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Bent Crank shaft

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  • #16
    Lawnmowers are really nice to reverse engineer the bend - just look at what blade took the spanking and at how far out on it's radius - hit same blade/holder on opposite side same distance... it's your best odds for going hack and sometimes hack "gits er done"

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    • #17
      I am not sure who makes (made) it but I have seen a tool which bolts to the crankcase and uses two push screws to straighten the crankshaft and a dial indicator to monitor the results. I have straightened crankshafts in the engine with a sledge hammer and also with a press and V blocks out of the engine. The sledge hammer works best if you support the crankshaft near the crankcase on the edge of an anvil or something similar. I am sure it happens but I have never known a straightened crankshaft to break later although I have seen broken crankshafts. I think crankshafts are actually fairly ductile.
      Don Young

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      • #18
        as AK boomer said , you have the perfect staightening jig ,the engine case. i save old cracked cases for this very reason, you dont want to damage a good case by hammering on it, might damage brearing surfaces, so find scoung,or buy at scrap yard busted engine cases. you should be able to get them for scrap prices.or use a hardwood 2x4 with bearing size hole drilled in it, and clamp 2x4 in vise insert bent crank and hammer away.
        FORD BEATING JAP CRAP SINCE 1941!! CAROLYN JONES(1930-1983 actress)may this lady never be forgotten.

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        • #19
          Originally posted by Don Young View Post
          I am not sure who makes (made) it but I have seen a tool which bolts to the crankcase and uses two push screws to straighten the crankshaft and a dial indicator to monitor the results.
          Hey, that sounds like me!

          I read some forum threads about bent lawn mower cranks and saw some photos showing gadgets you can buy for straightening bent crankshafts. I liked the idea of supporting the crankshaft near the main bearing while applying a controllable straightening force.

          The nice thing about having time, lathe, mill and pile of steel is making stuff like this, right?

          The fixture bolts to some existing tapped holes in the crankcase.

          The long hex head bolt is wound in to touch the shaft.

          The socket head capscrew is then wound in to straighten the shaft.

          I put a hole in the fixture for the dial indicator plunger, this means I could check run-out easily.

          I didn't post earlier, because the OP's crankshaft bend sounds more complicated (internal?) than the one I fixed. My shaft still turned freely in the main bearings, the bend was outside the engine.

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          Last edited by Peter S; 12-09-2013, 05:45 AM.

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          • #20
            Very clever! Much more professional than the long pipe and sledgehammer.... But perhaps not as much fun!
            http://pauleschoen.com/pix/PM08_P76_P54.png
            Paul , P S Technology, Inc. and MrTibbs
            USA Maryland 21030

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            • #21
              I agree. Very nice setup

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              • #22
                Foley-Belsaw did sell a fixture to fix bent crankshafts. They no longer have it in the catalog. Just the pointer and it is on backorder. Your fixture is well done .

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                • #23
                  Originally posted by kbertoson View Post
                  Foley-Belsaw did sell a fixture to fix bent crankshafts. They no longer have it in the catalog. Just the pointer and it is on backorder. Your fixture is well done .
                  Foley-Belsaw is no longer in the tool business- they're a correspondence school.

                  Foley-United sell turf equipment sharpening machinery ( we sell their products), but not crank-straightening tools (probably because of the insurance problem). They have limited support off the older Belsaw stuff.

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