USE OF ALUMINA CERAMIC MATERIAL IN A SHAFT DRIVE BICYCLE

Meghna Rajkumar Vadhyar

(meghnarajkumar.im17@bmsce.ac.in)

Department of Industrial Engineering and Management

BMS College of Engineering, Bengaluru, India

Khushi Soni

(soni.jeeny@gmail.com)

Department of Industrial Engineering and Management

BMS College of Engineering, Bengaluru, India

Kavitha Rani N

(kavitharanin.iem@bmsce.ac.in)

Assistant Professor,

Department of Industrial Engineering and Management

BMS College of Engineering, Bengaluru, India

Mayur Appaiah

(mayurappaiah.iem@bmsce.ac.in)

Assistant Professor,

Department of Industrial Engineering and Management

BMS College of Engineering, Bengaluru, India

ABSTRACT

Bicycles are a constant and promising mode of transport. The evolution of the bicycle is interesting and shows the improvements in design over many stages of evolution. This paper focuses on redesigning the drive system of a bicycle that is replacing the chain with a shaft. This negates existing disadvantages present in a chain drive bicycle.

Shaft-driven bicycles were introduced over a century ago, but were replaced by chain-driven bicycles due to the possibilities of gear ranges. However due to advancements in internal gear technology, a few shaft-driven bicycles have been introduced [1] that show increased performance and quality. These shaft-driven bicycles have advantages over chain-driven bicycle, namely the problem of maintenance in the chain-driven bicycle. This paper references the working mechanism of the traditional chain driven bicycle, including its drawbacks, as compared to a shaft drive system. The paper also shows that alumina ceramic is a suitable material for the drive shaft, with FEA results predicting a favourable Factor of Safety of 1.85.

KEY WORDS: Bicycle, FEA, Shaft Drive, Weight, Alumina Ceramics.

1. INTRODUCTION

Quality is one of the most vital features of any vehicle. A successful vehicle has the best possible design, safety and durability features, along with high performance and quality.

Bicycles have been a common mode of transport since the first models were introduced around 1885. Modern methods like Computer Aided Design (CAD) help develop newer and better models, improved performance and capability. Recent work in Mechanical Engineering Departments gives rise to the idea of “chainless” bicycles, as shown in Fig 1 below.

Fig.1. Representation of a Shaft Drive Bicycle

2. CHAIN DRIVE BICYCLES –WORKING PRINCIPLE AND DRAWBACKS

2.1 Working Principle

The chain runs over the sprocket and main gears, and the gear teeth pass through the links in the chain. When pedal is pushed forward, the front gear rotates transmitting the motion to the chain which in turn transmits the motion to the rear sprocket gear over which it runs. Hence the wheels are set in motion. Fig 2 below shows working principle of chain drive bicycle.

Fig.2.Working Principle – Chain Drive

(M.A. = V.R. = N2/ N1)The drive efficiency is given by the equation [3]

Where,

M.A.Mechanical Advantage

V.R.Velocity Ratio

N2number of teeth on Driven Sprocket

N1number of teeth on Driver Sprocket

Here, we observe that greater the Velocity Ratio, greater the efficiency. Mechanical Advantage (M.A.) of typical bicycle is therefore = 0.62, with N2 = 28 and N1 = 45

2.2 Drawbacks of a Chain-Driven Bicycle

a. Chain pins and bushings constantly rub against each other due to rolling action of the chain. This increases the inner diameter of the bushing and makes the pins groove out, causing an increase in chain pitch, i.e. chain stretch occurs. [4]

This results in slippage when a heavy force is applied to the pedals. It also causes skipping between gears. Hence performance reduces under chain stretch condition.

b. Dirt/Grit accumulating on the chain makes the contact parts wear out at a faster rate. This reduces performance considerably and gives rise to a poor quality ride. [3]

c. Smooth speed transfer is not possible due to ‘chordal action’ of chain drive, i.e. the position of engagement between the sprocket and chain fluctuates a lot which makes the chain fluctuate, hence reducing the smoothness of speed transfer and reducing performance.

3. SHAFT DRIVE FOR BICYCLE – SOME CONSIDERATIONS

In order to overcome above drawbacks in chain drive, shaft drive system is proposed.

3.1. Design Assumptions [3]

a. The shaft rotates at a constant speed about its longitudinal axis.

b. The shaft has a uniform circular cross section over major part of the length

c. All damping effects are executed

d. The shaft is perfectly balanced

3.2. Main Components

a. Bevel Gears: In place of the sprocket in traditional bicycles, a bevel gear is placed, which meshes with another bevel gear mounted on the drive shaft. (Fig.3) Similarly, a bevel gear is mounted on the rear wheel hub which meshes with a bevel gear placed in the position of the rear sprocket. The use of bevel gears allows the axis of the drive torque from the pedals to be turned through 90 degrees. The rear bevel gear combination cancels out the first drive torque change of axis.[3]

Fig.3. Bevel Gears

b. Drive Shaft: A shaft takes the place of the chain in the traditional chain-driven bicycle. It must transmit torque from the transmission to the foot pedal. During the operation, it is necessary to transmit maximum low-gear torque developed by the pedal. The drive shaft must also be capable of rotating at the very fast speeds required by the vehicle.

c. Bearings: Used for smooth operation of the shaft.[3]

3.3 The Mechanism

Fig.4. Shaft Drive Mechanism - Assembled and Exploded View

The Shaft Drive Mechanism is as shown in Fig 4 above.

3.4 The Advantages and Disadvantage [3]

a. Does not produce noise. That is; it runs silently.

b. Does not need much maintenance, only lubrication oil is changed at prescribed time intervals.

c. Shaft Drive gives more ground clearance: for obstacles in its path.

The main disadvantage is that weight of the mild steel shaft is more than an equivalent chain. This increases the weight on the rear wheel and reduces performance.

3.5. Shaft and Chain-Drive Bicycle: A Comparison

Table 1: Comparison of Chain and Shaft Drive

Parameter

Chain

Shaft

Maintenance

High: Cleaning and Lubrication required every 500-800 km[12]

Low. Every 2000-2500 km

Cost of Maintenance

Higher

Nil

Life

Low life due to wear and tear, stretch of chain

High life

Noise and Vibration

High

High Damping Capacity.

Low noise.

Power Transmission

Lower

Higher

Compactness

Not as compact as the shaft

More Compact than the chain

5. A SOLUTION TO REDUCE SHAFT WEIGHT

Mild Steel, though strong and less likely to deform under loading, is very dense / heavy. This causes performance reduction in shaft drive bicycles.

An approach to solve this problem by use of ‘Alumina Ceramic’ material (94% Aluminium Oxide) is considered. The material offers good performance and relatively good strength due to the strong ionic, inter-atomic bonding. Aluminium Oxide being a very hard material also has excellent wear resistance. It has high corrosion endurance, temperature stability and low thermal expansion. Important Properties of Alumina ceramic and Mild Steel are shown in Table 2 below.

Table 2: Comparison of Mild Steel and Alumina Ceramic

Material

Density

Hardness (Knoop)

Tensile Strength (MPa)

Shear Strength (MPa)

Mild Steel

7.85g/cc

145

400

231

Alumina Ceramic

3.69g/cc

2000

330

330

The performance of the Alumina Ceramic material subjected to torsion is predicted using Finite Element Analysis. The shaft is first created using CAD, and the material properties are added to the Material Library. The element meshing is done, as shown in Fig 5 below, and the required loads are applied. The required Stress Plot of Factor of Safety and Shear Stress is Obtained, as in Fig. 6 and 7 below.

(Torque = Force X Radius)Calculation of Torque: This is given by the equation below.

A rider weight of 80 kg and a pedal length (radius) of 0.17 metres give a torque value of 80 X 9.81 X 0.17, which is approximately 137 N-m. For our purpose, we consider the torque value as 140 N-m.

Fig. 5: Meshed model of the Shaft

Fig. 6: FEA showing minimum Factor of Safety as 1.85

Fig. 7: FEA showing maximum Shear Stress as 177 N-m

8. Conclusion

A shaft drive system can replace the chain-sprocket system in a bicycle and the weight can be reduced by replacing Mild Steel with Alumina Ceramic material.

The predicted Factor of Safety of 1.85 is greater than the required value of 1.5, thereby suggesting the suitability of the material.

The Alumina shaft gives rise to reduced weight and greater durability/life of the cycle. It reduces cost of maintenance and keeps the cycle clean, thereby increasing performance and quality.

REFERENCES

1] Amit Kumar Singh, Arvind Yadav, Vinay Kumar Chaurasiya, Ankit Yadav, Niteesh Kumar Mishra (2017), “Propose and Manufacture of Chainless Bicycle”, Research Article, Vol 7 Issue No.6, pp. 1-3

2] Dandage R.V., Patil A.A., Kamble P.N. (2017), “Design, Analysis and Fabrication of Shaft Driven Bicycle”, Recent Development in Engineering Science, Humanities and Management pp. 14-15.

3] Ankit Sinha, (2017), “Study of Various Motorcycle Transmission Drives”, Vol 3 Issue No.4, pp. 1402-1403

4] P. Naresh, A.V. Hari Babu, V. Madhava, M. Sudhakar Reddy (2016), “Design and Fabrication of String Bicycle”, pp. 44-46