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).
Road wheel dynamometer tests, investigating power loss and carburettor performance.
| Identifier | ExFiles\Box 109\4\ scan0096 | |
| Date | 26th June 1939 | |
| 666 + 1320 To By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Da{Bernard Day - Chassis Design}/Ev.{Ivan Evernden - coachwork} c. to Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}1/JR.{Mr James Royce}26.6.39. 30.G.VII. Road Wheel Dyno. Tests. Attached are power curves obtained in direct gear on the road wheel dynamometer. The tests were made on 6.50 x 16 Dunlop Track Racing tyres since these have a small loss at high speed. All the curves obtained are very badly down when compared with the test bed clutch H.P. curve obtained on the same engine under similar silencing conditions (see sheet 2 for comparative curves). When curves A and B had been taken a general check over was made for the more obvious sources of power loss. Tappets and ignition timing were checked and found correct. A maximum flow figure was then obtained for the carburetter, and this was found to be only 79 pints/hour. Test bed figures show that the unit requires 80 pints/hour at 3000 r.p.m. when it is fitted with silencers. Hence it is certainly starved above 3000 r.p.m. and probably goes weak before this speed due to excessive fall in fuel level in the float chamber. A larger needle seating, .140" dia. instead of .112" dia. gave the improvement shewn in curve C comparative with curve A.{Mr Adams} There is still a lot of power to be accounted for, however, as curve C is directly comparable with the test bed curve E.{Mr Elliott - Chief Engineer} The fan appears to require 10 H.P. in still air at 4000 r.p.m. The small increase in power when the engine was run with the exhaust silencer removed leaving only the manifolds may be due again to a low fuel level in the carburetter. Under these conditions the unit requires 100 to 105 pts/hour, and even the .140" dia. needle seating gave only 110 pts/hr. | ||