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).
Letter from Humber Limited discussing methods for overcoming gearbox troubles, specifically the issue of gears jumping out.
| Identifier | ExFiles\Box 126\2\ scan0086 | |
| Date | 24th January 1939 | |
| HUMBER LIMITED, COVENTRY. To S.H.Grylls, Esq., Sheet 2 Date 24.1.39 certainly should be quite capable of taking the full drive. In regard to the other method of overcoming jumping out troubles, I am enclosing herewith a sketch which is fairly self-explanatory. This is applicable to the type of straight tooth gear which slides axially upon a splined hub, the said hub engaging with the mainshaft in the gearbox. The main idea here is to bell "mouth" the gear slightly so as to cause it to wind into engagement on the drive, as jumping out is the most difficult to control if this occurs on the drive and in order to prevent the resultant winding out which would occur on the over-run, we adopted a method of preventing this by mechanical means, jumping out on the over-run being easier to control than on the drive. I attach hereto a second print which indicates this latter point. The idea does to some extent increase the effort required to dis-engage first gear, but in practice this has not been found to be any serious disadvantage. on the over-run Theoretically I suppose if the jumping out force/were really severe, this idea would not prevent it, but in our case, it seems to have been completely effective, as we have had little or no trouble with jumping out of gear since we adopted it. The little device indicated by 'B' is purely to prevent engagement between the 2nd speed synchro mesh cones until the 1st speed wheel is actually moved out of dis-engagement with its corresponding mating wheel on the layshaft cluster. I hope this information will be of value to you and shall be very pleased to furnish you with any further details which may be of assistance. With kind regards, Yours sincerely, [Signature] | ||