The Matchless has been having a problem charging for a while and I've changed or played about with everything, but to no avail. Yesterday I found the problem, the dynamo sprocket has come loose somehow? The nut that holds it is still tight, so something sinister is going on. The problem I've got now is that I can't undo or tighten the nut holding the sprocket on as the sprocket is loose. How do I stop the dynamo spinning round, so that I can get the nut off?

It sound like your woodruff key has sheared Bill and of course the spanner flats on the back of the sprocket are useless now. Is there a faint hope that you could grip the sprocket with mole grips and strain it sideways enough the hold the shaft while you undo the nut. Otherwise it's out with the nut splitter if it's not too recessed. Ron

email (option): ronpier@talk21.com

It's a damn good suggestion Ron, but I've tried it until I'm blue in the face and it won't budge! I assume the woodruff key has gone, but there is no sign of it anywhere inside the case, which is odd? I'll have a go with the nut splitter, but there's not much room to get it in. To make a bad day worse, I opened the toolbox to get some tools out and everything was covered in rust! No drain hole in the bottom of the toolbox, water gets in but can't get out. At least that's easily remedied.

Last resort drill down the side of the nut then try splitting it, drill the biggest hole you can without touching the threads. I know its hard as the nut in in a recess in the sprocket. Its most likly chewed the taper on the dynamo anyway but its a last resort. If you take the end cover off you could but hand resistance on the communator but there is nothing you can hold with a spanner.
Good Luck

Tim W

email (option): t.j.walker@btinternet.com

Bill I expect the small key has sheared. Leaving half in the sprocket and half on the shaft? Ron

email (option): ronpier@talk21.com

An old tried & tested method is to shock it. get a nice long spanner that fits well, with the dynamo held wrapped in cloth or something in a vice so the spanner sticks out away from the bench. get a 2ft length of wood (3x2 ish) hold the nut end of the spanner in place with a gloved hand & take a serious swing at the very end of the spanner like you were killing a rat.
I use this method all the time & its the basic principal of the rattle guns garages use on wheel nuts. by the time the shaft knows what's happening the nut will be lose.

Air whizzer!!!

email (option): davmax@ntlworld.com

Can you not take out the long bolts that hold the dynamo together, you can at least hold the armature in your hand.

Got it!! Thanks for all the suggestions and help, but as a last resort I took a small electrical screwdriver and ground the shaft down so that it was square. I then jammed it down the side of the nut into the gap left by the missing woodruff key and bent it over until it snapped off, thus replacing the missing key. The problem is now that I've finally got the sprocket off, as expected, the woodruff key has taken a big chunk out of the Dynamo shaft on its way out. What would cause this to happen? I always make sure the chains are the correct tension and not too tight and the Dynamo has only done about 400 miles.

I do like my Matchless's! But I've always said that this is a daft idea, with two chains hurtling around with only a minute gap between them. Some years ago I loaned a G3L to a mate, and the chains must have come together and snapped the dynamo chain, which actually bent the end of the armature. Ron

email (option): ronpier@talk21.com

I think the whole Dynamo set up on the Matchless is the work of a mad man!! You can't get it out one way as the clutch chain case and so on are in the way and you can't get it out the other way as some berk has put the Magneto chain case in the way!!

Sorry Bill, but your post made me laugh again, I tried very hard, to get the Matchless dynamo to work, even with everything N.O.S. it would not last longer then 6 months! so forget about the dynamo, and just use a battery and some LED bulbs, no aggrevation, and problems anymore, just charge the battery every 2-3 months.

My 2 p's,

Lex

email (option): welbike@welbike.net

Matchli... ...With so many problems and being such a fiddle to work on I sometimes wonder what all the enthusiasm is about....Ian

email (option): ian@wright52.plus.com

I also had a problem with the inside of my tool box rusting up Ian, I suppose if I had bought a BSA I would have noticed this much sooner as I'd have been opening it more often?

I doubt it...it's hard to get at the fastener when you're riding,which you usually are on an M20 .As it happens my first bike was a Matchless... ...Ian

email (option): ian@wright52.plus.com

Now come on, this is starting to get nasty! We all know the Matchless is a terrific bike and I'm sure the BSA is fine if you're not in a hurry.

Yep...I guess the M20 is a bit like getting at the Matchless dynamo...'fine if your not in a hurry'...Ian

email (option): ian@wright52.plus.com

Touche Ian! You've got me there, the whole Dynamo thing on the Matchless is beyond stupid!! You get the idea that it's one of those things that was fine on paper?

I think the way this is going Lex may be onto something, I've replaced the bulbs with LED's and the rest of the system seems so temperamental, why bother??

I seem to remember something about changing the dynamo for an E3H from a magdyno set up being used if you machine the gear out, it wasn't a straight swap, but at least you get a proper bearing, not just the one in the bakelite cover

email (option): davmax@ntlworld.com

Ian Wright

Matchli... ...With so many problems and being such a fiddle to work on I sometimes wonder what all the enthusiasm is about....Ian

email (option): welbike@welbike.net

Well i don't have a problem with the Matchless system even though it is an awkward system.The taper system is used on many dynamos and also magnetos.The keyway is used as means of holding the shaft from turning for initial tightening. The taper is the main clamping force. Possibly the taper wasn't fully home and tightened in the first place.Or the nut ran out of thread before being fully pulled in om the taper. Remember there is no keyways on maggys?

I don't know what's happened Douglas. The old Dynamo I traded in was also chewed up around the key way, so I was very mindful of this possible problem when I put the new one in and made sure it was all as it should be. It's a bit of a pain, but these things happen with old machinery, I suppose you have to take the rough with the smooth?

In that case Bill. I would want to scrutinise the sprocket. Ron

email (option): ronpier@talk21.com

Hmmm, very interesting point Ron. I've got a couple of other sprockets somewhere, I'll dig them out and do some comparing. Cheers

Sometimes when you ride a thoroughbred race horse of a Matchless you have to accept that it we need more time and care spent on it to enjoy the thrill of the ride. Just one ride on a thoroughbred and you will never want to ride an old nag of an M20 cart horse again. Hate mail expected. JT

email (option): Tinley@btinternet.com

I don't think you'll be disappointed, there is bound to be plenty of hate mail on the way John!

I've been told by a local engineer that he can weld a new woodruff key into the old slot, thus filling up the divot made by the exit of the old key and making sure it won't come out again. This sounds a little dodgey to me? What do you think?

Of course Bill...As the old saying goes..'A good pedigree still won't sell a lame horse'... ...Ian

email (option): ian@wright52.plus.com

Is that from a BSA sales brochure Ian?

'Brand Loyalty' is a strange thing...Quite why one bike catches your imagination and the next doesn't is puzzling. I like Royal Enfields and have owned numerous examples...but they never seemed to appeal to the majority, despite the fact they were well made and serviceable..It was like it when I was a teenager and it's still like it now.
I've yet to hear a younger rider fiecely defending his Honda or similar either...In the case of modern bikes the phenomena does not seem to be present, the notable exception being Harley Davidson owners...Ian

email (option): ian@wright52.plus.com

That's very true Ian. I bought the Matchless by accident from ebay. It was cheap, so I put a bid on thinking I'd get outbid, but didn't. It could just have easily have been a BSA or an Enfield and then things would be different. I don't think it matters what you ride, as long as you ride it and enjoy it. It's been said many times before that we are not the owners of these historic bikes, just the temporary custodians. One day, (unless we are buried with them!) they will pass on to someone else and hopefully they will carry on the memory of the manufacturers and servicemen who made and used them.

I'm taking mine with me...Ian

email (option): ian@wright52.plus.com

HI Bill,the idea of welding the key into the shaft not only sounds dodgy but
bodgy.I would think that A,the possibility of cleaning up the shaft after welding
would be virtually impossible to get anywhere like a reasonable fit.
B the shaft is probably a carbon steel which will harden,as will the weld and the key itself (EN 6) making it hard to file etc,C the taper is of importance as previously stated,this could distort due to welding on one side,it may also
crack due to heat.
Best bet would be to re-cut a new keyway after cleaning up the damage and lapping the taper to the fresh sprocket.this could prove non cost effective unless the
contractor has the appropriate woodruff cutter already in house .
A feather key of similar size could be used instead but then the set up to machine this becomes more complicated (time = cost).
Also a fresh keyway may weaken the shaft as there is already one present.
Sorry to be a pessimist but this is my job and how i view repairs that land on my doorstep.
A fresh armature and sprocket may be the most cost effective way to go,but that is only my oppinion (no pun intended)
hope this helps,cheers Rick

email (option): richardholt@rocketmail.com

My thoughts exactly Rick, I'm no expert, but the whole idea just seemed a bit unrealistic and simplistic to me. I also wondered about what the heat of welding could do to the insides of the armature? I hate the idea of throwing a perfectly good armature away just because of a lump taken out of the key way, but it's probably the best bet in the end?

I agree with Ricks comments..another armature is the way to go. (and perhaps sprocket) Also you need to work out what set of circumstances caused the failure or you are likely to repeat it. You noted in your original posting that the nut was still tight but the sprocket was turning...Was the sprocket too narrow and even when tightened the nut wasn't doing anything? That would effectively cancel out the locking effect of the taper and put the entire load onto the key......Ian

email (option): ian@wright52.plus.com

Loctite the key the cog and the nut

email (option): cooperbaumber@yahoo.com

Just a question, why does a Matchless dynamo have a key and a taper yet a BSA twin only has a taper, never had a sprocket slip.

I've been using a magneto sprocket with no keyway on my matchy genny for 8 years now, because i didn't have the original.Loktite is the key!

And a magdyno dynamo shaft is parallel with either one or two keys!!...Ian

email (option): Ian Wright

Instead of rendering machines unsafe, destroying parts and moaning about poor design, why don’t some G3 and G3L owners use the correct parts to secure their Dynamo sprockets?

These parts are listed in parts books and were used pre-war, war and post war until alternators took over. They are illustrated in post war parts books.

STD-725 Sprocket, (has slots for STD-164 Locking Washer)

STD-572 Key, (Woodruff, prevents armature rotating while nut is tightened)

STD-164 Locking Washer, (has internal multihex to fit over nut, has external tangs to lock into sprocket slots)

STD-708 Lockring, (circlip, used to retain 164 to 611 nut)

STD-611 Nut, (special, deep nut with specially positioned groove for 708 circlip)

STD-10 Washer, (flatwasher, goes into sprocket under nut, important for correct assembled height of 164)

When above parts, in good condition, are correctly assembled to a good armature taper, no loctite is necessary (or desirable) for security of sprocket.

First do no harm.

email (option): n.gentner@bigpond.com

Thanks for the advice Neale, but I was using all the correct parts as per the parts book and locktite as well (belts and braces) and this has still happened. I've used exactly the same set up on my AJS and had no problem, just one of those things I suppose?

No! Its not "just one of those things"
Your description indicates that the failure was caused by either defective parts or incorrect assembly.

I find it contrary to established physics that the entire Key can simultaneously take a divot out of shaft and then escape and disappear completely, unless the taper-fit was run loose for an extended period, i.e. relative movement caused the key to gradually wear/fret the shaft away, rather than suddenly carving a chunk out.

In my experience, for a key to suddenly take a divot out of a shaft, the sprocket and therefore the nut must be very loose. (this can occur catastrophically during massive overload, but would also damage the AMC nut-locking parts)

In my experience a slightly loose nut results in a separated taper-fit and then the key shears.

Additional to previously mentioned causal defects to taper of shaft and sprocket:

The shape and "fit" of the Woodruff key is vital.
The worst scenario is a key which is too high and thus "bottoms" in the sprocket slot, thus the taper-fit never comes into play because the sprocket is riding on the key and only contacting the shaft on the opposite side.
Failure is ensured.

Regardless, careful analysis will identify your problem.

email (option): n.gentner@bigpond.com

email (option): ronpier@talk21.com

I agree with Neale, lots of problems are caused with woodruff keys that are too high. You sould be able to see daylight over the top of the key when the sprocket is fully tight. Why not just start again and buy a new armature and check your sprocket. The sprocket is a lot harder than the armature shaft so it has a good chance of being OK. If not I may have a good one if I have a look. Your dynamo should have the strap bolted to it, the strap fits between the engine plates and holds the dynamo in the correct position so the chain is automatically in line so the two chains have no chance of contact. These dynamos are a pain to get out so why not do it right first time.

Tim W

email (option): t.j.walker@btinternet.com

Tim, I'm not sure of your statement about the strap. As I remember from both mine, you can slide the dynamo about in the engine plates thus allowing you to align the chain to your own satisfaction before tightening the strap. I guess if the chains become slack with the small gap between them, any sideways whip can bring them together.
Ron

email (option): ronpier@talk21.com

Well I'm very sorry to Tim and Neale, but I assure you that all the right parts were present and there was Locktite everywhere there should have been Locktite. I've rebuilt loads of cars and bikes over the years and I flatter myself to think that I am now fully capable of slotting a Woodruff Key into a slot and winding the correct nuts and washers onto the shaft! If you'd like to come round and inspect the damage or oversee my future builds, just let me know and we'll sort something out!

Ignoring your misplaced sarcasm Bill,
But please tell all those less competent than yourself what caused your failure?

email (option): n.gentner@bigpond.com

lincoln bill stop faffing about dob a spot of weld on it and i bet it wouldnt be the first time that has happened

email (option): roger.beck@node6.com

Hi Ron, My old WD G3L had strap acroos the dyanmo to locate it at the correct position between the engine plates, The engine plates had a slot in them at the top so you could rotate the dynamo till the strap lined up with the slot in the plates and the dynamo could be pulled out. I thought this was standard but it could have been a good mod.

Tim W

email (option): t.j.walker@btinternet.com

Tim that does sound like an idea and I wondered what the slot in the plates was for. I guess they just got omitted over the years or maybe removed to give you that extra freedom of dynamo position. ron

email (option): ronpier@talk21.com

I have to say I agree with Neales view of this problem..It can't have 'all been correct' and still have a had problem. That statement defies logic on the assumption the basic design is OK...Accepting that the design is OK, if it was all good parts and was perfectly assembled there would have been nothing wrong with it, and it wouldn't have broken a key or damaged a shaft.
But it did...so it must have been defective in some way. Failure to identify the defect might just lead to a repetition of the same fault with similar results.....Ian

email (option): ian@wright52.plus.com

The strap screwed to the Matchless dynamo was a standard fitting. One identifier for these dynamos at the jumbles is the two tapped holes in the body that the screws go in to...Knowing Matchless though they might not always have been like that...it might have been introduced on the third version of the dynamo .(there's at least three versions of everything I believe)..Ian

email (option): ian@wright52.plus.com

I must say I'm very surprised at the aggressive tone some of you have adopted with this one? Neale especially is either calling me stupid or accusing me of telling lies? It's not as though the thing failed in the first five minutes, it worked splendidly for a good while. I don't have anything more to say on this other than the shaft has failed for some reason, the woodruff key and other components were all in place as they were supposed to be and I have the item here, you do not, so what the hell gives you the right to lay the law down like this and say what should or shouldn't happen?

I must say I'm very surprised at the aggressive tone some of you have adopted with this one? Neale especially is either calling me stupid or accusing me of telling lies? It's not as though the thing failed in the first five minutes, it worked splendidly for a good while. I don't have anything more to say on this other than the shaft has failed for some reason, the woodruff key and other components were all in place as they were supposed to be and I have the item here, you do not, so what the hell gives you the right to lay the law down like this and say what should or shouldn't happen?

I must say I'm very surprised at the aggressive tone some of you have adopted with this one? Neale especially is either calling me stupid or accusing me of telling lies? It's not as though the thing failed in the first five minutes, it worked splendidly for a good while. I don't have anything more to say on this other than the shaft has failed for some reason, the woodruff key and other components were all in place as they were supposed to be and I have the item here, you do not, so what the hell gives you the right to lay the law down like this and say what should or shouldn't happen?

I must say I'm very surprised at the aggressive tone some of you have adopted with this one? Neale especially is either calling me stupid or accusing me of telling lies? It's not as though the thing failed in the first five minutes, it worked splendidly for a good while. I don't have anything more to say on this other than the shaft has failed for some reason, the woodruff key and other components were all in place as they were supposed to be and I have the item here, you do not, so what the hell gives you the right to lay the law down like this and say what should or shouldn't happen?

I must say I'm very surprised at the aggressive tone some of you have adopted with this one? Neale especially is either calling me stupid or accusing me of telling lies? It's not as though the thing failed in the first five minutes, it worked splendidly for a good while. I don't have anything more to say on this other than the shaft has failed for some reason, the woodruff key and other components were all in place as they were supposed to be and I have the item here, you do not, so what the hell gives you the right to lay the law down like this and say what should or shouldn't happen?

I can't speak for Neale but would point out my tone was not intended to be 'aggressive'..As to the failure and the reasons for it it is in your own interest to determine what went wrong and contributors here are bound to express their opinions on the subject...I am merely pointing out that it strikes me as illogical to say it was correctly assembled with all good parts when a failure of that nature, in that type of assembly, indicates that may not have been the case...
One thing is certain...every failure has a cause and though this one may not be obvious it is no different..and as I have already said, in my opinion it is best to determine what that cause was to avoid a repetition.....Ian

email (option): ian@wright52.plus.com

Quite so Ian, I didn't mean you at all, your comments have been as friendly, constructive and knowledgeable as always. I agree entirely with you that unless I can find out why this has happened, it could well happen again. All I can say is that the Dynamo came from the source and was put together using the same parts and techniques as the Dynamo on my AJS and that is still purring away with no problems? I can understand why certain folks are a bit mystified by this catastrophic failure, I'm bloody well mystified by it myself! All I can say is that this is what has happened to me in this case and it just gets my back up a little when people try to tell me differently.

I think the hieght of the key mentioned in a previous post may well have been a factor..easily missed but having a big effect on the function of the taper as a locking mechanism...Also, you mentioned previously that the nut was tight but the sprocket was turning...so was the sprocket too narrow?..
No doubt you will be checking everything carefully (in a paranoid fashion) when it comes to reassembly... ...Ian

email (option): ian@wright52.plus.com

Hi Bill,just reading a post recently placed concerning the dynamo chain contacting the primary chain,could this be a contributing factor? I would have thought if this were the case it would just make a racket though.
cheers Rick

email (option): richardholt@rocketmail.com

Hi Bill, my thoughts were only ment as constructive to help you out, hope i haven't affended you, as you I have been putting pre war british bikes together for over 25 years and as new to this forum i only wish to pass some of my learnings on. I also may not be able to spell too well but i know i can screw a vintage bike together well, and to me that's what matters. But regarding loctite i would only use it for retaing slack bearings. A good taper, spring washer, chain alingment, and a good fitting key WILL solve all your problems.

Regards
Tim W

email (option): t.j.walker@btinternet.com

email (option): n.gentner@bigpond.com

When fitting the cog back on the shaft put key in slot and put something like blue loctite or thin paint fit the cog then remove it if it removes all traces of this it is to tight. enginers blue is the correct thing to use.

email (option): cooperbaumber@yahoo.com

bill i am sorry if was my funny comment about welding the cog it was only mean as a light hearted joke

email (option): roger.beck@node6.com

I think the amount of discussion on this one has to be put down to the fact that it just seems to be such an odd thing to happen. I've now tipped the old oil and found the offending Woodruff Key, or the remains of it anyway! It's quite badly chewed up, as you'd imagine, so I can't measure it and we'll never know if it was the correct sized one or not? All I can say is that it was the key in the old Dynamo before I traded it in and it seemed to fit just fine when I reassembled it and had been fine on the old Dynamo for God knows how long. I always keep an eye on the chain tensions and the chain seemed well within tolerances when I stripped it all down. It's either got to be a faulty shaft on the Dynamo (unlikely) or the wrong sized key (probable, but can't be proved either way). Just as a reminder, my original question wasn't about any of this at all, it was actually how to get a nut off a Dynamo when you can't stop the armature spinning. Surely we've covered this one now haven't we, I know I'm fed up with it?

No..we could go on for days yet Bill... ...Ian

email (option): ian@wright52.plus.com