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).
Modifications to the Peregrine engine's cam form to improve low-speed performance.
| Identifier | ExFiles\Box 1\10\ B001_X106 TO X 110-page058 | |
| Date | 1st October 1932 | |
| To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} Hs.{Lord Ernest Hives - Chair} Bv. X107. E.{Mr Elliott - Chief Engineer}/HP.1.10.32. re Peregrine Cam Form. It has been found that the long toed cams used on Peregrine resulted in/low speed M.E.P. poor Since, however, the variation in tappet clearance is small on this engine both during the warming up period and when finally hot it is permissible to return to the short toed type of valve lift curve. We now attach a print of LeC.3223 showing proposed modified curve and timing with exhaust and inlet periods of the same duration. The primary accelerating period or toe is arranged to lift .008" in 7 divisions and we found that this acceleration corresponded exactly with that used on the Silver Ghost lift curves, but the period is one dimension shorter. The proposed cold clearances are .002" inlet and .003" exhaust, which when hot will be .005" and .004" respectively. The secondary acceleration period has been shortened from what it was to make the cam more "snappy" and retain the existing floating speed. Nevertheless the heavy acceleration is no more than we are normally using and the cam can be ground with a wheel of adequate diameter. The features for graduated deceleration and compensation for closing of the inlet are retained in the design. As regards the timing, this is based on the summary of the bench results with experimental cams. The smaller the engine the less need we find for long duration timings, although a substantial overlap is desirable. We think the only doubtful point is the | ||