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).
Comparing the advantages and disadvantages of helical and straight gear oil pumps for Bentley chassis.
| Identifier | ExFiles\Box 149\2\ scan0130 | |
| Date | 24th December 1936 | |
| 1265. To HPS.{Horace Percy Smith - Experimental Factory Mgr} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}5/AP.24.12.36. OIL PUMPS (CHASSIS) It has been found necessary to standardise an increased capacity oil pump for Bentley on account of insufficient supply with original pump at high speeds. The choice of the helical gear pump for standardisation on Bentley was made in choosing between the helical gear and the straight gear pump each having the following disadvantages and advantages. Helical gear pump LeC.4288 22° angle The advantage of this pump is that the gears are usually quiet without attention. The disadvantage is that it has poor flow efficiency at low speeds and tends to be difficult to prime from dry with restrictions on the suction and pressure sides. Straight gear tooth pump (Ex.11955) The advantage of this pump is that it has higher efficiency and delivers to a lower speed than the helical pump. Also there is no difficulty in priming. The disadvantage is that the gears are usually very noisy and most require individual attention by hand to quieten. From the above you will see that although the Helical gear pump has been standardised it is not entirely satisfactory and we should be pleased if you could instruct for the following tests to be carried out on W.Bell's rig regarding the job as urgent. (1) Delivery against speed. (2) Effect of back pressure and restricted suction on low speed flow also speed at which delivery starts. (3) Priming characteristic of pumps, also gear chatter when starting with cold thick oil. The latter condition observed on the car only lasts for ½ minute, but is a common complaint. Whether this is due to restricted suction, results on Phantom III. with and without restriction washer would indicate this. continued | ||