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).
Mr. Royce's requested design changes for a 40/50 HP chassis die-cast piston.
| Identifier | ExFiles\Box 181\M11\ img146 | |
| Date | 6th March 1919 | |
| To Br.{T. E. Bellringer - Repair Manager} from R.{Sir Henry Royce} Copy to EFC. ORIGINAL 6th March, 1919. E1/G6319. X.34008/C RE 40/50 H.P. CHASSIS - DIE CAST TYPE PISTON WITH HIGH AND LOW PISTON PINS. RECEIVED In reply to your memo BY17/T28219, would you kindly note the following points resulting from Mr. Royce's inspection of Scheme No.356 :- (1) It is considered unnecessary to have .3 thickness of metal under the lower scraper ring on the piston with the high pin. This metal should be of about .2 thickness to agree with the local thickness of the piston wall. (2) The outside elevation requires an oil collecting groove shewing to correspond with the section view No.3. It is desired to shew the piston top as a taper, rather than shew it turned down to a shoulder. This, it is considered, will be more in accordance with what will be found in practice corresponds to "clearing away the metal where required". We expect Mr. Hives to experimentally find out what the dimension and shape of this taper should be. (3) Shallow bosses with normal faces should be left on the piston pin boss, where it is required to drill for piston pin locking screws. (4) For piston No.(2) with low piston pin, the circular band of metal should not be used in the skirt for engaging the split pins which lock the piston pin screws. It is only necessary to have a local boss for this purpose just near to the screw. In both pistons these features should be shewn on both piston pin bosses so that the pistons will be symmetrical, and cannot be placed in the jig the wrong way round. This latter refers to pistons having only one locking screw - see next item. (5) Mr. Royce wishes you to make a design in which two locking screws are incorporated of reduced dimensions, having stems .25" diameter instead of .312", and with all other dimensions suitably reduced. The idea is to have a locking screw on each side of the piston so that the piston will be balanced. (Contd.) | ||