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).
Piston gumming experiments, testing the influence of stiff and weak piston rings on a Phantom engine.
| Identifier | ExFiles\Box 182\M18\ img076 | |
| Date | 20th October 1926 | |
| to R.{Sir Henry Royce} from hs{Lord Ernest Hives - Chair}/ACL. c. to RD. Wor.{Arthur Wormald - General Works Manager} c. to RO.{C. C. Rose - Export Manager} E.{Mr Elliott - Chief Engineer} c. to DG. BY.{R.W. Bailey - Chief Engineer} hs{Lord Ernest Hives - Chair}/ACL/L/20.10.26. PISTON GUMMING EXPERIMENTS. The influence of stiff and weak piston rings on the tendency to 'gum up' in the grooves has now been tested on the Phantom engine. Three pistons were fitted with rings requiring 5.2 lbs. tangential pressure to close them to the same dia. as the cyl. bore while the other three had rings requiring only .5 lbs. tangential pressure. The equivalent pressure required by std. rings average approx. 1.5 lbs. In each case the usual clearance in the slot of .002 - .003" was allowed. The engine was run at full load between 1500 and 2000 RPM. for 22 hrs. and examination of the pistons made at the end of that time. All the weak top rings were stuck in the grooves while the stiffer rings were free, the test indicating an advantage to be gained by employing stiff rings. The rings which were gummed up during this test were not so firmly fixed, or carbonized in the grooves as were the std. rings of the previous test. The explanation probably lies in the fact that duration of the previous test was 46 hrs. whilst the recent test occupied only 22 hrs. It is probable that the amount of oil passing the rings has some influence on the problem. The pistons fitted with the weak rings overoiled considerably and those rings which were stuck in the grooves were held more by a gummy deposit than contd :- | ||