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).
Design considerations for a 25HP engine, focusing on head design and carburettor options.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan224 | |
| Date | 28th May 1931 | |
| ORIGINAL. HS.{Lord Ernest Hives - Chair} ) FROM BY.{R.W. Bailey - Chief Engineer} ) C. to SG.{Arthur F. Sidgreaves - MD} C. to HY.{Tom Haldenby - Plant Engineer} RHC{R. H. Coverley - Production Engineer} RECEIVED 29 MAY 1931 25HP. - FUTURE JAPAN 1s. R7/M28.5.31. 8570. x5680. At the moment the head is being drawn. A special feature is the easier machining of the combustion space, and little more clearance round the valve heads. Also there will be easier machining of top and facings, deleting some features found ineffective, and arranging for easier machining, and cork face to valve covers. We have embodied all the suggestions found advantageous: one or two were not. After a long struggle trying to get in two single carburetters we have decided to delete the magneto and move the water pump to this position. Many schemes of carburetters have been studied and it will be remembered that double ones are necessary for good metering with fixed jets. We (E.{Mr Elliott - Chief Engineer} and R.{Sir Henry Royce}) think that down draught are bad for fear of petrol (liquid) getting into the cylinders, horizontal are difficult for exhaust heating and also for silencing the intake, therefore vertical ones are safest (against liquid petrol and fire) and most likely to give satisfaction in long, and especially careless or ignorant, use. This vertical type is very difficult to get in hence moving the pump to make the crowding less. Werather foretell increased liquidpetrol trouble from the new fashioned horizontal and down draught carburetters, which are convenient for some types, but especially with such features as stranglers, are bad for cylinder and piston wear and seizing. We are taking some extra trouble to avoid these types Twin carburetters give too long an induction column of ingoing air for high speed, and do not save many parts, and are not such a good production scheme. Two single carburetters are twice the number and half the complication. The running lengths also vary more with twin, therefore the cylinder charges vary between themselves at different speeds - i.e. long ones charge better at the lower speeds, and short ones at higher speeds - bad for detonations and maximum average MEP. R.{Sir Henry Royce} | ||