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).
Discussion of pump performance issues and proposed modifications to address imperfect filling.
| Identifier | WestWitteringFiles\T\January1929-February1929\ Scan150 | |
| Date | 15th February 1929 guessed | |
| (2) So that we presume that it is the quick descent of the piston when the oil is hot, coupled with the imperfect filling, that is causing anxiety; (our information from Mr. Bijur was that 1 min. should be the minimum when hot.) As regards the first the increased pressure will hardly help that unless the resulting increased acceleration of the piston closes the valve more rapidly. The latter feature would improve the filling but one would think other things, such as reduced resistance to filling, would have more effect, while the increased pressure looks as though it would increase the leakage. What we suggest therefore on N. sch. 2830. is as follows: (1) A spring giving 100 lbs. per sq. in. on a 1.375 piston - .750 stroke, capacity 1.113 cu. ins. = 18.24 c.c., (to go to 20 c.c. would be to equal the largest Bijur pump which should surely not be necessary) and 18 c.c is 150% of the capacity 12 cu. ins., given by Derby to the RR. pump. At the same time much increased holes through the piston so reducing possibly 4 times the resistance to filling. [Handwritten:] To be used only if Derby are certain they need it. (2) An intermediate policy viz: a 1.375 dia. pump with a spring giving 87 lbs. per sq. in. pressure, combined with reduced filling resistance so that more capacity is obtained without much increase of pressure. (3) Some modifications to the existing pump requiring a new piston and spring only to improve the filling, and give a more flexible or more powerful spring, or both. With reference to the remaining points in HS{Lord Ernest Hives - Chair}1/LG5229:- The bore/stroke ratio of the new pump is 1.375 - 1.832 / .750 (nearly same as Bijur.) An air vent is provided but we thought that with the clearance between the piston rod and the top filter washer it would be impossible to prevent air getting in. We have removed the lock ring for the cork. We have indicated a head valve but R.{Sir Henry Royce} definitely did not wish this, and it will require modifying. [Handwritten:] Justifying. WE WILL SEND THIS ON MONDAY Though Derby say the suggestions on N. sch. 2736. are not equal to the Bijur, we presume that they were an improvement on N. sch. 2647? Is the incomplete filling due to slow shutting of the valve or resistance to the oil passing through [Handwritten insert: head] valve, and is this due to velocity or viscosity? The time taken to depress the pedal and the quickness with which it was released would give indication of this one would think. The pedal pressure has to be considered. Bijur seems to want 36 1/2 lbs. apart from mechanical efficiency. We should like to keep under 25 lbs. if possible. DA.{Bernard Day - Chassis Design} | ||