1939 Model 26 Dynamo

Information relating to Matchless and AJS Models built prior to 1939
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clive
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Re: 1939 Model 26 Dynamo

Post by clive »

hi Bruce as a guest you will not be able to add a photo. Cannot help with the dimensions on the dynamo sprocket as all mine are attached and inside a chaincase. However if your problems continue you might want to consider using a magneto sprocket (there are two types one deeper than the other) they are less deep and have the same taper. Of course you would not be able to use the correct locking washer but if you can devise a method of holding the sprocket whilst you do up the nut If you use Loctite you should be ok (I have used a screwdriver in the chain but this is not a recommended engineering method). Once tight the sprocket always locks on the taper and needs a puller to remove. Locktite on a clean thread should fix the nut, you can use the original one.
I had to employ this to fit one of the early Alton alternators to a G3L with a CP gearbox as it would not move far enough across before hitting the case. If I understand this seems to to the problem for you. 30 years later it is still there.
clive
if it ain't broke don't fix
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Duncan
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Re: 1939 Model 26 Dynamo

Post by Duncan »

Hi Bruce

I am not familiar with the E3H does it still have a tapered shaft and keyway? , on my 39 bike I have a E3N fitted I have attached a picture of the end clearance before the CP gearbox for reference, it sounds like the body you have is too long the E3N is 7/8" shorter than the E3L but I am not sure about the E3H.
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Groily
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Re: 1939 Model 26 Dynamo

Post by Groily »

The bike would originally have had an E3AR dynamo according to the Lucas Parts Lists.
For which the E3N is a straight improved replacement - much better for having a more robust brush-end bearing arrangement. (With its outer race mounted in metal not bakelite!) Both have the standard tapered nose with thread which is what a sprocket needs.

Like Duncan, I'm not sure if E3Hs came in a tapered & threaded armature version or not. The various part numbers make even those with 20:20 vision go cross-eyed pretty quickly trying to check them out. I thought they didn't when I started looking (and remain doubtful having gone cross-eyed!) but it's very easy to be caught out because the Lucas lists are thin on pix of all the various armatures, settling for just a few representative ones. The part numbers on their own, while helping a bit if one part seems to be 'unique' to a certain model (and you know what it looks like), aren't sufficiently intuitive for detail differences to be obvious.

Whatever the case, armatures can be jiggled to be interchangeable probably, which may be what has been done? The H will have had an oilite bush at the brush end and a longer 'tail' spindle than on the AR or N armature to go into it, but if things can be centralised properly so the brushes sit comfortably, I think the mix 'n match can work as the spindle diameter for the small bearing per E3N is the same diameter as the shaft that goes into the oilite bush, and the drive end dimensions are pretty much the same bar the bit 'o thread on the tapered ones for the nut.

Bit of a minefield really, but it sounds as if a plan is coming together . . . .
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