You might recall that when I re-built the dynamo the first time I had a lot of trouble getting the main bearing on. Freezing and heating the armature and bearing respectively didn't help and I was concerned about the amount of force (applied with the aid of a large "persuader") that was necessary to drive the bearing home.
Subsequent investigation revealed the bearing probably still didn't quite make it home as you can see the witness of the inner race stops somewhat short of the armature step. Of course the trouble is the bearing is hidden by the end plate when you assemble it so you can never be sure!
Bearing small.jpg
I can only conclude that the ~1.5mm discrepency caused the commutator bearing to be side loaded which it didn't take too kindly to and after a grim battle during those 5000 miles gave up the ghost.
Anyway, after a thourough clean up of the body, end plates, brush housing etc and the purchase of the necessary new bits re-assembly commenced. Fortunately it turned out that a friend of a friend has the required pole expander and lever screwdriver to change the field coil, so he did and many thanks to him!
The new main bearing was a better but still too tight fit on the new armature and in the end (after some proper engineering sense having returned before I got the hammer out) I took a very light skim off of the bearing surface to make the bearing a good, tight but manual push fit and ensured that it was sure to go right up to the step on assembly before putting the end plate in position.
Armature Fettling Small.jpg
After studying the Lucas catalogue it became clear that the dynamo was originally missing not only the bearing retaining plate (mentioned in a previous installment) but also the bearing retention nut which comes in two forms, half and full. The need for this wasn't realised first time around because that bearing wasn't going to move on the shaft anyway! Of course now, with a more correctly fitting bearing, the need for it became more obvious. I don't know what thread it is but its ~15mm over the threads at 18tpi.
By yet more luck, my neighbour just happened to have a full nut (great neighbour!) but of course (and according to somebody's Law) in this application the half nut version is required. No problem, I'll just turn the nut thickness down to suit and all will be fine. Having done so, I used the old armature thread to clean the thread up so that it was a nice, smooth fit on the thread.
Unfortunately, the thread on the new armature had not been cut deeply enough and the nut refused to go very far onto the thread. Sadly, my neighbour didn't have a suitable die to run down the armature thread ...........
...... but he did have an 18tpi thread file which after a bout of manual fettling allowed the nut to do its job.
Having done that, re-assembly was completed and the dynamo was motored on the bench to check that it did and that it motored in the correct direction (see, I'm learning!)
All Done Small.jpg
It was then installed back on the bike and after a bit of fiddling, powering the field off of a battery and putting a bulb on the output the addition of many RPM caused the bulb to light.
Last job then was to re-wire back onto the bike and give it a test. Well, it sort of worked
No charge was produced unless the bike was travelling at more than 30mph or so and then, current delivered was proportional to speed.
I concluded that maybe, in the previous dynamo's death throws it had blown up the DV2 regulator so I ordered a replacement. Having done that, I thought I'd take the old one out in readiness which is when I noticed that the (positive) earth wire had parted company with its soldered on bullet. In for a penny and all that, I re-made the conection and gave it a try. It works perfectly
Looks like I'll have to get another bike to go around the new DV2 regulator when it arrives!
So, lessons learned:
1) Very rarely should you need a big hammer, if you do, there maybe a very good reason!
2) Modern replacement parts seem to be more of a "Starting point" rather than an "End Product" in some cases so keep your wits about you (anyone seen an oil filter?)
3) The DV2 regulator seemed to handle the abuse of one of its wires dropping off in its stride with hopefully no long term ill effects
Alan
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