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).
Tests conducted on a Phantom engine to determine the effect of piston ring clearance on gumming.
| Identifier | Morton\M18\ img074 | |
| Date | 18th November 1926 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} C. to BY.{R.W. Bailey - Chief Engineer} X741 Hs{Lord Ernest Hives - Chair}/ACL1/LG18.11.26. GUMMING UP OF PISTON RINGS. X.3996 X.741 X.1919 X.8040 We have made some tests on a standard Phantom engine to see what effect the clearance of the rings in the grooves had on the gumming up tendency which is manifest on the F.X. engine. A std. Phantom was run for 46 hrs. under conditions of varying load from two-thirds to full throttle at speeds between 500 and 2000 r.p.m. On three of the pistons the rings were allowed a clearance in the grooves of .008 - .009" while three others had the std. clearance of .002 - .003". The oil was Prices Motorine 'C'. Examination after the run shewed that in all cases the top rings were completely stuck in the grooves. The second rings with the larger clearance were all free while the second rings with the std. clearance were either completely or partly gummed in their grooves. A point noticed was that all the top rings were com-pressed to their minimun dia. i.e., they had no clearance between the ends and were consequently clear of the cyl. bore. Some had a film of carbon encasing them. This result seems to indicate that the top rings coll-apse under the explosion pressure, then being insulated from the cool cyl. wall and surrounded by hot gas, they become car-bonised in their grooves. contd :- | ||