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).
Tests on an agreed type servo using 35, 45, and 55 degree angle threads.
| Identifier | WestWitteringFiles\L\2April1924-June1924\ Scan105 | |
| Date | 12th July 1923 | |
| R.R. 403A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} ORIGINAL Expl. No. X9910 X1559 REF:Hs{Lord Ernest Hives - Chair}/1/L4 M.{Mr Moon / Mr Moore} 24. EXPERIMENTAL REPORT. S E C R E T. WW. AGREED TYPE SERVO. ------------------------ To R from Hs.{Lord Ernest Hives - Chair} c. to CJ. RG.{Mr Rowledge} c. to DA.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} c. to BY.{R.W. Bailey - Chief Engineer} WOR.{Arthur Wormald - General Works Manager} The original servo of this type was instructed with 35° angle thread. When it was tested it was found that we did not obtain sufficient assistance from the servo. It was tried with 45° angle thread - this was an improvement but still not sufficient. We have one running now with a 55° angle thread. This gives efficient braking with reasonable pedal pressure. The pedal pressure required is still more than required with the DES.60 with the cone servo, or the Hispano. With the 55° angle thread the servo does not release. In some cases the brake is stuck on until the car has brought to a stand-still. We are, so far, not very impressed with the action of the flat disc type of servo. There appears to be lag in the operation of the servo similar to that we experienced on the 50 HP. Renault. We are also now with the 55° angle thread, being able to appreciate the loss in pedal movement in taking up the clearance in the servo. The braking backwards does not appear to be sufficient. Hs.{Lord Ernest Hives - Chair} | ||