Hi,
Thought I would share this, I looked on the forum and cannot find anyone else having the issue.
I recently put a rotor on a A65 before the stator, turned the rotor by hand to check if there was any play in the key and keyway. The rotor turned a few degrees either way on its centre. I had another spare rotor which I checked and that was the same, so a new rotor on its way (expensive bit of metal). If the rotor is off the bike clamping the rotor centre in a vice and turning the rotor works, as the centre is bigger than the rotor.
I searched the internet and found a Triumph service sheet which addresses the issue and a few horror stories of rotors coming apart. I also read of a bodge of putting large star washers either side of the rotor locking the centre to the rotor, which maybe worth looking for.
I didn't have a tell-tale knock as described on the service sheet, although another clue could be the strobe timing not as expected.
Best wishes...
From pics of this type of rotor, it looks as though the centre with the key way cut in it is probably a press fit in the body of the rotor. If the original rotor is now scrap, it would be interesting to see if the centre can be pressed out. If it can, I would have thought a coating of suitable Loctite retaining fluid would then hold it firmly in position once the centre was pressed back in?
Hi Spaceman,
I have investigated and the centre cannot be pressed out, the zinc is cast on and the centre is made from hexagon bar. I believe the later rotors have the centres welded to the arms connected to the magnetic section which stops the possibility of loosening.
I guess you could melt all of the zinc off, weld the arms to the hexagon then the magnetic section on the arm ends. Wouldn't be something I'm going do.
Best wishes...
I assume this pic shows the construction and the hexagonal bar? At face value, I would be surprised that the centre could come loose or is the assumption that the magnets are starting to break up? In looking into this, I read a suggestion that the welded centre was just a marketing ploy by Lucas and didn't actually exist?
Hi,
Worth a look at a loose centre, both of mine are exactly the same:
https://www.youtube.com/watch?v=Ge9NUoBz3W4
Advertised as welded rotor, note the part number has changed:
https://www.feked.com/alternator-rotor-magnet-genuine-lucas-rm20-rotor-lu-54202299.html
Best wishes...
:) :) :) :)
I used a large punch and 'piened'? mine into the join and stopped the movement. Seems OK, Ill let you know.
Mike 8) 8) 8) 8)
Hi Mike,
Did you hear the rotor knocking when the bike was running? Or did you notice an issue when building the engine?
Best wishes...
Dave Smith mentions in his RR Unit single manual that 'The rotor has one main failing which is that the steel centre come loose in the surrounding magnets and aluminium..'
However, it can be 'resuscitated' but will need a lathe and some epoxy resin and turned to remove the rotor centre.
If you want to take this route and haven't got the manual, PM me with your address and I'll send you the full details
Below are some photos of a 1970 rotor, casting number 54212006. I thought it was scrap so melted off the casting material to see what was beneath.
First photo shows the heavy punching to stop the rocking.
Second photo same rotor same side with most of the casting material removed. When heating it to melt off the casting some oil seeped out from between casting material ane the pole pieces and the casting and the centre.
Third photo show reverse side, note the steel brace between centre and 4 of the pole pieces.
Last one shows the rotor and a shining mark where a magnet has been rocking on the hexagonal centre.
Hi Editor,
Thanks for your offer, I now feel Julian finding oil in the rotor internals would make me wary of any repair using epoxy. Coincidently the new rotor arrived in the post today, need some good weather to fit it.
Best wishes...
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Hi Bess.
I found it whilst doing rebuild. So no idea what my success or otherwise may be. If I have to purchase a new one where would it be a sound idea to try. I'm in no rush and in truth I'm never going to ride it just would like to get it right.
Mike 8) 8) 8) 8)
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I've just looked at the pics and wonder why the cover is actually there. Is it just to keep it dry or is it to stop rotation
, or???
Mike 8) 8) 8) 8)
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To continue from wrongly pressed button. If punching is unsuccessful I might try drilling in a couple of places and using roll pins.
Mike 8) 8) 8) 8)
Some more photos of the rotor bits. My concerns would be if the magnets and laminated pole pieces moved when the rotor heats in use.
Hi Mike,
I believe magnets are brittle and if drilled for a roll pin may cause more problems.
Best wishes...
:) :) :) :)
Thanks for the replies.
So I am in a nothing to lose situ, So I think shall strip mine into "scrap" parts and check.
Before I go there would someone answer following, Working outward from the Hex bar centre. Are the "square" bits fixed in any way..
Continuing outward how are the magnetic shoes attached. Are they simply held in place by the cover or are they fixed in place then the cover mounted around them.
What are the magnetic shoes made of.
Ultimately if I can fix the various bits in place do I really need the cover. I cant see why I should.
In the end it may be an exercise in futility, but I guess as stated nothing to lose.
Mike 8) 8) 8) 8)
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I have decided to give the "strip and weld" idea a go. Lots of things that I dont know about this lump of electrics. Wont be just yet but I'll keep you all up to speed. Boring bit by boring bit. A point comes immediately to mind. I doubt my efforts will be 100% balanced. What guesses about imbalance on such a short moment. I would have thought negligable---however.
Mike 8) 8) 8) 8)
Hi Mike,
I considered welding the components, but after researching magnet welding changed my mind, its worth a quick google.
Here's where I bought my new rotor: https://www.feked.com/alternator-rotor-magnet-genuine-lucas-rm20-rotor-lu-54202299.html
Best wishes...
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Hi Bess. Thanks for that.
I agree that it will be "a challenge". I have been giving this more than its fair share of thought and shall experiment with a different idea first. If you wish to get rid of your old one I would be interested cos I dont wish to remove mine at the moment. I'm more interested in keping it all in one piece to get the registration done.
I am thinking more in the Silver Solder route. Yes I saw that one at FEKED.
Mike 8) 8) 8)
Hi Mike,
You are quite welcome to a rotor, they are nearly 1kg in weight. Do you want me to parcel it up and send it?
Best wishes...
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Hi Bess.
Yes please. Let me know postage and I'll send it to you.
Question are they solid Zinc other than the obvious innards.
Mike 8) 8) 8)
Hi Mike,
They are zinc wrapped, you can take your pick.
Best wishes...
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Hi Bess.
Thanks again. Either is good so I'll take the lighter one if thats OK by you. I'll PM my address
Mike 8) 8) 8) 8)
Hi Mike,
Its in the post £3.49, can you put the money in an air ambulance charity box?
Regards...
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Hi Bess.
Thanks again. Yes to the Air Ambulance. Easy for me a friend is a fund raiser for them
Mike 8) 8) 8) 8)
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Hi Bess.
The rotor was delivered this morning. Thanks.
I've done a bit of mejurin and the loose centre boss does not run true at 90^ to the perifery but it's only 0015"at most, so I guess thats wear. Impossible to tell how many times it has "shuttled" to and fro.. Anyway thats just a comment.
My thoughts are this can be done more simply than welding so I have another idea I'll try first.
I'll keep you up to speed here.
Thanks agen
Mike 8) 8) 8) 8)
Hi Mike,
Good to hear its arrived safely. The history of that rotor is that I bought an engine bottom end and the owner thought the main bearing/bush had issues. On strip down it was the rotor keyway which was oversized. On reflection I wondered if the rotor wear was the cause of the keyway distortion.
Hope you find use for the rotor and maybe come away with a fix.
Best wishes...
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Hi Gents.
As promised I would keep you psides with my efforts to tighten an A65 alternator. My first intention was to strip it and weld. That was a serious over kill.
The progress has really been mush better than expected and really relatively simple.
Hoefully my pics should be self explanatory but I shall enlarge on it should it be necessary.
I would point out that at this stage i Have only taken out any shuttle movement. It should cure any rotational move ment if not I have a couple of thoughts on that.
Mike 8) 8) 8) 8)
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Hope this is a better image
Mike 8) 8) 8) 8)
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Hi Again.
Julian sent me a knackered and stripped rotor to play with. Photo should be attached That I shall deal with in due course. I am attaching the pics.
Having also carried out various checks I have come up with( bear in mind I am only a user not in any field an expert) what I consider to be probabilities.
1. Assuming the front sprocket is fully "home" Once the Alternator centre boss is in place and torqued up it cannot possibly move laterally on the shaft.
2. Internally the alternator components are not fixed it place but only held by the magnets and the zinc??? casing.
3. Rotary movement between the magnets/casing is impossible-for the square magnets to
move on a square base it would need to increase the diameter of the whole item.
4. The only possible area of movement is the magnets sliding sideways, that is possible. They could also twist an extremely small amount probably no more than 001".
5. My thoughts are--Possibly the only part/s that is moving is the skirts of the casing.
6. Any rotational movement must be the boss on the shaft, likely as a result of inacurate broaching of the keyway.
7. Repairs? forget welding. If you use an electrical method you risk murdering the magnets. If you use a torch you risk melting the whole issue. So I would suggest the method of repair I have used in previous post is probably the only viable.
8. There are several ways of achieving that repair. At a later date I shall consider putting a plate on back and front and bolting it through with something like 3mm bolts/screws. Providing available clearance between alternator and front sprocket.
As you will see from pics the "shoes" are not solid but consist of about20 "blades" held by a cetral long rivet. The rotor that is already stripped I am going to attempt to weld/braze together and use without a casing(luck requested). Not for a while---busy.
So thats it in a nut shell. Phew Any Q's just ask
Mike 8) 8) 8) 8)
:) :) :) Try again with pics
If you use heat in repairing one of these rotors, I am sure it will demagnetise the magnets to some degree. This must have happened during the original manufacturing process and I assume Lucas would have needed to re-magnetise the magnets afterwards. Using epoxy to make a repair would obviously avoid this problem!
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I agree with that and is a consideration for the "rebuild" of the stripped rotor. I shall not even consider any welding or other heat on a built up rotor just the large washers and screws/bolts/ self tappers as per previous
Mike 8) 8) 8)
Hi,
Some failures:
Hi,
I think I will replace rather than repair,
Best wishes...
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Hi Bess
I intend to run the one that I've repaired on next machine rebuild. However I fully understand why you would decide not to repair.
Take acre and thanks again
Mike 8) 8) 8)