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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).
Issue of sticking air valves in the 20/25 HP carburetter series.

Identifier  ExFiles\Box 102\1\  scan0210
Date  7th September 1934
  
X5080
C O P Y.
7.9.34.

20/25 HP. Sticking Air Valves (Carburetter Series). Re memo. C9/C.22.8.34, with special reference to par. 6.

The recommendation in paragraph 6 is impracticable, as will be seen from the following.

It is necessary for the rise and fall of the air valve to be truly concentric with the dashpot, and it therefore follows that there must be two bearing surfaces present to make this possible.

If one or both of the diameters of the air valve in question were recuced, binding would be almost certain to take place.

The air valve mentioned in Wor{Arthur Wormald - General Works Manager}4/R.25.7.34 has only the large diameter reduced, but the second bearing surface is replaced by the stainless steel portion, which in itself embodies the two necessary bearing surfaces.

With reference to paragraph 8, it is our experience that although immediate relief is obtained by polishing the affected parts (thus slightly reducing the clearance) the trouble is always likely to recur. This can be explained by the fact that a sticking air valve is primarily caused by the presence of foreign matter. Reducing clearances is merely approaching the conditions already explained, i.e., allowing extra movement which has previously been proved to have caused binding.

C.T. Salt.
  
  


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