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).
Comparing a 25 HP integral cast iron crankcase and cylinder block against a standard unit, discussing flywheel rattles, weight, and cost.
| Identifier | ExFiles\Box 181\M13\M13.2\ img044 | |
| Date | 20th April 1931 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. Bg. c. Wor.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} c. Ds. Ry. Hs{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}1/AD20.4.31. ORIGINAL 85000 85050. 25 HP. INTEGRAL CRANKCASE AND CYLINDER BLOCK. We have now run the unit with the integral crankcase and cylinder block in cast iron some considerable distance. We have compared it with a standard unit in 18-GIV. The most noticeable difference between the two units is that the cast iron unit is smoother at high speeds and has no appreciable flywheel period even with the standard flywheel. It may be argued that this is not of importance in view of the fact that we have a lighter flywheel which gives us the same result which could be applied to the standard engine. This is correct, but the lighter flywheel has one serious disadvantage in that it brings up rattles in the continuous gears at the road speeds of about 40 to 45 m.p.h. on top gear. With the present standard production flywheel we are on the verge of trouble with these gear rattles and it is a costly job to work to very fine limits with regard to back lash etc. Since the lighter flywheel makes these rattles at least 50% worse in the cases we have tried, we think that this is a disadvantage which cannot be ignored. The increase in weight of the cast iron engine is approximately 68 lbs as the unit was made out of existing patterns there is a double thickness of metal in a number of places where it is quite unnecessary and therefore we should say that at least 20 lbs. of the excess weight could be saved were it properly designed. The nett saving in cost of this method of construction has been roughly estimated at £5. At the present moment there appears to be no alternative method of obtaining the rigidity which is so desirable for high engine speeds, unless we alter our method of valve operation, because we think that with an aluminium cylinder block the noise due to the lag of push rod expansion when warming up would be intolerable. | ||