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).
Oil system performance, addressing variations in operation and the presence of air in the system.
| Identifier | ExFiles\Box 27\1\ Scan115 | |
| Date | 8th March 1929 guessed | |
| - 2 - Perhaps the variation is due to differences in the relative air-tightness of the several systems, since on the relatively faster falls it is sometimes possible to observe that the plunger returns through the first half-inch rather faster than it does during the rest of the stroke. When the bonnet is warm this will be reduced to about 30 secs. In very hot weather it will be as low as 20 secs. In very cold weather (around zeroF) the plunger will take 10 minutes to fall with MobiloilA if the engine is not started in the meantime. If it is the oil will come mostly through the warm plugs and discharge will be complete in about 3 minutes. (Even under these conditions however the remote cold points like the front axle seem to receive plenty of oil. Of course they do not lose oil fast in cold weather.) (3) Air in system. Have you some point in the system under pressure where the bore of the pipe is more than 1/8"? If so (according to Bijur but also according to our own experience) it will be practically impossible to get the air out because the oil and air do not form "slugs" in the pipe. Again the construction at the front pivots might give a little bit of difficulty. Here the main pressure system is closed off by a drip plug without metering pin but with a non return valve opening at 15 lbs. Beyond this is a leak in the pivot and another set of drip plugs with 15 lb. blow off valves. When the system is operating there will be 90 lbs. on the axle, 75 lbs. at the leak and 60 lbs. at the ends of the drip plugs beyond the leak. As the pressure dies out the drip plugs cease functioning when there is still 15 lbs. at the leak, and one would expect, with small elasticities in the system, a certain amount of dribbling at the leak which might have to be made up at the next pressure stroke. I may be all wrong however, because you may not be taking pressure-oil to the axle. We have no difficulty whatever in getting air out of the system and take no precautions to force the air out initially. Taking a new chassis with an empty piping system we have to give it about four or at most six "shots" of the pump before the even fall of the pump handle shows that the air is out. -continued- | ||