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).
Spring fitting tolerances and the importance of poundage over piece numbers.
| Identifier | ExFiles\Box 154\2\ scan0155 | |
| Date | 13th October 1938 | |
| -2- The reason why it is desirable that works should be poundage conscious instead of piece no. conscious can be best explained by an example. A certain chassis requires a 1180 lb. spring. The works are told the 1200 lb. piece no. They may fit a 1210 lb. spring, the error being 30 lbs. There is a run on 1200 lbs. springs and a shortage. If they had known the poundage, they could have fitted a 1160 lb. spring with an error of only 20 lbs., and the supply situation is eased. At present there is an instruction that in emergencies works may go up or down a piece no., but without information as to poundage, a 1200 lbs. spring could be fitted with an 80 lb. error. The Americans state that "an error of 5 or 10 lbs. may have a marked effect on the riding quality or appearance of a car....... If it has low rate springs, and although we think 10 lbs. unnecessarily fine, we do want to work down to 20 lbs. on Bentley III. The present limit of 40 lbs. we consider too generous. The poundage system alone makes fine limits possible. RM{William Robotham - Chief Engineer}/AFW. | ||