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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).
The influence of stiff versus weak piston rings on 'gumming up' within the grooves of a Phantom engine.

Identifier  ExFiles\Box 16\1\  Scan183
Date  19th 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 DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer}

[Handwritten] X741

Hs{Lord Ernest Hives - Chair}/ACL1/LG19.11.26.

PISTON GUMMING EXPERIMENTS. [Handwritten] X741 [Handwritten and crossed out] X8040

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 3.2 lbs.
tangential pressure to close them to the same dia. as the cyl.
bore while the other three had rings requiring only .8 lbs.
tangential pressure. The equivalent pressure required by std.
rings average approx. 1.5 lbs. In each case the usual clear-
ance 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 advan-
tage 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 :-
  
  


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