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 comparison of Bosch and Delco-Remy contact breakers, focusing on the angular off-set of the pad.
| Identifier | WestWitteringFiles\Q\January1927-March1927\ 40 | |
| Date | 17th January 1927 | |
| TO R.{Sir Henry Royce} FROM E.{Mr Elliott - Chief Engineer} ORIGINAL E1/M17.1.27. C. to EFC. HD.{Mr Hayward/Mr Huddy} DY.{F R Danby} BOSCH AND DELCO REMY CONTACT BREAKERS. X4275 x8693 X4284 We have received and examined the above units, and what "hits one in the eye" about them is the considerable amount of off-set on the contact breaker pad relative to the cam in each case. We should estimate that there is a considerable difference between speed of make and speed of break. There is nothing to indicate the direction of rotation of the Remy, but from the condition of the H.T. wipe contacts it is certain to be clockwise. [Diagram of Bosch contact breaker] 25° APPROX Bosch. [Diagram of Delco-Remy contact breaker] 30° APPROX Delco-Remy. [Text between diagrams] DIRECTION OF PATHWAY OF PAD CENTRE CAUSES PAD TO RUN AT THE CAM ON THE BREAK & TO LINGER ON THE CAM DURING THE MAKE. By holding a set square against the models a very rough estimate of the angular offset is 25° Bosch, and 30° Remy. These quantities can be more accurately determined at Derby. We should like to see an RR. contact breaker arm tested with the same amount of off-set. If the existing cam is used we should lose a little stroke, but not in proportion to the change of radius because the geometry results in some magnification of the cam lift. [Diagram of RR Battery Ignition Contact Breaker] DOTTED LINES SHOW POSSIBLE POSITION OF OFF-SET PAD. EXISTING PAD RR BATTERY IGNITION CONTACT BREAKER. SCALE - 2/1. Other points are as follows:- FLEXIBILITY OF POINT MOUNTINGS. There seems to be very little in this. The Bosch screw is mounted on a very short stiff earthed contact (1) | ||