Design and Development
An integral part of the bikes performance design and layout is the development of the Simulator program. This allows design alternatives to be quickly compared, and the performance modelled, in much the same way as the stress and aero loads are predicted by other software packages. Similarly the program provides an ability of assessing changes and modifications without cutting metal, or in this case burning rubber…..burning rubber sounds more fun. Let us shoot the loon who thought it up.
As a tease, listed below are a few of the design factors, which you can play with:
(and for ABA members clicking the link below gives a logic layout of the program and some examples of how we ve used it)…
The various inputs can be broken down into some distinct groups:-
Ambient conditions:
- Ambient air temp,
- Ambient air pressure,
- Coefficient of friction (ground to tyre grip),
- Gradient
Bike shape details:
- Frontal area
- Cd value
- Height of CofP (Centre of Pressure) above ground
- Lift and downforce with speed relationships
Physical Details:
- All up mass
- Wheel base
- Position of CofG, (Center of Gravity), relative to wheel base
- Height of CofG above ground
Transmission and drive details:
- Front tyre dia
- Rear tyre dia
- Gearbox ratios
- Gear box loss%
- Differential ratio
- Differential loss%
- Chain pitch
- Dif sprocket diameter
- Wheel sprocket diameter
- Chain loss%
- Expected wheel slip %
Rotational inertial values:
- Engine
- Gearbox
- Drive
- Front and Rear wheel assemblies
Engine details
Engine ISO power output or torque curves
- These need to be at defined conditions (eg ISO conditions 15C 1012mbar), and ideally be true tested dynamometer , at the wheel , figures for the system under investigation.
- Also important is an understanding as to what aspect of performance is being modelled or investigated ,eg Wide Open Throttle ( as in drag racing), or performance over a measured distance. Or, Absolute max speed, or acceleration characteristics between ranges of speed. Or, Part load performance, or braking
From all these inputs, the Simulator then can predict:
Predicted Acceleration, Velocity profiles under different conditions. Eg the effect of changes in ambient conditions, Aerodynamic loadings, or engine output.
Also, and just as importantly the loads placed upon front and rear suspension components, and the ability to predict the effects of changes of loads throughout the run, (as if in real time) due to acceleration, motive force, aerodynamic loadings
And from these main results the effects of other changes can be investigated allowing comparisons between gear ratio and gear change points, gear, and chain loads, air/fuel flows, and the forces placed on parachutes and brakes.
For more details, if you are a Angelic Bulldog Association member you can see more information on the subject including a number of exciting graphs! … Click here…
