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Cast Iron

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  • Cast Iron

    ok, i know there must be a hundred cast iron post in here but my search does not locate one. So I will ask.

    I have a very large pulley wheel off an air compressor. Close to 18" in diameter and feels like 40lbs. It has the shaft center broke out, 6 cooling shaped spoke blades broke off also that holds the center piece in place.

    I've been reading and watching vids about cast iron welding, lot of BS out there. Who's right and who is wrong?

    My plan was to Tig using silicone bronze filler (because I have it) on DC, not to puddle the base metal and mix the filler much. It seems to bond but AC and just wetting the base metal seems to work better. I'm tacking the edges then grooving out the cracks, one side, weld then groove the other side and weld. it will take 24 welds.

    Its going to expand and contract no matter the preheat. I don't want to crack everything so preheating much bothers me. I've made 4 welds with and without preheat and have the same results thus far.

    I figure it will go well until the last couple welds, then what? When its finally tied together with no wiggle room I think I will run into big problems.

    Stick welding with nickel rods rubs me the wrong way. To much heat and mixing of metals can't be good. But if I knew what I was doing I wouldn't be asking.

    It belongs to a friend and broke by getting knocked over. I won’t be in the area when and if its ever started up. It will be behind his shop where only wildlife will be in danger but I'm asking him to let me build a guard for it.

    Is there a really great process for a limited shop to do this?

  • #2
    The question really should be "is it feasible?"

    Sounds like what you have is a standard air-compressor sheave, I think you can spend many hours horsing around with this, and when you get it done it still won't be true.

    I'd check Northern, Graingers, etc. for a new one first, then put the word out you are looking for one locally, old air compressors are probably the most common pieces of junk in peoples backyards and behind shops.

    Failing all else, you could probably buy a cheap compressor head from Northern, remove the sheave, throw the compressor head away, install the sheave on your compressor. It'll end up better and cheaper than trying to fix the old one.

    Note that I have run into many that have been repaired in the past -- but only the big, old ones that ran slow rpm, would be hard and/or expensive to replace. These were usually better iron than made today, and ran slow enough that a slight wobble wasn't a problem
    Obviously, I'm just a hack-artist, you shouldn't be listening to anything I say .....


    • #3
      A 40#, out of balance pulley, repaired by a poster who doesn't know what he's doing, sitting on top of a pressure vessel, SOUNDS LIKE AN ACCIDENT LOOKING FOR A PLACE TO HAPPEN.

      Spend the time looking for a replacement vs trying to repair what you have.
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      • #4
        JSFAB "is it feasible?"

        No, finding one is the better option. He said he has tried everywhere. I know thats not true, a person who has tried at least would know the brand. So without going there I understand he just wants to try and fix it.

        I have no other projects going on and I look at this as an interesting something to try. At least its getting me thinking and in the shop. I wish I could just go out and weld on it all day or weld/ work on something between my shift job.

        Maybe my original post made it sound like a problem. Its a challenge and if I fail, I learn, if I succeed, I learn and feel like I've done something. He's just like me, and will spend hours beating and banging to make something work.

        Sundown, If I get it right, does that mean I do know a little something? or just got lucky, LOL

        I'm gona do this even if a replacement appears on the doorstep. Hey I'll start the video this weekend.


        • #5
          Even if it was feasable which it isn't i wouldn't use silicone bronze. Just my thoughts...Bob
          Bob Wright


          • #6
            My $0.02 worth

            If you want to weld it for the challenge go for it and when you get done hang it on your wall where it can be admired. Never, never never install it. It is a cast flywheel as well as a pulley and should never be installed again. If it comes apart in service it can be deadly. Oh yeah and did I say Never! "Never." Best of luck. MM


            • #7
              Not recomending using this pully even if you fix it but for the all depends on the metal in the cast piece you are trying to weld. I have had good results using s/s filler as well as s/bronze...the s/s being better in most cases but not all casts react the same. Some of that crap you can't get nothing to stick to. Given the thickness of what you want to do I don't think s/s or bronze will do the trick. In this type of fix I have had good results with a oxy/a powder set up. With this process it's necessary to deep V the weld joint in order to fuse down to the root and leave no fracture spot. Of course alignment is the biggest problem...set it upon a flat plate and block the hub and wheel back into alignment best you can...deep V oppisite spokes and flip back and forth between spokes during welding...let it cool and repeat. In this day and age it's probably easier to buy a replacement but I have been in situations where it's fix it or go with out. If you really need to use this after you fix it make sure nobody will get hurt if or when it fails...that's a lot of weight to hit the ground spinnin...


              • #8
                I would stronly advise against trying to repair that piece and put it back into service. Even if you appear to successfully make the repair, that thing could have a hundred micro-cracks in it that are not visible to the eye. Spinning at the RPM that it does, it could come apart at any time. There is definitely the chance that it can kill someone. As posted before, weld it and hang it on the wall.

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                • #9

                  Well, I finished welding it but heard a crack during the next to last of the 24 welds. Took out in the sun after the last weld and found the crack. Its very short but that may not be the case with what I can't see.

                  Good deal on the how to Todd. Similar to what I've been doing but still out about 1/16".

                  Would brazing over and beyond the welds and any strength? or cause cracks?

                  But for now, everybody’s advice wins. It will not be used unless more confidence can be put into it plus a sturdy guard would be needed.

                  At least I know, I don't like cast.


                  • #10
                    If I can remember correctly, one of my welding instructors had us all sit down in front of the black board, then drew some thing like what you have described, and stated, if made from cast iron, this is most likely the hardest thing on earth to weld successfully, due to chasing the shrinkage around the spokes, listen to sundown, he is correct, but for the **** of it, try to repair it any way just for the experience