The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: markyboy64 on 08.12. 2015 22:53

Title: Dynamo Woe
Post by: markyboy64 on 08.12. 2015 22:53
Hello All,
So I finally have received my '53 Golden Flash back in Australia from my Isle of Man trip in August. Bit Mildewy from 6 or so weeks locked in a container. The guy who freighted the bike(s) was very pleased with me as the dripping oil has given the container some extra rust protection for a while. Hmmm !.
Riding the bike towards Felixstowe in the UK, the lights went out shortly before arrival with accompanying extra noises sounding like loose chain. Couldn't do much there, but back home and took the timing cover off to find that the Dynamo chain was very loose, to the point that it had been rubbing on various parts of the casting on the timing case. The drive sprocket had sheared the rivets that attach it to the drive hub and I suspect that the Dynamo had been mounted with a loose adjustment or had come loose whilst I was riding over there.
When I removed the smaller sprocket at the Dynamo, I noticed that it wasn't snugged up on the taper, rather it bottomed out on the bearing boss and had a lot of wobble in the taper. It could be the wrong sprocket perhaps, incorrect assembly on the Dynamo perhaps, or the nut has been loose at times (it was tight this time) and worn the taper down on either the Dynamo or the Sprocket. First thought was to turn a little off the rear of the sprocket but this would misalign the chain somewhat.
Anyone had similar ???
Title: Re: Dynamo Woe
Post by: chaterlea25 on 08.12. 2015 23:26
Hi,
I would sling the chain & sprockets in the bin and fit a toothed belt drive kit *ex*
The rivited up sprocket seldom runs true *problem* Most have  been levered off at some time or other
so its almost impossible to get an even chain run *problem*
The new pulley will show whether the dynamo shaft is ok or otherwise  *????*

HTH
John
Title: Re: Dynamo Woe
Post by: markyboy64 on 09.12. 2015 00:16
That mod  may be something I do in the future if the bike wants to live with me. For now but, have already got another drive sprocket (Thanks Modak), and want to get it running with the original set up.
If my thinking is right, I would design the Dynamo shaft to be harder than the sprocket, thus wearing out the cheaper part should it spin on the shaft ???

I may just grab a driven sprocket as well.
Title: Re: Dynamo Woe
Post by: beezermacc on 09.12. 2015 07:57
It is very unusual for the dynamo sprocket to be a poor fit on the armature, normally they are a bu88er to get off! I suspect yours is a victim of previous abuse; maybe the armature taper is non-standard due to wear or abuse. I would recommend you give the dynamo a refurb before refitting it as it sounds like it has been shaking about which, if left unattended, will lead to further problems. A new armature, bearings etc isn't a fortune if you do the job yourself. I agree with previous comments about the poor dynamo drive arrangements and, without doubt, the belt kit is a big improvement. If you don't want to throw more money at the job it is possible to get the original arrangement to work in a satisfactory manner but you need to make sure that your chain is tensioned to avoid tight spots which will inevitably lead to slack spots which were the cause of the chain rub on the timing case, again very common.
Title: Re: Dynamo Woe
Post by: RichardL on 09.12. 2015 12:10
I would think that any wear on the armature shaft that was great enough to cause a correct sprocket to be loose would be visibly obvious in the form of scoring, spalling or discoloration from overheating. Others may correct me if I'm wrong. If the armature shows any of these signs, i suppose its replacement is due and a belt kit should wait for that. If there are no such signs, or you've replaced the armature, new sprokets should be easy to find (should you want them) due to all the folks replacing them with belt drives.

Richard L.
Title: Re: Dynamo Woe
Post by: Topdad on 09.12. 2015 15:22
Glad the outfit is home without major problems. If you need sprockets I've a fair selection you can have ,I won't be using them for the reason mentioned by Richard , just let me know may even have a chain , Bob.
Title: Re: Dynamo Woe
Post by: markyboy64 on 09.12. 2015 21:45
Thanks all, Both the armature and sprocket were clean with no obvious signs of stress. If it had worn that much to loosen off, I would have expected some filings inside the case as well. Will continue being a Luddite for the time being, if only to solve the problem. Maybe buy myself a belt drive in the future.
Title: Re: Dynamo Woe
Post by: trevinoz on 09.12. 2015 22:46
Mark,
The sprocket should have clearance between the bearing lock ring and the bottom of the sprocket.
Maybe the lock ring wasn't tight before the sprocket was fitted.
Title: Re: Dynamo Woe
Post by: markyboy64 on 12.12. 2015 22:12
Bang on the money there "TrevinOz" !

It's not until we dismantled the Dynamo further that the lock ring was noticed. The outer nut securing the sprocket was tight however, so someone previous must have missed it also and tightened the sprocket onto it without ensuring it was home. See Pics.
I made up a little tool to do up the nut. I don't know if anyone has a better version. Wouldn't mind seeing a photo to compare.

Look, I may end up with the belt drive conversion somewhere down the road, but it's nice to chase and erase a mystery as well.

Title: Re: Dynamo Woe
Post by: duTch on 12.12. 2015 23:27
 I'd forgotten about this tool I made for that...
 May be a bit hard to see well, and forget how I did it, but seems I put a couple of blobs of weld on opposing sides of a fine thread nut, big enough so when I drilled out the thread it fits snuggish on the big part of the taper, then just dressed up the tangs to fit- must've worked ok

 I'd call it a 'dynawoe ' *eek*....ok-I'll do it myself *bash*
Title: Re: Dynamo Woe
Post by: markyboy64 on 13.12. 2015 00:16
Hello DuTch, Your idea may work better than mine. The only way I can see to hold the armature still while tightening is to insert something through the split pin hole ? My Doodad gets in the way.
Thanks
  ;)
Title: Re: Dynamo Woe
Post by: duTch on 13.12. 2015 09:58

I can't remember what I did there, only thing that comes to mind is hold the armature in one hand while tighten the ring with the other- then assemble.... *dunno*
Title: Re: Dynamo Woe
Post by: Greybeard on 13.12. 2015 10:48
The only way I can see to hold the armature still while tightening is to insert something through the split pin hole ? My Doodad gets in the way.
Ooh, nasty!
Title: Re: Dynamo Woe
Post by: trevinoz on 13.12. 2015 20:54
Mark,
               The only way to tighten the ring is to dismantle the generator and hold the armature in a vice, use aluminium angle or such to protect the armature from damage and don't over tighten in vice.
Title: Re: Dynamo Woe
Post by: markyboy64 on 14.12. 2015 00:13
I've got mine reasonably tight and will place an O ring between the lock ring and sprocket.
The lock ring will then have a resistance to unscrew itself.
Title: Re: Dynamo Woe
Post by: terryg on 14.12. 2015 09:22
Is there enough thread on the armature end to get two thin nuts on, in a locking arrangement?
I haven't got the bits in front of me but I'd be inclined to look at that possibility, together with a suitably thinned version of Dutch's peg spanner.
Title: Re: Dynamo Woe
Post by: trevinoz on 14.12. 2015 20:14
Trouble is, Terry, the thread is 15mm, 18 tpi. It becomes a lot of work for something which is not necessary.
Don't even think about using Loctite on the lock ring either because when it needs to be removed usually flame is involved.
Title: Re: Dynamo Woe
Post by: terryg on 14.12. 2015 20:56
Thanks Trev. Is that a PG9 thread?
PG = Panzer Gewinde.

If it is then taps are a bit pricy, I agree.
Title: Re: Dynamo Woe
Post by: morris on 14.12. 2015 21:57
I tighten the nut by hand and give it a couple of knocks with a small aluminium drift. Did several like that and never got one to come off.
Title: Re: Dynamo Woe
Post by: trevinoz on 15.12. 2015 21:31
Terry, I don't know whether the thread is a PG or not but I suspect it is just a Lucas special.
They did the same on voltage regulator adjusters and Altette push rods, seemingly a thread for a task.