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Now we all know what we’ve got to do, we are able to get began with the rebuild helped by these beautiful new bushes from Geoff at AOMCC Gearbox Spares
First job is to take away the 2 Welch plugs over the layshaft and camshaft; I drill a gap in these and lever them out:
With some warmth within the casting, you’ll be able to drift the layshaft and camshaft bushes out from the drive facet:
The sleeve gear bushes come out with a little bit of tube; the brand new ones go in with a big flat drift. They go in fairly simply with a hammer (you do not hit the bush immediately), but it surely’s occasions like this that I want I had a press.
The brand new drive facet bushes will be pulled in with appropriate studs and washers:
You’ll want to watch out with the layshaft bush. It is easy to get it misaligned, and there’s an anti rotation pin designed to maintain the grease groove on the prime. On the manufacturing unit this was drilled and fitted from the drive facet, bit with a alternative bush you could align the slot within the bush if you put it in.
All this work culminated in 0.13 mm finish float (5 thou) on the layshaft. That is higher than the 9 thou I had earlier, and I’ve the correct gasket fitted now.
What’s not so good is the 0.37 mm I’ve on the camshaft. That is about 15 thou and must be sorted with shims.
I’ve additionally determined to discard these two nuts and make some new ones. The threads are poor and the nuts could be higher twice that thickness.
We’ll repair the camshaft finish float with this 0.3 mm shim. It is a commercially out there 26 mm ID shim that I’ve opened out to suit:
This shim suits contained in the inside cowl. Sadly, I came upon later that this can be a 0.5 mm shim in a wrongly-labelled bag – testing revealed a selector shaft that was firmly clamped in place.
Here is the selector shaft assembled and greased able to go in.
A trial match, with shakeproof washers beneath the BSW nuts (to forestall them coming unfastened) revealed the shim downside. I went via two luggage of shims with a micrometer and located that each one the shims within the 0.5 mm bag have been 0.3 mm and all those within the 0.3 mm bag have been 0.5 mm…
Simply discovered and stuck, happily. It pays to measure and check at each step.
With that mounted and the selector shaft displaying about 0.05 – 0.07 mm (2 thou or so) finish float we are able to set as much as measure the mainshaft and sleeve gear finish floats.
The mainshaft endfloat nonetheless measures 0.88 mm or 35 thou: not stunning, since we have not modified something.
The sleeve gear exhibits 1.11 mm when in prime gear:
A name to AOMCC gearbox guru Geoff recommended I make a spacer to scale back that to 0.11 mm, 4 thou, to maximise spline engagement. Geoff supplied a helpful spacer to make that from:
That is the spacer that sits beneath the gearbox sprocket, contained in the oil seal. It components off fairly simply on the mini-lathe, when you do not forget that you do not need the lathe in excessive gear!
The spacer suits neatly on the within of the principle sleeve gear bearing, pushing the sleeve gear splines into additional engagement with the mainshaft sliding gear splines.
To cope with the surplus mainshaft finish float, I’ve machined a 0.5 mm recess into the mating facet of the nut. This may prohibit mainshaft journey a bit of extra and will deliver the tip float all the way down to someplace close to 0.38 mm, or about 1/64″.
Reassembling the gearbox reveals sleeve gear motion at 0.8 mm; I will need to have measured that wrongly as I assumed I had 1.11 mm and added a 0.75 mm spacer. Mainshaft finish float is now 0.6 mm, down from 0.88 mm and round 25 thou. That is 1/40″, inside Ariel’s stipulated vary of 1/64″ – 1/32″.
All excellent news; nevertheless, since tightening the inside case nuts for what I assumed was the final time, I’ve realised that the camshaft is just too tight. It turns, however that 2 thou finish float has clearly been taken up by gasket compression – I could relieve the bush a bit of or I could match shims to 0.2 mm (8 thou) relatively than the 0.3 mm at present fitted (12 thou) which ought to give me what I would like.
Because it turned out, smoothing the floor of the camshaft bush was all that was required to return to regular operation, so I tightened up the tip cowl. The final step was to suit the 2 Welch plugs, which need to be achieved earlier than the sprocket goes on for the final time. It could have paid to make sure the bores for these have been clear earlier than the bushes went in, as enthusiastic staking on the manufacturing unit had left plenty of materials within the layshaft bush bore which needed to be scraped out with a twist drill floor flat, like an finish mill.
Subsequent job is to shut up the opposite finish of the gearbox, however I am unable to do this with out the clutch in place as I am unable to maintain the mainshaft to do the nut up by myself.
Extra subsequent time.
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