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Quick and dirty dynamo fix needed...
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Bitumen Boy



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

PostPosted: Tue Aug 13, 2019 8:07 pm    Post subject: Quick and dirty dynamo fix needed... Reply with quote

I have a problem with the dynamo on my Herald - nothing exotic, it's a bog standard Lucas C40. Basically the (plastic!) fan pulley has been rattling round loose for a while and has managed to chew up both the woodruff key and the keyway in the armature shaft, both of which are now effectively scrap. The fan pulley, meanwhile, appears like new which I can't honestly say I understand, but there we are.

I need a quick fix for this as I need the car back on the road pronto - the modern is in dock with a non-operative clutch and won't be sorted until Friday at the earliest (and that could be optimistic) while I have work Thursday through to Monday and then only Tuesday off. Work is 20+ miles away in Newport and, while there is a bus, it takes forever and the fares can only be described as larcenous, while the Sunday service is no use at all.

There's been a rattling noise at the front of the engine for a good while now, but I decided to let it develop as I couldn't be sure what it was. Back in the winter the waterpump started leaking and was duly replaced - I thought it might have been that - but the dynamo appeared sound at that point. This last week or two I've become fairly sure the dynamo was the culprit and resolved to swap it for one on the shelf, I figured the front bearing had gone bad. Once the belt tension was released, however, the real source of the noise became apparent.

I have a replacement dynamo, but I don't have a woodruff key or a pulley (it looks OK, but I'm not sure I trust it after this). The chance of getting parts delivered in time is nil, so I'm looking at a bodge to get the car operative again until parts arrive or the modern is sorted. At the moment I'm thinking about bodging the key into the keyway with epoxy putty and fitting the fan likewise before tightening down well with a bit of thread locker for good measure, hopefully given time to cure properly it will hang together until I have alternative transport and can sort it properly. What does everyone on here think?
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Rick
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Joined: 27 Apr 2005
Posts: 22429
Location: UK

PostPosted: Tue Aug 13, 2019 8:58 pm    Post subject: Reply with quote

Alternatively, could you live without charging for a few days and just use a shorter belt (if available), bypassing the dynamo altogether? Even if it meant charging the battery up overnight at home? Would the battery last long enough for your return daily trip? Just a thought, without looking at the engine in front of me I've probably ignored something important that means it wouldn't be feasible.

RJ
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Bitumen Boy



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

PostPosted: Tue Aug 13, 2019 9:53 pm    Post subject: Reply with quote

It's something I've considered, Rick, but I'm not sure I'd have enough charge for the return trip and in any case the logistics of obtaining a shorter belt are nigh-on impossible since the local factors shut down.

At the moment I'm inclined to bodge it for now, try it tomorrow evening and if it fails straight away I know I need to be up early to catch the first bus...
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ukdave2002



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

PostPosted: Tue Aug 13, 2019 10:11 pm    Post subject: Reply with quote

Could you Araldite the pulley on the shaft, and don't tight the belt up too much?..a bodge but sometimes needs must.

Dave
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Bitumen Boy



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

PostPosted: Tue Aug 13, 2019 11:58 pm    Post subject: Reply with quote

That's pretty much what I've ended up doing, only on closer inspection the wear on the shaft and in the pulley bore means something thicker was needed. I've ended up using Milliput, it's meant to be good but time will tell! Had to cut a new woodruff key out of scrap too as I managed to knock the worn original to the floor, never to be seen again - bonus is the one I knocked up by eye seems to fit a little better than the knackered original, but I sure know it's the 13th today! I'll reassemble tomorrow, obviously as little belt tension as possible, and see what happens. Maybe it'll work, maybe it won't - who knows?

At least I don't need to feel bad about bodging a Lucas C40, it's toast anyway with the worn armature shaft so I'll be weighing it in sooner or later.
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Kenham



Joined: 12 Mar 2012
Posts: 209
Location: Kent

PostPosted: Wed Aug 14, 2019 12:24 pm    Post subject: Reply with quote

I would think with your new key and a bit of shim between pulley and shaft it would effect
a good repair to last a long time.
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47Jag



Joined: 26 Jun 2008
Posts: 1480
Location: Bothwell, Scotland

PostPosted: Wed Aug 14, 2019 12:56 pm    Post subject: Reply with quote

BB,

Armature out and in a vice, then try two washers each side of the pulley hub. The inner one will push against the bearing spacer and the outer against the pulley face. Reassemble and get the pulley running reasonably true and tighten up tight. Any minor run out should be absorbed by a not too tight belt.

Art
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Bitumen Boy



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

PostPosted: Wed Aug 14, 2019 3:04 pm    Post subject: Reply with quote

47Jag wrote:
BB,

Armature out and in a vice, then try two washers each side of the pulley hub. The inner one will push against the bearing spacer and the outer against the pulley face. Reassemble and get the pulley running reasonably true and tighten up tight. Any minor run out should be absorbed by a not too tight belt.

Art


I'm not sure that would have worked tbh - the pulley is a chunky plastic (similar to bakelite, it seems) thing and the nut is only just on the shaft now.

Anyhoo, this morning it felt solid so I've refitted the dynamo to the engine with the pulley keyed and puttied in place, and plenty of threadlocker on the nut. I doubt it runs quite true but it's much quieter than it was and seems to be giving a healthy charge with the belt set quite slack - I pulled a new belt from stock as I figured there would be more bearing surface on an unworn belt. A test drive hasn't shown up any issues so I'm inclined to chance it, though I doubt I'll be harassing the slower moderns on the Cwmbran bypass like I usually would... Hopefully it'll last long enough to tide me over.

Meanwhile a new pulley and key is on order to fit to the spare dynamo, and I've found that spare armatures for this model are both readily available and comparitively inexpensive, so this unit may live again albeit in "Trigger's broom" fashion...
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lowdrag



Joined: 10 Apr 2009
Posts: 1585
Location: Le Mans

PostPosted: Wed Aug 14, 2019 7:31 pm    Post subject: Reply with quote

Beg borrow or steal a spare battery and get a shorter fan belt. Seems the only way in the time allotted.
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Kenham



Joined: 12 Mar 2012
Posts: 209
Location: Kent

PostPosted: Wed Aug 14, 2019 8:52 pm    Post subject: Reply with quote

I find it is best if you think it is going to fail every part of the journey as things never go wrong when you think they will, always when you are thinking of something else. I am sure it will get you out of trouble.
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Bitumen Boy



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

PostPosted: Thu Aug 15, 2019 4:56 pm    Post subject: Reply with quote

Well, 40-odd miles later I'm home from work with, touch wood, no issues to report. The dynamo is still quiet and charging well, let's hope that lasts as it needs to do at least one more round trip before the modern is sorted...
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Bitumen Boy



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

PostPosted: Thu Aug 15, 2019 10:16 pm    Post subject: Reply with quote

Incidentally, does anyone know what the thread is on the nose of the armature shaft, as a new nut would be handy?
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Bitumen Boy



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

PostPosted: Fri Aug 16, 2019 5:44 pm    Post subject: Reply with quote

Another 40-odd mile round trip under the wheels, and the bodged dynamo has held together and done its job. Thankfully the modern is now fixed and with luck the spare dynamo should be sorted properly and fitted sometime fairly soon Smile Sometimes it's worth trying a bodge when you're in a hole.
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Bitumen Boy



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

PostPosted: Fri Oct 18, 2019 1:41 pm    Post subject: Reply with quote

An update on this. Been busy at work and so it took me a while to get the spare dynamo sorted and fitted - only put it on the engine last night - but luckily it's quiet and giving a healthy charge.

The bodged one, on the other hand, feels rough in the bearings and is squealing when turned by hand, not enough to be heard over the other noises made by a car of this age, but suggesting all is not well. Probably running with the pulley out of true has done the damage, but as it was going to need extensive work anyway it's no great loss. Parts are available to thoroughly overhaul it, but as the armature shaft is scrap it's probably more economic to overhaul an undamaged s/h example instead. Still, the bodge did the job and got me out of a hole Smile

I did figure out the thread on the shaft nose too, but have now forgotten it... it's written down somewhere in the garage so when I find that I'll post it on here for reference.
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