Laydown gearbox 3rd gear mainshaft

Previously david_chambers wrote:

Previously anthony_bolton wrote:

Dear Members,

I have a spare 3rd gear mainshaft gear, N8036 22 tooth, which has slightly worn dogs on its three leading edges. My existing gearbox has now started to jump out of third only when changing up. Does any member have experience of judiisciously grinding off the burring over of the dogs to true them up again sufficiently for re-use. I am concerned that by doing so I might be destroying any residual case-hardening and end up with a situation worse than I have now. Any advice would be appreciated.

However if a member has a spare N8036 22 tooth gear that is either new or eminently serviceable I would be pleased to buy it subject to photos. An image of my present "rounded off dogs" N8036 is attached to compare.

Regards,

Peter Bolton

Hi Peter,

I know your problem from my own experience. All of my gearboxes have the same problem. All of the gears are afflicted to some extent. I've bought other peoples junk it seems. The problem stems from cost cutting during manufacture. The drive faces of the dogs should radiate from the centre point of the gear, ie the centre line of the shaft so that the load applied is evenly distibuted over the whole face of the dog. They dont so that the load is borne by a small portion of the drive face which can't carry the loads and the dogs jump as a result. Also, the majority of the gears aren't undercut on the dog drive face to better engage with one another. So, to overcome your problem, take the gear clusters and shafts to a specialist auto engineer/machinist and have the dogs ground to be true to the centre line of the shaft and have them slightly undercut as well. The engineer will know what to do.I have been ressured by one of the leading lights in Nortondom that this quite safe to do as the dogs are quite strong enough given the power output of these engines.

Cheers David Chambers

David,

I can now see, thanks to your description, exactly why these dogs should be ground radially as opposed to straight across.

I'll undertake the work over this coming winter - the machine runs OK for the moment.

Any member got a good 3rd gear mainshaft gear N8036 with non-rounded off dogs they would be willing to sell?

Peter Bolton