# Initial Acceleration of a motorcycle

1. Jun 8, 2010

### Tdanx

My senior design project is to build a hybrid motorcycle. Using a hydraulic engine we are converting the breaking power of the motorcycle into stored energy for use when the motorcycle accelerates from a stop.

The question is how to find an appropriate initial acceleration. The acceleration should be more than enough for the motorcycle to overtake friction but it should not be too high so as to waste all of the potential energy too quickly.

Knowing that the motorcyle with a rider weighs approximately 500lbs, how would I go about find acceleration? Would I first have to find the angular acceleration of the wheel and convert it to forward acceleration? My question is, what is the simplest way to go about this so that I can repeat the problem for a variety of situations quickly to find the optimal acceleration?

2. Jun 9, 2010

### Lok

Usually breaking decell in cars can be use for comfortable accell as you get pushed into the seat.

Not the case for motorcycles as a 1 G accell means you have to hold 70% of your body's weight horizontally by your hands gripping the handles and feet squeezing the bike. A bit much for the average plain rider. 0.5 G is a great value IMO, if you manange to deliver it in an constant or gaussian manner.

3. Jun 9, 2010

### Lok

Best to just look for a comfortable average acceleration on the internet as these things have been analyzed for ergonomic purposes for many years.

4. Jun 9, 2010

### Tdanx

Thanks for the help, it does seem like the best idea is to look through the web instead of crunching numbers.

5. Jun 9, 2010

### jack action

You need to find the force at the tire contact patch (with the net torque and radius of the wheel), subtract rolling resistance and aerodynamic drag (which all basically = 0 at low speed) and divide by the mass of the vehicle.

The average driver accelerate at 0.2g; 0.3g max. At around 0.5g, you begin noticing the acceleration (sinking in you seat).

The maximum acceleration possible depends on the tire-road friction coefficient and the weight (+ the aerodynamic downforce) on the powered wheel(s). Putting more torque on the wheel will result in spinning. Assuming full weight on the powered wheel(s) and no downforce, the max acc is equal to CoF, which for a typical touring tire on asphalt would be 0.85-1.0. (So 0.85g to 1.0g)

6. Jun 9, 2010

### rcgldr

Why cant the acceleration be thottled? In a real world situation, your acceleration is often limited by a vehicle that is in front of you.

7. Jun 11, 2010

### Tdanx

What I believe I really need to know is what the minimum acceleration for the bike to still begin moving is. This way I will know that as long as my acceleration is larger than this it will not fail to start...

8. Jun 11, 2010

### jack action

The minimum acceleration needed such as the bike starts moving is 0+ m/s. If you have an acceleration, the bike will initiate motion by definition.

But if you have a constant acceleration of, say, 0.001 m/sÂ˛, it will take you 75 s to reach 10 km/h !

You either want the greatest acceleration possible (limited by traction as stated above) to obtain the best performance or you want the greatest acceleration possible without creating discomfort to the passengers, which is is somewhere along 0.2-0.3 g.