Heart Transplant

grandpaul

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I'd install a junk crank (I think Dave might have one, now) and junk set of bearings (perhaps those, too), THEN weld up the hole. Crank should hold the affair in alignment.
 

grandpaul

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Don't know the composition of the original cases, but should the filler rod material be the same?
 
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The original material would have been selected on the basis of its end properties and how well it cast, the best filler rod would give the same end properties and also weld well which may mean a different alloy is best, there is no need for it to cast well. Be guided by your welder and what he thinks will work.
 

Fast Eddie

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It’s surprising what can be done IF the welder knows his stuff.

I wanted to preserve the original cases in my TSS when they virtuall broke in half. I took them to Nigel Hall Smith (RIP), who did well known cases strengthening mods to Triumphs and he welded them up and strengthened them brilliantly.

He had specific jigs to hold and clamp them, and more importantly, he REALLY knew what he was doing.

Conversely, I had ‘the best welder in the county’ weld up some cases long ago, the welds were beautiful, text book quality. The cases however, whilst not bad at first glance, were unusable.

So, you don’t only look for a good welder... you need someone who’s done this before and REALLY knows what they’re doing.

I read that you’re sending yours to Mr Comstock Dave, so I think they’ll be in good hands.
 
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Do you know how it was welded, particularly how warping was overcome? When aluminum castings are welded, a lot of residual stresses are built in due to the rapid cooling of the material. These may have to be releaved by post-weld heat treatment, but I doubt PWHT will prevent defomations. I tried welding a cracked slider once. The slider ovalised severely and now graces my workshop. I am happy for you if you can make the crankcase fit for service again.

-Knut

As far as I am aware they were tig'ed, the holes were enlarged and repair pieces were milled from alloy and "V" grooved into place prior to Welding. the guy that did the prep work for me really went to a lot of trouble to get things done properly.
He even went as far as making a new piece (the bit that juts out on the case for the middle front barrel stud) as mine had broken in the past.
There is still a little bit of machining left to do but its pretty much done.
Pics in my rebuild thread when they are going back together
 

grandpaul

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For the fork legs, I would stack a stanchion tube with 18" of used, clean, lower bushings and insert it fully before any welding. Should keep things in shape.

[edit] Add a large, hardened washer (OD just under the fork leg ID) at the bottom of the stanchion before stacking up the bushings, with a length of heavy allthread rod nutted in place, to extract the bushings out after welding, in case they bind up. Also, "stroke" the stanchion every few seconds while welding, to ensure they DON'T bind up.
 

grandpaul

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Considering brand new sliders are $200 I’m not sure I’d bother asking someone to weld one up.
I've got a local welder that has done all my aluminum welding for many years, he'd charge about $50 - $60, so I'd definitely be willing to have a try on my own personal bike.
 
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For the fork legs, I would stack a stanchion tube with 18" of used, clean, lower bushings and insert it fully before any welding. Should keep things in shape.

[edit] Add a large, hardened washer (OD just under the fork leg ID) at the bottom of the stanchion before stacking up the bushings, with a length of heavy allthread rod nutted in place, to extract the bushings out after welding, in case they bind up. Also, "stroke" the stanchion every few seconds while welding, to ensure they DON'T bind up.

Pretty obvious you've never done any welding ..
 
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I'd install a junk crank (I think Dave might have one, now) and junk set of bearings (perhaps those, too), THEN weld up the hole. Crank should hold the affair in alignment.

Unfortunately, a dummy crankshaft will not prevent warpage at the case mating surfaces. Jigs and fixtures may help to reduce distortion (residual stresses are still there), and an extremely skilled welder may perform balance weldments so as to counteract distortion. Still, I'd be very surprised to learn that patching up the hole shown above does not require the mating flange to be machined. Amateur welders may be tempted to overcome distortion and join case halves by brute force (i.e., tensioning the case bolts) - this can only lead to shaft misalignment and cracking cases later on.

https://www.esabna.com/us/en/education/blog/distortion-in-aluminum-weldments.cfm

-Knut
 
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You should. Please report back! :)

You never know, sometime there is some guy who has been welding longer than we've been alive and is an artist with a welder. I'm never eager to dismiss someone until I've seen their work.
 
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Before I spent any money welding I would find out with a dye test
how many cracks are coming away from that huge hole. To blow a hole that size it had to have effects all around it????
 
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Before I spent any money welding I would find out with a dye test
how many cracks are coming away from that huge hole. To blow a hole that size it had to have effects all around it????
I would say so too,
mine had a couple of extra cracks in it
 
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Sorry, I thought you were kidding about fixing it. I'm pretty sure if we could see this event happen on the spintron your decision would be easy??
 

baz

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It's surprising what can be repaired and to what level
Also it depends on how the cases will be used after a repair IE if your going racing it's probably not good, even standard original cases are not up to that!
But for pottering about /sunday rides it's probably fine
Luckily there are still crankcases available for replacement
I wonder if anyone would question whether or not to repair if the engine was a Vincent?
 

baz

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When I was a 17year old clueless apprentice I was given a long stroke bsa a7 engine
It had thrown a rod and had a similar size hole in the drive side crankcase
My solution to this was to clean up the ragged hole with a file then I bashed a bit of tin to the same shape of the crankcase covering the hole
One of the apprentice jobs was to melt down scrap aluminium into holding down blocks for our kaltenbach metal saws
So with a thick pair of gloves I held the inverted crankcase in my hands whilst my mate poured the molten aluminium into the case filling up the hole as I swilled the alu into the hole trying to keep the thickness the same
When it cooled I bolted the cases back together and tigged it up
I'd love to say it all worked perfectly but I just don't know as I couldn't get hold of crank/rods or barrel for that motor so I never got to run it
I sold it a few years later
 
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