I had to replace the worn 1st motion shaft bearing and the 3rd motion shaft bearing in the four speed synchro gearbox for my 1936 Tourer. The gearing and the synchro cones look to be in good nick as does the lay shaft assembly. On further inspection of the layshaft assembly I notice that only one of the three oil holes has been drilled through. There is no discernible wear in the bushes or on the shaft so it would appear to have had reasonable lubrication. My question is whether I should drill the other holes.
Hi Peter, when you say no wear in the bushes have you checked the end faces? As end float tends to be the greater issue.
I guess the three holes were drilled in order improve the chances of one lining up on assembly; whether drilling out the other two would improve lubrication is hard to say. Working from memory I think the grooves in the bushes are oriented to draw oil into the cluster, and the hole allows spent oil to be centrifuged out - personally I left it alone...
I'd stress though that I use engine oil in my gearbox (as The Lord intended).
Peter is this the hole in the centre that you are referring to these are the oil exit holes, the oil collection holes can just be seen at each end of the laygear assy.
As Chris says the bushes have oil groves that draw the oil into the shaft, end float of the gear assy only needs to be a couple of thou and use a light gear oil it reduces wear 75/90 GL4 they did not have light gear oil in the 30's.
Terry.
Thank you Chris and Terry for your comments. I had actually missed the cunning method of introducing oil to the shaft. I have an end float of .015” Mr Woodrow suggests a maximum of .010” so I will leave it as it is for the present until I have sussed out the local machinists and put some miles up. I was using a 90 grade gear oil but I suspect oil of that viscosity does not help the synchro to work properly. I have been using 20/50 for the engine as I feel that the SAE 30 engine oil here in tropical North Queensland is too thin for the hot weather here.
Cheers,
Peter.
Peter, it's fairly common practice to re-face a worn layshaft bush (easily done by hand on oiled emery paper on a flat surface) and arrange a suitable shim behind it rather than replacing. The tricky part is drifting out the bush without damaging it & it may be worth your while fashioning a simple tool or drift to do this. Minor burrs can be filed out.
You may have discovered by now that most of the close-fitting parts go in and out much more easily if the case is warmed up first. However make sure it's all settled to room temp before measuring the end float or you may get a false reading.
Finally just a heads-up that it's impossible to re-assemble the box with the layshaft already installed as per Terry's beautiful photo... Pop the cogs in the bottom of the box, install the upper clusters, then slip the layshaft through the lay gears as last step. Sorry if teaching to suck eggs...
Thank you Terry and Chris for your most useful comments and the excellent sketch. I think I will take a little more time and do the overhaul properly. I now feel like a true Austineer; whilst doing a trial refit of the main shaft I accidentally lost control and the first gear slipped out and discharged a spray of balls and springs to every corner of my workshop. It is perhaps worth noting that the balls travel much further than the springs. I managed to find the springs and balls and using the esteemed Mr Woodrow’s tin can assembly sleeve, reinstalled the springs and balls at which point I lost control of the tin can and sprayed the lot around the workshop yet again. At this stage I am one ball short so can’t see if I can do it a third time until I get back from the bicycle shop where, hopefully, I can purchase some more balls. I vaguely recall a post where the suggestion was made to do synchro assembly in a tent. Perhaps I should also take the time to clean up the mess in my workshop.
I think you can view it as a rite of passage Peter! And yes I'd wholeheartedly agree - do it thoroughly once and there should be no need to go inside the box again.
For what it's worth here's the gadget I use for the balls & springs - it's stiff enough that you can simply rotate & pop each one in in turn without the others popping out. Then squeeze up with mole grips and a sharp whop with a hide hammer (or equivalent...) will snap the sleeve into place.
They also do all sorts of engineering supplies; I just noticed that they supply "Wave Washers", familiar to the Vintage Gentlemen who insist on using 1 1/8" crankshafts.....
Very quick service from their online ordering facility as well.
