Thread: true and weld a crank ?
09-08-2007, 06:02 AM #1
true and weld a crank ?
We all hear of "true and welded crank" but what is really involved ? I know the pins get tig welded but what is the "truing" ? does the crank warp when welded or is it just checked for proper indexing then welded? I ask because I just bought a new oem crank and we have 3 syncrowaves ,so welding is not a problem. I prefer to do all my own work.thanks in advance.
09-08-2007, 07:00 AM #2
Crank is set up in V-blocks and checked for accuracy. Crank is just pressed together and can be out +/- 2 degrees.
Only a few people I trust that can move these around and get to 1/2 degree or less tolerance. Lowell, TJ, Crankworks, Falicon.
09-08-2007, 09:49 AM #3
Indexed, as you put it, then welded to lock it all in place... some members do have their T&W'd crank rechecked on the next build.. IMO good insurance
09-08-2007, 07:59 PM #4
Truing is measured in thousands of an inch... not degrees
Crank Phasing is measured in degrees.
To phase a crank, special jigs are needed for every particular crank model. New or rebuilt cranks are assembled in these jigs and unless these jigs are off, the phasing is usually spot on... not the truing though,
two different things.
Not saying a crank can't go out of phase, they do.
All I am saying is a trued and welded crank does not get phased unless it is disassembled and pressed back together in an assembly jig, this is not included in most shops, truing & welding job.
On new or rebuilt cranks done by a reputable shop, the phasing has to be right or their jig is wrong. Welding up a new or rebuilt crank locks the phasing in place. With a good weld job the crank pins can't rotate to change the phasing but they can move back and forth slightly to change crank run-out/truing even after welding if a crank is knocked about.
see this thread
Last edited by allcool; 09-08-2007 at 09:38 PM.
09-09-2007, 06:33 AM #5
Way Cool All Cool...good reply...I got all the equipment im gonna give it a try...whats the worst that can happen anyway....blow the crank out the bottom of the ski and sink while in the middle of water moccosin creek thanks for the reply. do you happen to know which ss rod is used ? 308,309,356???
09-10-2007, 09:31 AM #6
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