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 committee meeting report on experiments with four-wheel servo-assisted brake systems, comparing various schemes.
| Identifier | ExFiles\Box 73\2\ scan0347 | |
| Date | 4th May 1924 | |
| SECRET 9940 R.{Sir Henry Royce} Cl. H.{Arthur M. Hanbury - Head Complaints} Ms. Hy.{Tom Haldenby - Plant Engineer} ExL. FOUR WHEEL BRAKES. E.A.C. 3 DESIGN COMMITTEE MEETING Also present Mr. A.{Mr Adams} By.{R.W. Bailey - Chief Engineer} We now have running on our experimental cars three modifications of the servo system, the production parts remaining practically identical in each case. In addition to these, the Hispano Car is a check against our results. We have all of these cars running, and our impressions from the results (allowing for differences of the ratio of direct braking to servo braking by detail modifications to levers etc.) are that the agreed scheme is the equivalent of the Hispano as was intended. The M.DMS.60 is also the equivalent of the Hispano with the addition of better braking backwards. The R.R.M. scheme is at present better than any of them. We are finding it very difficult to get over the delay of the servo coming into action when pulling up in traffic, and this we consider except for minor modifications to mechanical details, is the same on the agreed scheme, the Hispano, and the M.DMS.60. It is largely a question of the ratio of the effectiveness of the direct braking and the servo braking. The R.R.M. has a definite advantage in this respect, as the direct braking is more powerful and gives us a better ratio than can be obtained in any other way. On test the importance of this point appears to be greater than would be expected from purely theoretical considerations. Our experiments show that the gap is not all together the simple one due to the geometry of the levers but due to the lag in the servo deflecting the parts of the brake mechanism under load. It is proposed to bring four cars, including the Hispano, down to West WitteringHenry Royce's home town for R's inspection on Tuesday morning next, 6th. May. If R.{Sir Henry Royce} wishes to see them earlier they will probably be in a XXXXXX less completely developed state. We hope it will be possible to decide on Tuesday next on the final details of the scheme and to arrange for despatching further cars to France for the 10,000 miles testing. Rg.{Mr Rowledge} | ||