Gearbox intershaft bush

[Bob Culver]

Post war Minxs had this arrangemnt. The manual places considerable  emphasis on the correct clearance of .0015 on both internal and external surfaces.
I trust the conversion suits all situations, including lowered oil level. The situation on racers may actually be less onerous than road cars which can toil up hills in 2nd for mile after mile. 
The modification was common on Jowett cars but with 60 bhp the bearing usually emerges looking distressed.

I take it the cones are old ones worn smooth. If considered worthwhile, the grooves can be tediously cut with a fine square edged tool, but the edge of a fine thread tap is much quicker.

[Derek Sheldon]

   


Made the same error yesterday . Made a puller. Wooden one did not work. Even though the unit was turning

[Hedd_Jones]

Never heard of that Timesaver stuff so looked it up. Seems like one of those things that's been around for ever (longer that Austin 7s even!) and does work for certain things very well. If I could get it I would definitely try it but of course not available locally and once you find someone who will send overseas it costs so much not to be worth while.

Simon

Its availible in the uk. Mail order. Posts the same day. Adam who sells it posts here occasionally and has a chummy amongst other stuff (including a Morris!). I think he even sells it in smaller pots to make the cost tolerable. 

Its one of those things you buy. And sits on the shelf for 20years, but is a 'thing' that just saves time and hassle during fitting work.

[Jeff Taylor]

I think Hedd posted this link some time ago - Timesaver is available online here in the UK from Heritage Steam Supplies - the 3oz pots are £13.12p ex VAT and they offer international shipping.

https://www.heritagesteamsupplies.co.uk/...=timesaver

[Steve Hainsworth]

I've always been told bushes that are a push fit will close up slightly once pushed in place. This one I definitely had to push into the first motion shaft (using a vice and a socket as a pusher on the face) but it wasn't hard to do. When I checked it on the shaft I might not have made sure it went all the way down. I've been caught out with that before with a spigot bush on an MGB which prevented me from getting the gearbox to mount as the gearbox input shaft wouldn't fit into the bush in the crank. I ended up having to remove the bush with the toilet paper and wooden plug and BFH method!

It definitely doesn't turn as you mention Steve. Turbocharger bushes work that way and have quite a bit of play but then they run lots of oil pressure too. This is definitely a tight fit in the first motion shaft. I will try the Brasso method as it feels only just tight. I suspect the problem is the shaft and where it is worn not the bush.

Never heard of that Timesaver stuff so looked it up. Seems like one of those things that's been around for ever (longer that Austin 7s even!) and does work for certain things very well. If I could get it I would definitely try it but of course not available locally and once you find someone who will send overseas it costs so much not to be worth while.

Even if I have to lap it in it will still be far tighter than the worn bearing that came out so I think it will work fine. The other thing I considered was polishing the gear shaft but only where it isn't worn by the old roller bearing. I would have thought the bush was made to fit based on an unworn size though.

Simon

Hi Simon,
That bush does need to turn inside the first motion shaft . If it is tight it will mean you have less than half the bearing surface you should have, the bearing is obviously not machined to the correct tolerance on the outside- as a previous message states there needs to be room for oil  (.001" ) The tight fit will have shrunk the I.D and made it tight on the 3rd motion  shaft spigot

[Terrytuned]

The problem is not the bush, when a new c/ratio gear is fitted to the 1st motion shaft they are pressed on and welded in place this can shrink
the bore of the 1st motion shaft so the bush will go part way in and then go tight. Some need a light polish to the bore to give clearance
or you may need to grind the bore out with a small grinding point while rotating the gear as its the far end of the bore that shrinks the most
then polish with a small emery drum. I have had to do this to most of the c/ratio sets I have fitted.

Terry

[jansens]

Thanks guys, have arranged to visit Steve tomorrow for another pair of eyes and some engineering knowledge to help me out. It should have been obvious to me, thinking back now, that the grooves on the outside of the bush indicate there should be clearance there too. Will report back later.

[jansens]

I got the bush out easily enough and tested it on the shaft and in the old 1st motion shaft and it runs freely on both so yes, it seems the CR one has shrunk and definitely more closer into the gear where the heat would have been as Terry says.

[Bob Culver]

Removal of just the taper by internal grinding is a tricky operation. If you turn up test plugs, can the bore be corrected wih a single stone from a brake hone or a piece of half round slip stone, pressure applied at one end with a stick or suchlike?
Clearance on outer surface sufficent to tolerate heat expansion would seem essential.