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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).
Engine oscillation tests using a cam-balancer, camshaft flywheel, and tensioners, with a comparison of valve spring loads.

Identifier  ExFiles\Box 113\5\  scan0183
Date  28th January 1937 guessed
  
-2-

(1) Cam-balancer.
Camshaft Flywheel.
One tensioner (Slack Side)

Result.
1100 R.P.M. - slight oscillation.
1600 "
2300 " just overcomes tensioner. Bad oscillation on driving side (tensioner removed).

(2) Cam balancer.
One tensioner (slack side).

Result.
1100 R.P.M. slightly worse than previous test.
1600 "
2300 " much worse than previous test.

(3) Cam Balancer.
Two tensioners.

Result.
1600 R.P.M. Very slight period (not so bad as previous test)
2200 R.P.M. - oscillation starts.
2800 " - Peak of period of oscillation.
3500 " - Period fades out.

Conclusion.
These results show that with the present camshaft it is necessary to use both tensioners with the camshaft flywheel and a cam balancer.

We would undoubtedly get some help in the question of chain oscillation from lighter reciprocating loads, as affected by the valve spring load. We give here comparative loads between this engine and standard.

Valve Spring loads.
Standard 4 1/4-litre Bentley.
Inlet and Exhaust. Valve closed Valve open
H.B. 175. 45 lbs. 88.5 lbs.
  
  


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