Rolls-Royce Archives
         « Prev  Box Series  Next »        

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).
Comparative analysis of engine design features, including valves, temperatures, ignition, and cooling, with reference to Coventry Climax engines.

Identifier  ExFiles\Box 134\2\  scan0091
Date  9th November 1936 guessed
  
-2-

Valve Sizes and Gas Velocities.

Coventry Climax have done very little in the way of valve sizes, due to the fact that they had not tumbled to the necessity of shortening the duration when using larger valves. In addition their valve lift was to our standards, rather small, and this makes the comparative BHP/litre curves show up in a rather better light.

Exhaust Valve Temperature.

If the cylinder and head have been properly designed, then the result is an exceptionally cool exhaust valve. No tests of this on our unit have so far been carried out, but it is proposed to do some comparative temperature tests on the high Power and Bentley Single Cylinder Units, and in the event of this proving favourable for the O.H.1 job it is another point in its favour, as silchrome exhaust valves will be a considerable better proposition. Incidentally, this material - unstelliteḍ - is standard in Coventry Climax engines.

Smoothness and Ignition Advance.

It is claimed that this engine is remarkaby smooth, even though requiring only a very small ignition advance. A curve shown us for an automatic ignition governor gave figures of 5º advance at 500 R.P.M. rising in a straight line to 15º advance at 1400 R.P.M. and then remaining constant. This unit was stated to be quite smooth.

Cylinder Distortion and Block Cooling.

Messrs. Coventry Climax claim that they do not experience any distortion on their engines as they do not normally suffer from over-oiling, ring gumming, or cracking of cylinders. One spasm of cracked cylinders between exhaust port and cylinder bore was put down to faulty water circulation due to the rubber hosing collapsing, this being on a supercharged unit.

A cure for the rubber tube trouble was effected, but recently the block has cracked again and tentative reasons put forward are that overoiling occurred, the oil carbonized on the exhaust valve seat allowing blow past the valve with consequent local overheating between the port and the bore. A dope fuel consisting mainly of methonal was used. This explanation would involve the assumption of cylinder distortion and it would probably be better not to take their statement as regards this too literally.

Cooling of the block at this point is effected by allowing ample water space and also in one or two cases running a tube with jets along the block and directing the water on to the hot spot. This idea is already in progress on our unit.

continued.
  
  


Copyright Sustain 2025, All Rights Reserved.    whatever is rightly done, however humble, is noble
An unhandled error has occurred. Reload 🗙