Author Topic: Crankcase repairs & rear QD hub question  (Read 1014 times)

Offline te_52A7

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Crankcase repairs & rear QD hub question
« on: 30.08. 2010 00:02 »
Hi guys, the resto is still progressing but have come across a few speedbumps. The first (and probably the biggest concern) is the drive side case has a chip out of it right where the crankshaft bearing is pressed into. It is about 1-1.5 cm long so maybe it is about 1/10 of the total circumference. it is on the top inside edge. Also the remaining case lip surrounding the bearing has been peened about 30 times to prevent the bearing outer race from spinning (i presume).  My first question is can this be repaired to a suitable strength for this critical location. I thought being on the top it might be OK?, I have searched hi and lo and haven't really found a definitive answer on this. Has anyone had a similiar repair done and how successfull was it, and if so is there anyone in Australia that can be recomended. The main reason I'm looking to repair instead of replace is that the cases and frame are a 52 Star twin (with HC stamped as well just below the eng #) and I would prefer to keep them as an item (also avoiding the eng # complications for registration/ insurance, etc). There has also been a repair done on what was obviously a crack on the rear flange that sticks out aft (where the trans shaft goes through). It is about half way between the eng case and the hole for the trans shaft. It looks like it has been done quite a while ago and appears to be holding OK. Do these two together make it not worthwhile??
The next question is related to the rear hub, 52 plunger quick disconnect type. I have removed the spokes/ rim and have cleaned the hub up in preparation for repaint and have noticed some movement between the L & R halves of the hub. It looks like there is an inner sleeve that has been riveted to the two halves to make a whole and that there is some wear on the rivets. This allows aprox some small movement (maybe .25mm but enough to be easily seen by eye and feel). is this acceptable, does the movement get stopped when all the spokes are in and tightened. I certainly didn't notice any when the wheel was together (but I wasn't looking for it either), it was only apparent after the cleaning. Or can the rivets be drilled out and replaced somehow.  So hopefully amongst the pooled wisdom out there somebody has come across either of these challenges.........and has a solution/ answer ........Cheers    Todd

Online Brian

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Re: Crankcase repairs & rear QD hub question
« Reply #1 on: 30.08. 2010 00:25 »
Hi Todd.

First the rear wheel, thats a common problem. You can re-rivet it or weld the two halfs together or find a replacement hub.

With the cases can you put up a photo of the damaged area so we can get a better idea of just how bad the damage is or isnt. I can understand you wanting to keep the cases and most things can be repaired, it boils down to how difficult the repair will be and how costly but if these are the original cases for your frame then its worth the effort to repair them.

Offline tombeau

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Re: Crankcase repairs & rear QD hub question
« Reply #2 on: 30.08. 2010 07:31 »
SRM Engineering offer a kit to repair the hub. Check out their website.

Offline iansoady

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Re: Crankcase repairs & rear QD hub question
« Reply #3 on: 30.08. 2010 10:00 »
Like others say, it depends how bad the bearing housing is. Lots of Velo singles have a problem with the drive side main bearing housing and these can be reclaimed with a "top hat" machined component pressed into the crankcase after machining out an appropriate recess. Not sure whether anyone has done this with a BSA twin though - it depends how much meat is left around the housing. It may also be possible to build up with TIG weld then remachine. In either case you need a good machine shop with experience in this type of repair.

As someone has peened it it sounds as though the bearing has been spinning.
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Re: Crankcase repairs & rear QD hub question
« Reply #4 on: 30.08. 2010 11:00 »
G'day Todd,
                    as Brian said a photo would help greatly. If it were mine I'd bore it out and make a shrink fit sleeve then bore it to size. About 2mm wall thickness sleeve with about 2 thou " interference fit. Most GOOD engine reconditioners could do it.
 If I went the weld up way I'd set it up in the lathe and dial off the original bore, then weld insitu and re-bore the hole. Both methods with a 1 1/2 to 2 thou crush on the outer bearing.
 If the other repair seems to be holding leave it be. There is very little stress on that part and is supported by the outer cover.
 Too bad I just sold my 1936 Colchester lathe that could swing it.
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Offline te_52A7

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Re: Crankcase repairs & rear QD hub question
« Reply #5 on: 30.08. 2010 23:04 »
Thanks for the replies, I gotta say that I'm relieved by the replies. Didn't even consider a sleeve option but that sounds relatively simple and effective, and probably less riskier than welding. I am away with work at present but will post a photo on my return. There is a great engineer here in Toowoomba I have used to reband my rear sprocket and make up some other bushes,so I will take it to him and see what he says. I will post up the outcome.  The wheel I will also tackle on my return.....Thanks again guys for the advice....cheers   Todd