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).
Test report on a Stromberg DA-42 carburettor, detailing issues, adjustments, and comparison to another model.
| Identifier | ExFiles\Box 102\1\ scan0365 | |
| Date | 6th August 1935 | |
| To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation} Hs{Lord Ernest Hives - Chair}/GR.{George Ratcliffe}14/KW.6.8.35. Stromberg DA{Bernard Day - Chassis Design}-42; 18-G-IV. The following tests were carried out on the above. The main metering jet was finally set at 064 and is at present fitted with a slotted delivery tube having only one hole at the base. This single hole delivery tube was found to be the best; with more than one feed hole at the base and a stage weaker main jet fitted, "luffing" trouble was experienced upon closing the throttle. Fairly good slow running was obtained at .015" tappet clearance. This alteration necessitated considerable weakening off (one full turn) of the idling air bleed screw from its original setting. Previously, the spitting in the silencer when coasting was exceptionally bad. This fault is now improved 75%. A demonstration of the effect of inaccurate idling setting, both weak and strong, upon spitting in the silencer when coasting, was given to the Stromberg representative, Mr. Fisher. Our own expanding carburetter does not have this fault. There is a difference in the method of feed between the two carburetters. On the R.R. it is taken direct from the float chamber, and on the Stromberg, from the base of the main delivery tube. The top speed or maximum power remains to be corrected. This should be corrected by fitting an .032" bypass jet. At present .028" is fitted; with the following .030", .032" and .034" bypass jets left by Mr. Fisher for correction either on the test bed or track. | ||