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).
Comparison of a Bentley oil pump with helical gears against the standard pump with straight-cut spur gears.
| Identifier | ExFiles\Box 149\2\ scan0078 | |
| Date | 5th September 1933 | |
| from RHC.{R. H. Coverley - Production Engineer} c. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} X238 RHC.{R. H. Coverley - Production Engineer}7/BE5.9.33. BENTLEY OIL PUMP WITH HELICAL GEARS We have produced a Bentley oil pump having helical gears, and have tested this pump for efficiency on the rig in comparison with the standard type of pump having straight cut spur gears. Below are particulars of two sets of gears:- Standard Gears No. of teeth. 13 D.P. 12 Pitch dia. 1.1666 Angle of obliquity. 14 1/2° Type. Fellowes Chordal thickness .137 Corrected pitch depth. .0873 Helical Gears No. of teeth. 12 D.P. 12 Pitch dia. 1.1666 Helix Angle. 31° Spiral. R.H. Lead. 6.0997 Obliquity. 20° In order to cater for the increased thrust of the spiral gears, loose phosphor bronze washers were inserted in the casing and cover, the inserts being made to stand .0005" proud of the top and bottom faces in order to ensure that the latter were definitely relieved of any wearing action. Also the casing and gears were made 1/8" deeper than standard in order to compensate for any loss of efficiency arising from the increased clearance at the ends of the teeth due to these inserts. On the rig, the helical gear pump gave a slightly less delivery than the standard pump at low speeds, but shewed up to advantage above about 1250 r.p.m. under the same conditions of oil temperature and pressure. It is possible, therefore, that the slight leakage of oil past the gears due to the increased end clearance does influence efficiency at low speeds. It may also be that the helical gears do not pick up oil so readily owing to the spiral angle of the gears tending to empty the tooth gap on the suction side of the pump. continued. | ||