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).
Design and effectiveness of servo-assisted braking systems and a new simplified linkage design.
| Identifier | ExFiles\Box 2\7\ B002_X 140 to 143-page07 | |
| Date | 12th December 1932 | |
| 8 141 HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} R3/WD{Mr Wood/Mr Whitehead}12.12.32. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design} (ESPECIALLY PEREGRINE.) X4383 Re SERVOS. I was pleased to hear RM.{William Robotham - Chief Engineer} say the present type on Peregrin is doing well. I understand that on these smaller cars at least you favour picking up 4 brakes at once, not letting the pedal operate on the rear brakes only. It is quite probable that at least on the smaller cars we may get sufficient direct braking for ordinary purposes, shunting, etc. I think we ought to very carefully investigate the relative leverages of the foot pedal and servo, so that the pedal does not move through too big an angle for it to be too sensitive to clearance and wear. If it is the leverage should be reduced and the braking made up to the required effectiveness by the servo assitance, whatever multiplication by the servo this may demand. We are expecting however that it will only be about 1 to 1 with the smaller car: increasing to 1 to 3. or 1 to 4. for the large car. The servo should run as slowly as is found to have no ill effect, and for good progressive braking, and constancy, only contribute the minimum assistance. I would like here to remark that I consider our braking, generally speaking, too effective (skidding the wheels too easily) and I believe this is the reason why the racing men use unassisted braking that requires high pedal pressur to be effective. BENTSPORT We have arranged this so that you can fit it up with the 25HP. servo. At the same time we have designed a completely new servo with a simplified linkage system. This is of the drum type like the road wheel brakes, and can therefore be of cast iron drums wit cooling ribs, so that the heating of the friction surfaces will be much reduced. It has another great advantage that the lineabiliy of the driven shaft need not be anything like so accurate. a little more care will be needed in the original adjustment, but we think this will soon fade away. In connection with this type we have schemed a simpler linkage down to the balance lever, doing away with one of the 3rod and one of the 2 slack, and we are thankful to be able to eliminat any one piece as it gives us so much better chance of making a goo job of that which remains, as well as that fact that we decrease the cost. DA.{Bernard Day - Chassis Design} has sent some drawings to Derby of this scheme as it may be patentable in a narrow form. R.{Sir Henry Royce} | ||