[SEL] Crankshaft extending

[David Rotigel]

Damn Curt, You are not usually that far off!
	Dave

On Sep 12, 2007, at 4:18 PM, Curt wrote:

> 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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