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).
Priming tests for Bentley helical gear oil pumps, comparing performance with a 'roof' type filter versus a standard filter.
| Identifier | ExFiles\Box 149\2\ scan0108 | |
| Date | 16th September 1935 | |
| X1265 16.9.35. LeC.4288 Bentley Oil Pumps. Priming Tests - Helical Gear Pumps. Further to previous report 17.7.35. Verification of the success attending the adoption of the "roof" type filter in conjunction with the helical gear pump on the test rig, has now been obtained under engine conditions. This filter was fitted into B-1 unit, and with the standard pressure pipe fitted, the pump self-primed after draining the sump, on three occasions. Such was not the case, however, when the test bed installation was connected, due to its excessive resistance. On releasing the delivery connection on the pump, delivery soon commenced, and on re-tightening the connection, pressure was registered almost immediately. The standard filter was refitted, and again on three occasions the pump failed to prime after draining the sump - with the standard delivery pipe fitted. The position is therefore that helical gears can be self-priming, but not with the existing filter. The difficulties attending the adaption of the "roof" type filter have already been quoted, but it may be possible to modify the existing filter to give satisfaction, although it may mean a reduction of the filter area. Gears having 5° and 10° helix angle have been instructed but are not yet to hand, special cutters being required. N.B. A straight toothed increased capacity gear pump was recently tested for B-18 unit, and by comparison with a helical gear pump was exceedingly noisy. If this is quiet on the engine, the straight toothed pumps can be used, and our standard of "noise" revised accordingly. If not, then further experiments, following on Phantom experience, will be required. The difference between the two types of pump - assembled under similar conditions - was very marked. The delivery of the straight toothed pump at low speeds was, however, much better than that of a helical type. He/W.Bell. | ||