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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).
Problems with hydraulic tappet adjusters on the Phantom III and proposing experiments with alternative solutions.

Identifier  ExFiles\Box 96\2\  scan0097
Date  16th January 1936
  
To RHC.{R. H. Coverley - Production Engineer}

x357

Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}3/KW.16.1.36.

Silent Tappets on the Phantom III.

The more we see of the hydraulic tappet adjusters on the Ph.III, the less we like them. Apart from the manufacturing cost, which must be considerable, they tend to cause the valves to stick open in cold weather, which makes starting difficult. They also need chromium plated tappets which are expensive and necessitate specially strong valve springs, which are likely to cause the valve heads to drop off and caused us to re-design this feature.

We have been doing some experiments to see if we can make the valves function in a quiet manner without these silent tappets. The reason they have been used on the Ph.III is because it has an aluminium block which means there is large expansion and the tappet clearance when warming up is likely to be very great.

By increasing the efficiency of the oil cooler, however, using stellited silchrome valves which have a lower coefficient of expansion, fitting the valves with very fine stem clearance, and altering the Ph.III camshaft to give it a long silencing toe, we believe we shall be able to throw the silent tappets away.

We are doing most of the valve experiments on the Bentley, and when we have got some results will instruct a set for the SpectreCodename for Phantom III.

In the meantime we shall be glad if you will put in hand a camshaft Herper Hs{Lord Ernest Hives - Chair}/Smth.10/KW.11.1.36, which has the toes we require. This matter is somewhat urgent, as if we get results quickly we may be able to save the machining costs of the first 50 sets of hydraulic tappets.

Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}
  
  


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