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 increased capacity helical gear oil pumps on Bentley engines.
| Identifier | ExFiles\Box 149\2\ scan0109 | |
| Date | 17th August 1935 | |
| X1265 17.8.35. LeC.4288. Bentley Oil Pumps. Priming Tests - Helical Gear Pumps. After draining the sumps of Bentley engines fitted with the above increased capacity helical gear oil pumps, priming difficulties were experienced. Normally, with the standard straight toothed gear pump, any difficulty was easily overcome by priming the pump, but with the helical gear type, several attempts at priming were sometimes necessary. When testing helical gear pumps, prior to despatch, no difficulty was experienced in this respect, the tests being performed with an inlet pipe similar to standard, but without a filter. Using a standard Bentley lower half complete with filter and pipes - including gallery and bearing connecting pipes - tests were performed with a helical gear pump, the latter for convenience of driving being run horizontally instead of, as normally, vertically, but the relative positions of the lower half outlet, and the pump inlet, were as standard. Using Motorine 'C' at approximately 25°C., and allowing a maximum priming time of 3 minutes at 150 to 200 P.R.P.M., it was found that if both the sump, and the delivery pipe were drained, the helical gear pump self primed, and delivered at full pressure, (25 to 30 lbs/sq.in.) in 25 secs. If, however, the lower half only was drained, the delivery pipe being left full, the pump would not prime within the time limit. With the filter and filter pot removed, repeated tests showed no difficulty in priming after draining the sump. Various methods of breaking down the air bell effect of the filter pot, such as drilling small holes in the top of the filter pot, and in the section pipe (below the oil level) were tried with indifferent results. Finally, the standard filter was replaced by a "Silver Ghost" type, i.e., a shallow "roof" type. This proved to be successful, and we suggest that this filter should be tried on a test bed engine. It is not suggested that this should be used on customers' cars owing to the difficulty of cleaning it without removing | ||