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).
Letter from Bendix Products Corporation discussing car weight, brake sizes, and potential causes for brake drum issues like squeal and bell mouthing.
| Identifier | ExFiles\Box 120\2\ scan0238 | |
| Date | 16th November 1937 | |
| 1029- BENDIX PRODUCTS CORPORATION SUBSIDIARY OF BENDIX AVIATION CORPORATION GENERAL OFFICES AND PLANT SOUTH BEND, INDIANA A.F.M. November 16, 1937 Mr. W. A.{Mr Adams} Robotham Rolls-Royce Limited Derby, England Dear Mr. Robotham: I am extremely apologetic about the delay in answering your letter of August 28, 1937, and which has not been due to lack of interest in your difficulties, but rather because of the fact that almost immediately after receipt of your letter, I was called out of the city and have been away practically continuously ever since. In the meantime, however, certain of our organization were asked for their comments and they are being incorporated in the following statements. In the first place, I hope you will not misunderstand our position. We are trying to help, not criticize, and obviously all we can do in view of the fact that one of the cars is not available for detailed investigation, is to draw conclusions based on our experience in connection with brakes in this country. WEIGHT OF CAR It is noted that the weight of the car in question is 3650#, and that the brake size is 11-3/8 x 1-6/10" front and 11-3/8 x 1-8/10" rear. The size of brake which we use for that weight of car is 12 x 1 3/4 front and rear. This difference may not have any relation to the question of squeal, squeak or chatter, but is nevertheless, given you for whatever it may be worth. DRUMS Our experience with drums, particularly of the general type used by you, is that they must be very definitely and securely fastened between the rim and the plate which serves as the back of the drum. If the points of attachment are not substantial and secure and sufficiently close together, trouble will be experienced with squeal and chatter. We also note that there is a possibility of "bell mouthing", meaning that the diameter of the drum at the open end may become larger than the diameter of the drum at the closed end, caused naturally by the heat developed during a brake application. It is true that this bell mouthing would not be as severe in the case of your drums as in those which are not ribbed, but on the other hand, we have found it advisable to have a very substantial rib at the Page 1 ..... | ||