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).
Carburettor configurations, comparing single versus double setups, and considering a new semi-expanding carburettor design.
| Identifier | ExFiles\Box 179\1\ img098 | |
| Date | 19th November 1931 | |
| HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BT.{Capt. J. S. Burt - Engineer} R5/M16.11.31. Sent off 19.11.31. X7080 X5080 X1487 CARBURATION. We have for a long time understood that it is advisable with double carburetters to have some connection between 2 sets of three cyl. induction pipes. We have for some time seen that double carburetters can help towards distribution by putting into each 3 cyl. section of the induction pipe the proper quantity of fuel. The exact size of the straight through connection between the 2 pipes can of course be increased or decreased at will until it is the size of the straight induction pipe which is now found to be the best for power at high engine speeds. We think it would be worth while to fit up my (or another J.{Mr Johnson W.M.} 1.) with the 2 single carburetters that you have on to a straight 6 cyl. induction pipe. The doubt would be as to whether you can get correct metering under all conditions, but RM.{William Robotham - Chief Engineer} says that the Chrysler does this with a single carburetter with fixed jets, an achievement which was considered very unlikely to be obtained even with 2 fixed carburetters if they fed into a single 6 cyl. induction pipe. Regarding the semi-expanding carburetter which we have just sent you we have just succeeded in simplifying the construction of one or two of the features, but it is a little bit doubtful as to what size we ought to make this carburetter. It has been arranged suitable for the 40/50. at 160 BHP. It might be scaled down and tried as a single carburetter of half the area, about .7 of the linear dimensions, for J.{Mr Johnson W.M.} 3., in which case it could be tried as two carburetters on a single induction pipe for P. 2. We should then be making carburetters exactly alike for the 2 engines. We have however arranged this so completely for P. 2., and as a single carburetter is so much simpler to fit especially as regards the controls, we think it will be worth while to construct this in the large size as we have drawn it as quickly as possible, and try it on P. 2. It includes the connections to the governor. We can only think the S.U. possible as an horizontal carburetter. Even then it seems to lack qualities which are thought necessary for complete satisfaction, as follows: (1) Starting device. (2) Throttle edge carburation. (3) Emulsion jet. (4) Central core of petrol. (5) Absence of needle wear. R.{Sir Henry Royce} | ||