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).
Carburetter modifications, alterations, and subsequent performance during slow running and road tests.
| Identifier | ExFiles\Box 13\4\ 04-page101 | |
| Date | 6th February 1933 | |
| -3- Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}5/MA.6.2.33. Cont'd.{John DeLooze - Company Secretary} trouble and at the same time the .9 H2O higher stand pipe depression over that of the float chamber being sufficient to ensure that petrol remains in the stand pipe. Details of the extension are shown in (V.1507). With the modification (V.1507) good metering of the mixture at all speeds was obtained by the following alterations. (a) Delivery holes in the diffuser opened out from 4, .125 dia. to 4, .138 dia. otherwise as (E.{Mr Elliott - Chief Engineer}) (b) Main jet orifice increased from .150 dia. to .172 dia. (c) Needle to (V.1509) being straight sided taper .167 dia. at the large end and .095 at the small end. Distribution at 500 R.P.M. full throttle is inclined to be unsteady and a diffuser is being made for test with 6, .109 delivery holes, these being the nearest equivalent in area to 4, .138 dia. holes. .138 diameter holes appear large and we think that .109 diameter holes would effect better atomization and improve the consistency of the spray from the diffuser. Slow Running. Good idling down to 200 R.P.M. was obtained with the R.R. two hole system to (Lec.3132) and confirmed on the road by even running in top gear at 4-5 M.P.H. The slow running unit used, was the original double sleeve arrangement to (E.82875) and (E.82876) in conjunction with a standard .031 dia. jet (E.82878) fitted with an extension .500 long. Modifications carried out in respect of the slow running unit should be to incorporate the sleeves (E.82875) and (E.82876) in one piece with the adjustment as is now provided on the standard Phantom II expanding carburetter. Road Test. The performance of the carburetter gave a good impression both with regard to metering, power and acceleration although no comparative figures were taken. | ||