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).
Power improvements and valve timing modifications on the Peregrine engine.
| Identifier | ExFiles\Box 1\8\ B001_X100 Engine Chassis-page186 | |
| Date | 2nd June 1932 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} By.{R.W. Bailey - Chief Engineer} X4027a Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}8/KT.2.6.32. PEREGRINE ENGINE. We have now some more information on this power unit :- Rm.{William Robotham - Chief Engineer} Pr.1. This shows the power improvement using long reach plugs. Rm.{William Robotham - Chief Engineer} Pr.2 This shows that the low speed M.E.P. is considerably improved by cutting out the initial part of the cam lift, and that in this respect the inlet valve is probably more important than the exhaust valve. It is probable that if this alteration could have been made without loss of lift, there would not have been even the slight loss of power recorded at 4500 r.p.m. Rm.{William Robotham - Chief Engineer} Pr.3. This indicates that the .013 cam toe causes more loss of M.E.P. than the portion of lift from .013 to .020". The timings for the three tappet clearances are also shown. We give some tappet clearance figures which indicate that the variation [redacted] will be small with this engine. We note that the Alfa open and close their inlet valve more rapidly than we do between .013" and .020". We also observe that pro rata, the Peregrine inlet and exhaust valves are 20% larger than Chinas. We think that a large valve, whilst being an advantage for high speed power, emphasises the effect of the long duration small valve opening on the silencing part of the cam, and in doing so drops the low speed M.E.P. Therefore with large valves it might be advantageous to reduce the slow opening duration of the Peregrine camshaft, especially as the variation in tappet clearance is so small. We are trying two other angles between the cams with the existing cam forms, opening the exhaust valve later as we understand you suggested, and also getting water under the sparking plug as suggested by E.{Mr Elliott - Chief Engineer} The engine has been stripped and a superficial examination indicates that its condition is exceedingly good. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||