From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of vehicle dynamics during braking, focusing on weight distribution and wheel adhesion.
| Identifier | ExFiles\Box 24\1\ Scan040 | |
| Date | 12th December 1931 guessed | |
| 6. under these particularly onerous conditions in which failure may be followed by the direct consequences that the loads on front and rear wheels should be equal to give maximum power of adhesion. With a modern car fitted with powerful brakes the distance necessary to bring to car to rest from a speed of 60 m.p.h may be taken as 160 feet which corresponds to a decelleration of about 24 ft per sec. With normal height of centre of gravity above the ground this decellerating force increases the weight on the front wheels and decreases that on the rear wheels by exactly the amount corresponding to a shift of the centre of gravity through a distance equal to one sixth of the length of the wheel base, with a result that during such decelleration the adhesion load on the rear wheels is reduced to only one third of the weight of the car. Thus, to secure the maximum possible adhesion under such conditions it appears to me desirable that the car should be designed so that the position of the centre of gravity under static conditions is situated at a point distant one third of the length of the wheelbase in front of the rear axle. In this case the resultant load on all of the wheels will be equal under conditions of maximum decelleration. Recent work carried out at the National Physical Laboratory by Bradley and Wood, the results of which were published in the Journal of the Institute of Automobile Engineers, Noevmber 1930, in which the relation between the position of the centre of gravity and deviation from straight line motion under extreme retardation was investigated, appears to confirm the above conclusion. The observers found that the effect of moving the centre of gravity backwards was to decrease the distance required to stop the car as well as to reduce the amount of deviation and angular rotation when the braking action was not entirely symmetrical over the four wheels. Their final conclusion was that the optimum position | ||