By: Prof. John Fieldhouse
A pragmatic approach to braking a road vehicle: Part 2 of 2
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4 Comments
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Response to Comments:
From the outset can I thank both colleagues who responded to the Blog. It was always the objective of the Brake Academy to stimulate discussion, and I sincerely hope this is the start of an increase in such exchanges.
I respond to both as they arrived.
drbrake2:
You make one comment that requires addressing – your second paragraph.
The brake system torque distribution can be determined by determining dynamic wheel loads the and distributing the braking torque accordingly. That gives the proportion to the front and rear and the braking ratio. Within this calculation there is a need to determine the static wheel loads and then include the load transfer effects (LTE). As such the distribution i…
Agree, an interesting topic but have some concerns with the pragmatic approach.
In reality the typical vehicle DOES have tires in contact with the ground and as such the mass & / or rotational inertia of vehicle can be braked by any wheel or any axle up to the adhesion limit of that wheelend. The adhesion limit is not considered in this example at all so i'm assuming that there is complete adhesion as would be typical in most real world situations. Yet in this example 0.8g decel is mentioned so there is a distinct possibility of rear wheel lockup which would completely change the work done calculation too.
Correspondingly I feel it is incorrect to show a front drive…
Very interesting. In all my years of doing system analysis I never considered the rotating ineria of the wheels, tire and brakes. Obviously this in not correct and the roating inertia of these parts and the drive train should have been considered. To my knowledge, none of system analysis calculations of any of the suppliers I worked with or Mercedes Engineering considered the rotating inertia either.
In addition the allocation of the rotating inertia to the individual axles may not be correct because the front to rear brake force distribution is a function of the brake system torque distribution and is not effected by the actual weight distribution of the vehicle.