[SEL] Crankshaft extending

[Curt]

George,
I'd need to correct the temperature range as I remembered incorrectly. 
400 to 450°F is sufficient for 4340 material.
Curt

Curt wrote:
> George,
> The vast majority of crankshafts are made of 4340 material. What you 
> describe would work but perhaps is overly complicated. since you are 
> only trying to accomplish crankshaft extension you aren't trying to get 
> it so exact that it needs to line up dead true with another bearing for 
> example. You want it straight enough to accommodate the flat belt pulley.
> Have you considered putting a full chamfer on the end of the crankshaft 
> and on the end of the extending piece, and then clamping the two 
> together using a good piece of angle iron. I'd have to look it up in the 
> welding books but I think the proper preheat temp for 4340 is around 
> 800° F. Then tack weld, continue preheat, and then work around as you 
> fill the chamfer in until you are filled in.
>
> Another derivation would be to use a larger diameter piece steel for the 
> extending piece. Also make it an inch or two longer than you will need. 
> Chamfer on the end you will be welding and go ahead and add a center to 
> the other end. Nest and clamp the crankshaft and extension as above to a 
> piece of angle, but you'll have to add some shims under the crankshaft 
> to match the diameter of the larger extension piece. Preheat and weld. 
> Once cooled you can chuck and use the new center on the tail stock end. 
> Then you can turn the diameter of the extension and the weld even with 
> the rest of the crankshaft. A little hand filing and blending and you'll 
> be the only one who knows the story the crankshaft could tell of the 
> night Lorena Bobbitt got a hold of it.
> Curt
> *
> *
> Best, George wrote:
>   
>> I've got an engine where someone took a hacksaw and shortened the
>> crankshaft for some reason.  Maybe it stuck out too far and they didn't
>> want to use a belt pulley on it.
>>
>> I'm wondering if it is feasible to extend the crankshaft, or should I
>> find replacement crankshaft instead?
>>
>> What I'm thinking is that I could put the crankshaft on the lathe and
>> true up where they cut the shaft.  Then center bore the shaft.
>> Make an extention piece with a stub to fit the bored hole in the
>> crankshaft.
>> Press the extention piece in.
>> Weld the seam.
>> Then clean up the joint in the lathe.
>>
>> Does this sound like a feasible way to fix the crankshaft?
>>
>>
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