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).
Analysis of engine starting depression levels and air intake bend performance with different carburetter configurations.
| Identifier | ExFiles\Box 103\4\ scan0148 | |
| Date | 23th January 1936 | |
| -2- (3) Initial Starting of Engine. With hand controlled choke closed and throttle half open - At 100 r.p.m. depression = 4.7" Hg. " 60 " " = 3.0" Hg. " 45 " " = 2.0" Hg. With hand controlled choke wide open, and throttle half open - At 100 r.p.m. depression = .25" Hg. " 60 " " = .15" Hg. Note. The ball will be on its seat, down to approx. 30 r.p.m., but below that speed the depression is not constant, due to uneven torque (turning over compression strokes). Conclusion. The most important part of this mechanism is the seating itself. We suggest that a forced bedding is obtained with a .312" steel ball, before the Dural ball is fitted. Air Intake Bends. Curve No.1 shows the distribution obtained with a DA{Bernard Day - Chassis Design}-42 Stromberg Carburetter fitted to the induction pipe Ex.21111. This is good distribution, and was only obtained after a lot of trouble had been taken, in matching this downdraught carburetter with our particular engine. Curve No.2 shows the effect of merely fitting the bend E.60657 (alone). The direct comparison looks bad, but actually this distribution (curves 2 & 4) is not as bad as the present standard 20/25. Curve No.3 shows a big improvement by fitting a connecting pipe 3.7" long (no silencer). (N.B. - this connecting pipe is the usual connection between the bend and air silencer). Curve No.4. The only difference from curve 3 is that an air silencer has been fitted, using a 1.0" long connecting pipe (this is necessary to maintain the present position for the silencer). Fitting the 3.7" long extension between bend and silencer does not improve matters. | ||