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Crankshaft keway repair -also posted at PM

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  • Crankshaft keway repair -also posted at PM

    I have a friend with a 5hp Salsbury scooter that has a damaged keyway on the crankshaft where the flywheel attaches. It has "slopped out" one of the sides that is parallel with the crankshaft. I was thinking of making a copper woodruff key, clamping it in place and tig welding up along the side - while the engine is still assembled.

    These engines are too valuable for me to screw up; they are ridiculously priced nowadays (think $2,000). What say ye, all you wise old salts?

  • #2
    Cut a new keyway on the other side, all else will fail.
    Is the shaft hardened? If yes, welding up will completely ruin the shaft.


    Nick

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    • #3
      Now knowing what the crank metal is I don't think I would weld on it. If you do weld it you need to remove the crank to do the welding.

      As Nick said it may be better to cut a new keyway but you would have to cut a corresponding keyway in the flywheel. Then there is the weakening of the crank with the extra keyway.

      Personally I would try to find out what metal the crank is and if I welded it I would put all of the crank except the end I was welding under water. If you weld it make the copper key narrower than needed and machine it out to size.
      It's only ink and paper

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      • #4
        Cranks are not hard at all, they machine very easy, if not too easy.

        Jim Caudill;s Idea will work.

        His copper key core idea has worked for me too but I used aluminum clamped on the back of a big oval hole in steel, welded it closed with steel and there was almost nothing to grind on.

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        • #5
          I have done exactly what you are proposing on two Subaru engine cranks. I did it in place, in the car. The woodruff key slot for the harmonic balancer was messed up like you describe. Got over 4 years out of the first one, and it was still running when I sold it. We would see it driving around town for a year or two after that. The second one lasted 2+ years then we sold the car due to tranny issues. Engine was still going strong.

          I don't know anything about Salsbury scooters, so no advice on that from me. I was in a "little to lose" situation, and it worked for me.

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          • #6
            I won't weld on an assembled engine. We always disassemble them before welding anything on them. Electricity takes the path of least resistance, People are always of the opinion that if the ground is right next to where you are welding it will go there and no place else. I have seen it do otherwise, a number of times. Last thing you want, is the current wandering up and down your crank and arcing over to various rod or main journal bearings. That will wipe the engine out in short order. 3-5 hours of disassembly/assembly Vs $2,000.00. Remember, no good deed goes unpunished.

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            • #7
              crank

              If the flywheel is for the ignition you need to get it right or it probably won't run right don't ask me how I know. The key way is your timing.

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              • #8
                The important thing here is to find out for sure what the crank is made of, if it is cast iron then DON'T weld it with a steel rod use a Nickel rod for iron castings such as Ni99 or Ni55. The very high Nickel Ni99 is the easiest to machine if that is going to be required but it is quite soft and while the lower Nickel rods are somewhat harder some are all but un-machinable. If it turns out that it is steel then a mild steel filler would be a good choice, welding on cast iron with any kind of carbon steel is a recipe for disaster since the weld will become so hard grinding will be about the only practical way to cut it and the likelihood of cracking will increase dramatically.



                Also brazing with a Bronze rod would be another option but whatever method you decide on take steps to prevent warping from the heat.

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                • #9
                  Originally posted by ADGO_Racing
                  I won't weld on an assembled engine. We always disassemble them before welding anything on them. Electricity takes the path of least resistance, People are always of the opinion that if the ground is right next to where you are welding it will go there and no place else. I have seen it do otherwise, a number of times. Last thing you want, is the current wandering up and down your crank and arcing over to various rod or main journal bearings. That will wipe the engine out in short order. 3-5 hours of disassembly/assembly Vs $2,000.00. Remember, no good deed goes unpunished.



                  I could not agree with you more on that! I know of one case in particular where a finial drive bearing and a metal seal were destroyed in a D10 bulldozer because a guy grounded to the track and welded on the frame. Grounding to an engine case and then arc welding on the crank is scary to even think about! I can just picture the tiny arcs going on between the crank surfaces and bearings!

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                  • #10
                    Local machine shop used to get woodruff keys made from carbon (maybe graphite) somewhere, weld them in, chip it out, machine the OD and have a perfect new keyway.

                    OR...
                    Friend had a loose harmonic balancer on a Detroit Diesel over the road tractor. Options were remove the crank and rebuild; weld it on (it couldn't hurt the crank any worse than it was already; or the one he chose - glue it on with Catapillar brand epoxy. It had been done before and it worked for him.

                    Go for it.

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                    • #11
                      Originally posted by ADGO_Racing
                      People are always of the opinion that if the ground is right next to where you are welding it will go there and no place else.
                      I'm one of them.

                      Comment


                      • #12
                        Originally posted by GKman
                        Local machine shop used to get woodruff keys made from carbon (maybe graphite) somewhere, weld them in, chip it out, machine the OD and have a perfect new keyway.

                        I saw something similar done once and although it was not a keyway it was a guide slot in a shaft that was fairly close tolerance. In this case the guy took an old generator brush and ground/filed/sanded it to size and shape then used it in the same manner you are describing, made a perfect fit.

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                        • #13
                          Originally posted by GKman
                          I'm one of them.


                          Only if it is the same part you are welding on! Any other part may or may not work without damage, depends entirely on how well the other part is grounded to the one being welded. It does not matter how far away the ground clamp is, within reason of course, as long as it is attached to the same piece of metal being welded but it could be an inch away and cause serious damage if the current has to flow between two poorly connected parts-such as a bearing and a crankshaft separated by a film of oil? If the current has to flow through bearings to reach ground then damage is very likely.

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                          • #14
                            Even if the ground clamp is on the same part, it is still possible to have problems. Not as likely, but it still happens. I have seen enough arc damage to other associated parts that I won't weld something while it is assembled. I do it right or someone else can do the damage. One think that really pisses me off is having to fix stuff that I screwed up, and should have known better. This is one of those situations where I know better.

                            What about just machining a new larger keyway, in place of the old one? Then broach a larger keyway in the hub? Key doesn't necessarily need to be a woodruff key either. Job becomes a little more complicated if it is a tapered fit, but still an alternative fix.

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                            • #15
                              Originally posted by GKman
                              Local machine shop used to get woodruff keys made from carbon (maybe graphite) somewhere, weld them in, chip it out, machine the OD and have a perfect new keyway.

                              Go for it.
                              Yes,carbon is your friend.I've done oil holes in cranks and chevy blocks that were missing half a starter mount hole.
                              I just need one more tool,just one!

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