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).
The handling faults of front-wheel drive cars at high speed and potential cures.
| Identifier | ExFiles\Box 170\3\ img104 | |
| Date | 31th October 1936 guessed | |
| -2- lowering of its standing height, might change the wear from a local-ized wear on the inside of the tread to an even wear across the tread and would also tend to prevent the tire lifting off the ground so far as to give a power-slip. My picture of the thing is as follows: (a) Such a large proportion of the overturning couple is carried on the front wheels, that the inside wheel is carrying only a small proportion (probably less than 50%) of its normal load. (b) At 175 mph a large contribution to this load reduction may be the couple caused by head-resistance of the vehicle multiplied by the height of the center of wind-pressure above the ground. This, it seems to me, is a basic fault of front drive cars at high speed. The driving wheels are unloaded by the wind pressure. *also, if the car is streamlined, the whole car is tilted by the wind.* (c) Evans' chart of cornering power with load shows the immediate effect of load reduction on the outside wheel. The cornering power of a pair of wheels falls off rapidly when a large overturning couple is applied. So the slip angle of the front wheels must be very high. Perhaps as much as 5 degrees, or, more than this since the car is nose-heavy. (d) The outer wheel is probably still doing a fair job of cornering. But reduction in load causes cornering power to fall off much more rapidly than overload. So the inside front wheel is probably al-most hors de combat for cornering. (e) Add to this a big demand for power and a continuous power-slip on the inside wheel becomes almost inevitable. I would guess that a rev. counter on the two front wheels would show the inner travel-ling 10% faster than the outer. My guesses for a cure would be: (1) Lock the differential. I imagine that a conventional differential is fitted, although I have never been able to understand why a differential is anything but a total liability on a racing car of this type. It adds weight, dissipates power at all times when one wheel leaves the ground, and, at least on a rear drive car - does not help the steering, as a Delavaud or Zahnrad-fabrik differential must do. (2) Either soften the front springs or fit a roll stabilizer at the rear, or both. So as to transfer as much as possible of the roll-couple off the front tires on to the rear tires. If this is carried too far the car will oversteer, i.e., rear end will side-slip. But most front drive cars, being nose heavy, | ||