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).
Technical report on the investigation of spongy 'Spectre' brakes, including measurements and adjustments.
| Identifier | ExFiles\Box 92\4\ scan0013 | |
| Date | 21th September 1934 | |
| 4694 306 To E.{Mr Elliott - Chief Engineer} C. to Da.{Bernard Day - Chassis Design} Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}35/KW.21.9.34. SpectreCodename for Phantom III Brakes. As erected in the fitting shop the tipping shoes were set at .020 and we understand the springs under them are far too strong. The brakes on the road were very spongy, it being possible to push the pedal down on to the cross member without locking the wheels. Measurements were therefore taken with the rear wheels jacked up using the brakes against 1st gear, the pedal in every case being pushed down to the cross member which it reaches before the floorboards, sufficient throttle opening being provided so as not to stall the engine. At the input lever of the equalisers the measurements were :- Front Rear. Clearance 1.1 (÷ 18.5 at cam) .9 (÷ 15.5 at cam) Sponge .750 .575 The front tipping shoes were made solid and further measurements were taken at the last external 3.75 CTS{C. Trot Salt - Carburation} lever giving .650 (÷ 12 at cam) clearance and .600 sponge. (The value of notch adjustment is about .150 at this lever). The sponge inside the drum was then found to be made up of :- (1) .030 relative movement of the 2.85 CTS{C. Trot Salt - Carburation} lever and the cam at .700 radius due to sponge in the adjusting mechanism. (2) .005 increase in radius of the drum at right angles to the radius through the cam. | ||