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).
Ongoing problems with piston knocks, including a type referred to as 'rippling knock', despite design improvements.
| Identifier | WestWitteringFiles\Q\February1927-March1927\ 49 | |
| Date | 1st February 1927 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c. to BJ. Wor.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} EY. c. to OY. PISTON KNOCKS. +4190 +8040 Since the adoption of the stiffer cyl. skirts. trouble from piston knocks have been considerably reduced but there still occur cases where knocks are manifest and when these arise they prove particularly troublesome and result in extra time and labour being spent before a car can pass off test. We have used pedestal pistons and while these give us greater flexibility in the skirt and are an advantage from the point of view of gudgeon pin fixing and in avoiding tightness which gives rise to another type of knock - usually described here as a 'rippling knock' due to its frequency being greater than that of the more usual one - they still possess about the same variation in performance, or susceptibility to knocks, as the ordinary standard pistons when tested in quantities. Increasing the flexibility still further by either increasing the length of the circumferential split or thinning down the skirt, we encounter trouble with rattling at the higher speeds. Referring again to the previous test we found that by moving a piston, attached to a rod, up and down by hand in a steam heated bore we could usually reproduce the same type of knock at the end of the stroke when reversing the motion and at this point increased resistance to motion could be felt. This was more noticeable, and | ||