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).
Pierce Arrows' oil-adjusted tappets and a diagram of their bleed hole design.
| Identifier | ExFiles\Box 173\1\ img172 | |
| Date | 2nd February 1934 | |
| -3- Pierce Arrows. I called in to ask them about oil adjusted tappets. Their experience has been exactly the same as ours; greatest difficulty is in getting the air out of the oil when the latter approaches 100°C. Their tappet is just like the one Jardine sent us as far as I can see. They say the secret which finally got them clear of the oil was the bleed hole X at the top of the tappet which is only open when the valve is on the seat. This is a thing we should try; i.e., air bleeds out all the time except when the heavy load is on the hydraulic plunger. They are using 1/4 thou. clearances on plunger or less, but they are not sure it is necessary. I think that they realise it isn't, as they have much longer leakage paths than we have and are pressure fed. [Diagram Text] AIR BLEED X CLOSED BY VALVE WHEN LIFTED AIR ESCAPE OIL FEED USUAL NON RETURN BALL OIL AT MAIN PRESSURE SPRING 20 LBS LOAD CRANKCASE SETTLING CHAMBER FOR SLUDGE | ||