Sure Stopper - Design Project1 Tech Report

8/6/2019 Sure Stopper - Design Project1 Tech Report

http://slidepdf.com/reader/full/sure-stopper-design-project1-tech-report 1/15

Design Project #1 – The Sure Stopper SEEngineering 10B – Course # 001

D.I.M.D. Engineering GroupDenise Fordham, Ivan Chiu, Michael Spangenthal, Daryl Shee

City College of San Francisco, San Francisco, CAOctober 10, 2006

Table of Contents

List of Figures ----------------------------------------------------------- 2

List of Tables ------------------------------------------------------------ 2

Abstract ------------------------------------------------------------------ 3

Introduction -------------------------------------------------------------- 4

Procedures ---------------------------------------------------------------- 5

Results --------------------------------------------------------------------10

Discussion --------------------------------------------------------------- 11

Conclusions --------------------------------------------------------------11

Appendix A --------------------------------------------------------------12

Appendix B --------------------------------------------------------------13



List of Figures

Figure 1: Scheduling chart for design project #1.---------------------------------------------------- 5

Figure 2: Initial sketches of first ideas. --------------------------------------------------------------- 6

Figure 3: Assembling the Sure Stopper -------------------------------------------------------------- 6

Figure 4: Version 1 of the Sure Stopper -------------------------------------------------------------- 7

Figure 5: First tests of the Sure Stopper -------------------------------------------------------------- 7

Figure 6: Version 2 of the Sure Stopper -------------------------------------------------------------- 8

Figure 7: Mockup of a “Friction Inducer” for the Sure Stopper ----------------------------------- 8

Figure 8: Drawings for the “Friction Inducer” for the Sure Stopper ------------------------------ 9

Figure 9: Version 3 of the Sure Stopper with “Friction Inducer” ready for testing ------------- 9

Figure 10: Mission accomplished – the Sure Stopper SE stops on the mark --------------------10

Figure 11: Detail drawing of spindle mechanism --------------------------------------------------- 12

List of Tables

Table 1: Tracking and Stopping Performance Week of September 30 - Test at School ------- 10

Table 2: Performance of Car Components ----------------------------------------------------------- 13

Table 3: Tracking and Stopping Performance Week of September 16 ---------------------------13

Table 4: Tracking and Stopping Performance Week of September 23 ---------------------------14

Table 5: The Sure Stopper SE Materials List -------------------------------------------------------- 14

2



AbstractOur mission is to design and manufacture an automatic car-stopping device that activates

when the vehicle becomes a runaway car. This report details the design, fabrication and testing

of the Sure Stopper SE, a car designed to stop automatically at any configured distance. This

design can be applied to the vehicles on the road today and incorporated into the manufacturing

of vehicles for tomorrow to insure pedestrian and driver safety.

3



Introduction

Runaway cars are a deadly problem in San Francisco. They are responsible for injuries

and death and create property damage that can exceed hundreds of thousands of dollars every

year. While it is entirely possible for someone to stop a rolling car while sitting inside the

vehicle, there is very little one can do to stop a runaway car when outside of the vehicle.

The focus of our report is to present a device that will automatically stop a runaway car

by sensing there is no driver or passenger inside and thereby locking the rear axle and wheels,

stopping the car before it can cause damage and harm.

4



The Sure Stopper SE

Procedures

The design group begins by brainstorming ideas. The group’s focus is to develop a

stopping mechanism that can be incorporated into a car design to prevent it from rolling out of

control. Our brainstorming generates the idea to create a device that stops the car once it senses

movement of the wheels. After a specified number of revolutions of the wheel the mechanism

locks the axle preventing the car from further rolling.

The group identifies tasks and develops a schedule to help meet our deadline (Figure 1).

5

Engineering 10B - 1st design Project - Runaway Car!September October12 thru 18 19 thru 25 26 thru 2 3 thru 9 10

Brainstorm Session

Web and Lit. Search

Prototypes

Test PrototypesRedesign and Test Final

Drawings

Write Power Point Presentation

Write Paper

Competition & Presentation



Figure 1. Scheduling chart for design project #1.

A prototype design is constructed incorporating some of our initial ideas (Figures 2 and

3). The stopping mechanism is a string wound around a spindle assembly that is attached to the

back of the car. The string is cut to a specific length and secured to the rear axle at the other end.

When the car rolls it can only travel a certain distance before the string stops the car. For a

detailed schematic of the spindle assembly see Appendix A Figure 11.

Figure 2 . Initial sketches of first ideas

6



Figure 3 . Assembling the Sure Stopper

With prototype in hand testing begins. We note the flaws and strengths of the design.

Over the next three weeks we make modifications to maximize its performance.

Figure 4. Version 1 of the Sure Stopper

Special consideration is given to using strong yet lightweight materials. First tests involve

the use of wooden wheels with a cloth string as the stopping element. The body is constructed

out of Gatorboard, a lightweight yet strong material made out of paper and foam. Gatorboard

allows us to easily attach car components mechanically or by gluing (Figure 4).

From our test results we immediately see that the wood wheels do not give us the traction

7



needed to control the car during stopping (Figure 5). The cloth string also poses a challenge by

not consistently performing well during the tests. For detailed results see Appendix B Table 2

and 3.

Figure 5. First tests of the Sure Stopper

The wood wheels are replaced with wheels with rubber tires and the cloth string is

replaced with 25 lb test monofilament (Figure 6). Tests are then repeated.

Figure 6. Version 2 of the Sure Stopper

8



Solving these problems allows us to identify the next problem, which is controlling the

momentum of the car while it is rolling down the incline. If the car is allowed to pick up speed,

stopping performance drops. See Appendix B Table 4. Controlling the speed of the car is now

the major challenge. A mock-up (Figure 7) and drawings (Figure 8) are created to address this

problem and modifications ensue.

Figure 7 . Mockup of a “Friction Inducer” for the Sure Stopper

9



Figure 8. Drawings for the “Friction Inducer” for the

Sure Stopper

Figure 9 . Version 3 of the Sure Stopper with

“Friction Inducer” ready for testing.

The final modifications include addition of a back panel called the “Friction inducer” that

drops down and engages the road to slow the car’s momentum (Figure 9). Strengthening and

reinforcing the back end of the car with aluminum is necessary to accommodate the

modifications. For a complete materials list see Appendix B Table 5.

10



Results

With these modifications and the balancing

of weight we are able to successfully control

momentum and stop the car exactly at our

predetermined distances of 12 feet, 24 feet

and 36 feet (Figure 10).

Figure 10. Mission accomplished – the Sure Stopper

SE stops on the mark.

Table 1 below shows the results of our testing in detail and efforts to fine-tune the

stopping mechanism to achieve the desired results.

Table 1 . Tracking and Stopping Performance Week of September 30 – Test at School

Modification Trials Notes-added friction inducer 34in string: 278in, 308in, 256in, 281in,

320in, 307in-8oz weight at the back dragging

-big and 8oz weight in front, metal plateat back

34in string: 309in, 314in -Not consistent

-32in string 32in string: 307in, 282in, 296in, 267in -Not consistent

-Lengthen string .5in 32in string: 267in, 284in, 285in, 287in,285in, 288in

-Let the friction inducer catch our handwhen releasing-Very consistent-Our best result

-51in string 51in string: 420in, 367in, 413in, 384in,400in

-Careful with winding

-lengthen string 1 in 52in string: 450in, 420in, 429.5in,441in, 436.5in

-Careful with the angle

-shorten string.5in 51.5in string: 432in, 453in, 441in -Take one rubber washer off -shorten string .5in 51in string: 445in, 441in -Consistent-shorten string .5 in 50.5in string: 442in, 435.5in, 453in,

445in-Consistent

-shorten string .5 in 50in string: 445in, 419in, 453in, 431in,439.5in, 448.5in

-Consistent

-shorten string .5 in 49.5in string: 435in, 437in, 434in,435in, 429.5in, 415in, 437.5in, 437.5in

-Faster speed longer distance-Slower speed shorter distance

-shorten string .25 in 49.25in string: 431.75in, 432in, -Best result

11



431.5in, 432in -Start angle at 2.5 in

Discussion

Controlling momentum to accurately stop the car became the biggest obstacle. Adding

the friction inducer component that slows down the car’s speed helped us to achieve positive

results. Improvements to this design would include the ability to more accurately control both the

force of friction applied and its timing.

Conclusions

• The heavier the car the faster the momentum especially over longer distances.

• On steeper inclines the car gains more momentum and becomes harder to control.

• At faster speeds more stress is put on the stopping components.

• It is important to control speed first and then control stopping.

• The design and maintenance of the spindle/braking system is critical for the consistency

of the stopping power of the car.• Application of friction is an important component to controlling and stopping the car.

12



Appendix A

Figure 11. Detail drawing of spindle mechanism

13



Appendix B

Table 2. Performance of Car ComponentsMaterial Effect Good BadWood wheel Skid too much Easy to make, cheap little friction with

concrete groundRubber wheel Produce good friction with

concrete groundGood friction none

Cloth string (Thin) Wind up very good, veryconsistent on the runs

Wind up good on the axle Easy to break Stretch a lot

Cloth string (medium) Wind up good and tougherthan thin Cloth string

wind up good on the axle Tends to break

Cloth string (Thick) Not consistent run Tough string Did not wind up goodMonofilament String(Thin)

Produce consistent runs Tough string none

Monofilament String(medium)

Not consistent run Tough string Bad winding

Monofilament String(thick)

Not consistent run Tough string Winding up not good

Weight (2.5lb) Make the test car heavier,thus more skid on the hill

none Too heavy, easily goover 3 lb

Weight (8ounces) Good additional weightadded to fulfill the weightrequirement

Make our test car just pass3 lb mark and not over toomuch, easy to handle

Not enough of these tomake up to 3 lb

Weight (1.0lb) Weight requirement Good combination with 8ounces weight

Not enough of these tomake up to 3 lb

Rubber Washers Hold string, slow the car Easy to install and takeapart

none

1/4” wood dowel Give control on the string Easy to take apart andinstall

none

Table 3. Tracking and Stopping Performance Week of September 16Modification Trials Notes

Cloth string, rubber tire back, woodtire front, 19in and 24in cloth string

24in string: 181 in19 in string: 147.5in, 150in,

-Skid-Not consistent result

-2lb Weight added 19in string: 149.5in, 135in, 133.5in,140in

-Tested on flat surface-A little push

-18 in Monofilament string 18in string: 140in -String did not wrap up nicely

-18 in thick cloth string 18in string: 121 in, 121in, 120in,131in

-Knot got loose so we get moredistance out of the string-18in thick cloth string, retighten theknot

18in string: 114in, 119in -Skid a little-Not consistent

-18in thick cloth string, retighten theknot

18in string: 135.5in, 133.5in, 138in -Skid-Not consistent

Rubber tire front and back, screwstring on to axle, recalculated string19.65in

19.65in string: 127, 128.75in, 128in,129.25in, 133.5in, 130in, 136in,135in, 132in

-Rubber tire produce good result

14



Table 4 . Tracking and Stopping Performance Week of September 23Modification Trials Notes

Test at school:-weighted 2lb 1.9 oz

19.65in string: 162in, 141in, 139in,

144in, 139in-Skidthe tire got loose

2.5lb weight, fasten tires, mediumcloth string, 19in string

19in string: 114in, 118.6in, 121.5in,124in, 122.5in, 126.5in, 118.25in

-Winding rule: clockwise, keep toone side neatly-Calculate string length

-adjust the wood dowel to bringcloser

19in string: 107in, 103.5in -Shorter distance

-adjust the wood dowel farther apart 19in string: 135.5in, 135.5in, 136in -Longer distance-new big cloth string 20.125in 20.125in string: 142in, 140in,

138.5in-Adjust the string

-new medium monofilament string 17in string: 103.25in, 99.5in, 144in,142in, 142.5in, 141.5in, 141.5in,142.5in, 143.25in, 143in, 142.75in

-Bring the dowel closer so the stringdoes not get loose

Table 5. The Sure Stopper SE Materials List

1/2” Gatorboard1/2” MDF1/4” MDF1/4” wood dowel5/16” Ø Brass Tubing1/2” Brass Flat Stock 1/8” Brass Round Rod1 1/4” Brass Hinges1/8” Aluminum Flat Stock

2” Ethafoam4 Rubber Tires25 lb. test MonofilamentBrass WashersRubber Washers#6 x 1/4” Sheet Metal Screws#6 x 32 Machine Screws and Nuts2 1/2 lb. Steel Weight3/16 x 1 1/2” Steel Weight

15

Sure Stopper - Design Project1 Tech Report

Documents

Transcript of Sure Stopper - Design Project1 Tech Report