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).
Analysis and review of Chevrolet hydraulic brakes, discussing performance, design, and potential improvements.
| Identifier | ExFiles\Box 111\3\ scan0174 | |
| Date | 7th May 1937 | |
| To Rm.{William Robotham - Chief Engineer} CHEVROLET HYDRAULIC BRAKES. The Chevrolet brakes are quite pleasant to use; the car pulls up square in a reasonably short distance with a moderate pedal pressure. The very soft springing causes dipping of the front of the car on braking and this increases the apparent brake performance which is actually 40 feet from 30 m.p.h. The pedal pressure to lock the rear wheels is 95 - 100 lbs. and 'fading' of the brakes is not obvious on a normal run but the car's performance is not exceptional. The hand brake is almost useless and this we regard as a bad feature on a car fitted with an unduplicated hydraulic brake system: we have had one complete brake failure due to a leaking union. The layout of the brake assemblies is interesting and the attached sketch Rm.{William Robotham - Chief Engineer}371 gives the important details. The shoes have not a fixed fulcrum but the heels are pivoted to swinging links. Strong spring dampers prevent relative movement between shoes and links except under brake loads and on releasing the brakes the single pull off spring rotates the shoes about the swinging links. The object of this assembly is twofold; first, it gives additional wrapping effect to the wrapping shoe, and it causes the extra wear on this shoe to take place at the heel of the shoe where it does not affect pedal travel. The wear of the unwrapping shoe is reduced by this arrangement but symmetry is necessary to ensure as powerful braking in reverse as in forward motion. This probably only need apply to the rear brakes. Adjustment is effected in the usual hydraulic way by limiting the pull off travel. Since this brake is sweet in action it might well be tried on Phoenix with the substitution of a wedge expander for the hydraulic cylinder. This would have the same effect. An adjustable wedge would be necessary. The original Girling wedge patent is for an adjustable wedge but as New Hudsons are not in production with this type we might be permitted to make it ourselves. The lining used is a Millboard base type. It is not practical to make this in the usual way thicker than 3/16" and this we assume was the original thickness of the Chevrolet's linings. The wear at various points on the periphery is marked on Rm.{William Robotham - Chief Engineer}371. Ferodos now know how to make this type of lining in any desired thickness. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} | ||