The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: BSA500 on 17.04. 2015 16:51

Title: ATD sleeve bolt
Post by: BSA500 on 17.04. 2015 16:51
Just got a new ATD sleeve bolt(thanks beezermac)but how do you get the old one out??
Title: Re: ATD sleeve bolt
Post by: wilko on 18.04. 2015 02:12
I'd like to know too?
Title: Re: ATD sleeve bolt
Post by: groily on 18.04. 2015 08:23
In theory, just keep unscrewing, using a bit of pulling power on the bolt after it's gone through the 'slack' section.
A left hand thread half way up the thing (it's a raised thread of larger dia than the shaft itself) should engage and then it will come out, usually stiffly. Some do, some are a pig, some refuse point-blank.
It wasn't the brightest plan to use the first thread of the raised left-handed bit to act as the shoulder to extract the thing, as it means the first turn of the thread is often messed up and won't easily engage. It's a design that offends against all sensible principle.
A more robust, but fiddly, plan is to make a centre bolt with a solid internal shoulder - but that means having to braze or weld (or otherwise lock, very stoutly) a nut onto the top of the shaft on the 'outside' after having fitted the thing into the ATD from the inside. (Downside is it then isn't removable at all if welded, but for all that I've made a few that way when in despair.)
Horrible things!
Cheers, Bill
Title: Re: ATD sleeve bolt
Post by: beezermacc on 18.04. 2015 21:59
I wouldn't advise trying to remove the centre nut unless it is completely unserviceable. I spent a bit of time on this in the workshop today and I believe I am approaching a solution. It is rare for the centre nut to unscrew ( clockwise because it is left hand thread)  because the start of the thread will be mashed because it has been used as an extractor. If you try to pull on it at the same time as unscrewing you may get it to start but you are likely to completely wreck the threads in the tube and on the outside of the nut. So, assuming the nut won't screw out in the reverse as it was assembled when new, and assuming you have stripped the ATD down to its basic parts there are two ways I can find of removing the old nut. One, very crude,.....! Saw the tube and nut in half (like chopping a cucumber) , saw the head off the nut, remove the bits of nut and weld the tube back together again, clean the tube off (inside and out) on the lathe. I know..., sounds terrible, but I've done it and it works! Obviously you need to secure the tube straight as you weld.  Two, a bit more sophisticated.... Fit the head of the nut in a lathe and put a 7mm drill in the tailstock, use the drill to centre the nut, tighten the chuck. Use ever increasing drills up to 11.5 mm and drill right through the nut. Be very careful as the nut is slightly waisted under the head and an 11.5mm drill is likely to break out at that point. This leaves the wall of the nut so thin you can remove it with a sharp punch. I was also tempted to put a junior hacksaw blade through it, along the length, but this would damage the taper on the end of the tube, maybe not so much that it would matter. In the end I didn't need to as I was able to break the wall with a punch. Inevitably you will need to clean the threads of the tube with the correct left hand tap (I have one but can't remember the size. I'm in the house, the tap is in the workshop!). When drilling the centre of the nut out you could also use a boring bar to avoid the problem of breaking the drill out of the waisted part of the nut. Fortunately new nuts are available. Groily's idea of supplying a nut with a plain shoulder sounds interesting but I can't figure out how to fit it because the shoulder needs to be bigger than the narrow end of the taper, so it can't be fitted through the taper end of the tube. I'd be interested to hear how this has been achieved as it is worth pursuing.
Title: Re: ATD sleeve bolt
Post by: RichardL on 19.04. 2015 02:57
So, piece of cake, right ?;)
Title: Re: ATD sleeve bolt
Post by: beezermacc on 19.04. 2015 08:29
So, piece of cake, right ?;)

Yeh, but not very nice cake, better leave it on the plate!
Title: Re: ATD sleeve bolt
Post by: groily on 19.04. 2015 12:03
Awful cake as we all agree!
I'll have a look at how I've made them with a shoulder on the inside Beezermacc and report back. I think I have got one, or half of one, lying about somewhere  . . . . It's not a straight replica and requires more than just the bolt  . . . .  I have used up nearly all of an old stock of - would you believe - worn Riley Nine cam followers I had lying around - to remake the centre pillars of ATDs, which I bore to work with a square-shouldered centre bolt which will pass through from the inside and then has a hew brazed atop. Yup, a lot of messing about with flames and heat, and a lot of measuring and some fine dimensional stuff to make the ATD's outer half a good press fit on the centre tube. Plus some taper turning just to add some fun. And absolutely NOT a good use of quite a lot of time!
I remain amazed that Lucas, whom I think rather more highly of than many people, went about this particular item the way that they did. It's just not a proper way of doing things and I'm surprised whoever drew up the design got away with it as other options would not, I'd have thought, been much pricier. Let alone that the factory made hundreds of thousands of the little darling!
Title: Re: ATD sleeve bolt
Post by: BSA500 on 19.04. 2015 14:06
So basically I have a bolt I can't use( I don't have anything like the time or equipment -or if I am really honest the skill  :! ). I will just have to tidy up the nut I do have.
Title: Re: ATD sleeve bolt
Post by: groily on 19.04. 2015 16:09
If this works (and for what it's worth anyway!) some pix of outer half of an ATD with solid shoulder inside (left in the pix) and a Lucas one (right in the pix), with the last of some old cam followers I've used used for making centre pillars.
Original Lucas 'top' part is press-fitted; inside the pillar on the left is a now-captive bolt, with threaded hex brazed on after fitting. Taper machined into bottom of replacement pillar, various registers replicated near-enough for retaining collar on inner end, and for fitting arm on the top.
Tube has to be thick-enough walled obviously to provide taper and shoulder.
This one was a prototype and came out 1mm short, but works and will never fail to auto-extract.
Lucas centre bolt's raised left-hand thread as shown in 3rd pic is k-nackered as they so often are, but does still go in and out just.
Downside of the home-made job is the bolt won't come out without sawing the head off. Upside is the thing is bullet-proof provided the press-fit for the arm is good (dab of weld would be better maybe, but didn't want to distort anything as my welding is a bit farmyard, even with the Mig). Cheers, Bill