45,207) (43,890)(3,474) (3,330) (3,191) (3,058) (2,929) (2,806) (2,687) (2,572) (2,462)

($4,167) ($4,292) ($4,420) ($4,553) ($4,690) ($4,830) ($4,975) ($5,124) ($5,278)

($4,167) ($4,049) ($3,934) ($3,823) ($3,715) ($3,609) ($3,507) ($3,408) ($3,312)

($875) ($849) ($823) ($799) ($775) ($751) ($729) ($707) ($686)($875) ($823) ($773) ($727) ($683) ($642) ($604) ($567) ($533)$3,292 $3,226 $3,161 $3,096 $3,031 $2,967 $2,904 $2,841 $2,778

2019 2020 2021 2022 2023 2024 2025 Total(5.44) (5.60) (5.77) (5.95) (6.12) (6.31) (6.50)

(136,023) (140,103) (144,306) (148,636) (153,095) (157,687) (162,418) (1,059,062)68,011 70,052 72,153 74,318 76,547 78,844 81,20940,256 39,116 38,009 36,934 35,888 34,873 33,886 419,379

(55,599) (55,599) (55,599) (55,599) (55,599) (55,599) (55,599)(42,612) (41,371) (40,166) (38,996) (37,860) (36,757) (35,687) (445,887)(2,356) (2,254) (2,157) (2,062) (1,972) (1,885) (1,801) (26,508)

($5,437) ($5,600) ($5,768) ($5,941) ($6,119) ($6,302) ($6,492)($3,218) ($3,127) ($3,038) ($2,952) ($2,869) ($2,788) ($2,709) ($33,523)($665) ($645) ($626) ($607) ($589) ($571) ($554)($501) ($471) ($443) ($416) ($391) ($368) ($346) ($6,227)

$2,717 $2,656 $2,595 $2,536 $2,477 $2,420 $2,363 $27,296Mai

nten

ance

Savings in Maintenance [$2010]

Cost Savings [$ Current year]

Cost of Install for FleetCost of Install (Annuity over 15 years [$2010])

Gas

olin

e

Cost Savings in gasoline [$2010/year]

Inst

all

Cost Savings Overall per Year [$2010]

Mai

nten

ance

Cost of Replacing Brakes for fleet [$ Current Year]Cost of Replacing Brakes for fleet [$2010]Cost of replacing fluid [$ Current year]Cost of replacing fluid [$2010]

Inst

all Cost of Install for Fleet

(Annuity over 15 years [$ Current Year])Cost of Install (Annuity over 15 years [$2010])Cost Savings Overall per Year [$2010]

Life Time Cost Savings AnalysisG

asol

ine Price of Gasoline [$/gal Current year]

Cost of Fuel per Year [$ Current year]Cost Savings [$ Current year]Cost Savings in gasoline [$2010/year]

Average MPG (USPS source) Cost to replace BrakesMiles Driven Per Year # times to replace brakes

Number of Vehicles in the fleet Amount of fluid to be

Total Cost Saving Over Fleet Lifetime [$2010] = $788.32

Cost of gasoline (2010) Fluid Replacement Time

Cost of retrofit kit

Inflation Rate Cost of Hydraulic Fluid Interest Rate

Savings in Maintenance [$2010]

Cost of Replacing Brakes for fleet Cost of Replacing Brakes for fleet Cost of replacing fluid [$ Current year]Cost of replacing fluid [$2010]

Price of Gasoline [$/gal Current year]Cost of Fuel per Year [$ Current year]

Team 4 – Page 74

Appendix F. Scheduling Documents

Team 4 – Page 75