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).
Investigation into the cause and potential solutions for brake judders on a Bentley.
| Identifier | ExFiles\Box 84\2\ scan0201 | |
| Date | 7th December 1934 | |
| To Sg.{Arthur F. Sidgreaves - MD} From Hs.{Lord Ernest Hives - Chair} c. to Wor.{Arthur Wormald - General Works Manager} c. to R.{Sir Henry Royce} c. to Hy.{Tom Haldenby - Plant Engineer} c. to Ip. BENTLEY BRAKE JUDDERS. We found on Ip's. car which you returned to Derby for brake judders that the pin on the front axle control bracket was broken. We have since replaced this pin and the car is now standard. The pin which failed had run 35,000 miles. It was also a non-standard part. The Standard pieces on Production are stronger than the one which failed and therefore we do not anticipate that this trouble will occur on customers cars. We have recently been carrying out extensive investigations as regards brake judders on the Bentley. The judder is due to the spring in the axle from the pivot to the road spring. The reason we do not get this trouble on the 25 HP. or Phantom cars is because the front axle is considerably stiffer and also the overhang is not as much. This means the Bentley axle has been spread out more in order to obtain better steering lock which considerably increases its flexibility. We have at the present time a Bentley car running about in which the front axle torque arm is fixed close against the pivot which avoids twisting the axle. So far from our tests this has entirely eliminated the brake judders. We wish, however, to carry the test further before issuing a definite report. To confirm that this trouble is due to the flexibility of the system we find that with cycle type wings which are bolted direct on to the axle that this entirely cures brake judders, that is, if the car is run without them the brake judders can be brought up, but as soon as they are fitted the complaint is eliminated. The failure of the front axle control on Ip's. car satisfactorily explains the judders when the brakes have been dried off. This still leaves us with the original fault of the brakes juddering when wet and at the moment we have no immediate cure for this. 5-B-IV. car is fitted up with an improved torque arm on the front axle. We hope in a few days to be able to test this out and see whether this modification can reduce the complaint of brake judders. on existing cars. Hs.{Lord Ernest Hives - Chair} | ||