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).
Four recent modifications and improvements made to the New Phantom steering system.
| Identifier | WestWitteringFiles\O\January1926-March1926\ Scan106 | |
| Date | 4th March 1926 | |
| TO HS.{Lord Ernest Hives - Chair} FROM DA.{Bernard Day - Chassis Design} Copy to - DA{Bernard Day - Chassis Design}2/M4.3.26. ORIGINAL 8/3/26 NEW PHANTOMCodename for PHANTOM I STEERING. x8430 x4214 Replying to HS{Lord Ernest Hives - Chair}3/LG2326, there have been four broad improvements made in the steering by the recent modifications - (1) Better lubrication; this is applicable to all the steerings with outside pendulum lever. (2) Greater irreversibility. (3) Greater area in the worm threads. (4) Increased ratio between the hand wheel and the road wheels. Nos. (2) (3) and (4) are bound up with one another and cannot very well be separated, that is to say, in order to keep the pressures on the worm, on the cheeses, in the worm shaft and its thrust bearings etc to a reasonable amount we have to fix on a certain length of rocker arm, and this length gives us a certain length of lead on the worm, and this in its turn in order to obtain an irreversible angle compels us to have a certain diameter of worm. We can alter these proportions a little of course but it may be said that they cannot be altered very much. Advantage (3) - that is - the greater area of the worm is of course capable of being varied by altering the length of the worm, the number of starts, and the size of the worm teeth. This is the advantage we think you are enquiring about in the last para. of your letter. It is of course evident that we obtain greater irreversibility by reducing the efficiency in the reverse direction, and we cannot very well get reduced efficiency in the reverse direction without also reducing the efficiency in the forward direction. This of course is independent of the question of lubrication. In order to off-set this increased inefficiency the ratio between the hand wheel and the road wheels has been increased. On the other hand the superior lubrication probably gives us a steering which ought to be as efficient as the old 40/50, if not more so. We have examined the efficiencies you obtain and they appear to be what we should expect. We send a little curve which shews that at efficiencies such as you are obtaining the co-efficient of friction has a very pronounced effect and the trouble seems to be that this co-efficient of friction varies as far as we can see due to the oil being squeezed out. We are sending a suggestion for giving a coarser thread so that there may be a better (1) | ||