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Odd noise from Lucas C40 dynamo
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Thu Apr 18, 2013 2:21 pm    Post subject: Odd noise from Lucas C40 dynamo Reply with quote

Hi all, my dynamo - recently rebuilt with new bearings, brushes and springs - has started making a strange noise. It sounds rather like the freewheel on a bicycle, not terribly loud, but is noticeable at tickover with the bonnet up. I had it off the engine the other day and stripped it but couldn't find anything amiss, it's gone back together and is just the same. The noise seems to be coming from the rear end and only when turned in its normal direction. I came back up from Cardiff in the dark last night and started this afternoon no problem so it's obviously charging OK. I did wonder if maybe the new brushes are a trifle undersized and vibrating in the holders, maybe the holders are worn but I wouldn't have thought they were subject to much wear. Has anyone had something similar?

Also, I lost the nut that clamps to the adjuster link, where the bolt screws throught the lug on the dynamo. Managed to find one in one of my odds tins, but does anyone know what the thread is so I can get a spare? I'd hazard a guess at 5/16 UNC, but have nothing to try it with.
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Thu Apr 18, 2013 3:24 pm    Post subject: Reply with quote

Is the fan on the right way round?

Dave
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DM



Joined: 21 Dec 2008
Posts: 212
Location: North Cornwall

PostPosted: Thu Apr 18, 2013 3:48 pm    Post subject: Reply with quote

Did you bed the bruhes in when you fitted them ?
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Fri Apr 19, 2013 12:38 pm    Post subject: Reply with quote

Dave, the fan is a plastic one, made in one piece with the pulley and will only fit one way round.

DM, as I've never heard of bedding the brushes in I'd guess not. Tell me more! It wasn't making any noise at first but it's come on now it's done maybe two or three hundred miles on the road.
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Fri Apr 19, 2013 2:11 pm    Post subject: Reply with quote

Hi BB,

If you slip the cover off you might be able to what's causing the noise.

It would allow you to check that there is nothing odd about the commutator.

Peter
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sat Apr 20, 2013 4:54 pm    Post subject: Reply with quote

Could be some loose insulation on the field windings?

Dave
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Sat Apr 20, 2013 10:01 pm    Post subject: Reply with quote

Peter & Dave, I had it apart a few days back. Nothing obvious to see, commutator looks fine, as for the insulation I didn't inspect it too closely but when I did the rebuild I sprayed inside (didn't remove the field windings) with some stuff for insulating printed circuit boards - had it on the shelf and it seemed like a sound precaution.

Actually I had it out today and didn't notice this particular noise so maybe it's just gone... I hope so!
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Wed Apr 24, 2013 5:23 pm    Post subject: Reply with quote

No such luck, the noise is back. When I did the rebuild - prompted by noisy, slack bearings - the old brushes were only about half worn and I put them away safely for possible future use. I came across them the other night and so might try refitting them and see if that makes any difference. Will also have to strip and inspect the spare dynamo that came with the car, see if that's fit for use if I need it, not really inclined at this point to bother with another DIY rebuild if the parts I can get are no damn good anyway... Sad
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Kelsham



Joined: 18 Jan 2009
Posts: 349
Location: Llandrindod Wells Powys

PostPosted: Wed Apr 24, 2013 5:31 pm    Post subject: Reply with quote

The brushes might be loose in their holders and moving when running.

As for bedding the brushes in, it used to be advised that glasspaper be used seated on the commutator and rotated back and forward under the brushes to make the brushes seat into the commutator by removing material until they took up the shape of the commutator.

Kels.
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PAUL BEAUMONT



Joined: 27 Nov 2007
Posts: 1281
Location: Barnsley S. Yorks

PostPosted: Thu Apr 25, 2013 1:25 pm    Post subject: Reply with quote

Are you sure that it is the dynamo and not a decaying fan belt, or noise from something else travelling up the belt? As it is a dynamo you can run the engine minus the fan belt briefly and see if the noise is gone.
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Thu Apr 25, 2013 1:54 pm    Post subject: Reply with quote

PAUL BEAUMONT wrote:
Are you sure that it is the dynamo and not a decaying fan belt, or noise from something else travelling up the belt? As it is a dynamo you can run the engine minus the fan belt briefly and see if the noise is gone.


Afraid so, it's not only obvious with a stethoscope while running but also just turning the dynamo by hand on or off the engine.
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Kelsham



Joined: 18 Jan 2009
Posts: 349
Location: Llandrindod Wells Powys

PostPosted: Thu Apr 25, 2013 3:56 pm    Post subject: Reply with quote

The bearing damaged whilst fitting, Big hammer?

Kels.
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Thu Apr 25, 2013 7:30 pm    Post subject: Reply with quote

Kelsham wrote:
The bearing damaged whilst fitting, Big hammer?

Kels.


Pushed in slowly and carefully using the vice, not a very tight fit but not rattling round loose either. Of course if it does eventually turn out to be the bearing heaven only knows what the quality was like to begin with, but seeing as I could only find one lonely ebay seller who did rebuild kits at all - rather than an old dynamo with a coat of cheap black paint or £££'s for an alternator conversion like everyone else wants to sell... Rolling Eyes
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DM



Joined: 21 Dec 2008
Posts: 212
Location: North Cornwall

PostPosted: Thu Apr 25, 2013 10:59 pm    Post subject: Reply with quote

Glad to see someone answered about bedding in brushes.

If you get stuck for parts I still have an account with a supplier of starter, alternator, dynamo's and dynastarter components.

They still list lucas dynamo bit's, armatures, field coils, brushes and even end plates.
I'd have to check with them but they used to supply remanufactured dynamo's at a sensible price.
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Sun Apr 28, 2013 1:38 am    Post subject: Reply with quote

Not much to report, haven't had time or inclination to have it off the engine yet. Did manage to strip the spare dynamo to find that I needn't have bothered rebuilding the other one as it's a recon that doesn't appear to have been used at all, all it needed was a drop of oil for the rear bearing and a little grease worked into the front and it should be good to go. Had a go at bedding in the brushes on that one, put it all back together and found it makes pretty much the same noise as the first one... It could in fact be that there's nowt wrong with the one on engine after all. My ears are very sensitive - probably comes of being incredibly short sighted - and it wouldn't be the first time I've been caught out by noises other folks just don't notice Confused Think I'll just give it time to develop and see what if anything happens Smile
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