The BSA A7-A10 Forum

Technical (topic titles must be descriptive) => A7 & A10 Engine => Topic started by: Simon59 on 24.03. 2018 18:44

Title: Can't get my magneto off - help!
Post by: Simon59 on 24.03. 2018 18:44
I’m trying to remove my magneto, (1955 A10) which has the automatic advance inside the drive pinion. I know that the nut is supposed to act as an extractor, to get the gear off its tapered shaft, but it just turns and turns. I’ve tried everything I know – replacing the three magneto nuts (including the long one) to give the extractor something to pull against, putting a lever behind the nut whilst turning to encourage it onto its extractor threads and tightening it back in and trying again. In your view, do I now need a puller to get the gear off? There doesn’t look like there’s much room to get one in… Any hints and tips much appreciated.   
Title: Re: Can't get my magneto off - help!
Post by: edboy on 24.03. 2018 20:56
hi,
the tapers arnt generally that tight. i would remove both springs, extract the lht bolt and use 2 hefty screwdivers or prise bars to lever behind the metal centre where the bob weights are. and bobs you uncle.
Title: Re: Can't get my magneto off - help!
Post by: chaterlea25 on 25.03. 2018 22:56
Hi
In a situation like this I have removed the three nuts, loosen the  centre bolt one or two threads
push the mag and  ATD back against timing case and smack the centre bolt head

No liability accepted with this "method"  *fight* *pull hair out*

John
Title: Re: Can't get my magneto off - help!
Post by: muskrat on 26.03. 2018 08:11
I was thinking that as well but have only had to resort to that with a manual advance type.
Cheers
Title: Re: Can't get my magneto off - help!
Post by: Simon59 on 26.03. 2018 19:51
Thanks guys, I know I can rely on you for some possible solutions.

After more turning and levering, the nut came out, and as you can see, the external threads are all but gone.

So I might screw it back in and give it a whack, sounds like it might work. Maybe a tap or two first?

The other thing I thought of was to buy a new nut, screw it in and then unwind it to (hopefully) release the gear.

One way or another, I need my magneto off!

Title: Re: Can't get my magneto off - help!
Post by: groily on 27.03. 2018 09:10
Pretty well done to get it out I reckon. As you can see, a really lousy design, relying on the first turn of raised lh thread to force the thing off the taper. Should have been obvious to one of the meanest intelligence what was going to happen down the road.

I think it would be worth filing off the remains of the raised thread and screwing the thing back onto the armature, and with the mag nuts off (as they are) giving a sharp tap to see if the mag will back off the gear, as you suggest.
I don't think a new nut would do it, as the distance between the lh thread and the rh thread on the mag isn't big enough for you to get the whole of the lh part 'inside' to do its extraction thing (because you'll be up against the rh thread too soon).

The quite good news is that usually the lh thread in the atd survives the failure of the sleeve nut, and the better news is that the nuts are available. Andrew at Priory Mags has them I think, for Beesas and for Triumphs, which have slightly different dimensions.

It really goes to show what a pure c**p design this particular bit is. It's so obviously plain daft. It could have been done using a square shoulder for extraction, but it would have required the head of the bolt to be welded/brazed/otherwise pinned on after making the rest of the thing so it could be fitted, and that would have added ninepence to the cost I suppose. The maker saves a few cents and the owner gets a headache he'd have happily paid to avoid  . . . . it is ever thus!
Title: Re: Can't get my magneto off - help!
Post by: Rex on 27.03. 2018 09:28
Be fair Bill, it has taken decades to get to this state!
Title: Re: Can't get my magneto off - help!
Post by: groily on 27.03. 2018 09:44
Tis very true Rex - but they don't all take so long!! Maybe this was a good one!
Title: Re: Can't get my magneto off - help!
Post by: Jim on 09.04. 2018 13:30
A bit of heat often works wonders.
Title: Re: Can't get my magneto off - help!
Post by: BSA_54A10 on 10.04. 2018 11:37
Pretty well done to get it out I reckon. As you can see, a really lousy design, relying on the first turn of raised lh thread to force the thing off the taper. Should have been obvious to one of the meanest intelligence what was going to happen down the road.

I think it would be worth filing off the remains of the raised thread and screwing the thing back onto the armature, and with the mag nuts off (as they are) giving a sharp tap to see if the mag will back off the gear, as you suggest.
I don't think a new nut would do it, as the distance between the lh thread and the rh thread on the mag isn't big enough for you to get the whole of the lh part 'inside' to do its extraction thing (because you'll be up against the rh thread too soon).

The quite good news is that usually the lh thread in the atd survives the failure of the sleeve nut, and the better news is that the nuts are available. Andrew at Priory Mags has them I think, for Beesas and for Triumphs, which have slightly different dimensions.

It really goes to show what a pure c**p design this particular bit is. It's so obviously plain daft. It could have been done using a square shoulder for extraction, but it would have required the head of the bolt to be welded/brazed/otherwise pinned on after making the rest of the thing so it could be fitted, and that would have added ninepence to the cost I suppose. The maker saves a few cents and the owner gets a headache he'd have happily paid to avoid  . . . . it is ever thus!

Well kindly inform us what other design is good for 60 years ?
Don't see may 60 year old cars around still running their original magnetos.
Unfortunately nothing can be so well designed or made to prevent ham fisted mechanical morons buggering them.
Title: Re: Can't get my magneto off - help!
Post by: groily on 10.04. 2018 12:07
Poor design is poor whether then or now, and there are plenty of examples of both across all eras. Same goes for good design.
Wear and buggering up by people are altogether different. Wear is inevitable, of course, but is accelerated by poor design; ruination by cack-handedness is unfortunate and may or may not be related to design (mostly not).
I stand 100% by my comments on the design of the auto-extract of these ATDs. It is not an engineering design, it is an abomination. The use of the first turn of a left hand thread as a shoulder for extraction from a well-made taper is just plain stupid. It isn't buggering about to undo it the way it was intended to be undone (there being no other way) - they fail because failure was built-in, assured even. Especially annoying as it is perfectly possible to design one of these properly using a proper internal shoulder, capable of lasting as long as you like.
None of us with shedsful of old toys expects to inhabit a wear-free or trouble-free zone - but it is perfectly legit, I reckon, to point out glaring examples of the plain bloody awful. Just as we point out stellar examples of the very good. For the most part, I happen to believe that the things we play with weren't at all bad from either the design or construction point of view - but I shall continue to regard this one particular thing as a classic 'How Not To Make Something', because the fundamental principle is fatally flawed!. Very comfortable agreeing to differ on this particular one!
Title: Re: Can't get my magneto off - help!
Post by: Simon59 on 10.04. 2018 12:56
Just as an update, I've still not managed to get the drive gear off it's taper. I work for a company that specialises in bearings, and we often have to extract them in various states and conditions from shafts of many designs and age. When I explained this non-work problem to one of my experts, he were amazed that such a design was intended to work after the warranty period was over. He was right, it doesn't, at least in my case.

I've tried most things now, from penetrating oil, to heat, to drifts, hammers and various pullers. I'm keeping restrained in the force that I use in case 65 year old metal succumbs to too much brute force.

The engine comes out of the frame next weekend, when I have another pair of hands, with magneto still attached. I plan to take it all to SRM for a strip and inspection so I hope and expect that they will have seen this particular problem before and will have the right tools and techniques to get the b****r off!

All the best, Simon
Title: Re: Can't get my magneto off - help!
Post by: a10gf on 10.04. 2018 14:02
Quote
penetrating oil, to heat, to drifts, hammers and various pullers.
but 'cold' missing from list :0)

Get the mag shaft down to "minus as much as possible", heat the advance center to "max temp without destroying anything". Then a few taps here and there, repeat process until it comes loose.
example https://www.bunnings.co.nz/crc-electrical-freeze-spray-300g-2039_p00648729
Title: Re: Can't get my magneto off - help!
Post by: duTch on 10.04. 2018 19:50

  Dunno if it'll hep, but I had a similar but not bike problem the other week; have a read of this- it surprised me
 https://www.a7a10.net/forum/index.php?topic=12775.0 (https://www.a7a10.net/forum/index.php?topic=12775.0)

 It may or not work for you...

 On another unrelated note, at work we need to periodically wash stuff with a common garden hose, and a site Ive been at has been storing the tap/hose fittings in the frezzer....yesterday I dug 'em to use, out but  plastic spray nozzle was stuck solid. left it on the deck and by the time I came to use it the sun had warmed it and was like nothing ever happened..
Title: Re: Can't get my magneto off - help!
Post by: BSA_54A10 on 12.04. 2018 10:49
Just as an update, I've still not managed to get the drive gear off it's taper. I work for a company that specialises in bearings, and we often have to extract them in various states and conditions from shafts of many designs and age. When I explained this non-work problem to one of my experts, he were amazed that such a design was intended to work after the warranty period was over. He was right, it doesn't, at least in my case.

I've tried most things now, from penetrating oil, to heat, to drifts, hammers and various pullers. I'm keeping restrained in the force that I use in case 65 year old metal succumbs to too much brute force.

The engine comes out of the frame next weekend, when I have another pair of hands, with magneto still attached. I plan to take it all to SRM for a strip and inspection so I hope and expect that they will have seen this particular problem before and will have the right tools and techniques to get the b****r off!

All the best, Simon

Wile we all sympathise with your problems, just because some past moron has used a bolt that should ave been binned does not make the whole idea bad.
It is in fact a very good one, designed so Joe Average can pul it off on the side of the road with nothing more than what is in the tool kit.
Now if you want to bitch about the lack of any means of locking the armature while you tighten the said same sleeve nut yo would have my undivided support or even the lack of a locating peg I might line up behind you.
However an A 10 was my very first bike, back in the days of pressed tin ratchet drivers ( remember those ) and I can not remember ever having a problem other than the armature slipping before the taper locked.
we have just finished going over an A 10 that will be loaned out to guests coming for the BSA National.
In this case it came off beautifully however we could not get it to lock.
The culprit was the C washer that had been extruded into a cone shape by a DPO in the past using impact guns to tighten it up.
The A 10 magneto is a lot easier to get on & off than my M20 one with fixed timing gear.
Title: Re: Can't get my magneto off - help!
Post by: Simon59 on 12.04. 2018 13:23
Thanks, I didn't think of using cold... I have access to some liquid nitrogen here at work, so I might be able to set up some kind of cold finger to cool the shaft and then apply some quick heat to the gear... This is all part of the fun of restoring an old bike of course! *smile*
Title: Re: Can't get my magneto off - help!
Post by: groily on 12.04. 2018 17:34
Don't want to flog a dead horse Bike Beesa, but I don't think it's quite fair to lay the problem at the door of morons using duff bolts. There actually is an inherent flaw.
Even fastidious owners can't tell in advance when the blessed thing is not going to extract the gear- whereupon the bolt can't be got out for examination or replacement. It only takes one very tight fitting taper to wreck the start of the lh thread, and then you're where Simon is. (Even when you have the unit off the machine and on the bench it isn't often that simple to get a damaged bolt out.)
I've got a few damaged ones lying around, which I keep as models for turning up replacements - so it's a problem I've seen a lot more of than I would ever have wished.

The principal of the auto-extract is perfectly fine, elegant and well- recognised, I completely agree. Excellent idea.  It's the detail execution of the particular item that isn't so fine or elegant. My own drives for attaching mags of varying diameters, tapers and threads to bench test equipment all self-extract - but they use proper internal shoulders. They are used a dozen times a day sometimes and they don't fail, even on the big tapers  found on a lot of 4 and 6 cyl mags. They all just need the one 3/8 BSF spanner from any ordinary toolkit, nothing fancy, same as an atd unit.

The number of times Simon's problem arises is too high, I think many would agree. My heart is always in my mouth when taking the things off machines, with that 'will it or won't it' worry. When it will, all well and good and then one can check the thing for condition, replace or whatever; when it won't, it can be a lot of time wasted. My point is not that the concept is bad, it isn't. But nothing will ever persuade me that is a respectable engineering approach to use the first turn of any thread as the load-bearer to get a tightly mating taper apart! 
Title: Re: Can't get my magneto off - help!
Post by: RichardL on 13.04. 2018 23:03
Thanks, I didn't think of using cold... I have access to some liquid nitrogen here at work, so I might be able to set up some kind of cold finger to cool the shaft and then apply some quick heat to the gear... This is all part of the fun of restoring an old bike of course! *smile*

I have a feeling this is not the answer, but readily admit others here may know otherwise. What you have at the taper is two very similar metals (steels of likely similar composition) with near identical rates of thermal expansion and contraction. What you doeth to one you doeth to both. Now for my suggestion of how much force to apply................................................................................................... *dunno* *shh* *conf2* *pull hair out*

Richard L.
Title: Re: Can't get my magneto off - help!
Post by: BSA_54A10 on 16.04. 2018 10:50
Don't want to flog a dead horse Bike Beesa, but I don't think it's quite fair to lay the problem at the door of morons using duff bolts. There actually is an inherent flaw.
Even fastidious owners can't tell in advance when the blessed thing is not going to extract the gear- whereupon the bolt can't be got out for examination or replacement. It only takes one very tight fitting taper to wreck the start of the lh thread, and then you're where Simon is. (Even when you have the unit off the machine and on the bench it isn't often that simple to get a damaged bolt out.)
I've got a few damaged ones lying around, which I keep as models for turning up replacements - so it's a problem I've seen a lot more of than I would ever have wished.

The principal of the auto-extract is perfectly fine, elegant and well- recognised, I completely agree. Excellent idea.  It's the detail execution of the particular item that isn't so fine or elegant. My own drives for attaching mags of varying diameters, tapers and threads to bench test equipment all self-extract - but they use proper internal shoulders. They are used a dozen times a day sometimes and they don't fail, even on the big tapers  found on a lot of 4 and 6 cyl mags. They all just need the one 3/8 BSF spanner from any ordinary toolkit, nothing fancy, same as an atd unit.

The number of times Simon's problem arises is too high, I think many would agree. My heart is always in my mouth when taking the things off machines, with that 'will it or won't it' worry. When it will, all well and good and then one can check the thing for condition, replace or whatever; when it won't, it can be a lot of time wasted. My point is not that the concept is bad, it isn't. But nothing will ever persuade me that is a respectable engineering approach to use the first turn of any thread as the load-bearer to get a tightly mating taper apart!

I can see where you and Simon are coming from, but if a part has worked fine for 60 years then there is not an inherit design flaw in it.
That does not mean that it could not have been done better, but it does mean it was done good enough for the purpose.
Design flaws are the problems you read about in the Agony Aunt columns of PERIOD PUBLICATIONS and the self extracting bolt never rate a mention in the magazines of the 50's 60's 70's & 80's.
It is a bit rude to criticise a design from the 50's 60 years latter when it was not a problem in the day.
Exactly the same applies to stiction between the slides & carb bodies and wet sumping.
None of these were a problem when the bikes were being used within their design parrameters.

I ran 2 A 10's in  very wild youth, one a fire breathing monster 11.5:1 running on a nitro benzene/ petrol mix and the other, a bog standard rat bike A 10 that I hoped would still be where I left it after lectures.
The only problems I had with the magnetos was ripping all the teeth of the drive gear on the Friday night drags along Friendship Rd Port Botany.
On both the bikes, pulling the magneto pinion was a weekly job so if I pulled one off I pulled a thousand off and never ever was there a problem.

Fast forward 30 years and every second idiot has got an impact driver 4 times the size of their IQ and they think it is perfectly fine to rattle a magneto onto a taper or smash it on with a 4lb hammer when all that is needed is a gentle squeeze, and this is where the rot sets in with tapers jambed on way too tight so naturally when some one tries to extract it it is beyond the shear strength of the threads and they strip.

We can do a lot of things a lot better now days and a lot cheaper to boot but remember BSA had to be competatively priced other wise they would have gone the way of Douglass, Vincient and all the other precision engineered motorcycles.
Title: Re: Can't get my magneto off - help!
Post by: groily on 16.04. 2018 15:35
I see where you're coming from too, I really do.
And some have lasted a long time, I know.
And I also agree about people with rattle guns and lump hammers. Unwise.
But I still think using a turn of thread as a lever is a very bad idea and I'm surprised it got from drawing office to production without someone saying 'hang on a minute, this should be done differently'. I bet BSA wouldn't have done it themselves. Mostly, though, I think Lucas were very good at producing value-for-money things that worked as well as anyone could expect.
Vincent used the same sort of ATD almost from its invention, to help get round the inherent problem of an assymetric engine running on an ignition system designed for symmetry (but clockwise drive) - and I've seen first-hand a few of their ATD centre bolts go exactly the same way, without any obvious help from rattle guns and hammers! Velocettes too.
Anyway, they are what they are, and I recognise we have to live with them! I'm living with one on my A at the moment, and another on my 650SS Notrun, so I'm not so very one-eyed about it. I just wish they didn't die so (relatively) often, and weren't such sods to deal with when they do, is all!
And of course I wish the fibre teeth stayed on too - been there more than once over the years.
Title: Re: Can't get my magneto off - help!
Post by: BSA_54A10 on 17.04. 2018 10:10
And there we will have to leave i Bill.
I am off now to pack the van for the run down to the All British
Annoy you all next week