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Some whereas after becoming the brand new headlamp and instrument panel, I turned conscious that the ammeter hardly ever confirmed a cost. On the time, I assumed it wasn’t centring correctly and resolved to drag it out and regulate the needle. Nonetheless, obsession being what I am identified for, I saved an eye fixed on it and finally realised the needle intermittently confirmed a cost. There needed to be one thing unsuitable.
Following the same old checks (voltmeter on the battery, linked D & F cables with voltmeter to earth, connectivity checks) I realised the dynamo was struggling to go previous six-point-something-small volts.
I went inside, and here’s what I discovered:
That is it – goop and copper mud. I sprayed it with brake cleaner and put it again on the bike, with the brushes now sliding of their holders. A couple of journeys confirmed a gentle enchancment, but it surely nonetheless wasn’t proper. Ready till I had a couple of hours I may dedicate to it (it is in day by day use, kind of), I took it off once more and stripped it down to search out the shims that one of many earlier house owners had fitted to accommodate the non-standard bearing had moved and reduce into the commutator, shorting out the segments intermittently.
I resolved, after a lot deliberation, to convey the bearing association again to plain. As a part of the method, I cleaned up the commutator on the lathe:
The bearing got here off after a couple of minutes with a grinding wheel within the Dremel. It would not budge for a puller, however the Dremel reduce by way of the outer race simply in order that I may cut up it and pry off the ball cage with out damaging the segments. I floor the inside race tangentially till I used to be virtually by way of to the shaft, when it cracked and got here free. The shaft was in good situation beneath, measuring a hair beneath 7 mm – odd, as a result of the Lucas components ebook suggests the interior diameter of the bush at this finish is 8 mm. This will need to have been enlarged put up warfare – this dynamo is marked 1943.
These are the culprits – two items of skinny metal:
I made a drift to knock out the outdated bush:
I turned the brand new bush out of a little bit of SAE 660 phosphor bronze I had. It is a bearing bronze that’s thought-about the usual bearing materials for gentle obligation purposes. It’s simply machined and the bronze alloy is difficult, sturdy and proof against put on. Apparently it additionally conforms properly to journal irregularities and is much less depending on lubrication than different alloys.
I drilled it 6.5 mm and reamed it 7 mm:
The outdated bush measured 11.2 mm exterior diameter and pushout out simply. I made mine 11.3 mm and while it went in with no bother, it was significantly tighter than the outdated one. I reamed it once more after I had it fitted and deburred the ends.
The clear armature journal fitted superbly and I reassembled the dynamo, pausing to have a look at the drive finish which appeared to have a variety of finish float, although actually it was round 0.5 mm.
I tried to motor the dynamo on the bench, however sadly the one unfastened 6V battery I had was fully flat. I refitted the dynamo to the bike, and began the engine to search out the ammeter kick over to the ‘cost’ facet with a couple of revs. Job performed, aside from the felt washer across the bush which I haven’t got in the mean time.
One other small job I needed to do was bush the top cowl retaining screw gap (3/16″ BSW) which has stripped. Sadly there may be not sufficient room to suit my most popular M8 bush, which is a lot large enough to faucet 3/16″ and even 1/4″ BSW if it’s a must to, so I re-tapped the outlet M5 which is slightly larger than 3/16″. I will have to consider that some extra – maybe go for an M6 brass bush which I can drill and faucet 3/16″ BSW.
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