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).
Insufficient axle-body damping and steering wobble issues on a 20HP car.
| Identifier | WestWitteringFiles\T\March1929-December1929\ Scan060 | |
| Date | 5th April 1929 | |
| HS.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} ) FROM R.{Sir Henry Royce} EV.{Ivan Evernden - coachwork} ) (At Le CanadelHenry Royce's French residence.) c. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} PN.{Mr Northey} EP.{G. Eric Platford - Chief Quality Engineer} ORIGINAL R1/M5.4.29. REC'D AT WW. 9.4.29. X5430 G.3. PROPOSED 10,000 MILE X5830 X5770 20HP. BROUGHT TO LE CANADELHenry Royce's French residence BY X5840 REYNOLDS AT EASTER, WITH MR. WORMALD. X5520 INSUFFICIENT AXLE-BODY DAMPING. The Hooper body is rather too high and unnecessarily heavy. The latter can be judged by the weight of the doors. DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork} will say how much this type of body should weigh for a 20HP. The overweight of the body I think is principally due to the heavy construction of the windscreen, and doors. The road springs were hardly stiff enough for the weight but not very wrong as a town carriage, on fairly good roads. Without very much trouble we were able to increase the recoil damping (downwards - high pressure -) by 50% by taking out the .072 washer from under the plug, and adding a .036 washer to the length of the spring. We did this because the 20HP. is insufficiently damped. The rear dampers were taken off and found to be otherwise quite in order, and of my favourite type. The upward damping should also be increased. I feel certain that our 20HP. damping must be increased by 50% total effectiveness, and the upward about 50% of the downward. There is another feature which for years I have been promised has been corrected: it is the steering arm, which is wrong, and ugly in shape. The increased damping was a very definite improvement, but I should like to have a little more upward poundage. But I only ask this because it now seems only about 30% of the downward. Actually the car now rides so well that one cannot hope for much improvement. The front strikes the buffers occasionally on these very bad roads. STEERING. Previous to touching the dampers we had on 2 occasions low speed (17/18 MPH.) steering wobbles, which came on at a level railway crossing, and again at a turn on a rough road. Then after several tries we could get it every time at the above MPH. There was absolutely nothing to be found wrong, and no change could be made unless the pivot lean were reduced a little more than 1° by taking out the taper packing (taper about 2 mm. in 3 1/2") and putting in a parallel one. Dodd and Reynolds could not get any sign of a wobble, and the steering was generally much improved going to Hyeres for confirmation on a high speed road to prove straight running. We have done some of this while Mr. Wormald has been away to the Italian border trying 18-EX., and learnt something of the difficulties of the roads here, and about the Riviera. Do we think that the new 20HP. axle (front) will be any better as regards susceptibility to low speed wobbles? I know it is better for high speed, and other good features. R.{Sir Henry Royce} | ||