auto advance mystery

[Klaus]

Hello Hans,

I have messured 3 ATD on one tapper. 6.7mm, 6.37mm and  6.04 mm.
Sorry I have no other armature to compare.


cheers Klaus

[duTch]

 I agree with above- Hans unless I missed something, you haven't said that you were actually using this magneto and/or ATD before....is either a new addition ?

 To me, that ATD definitely looks too close to the bearing, given the outer ring, casing and a seal still needs to be in there

 **edit I'd also send a photo of it to Dave Lindsey

[Happy Hans]

The magneto I send to him was not complete, only the housing and the armature,with other small parts existed, so that he had to complete it. The magneto was not in action at the bike before because the bike is built from bits and the mag was part of them. Also the A/R Unit was not used before from me, I bought it on fleebay. The two components were not been used together before. If I would have an idea which of the two parts is incorrect that would be a prospect. I think sending Mr. Lindsley this picture is also a chance.

Thanks guys.

[Happy Hans]

Yes he did rewind the armature, and like I can see it looks the same as the original one I send him because it has the same scratches I noticed on it before.

[duTch]

 hmmm, then it seems to be a bad situation. I guess you didn't try it for fit before sending it away? That would be ideal....If you told D.L what machine it would be used for, maybe he incorrectly assumed it had been in use...if you didn't tell, he should maybe have asked....I wonder how many different armatures there are that would fit K2F - I guess the gurus can answer that....previous owner/seller may or may not have clues .....

 Maybe as mentioned earlier, the taper may have been ground.....   in that case, if all else fails, you could try what I did and make a conical shim and so how that goes; not ideal but worked for me for ~ 2,000 miles until the maggie died a natural death anyway....I'll dig the cone out, I know it's not far away...

  Stay Happy Hans   

[groily]

Hmm.
 
Klaus' measurements seem dead right to me, on several armatures and with several ATDs. Always 6mm plus by way of gap.

The tapered section on a K2F (yours has the 18mm bearing at the drive end by the look of it, and if it is a 1954 it should) will be - in round numbers -
*15mm long from narrow end at base of thread to shoulder at the fatter end
*tapr diameter goes from 11mm to 14mm - again in round numbers.
*The threaded section is 11mm long.
*The overall length from face of the brass end cheek to the end of the threaded section is 38.5mm give or take.
(Earlier 15mm armatures are probably exactly the same, but haven't got one to hand to measure.)
If those dimensions are incorrect, then there's a problem with the armature.

I don't think Dave Lindsley has 'done anything' - he'll have worked on what he was presented with and the coil and parts will 99.9% for sure be the ones you sent. He'd have said if not, and there'd have been a discussion about the need for replacement parts.
Had he had the flea-bay ATD you wanted to use with the magneto, he'd probably have been able to point out the problem. If by any chance he did a trial fit of a known-good ATD, I wonder if that threw up any problem? If he did and there wasn't, then the ATD would be the likely area of difficulty. Worth asking the Q maybe.

So, either the armature has a problem with its dimensions or with the state of its taper - I still can't quite figure out why it protrudes only 19mm from the case per your original photo as that is definitely short compared to what I see on mags here - or the centre bolt on the ATD has an enlarged female taper. A small oversize goes a long way on these things as has been said. New bolts are available though.

There will be a solution, there always is, but it needs some careful comparisons with known good bits to get the diagnosis right.

Don't suppose you have a plain pinion or sprocket  you could offer up to the armature to see if that goes on and sits about right? I'm thinking that something might have fitted OK, as otherwise it would have been difficult to conduct dynamic tests on the repaired magneto. You can use a couple of nuts to drive the things anti-clockwise, but most people use tapered drive pieces I think.

[Swarfcut]

     Hans,  I can measure 7mm between the ATD  and the bearing inner race. My ATD grips with just hand pressure and the ATD taper is 12.9mm wide at collar. You should aim for something like these dimensions.

  Lots of good stuff for you to check, looks as if you have ended up with the worst of the worst. The magneto shaft /body dimension  needs sorting out.

  I reckon Mr Lindsley will have done a reasonable job, but has missed out on a bit of customer goodwill and confidence. I would continue to try and reach some agreeable compromise or dialogue with him.

   Thanks groily for your precision and sound reasoning.

   Swarfy.

[Happy Hans]

Thanks for the effort,

I measured the taper diameter of the armature, same as groily, goes from 11mm to 14mm.
The whole length of the threaded end of the shaft to brass end cheek also 38,5mm.
the length of the thread section of the taper also 11 mm.

ATD width at collar the same than swarfis 12,9 mm.

I suppose its not the armature, my suspision ist that the ATD is the part which is wrong. First I want to check the fitting with another ATD, for comparision, I try to organize that.

In this case its not Mr. Lindsleys fault because he hadn't the faulty ATD to recognize the problem.

[KiwiGF]

I’ve only just noticed this thread, it seems the required measurements have been provided but if there is anything else needing measuring let me know, I’ve “collected” a fair bit of mag stuff by buying my two basket cases!

[duTch]

 Well worded groily- I was doing my best to diplomatically *not* apportion blame or responsibility, but you did so much better...

 The tapers on the bits I have (1 Mag unit, 1ATD, 1 man. gear) all equate to 7/16" small end / 1/2" large end, over 7/16" taper length- much the same as above

[coater87]

 If the taper was fooled with just a little bit (internal or external) the fit could be ridiculously far off from new.

 Probably one of the hardest manual machining jobs there is, cut a matching set of internal and external tapers. Now add the difficulty of getting the whole show to be an exact, certain length?  the difficulty just goes up and up.

 Everything is pretty much a one shot, and to get 80% contact you might not get too many seating opportunities with course grinding paste.

 Lee

[groily]

Ain't that the truth Lee. OK with decent programmable machinery and a toolpost grinder maybe (but don't have either and probably couldn't work it if I did)  . . . but by hand and eye and  trial and error - seriously difficult work!

Luckily, in this case, a decent female component should be findable.

Hans: If you can't find one send a PM (or shout in public on here) and I'll lend you one, with an armature drive end piece to play with too if you want, so you can do some more measuring. Then at least you'll know what you are dealing with.

[Happy Hans]

Thanks groily for that kind offer,

but Klaus will do that for me, isn't that nice? I hope that the ATD is the guilty part. It would be harder to find and shurely much more expensive if I need another armature.

Regards, Hans.

[groily]

It is nice Hans, very nice. A10/A7 BSA people are good folk!
Let us know how you get on  . . . it will be good to hear the verdict.

[Happy Hans]

Hello,

just a short update. Meanwhile Klaus kindly checked the parts. The result was a mixture of a worn armature shaft and a worn ATD inner conus. So we decided to remove so much material from the ATD conus flange, and the inner surface of the fibre gear as needed that the ATD could move freely on the armature , in mounted state. The ATD has now a tight fit on the shaft and works as it should.
I have not run the engine yet, and I hope the fibre gear of the ATD is still strong enough to resist the power at running condition.

Hans.