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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).
Interim report on endurance tests of Tufnol rubbing blocks and pivot pin bush material for ignition contact breakers.

Identifier  ExFiles\Box 61b\1\  scan0192
Date  19th March 1934
  
By.{R.W. Bailey - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Wst.
c. to E.{Mr Elliott - Chief Engineer}
c. to Sft.{Mr Swift}

Hs{Lord Ernest Hives - Chair}/Wst.2/MA.19.3.34.

TUFNOI RUBBING BLOCK AND PIVOT PIN BUSH MATERIAL FOR R.R. IGNITION CONTACT BREAKERS.

We are running several endurance tests with rubbing blocks and pivot pin bushes made of Ellisons Tufnol material. We are running these for 500 hours at a distributor speed of 2000 R.P.M., one of them running with a Chromium plated steel pivot pin, another on brass, and another on stainless steel.

We are issuing this interim report as a guide to Production.

After 124 hours running the contact breakers were dismantled and the wear measured. The wear on both rubbing blocks was found to be only .001" which we consider is extremely satisfactory. With regard to the pivot pin bushes they did not show any signs of wear but we noticed a slight tendency for the bush to contract on to the pin. Ample clearance between the pivot pin and the bush should be allowed on Production to avoid any tendency for seizing up to occur.

We are continuing our tests but the results so far certainly appear to justify the adoption of these blocks and bushes as standard on production.

It is important that the rivetting should be carried out efficiently as the contact breakers depend to a large extent for satisfactory running on the flexible copper connector which is rivetted along with the rubbing block to the lever.

Hs{Lord Ernest Hives - Chair}/Wst.
  
  


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