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).
Confirming a conversation about fitting a Graham supercharger to a Bentley engine.
| Identifier | ExFiles\Box 126\1\ scan0129 | |
| Date | 15th June 1934 | |
| x209 To RHC{R. H. Coverley - Production Engineer}: Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}10/KW.15.6.34. Graham Supercharger for the Bentley. subject - Confirming our conversation on this (1) In order to get the right blower ratio this supercharger has to be run with 20/25 HP: dynamo speed which is 1 1/2 times engine. Therefore the 4-bearing crankcase which is being cast should be arranged to have the 20/25 HP gear centres and the scheme for the blower attachment should also take this into consideration. (2) You have ordered two pairs of gears to run opposite hand to the Graham and the same ratio, i.e., 4.84. We also require a drive ratio of 4.34 as previously instructed and you are arranging to make this in the Works, though we do not anticipate it will be silent. (3) Since we shall have to make a new casting for the Graham supercharger on the Bentley, and also a new gear drive, we should like you to produce the remaining pieces of the blower, i.e., the rotor and shaft drive, so that we shall have a complete set-up for the Bentley and we can run without the Graham having to stand idle whenever supercharger tests are taking place. (4) We do not want to tie the blower up with the 4-bearing crankcase. Will you therefore please put a 20/25 crankcase through with a mounting for the blower. (5) The 4-bearing crankcase having the 20/25 dynamo speed will not normally take the camshaft balancing cam. We should, however, like to have the balancing cam on this engine. This will necessitate a small alteration to the casting to bring it into line with the Bentley. Will you please arrange for this. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||