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).
Comparing brake servo multiplication and braking effort percentages between Phantom models.
| Identifier | ExFiles\Box 41\1\ Scan101 | |
| Date | 15th February 1927 | |
| COPY. Oy5-E-21527 February 15, 1927. To: Mr. Beaver cc Mr. Nadin Mr. Hulley Mr. Bagnall Mr. Burton Mr. Haldenby From: Mr. Olley Re Brakes England have standardized two levers C-73149 on the front equalizer shaft 4" long instead of 3" long, as first instructed and as we have. The effect of this is to reduce the front braking "to prevent the steering being affected when braking on corners". Comparison with 1766. To compare this correctly with our job one has to arrive at a representative figure for the "Servo Multiplication". This is arrived at by putting a spring balance in the pull rod from pedal to servo (called A), and another in the pull rod from T-equalizer to front brake equalizer (called B). The ratio of pulls B/A is called the "Servo multiplication". Corresponding to a coefficient of friction (Hale to steel) of .275, this ratio for original English Phantom is 1.95 and for us 1.43, because we have larger diameter engaging faces on the cam levers. 1.800 mean dia. and 50° angle instead of 55°. Thus we have - Percentage of Braking Effort Front Servo Rear Servo Rear Direct Total Rear Total Original Phantom 40% 40% 20% 60% 100% Latest Phantom 30% 40% 20% 60% 90% (or in percentage 33-1/2% 44-1/2% 22% 66-1/2% 100%) of new total 1766 29.3% 29.3% 20% 49.3% 78.6% (or in percentage 37.3% 37.3% 25.4% 62.7% 100%) of new total | ||