How to repair a 5' ring gear?
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  1. #1
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    Default How to repair a 5' ring gear?

    At Tuckahoe Steam & Gas Association (Tuckahoe Steam & Gas Association - Home), we are in the process of restoring our New Haven pulley lathe, ca. 1880. This is a faceplate lathe (if I'm using the term correctly); that is, the face plate is driven by a ring gear bolted to the back of the face plate rather than being driven by the spindle. Unfortunately, the gear is broken in 2 places. One of the breaks has been "sistered" with a bolted strap. The other break was never repaired. The ring gear is approximately 5' in diameter. We can get it off if necessary.

    We won't be stressing this lathe, but we would like to use it to turn flywheels and for similar projects. Suggestions on how to repair the gear would be welcome. We have considered rolling a strap to put around the entire gear, but the surface behind the flange (the outer surface opposite the teeth) is slightly conical.

    Thanks,
    Jeff
    Attached Thumbnails Attached Thumbnails 1-img049.jpg   1-img050.jpg   1-img051.jpg  

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    I would put the face plate on a vertical boring machine and square up the outside. Then shrink a ring around the outside.

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    Quote Originally Posted by enginebill View Post
    i would put the face plate on a vertical boring machine and square up the outside. Then shrink a ring around the outside.
    bingo....................

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    Maybe in 2 operations?
    #1 jaws and dogs hold pieces together, true circle inside gear. Turn OD down to height of dogs (set for 1/2 way, maybe). Shrink on ring. Possibly with suitable industrial adhesive.

    #2. turn over, dog/chuck on finished rim verifying internal remains round. Turn OD down to first ring & shrink on second.

    Once rings are in place, further tweaking or security can be accomplished with threaded fasteners.

    Of course is a suitable face plate and index could be contrived on the planer, I'd be all for rolling & welding a "substantial" ring or getting a burn-out contributed, and just planing teeth on a new one.

    smt

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    Wrap it with wire or steel tape and in a wound battleship gun?

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    enginebill had the best fix but, you would also need to add fasteners to pull the gear to the outer ring (mainly in the broken areas). While this is the best way to repair this gear you may not have the resources (Time, Equipment and Money) to get it done.

    If you can find a suitable fab shop, and be able to take them the entire faceplate assy, a good welder can fix the cracked area. I never was a believer in electric weld repairs for cast (with the exception of brazing) until one of my better welders convinced me otherwise. Some of the welding rods made now for use on cast are pretty amazing.

    The trick is to find a shop that has a welder with a good history of doing this. They need to convince you that they have done this instead of think that can do this.

    Walter

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    As for truing the outside, its already mounted on a lathe spindle. Unbolt that scab and true it up in-situ. You could borrow the compound off the lathe and make a temporary mount for precise control. If you don't have a way to power the spindle without using the ring gear, mount a power unit on the work side of the spindle. My choice for a power unit would be something like a Ridgid 300 or Ridgid 700 power pipe threader.

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    Shrinking a ring around the outside sounds like the safest option. Back in the days of steam locomotives, the tires were heated and shrunk onto the driving wheels, and if the shrink was correct, it worked fine. They didn't have to hit the dimensions perfectly - they would use a shim between the wheel and the tire if needed.

    The last time I shrunk a ring around a large center, it was very straightforward. We had the advantage of better equipment than in 1900, so we didn't need to do any shimming. We tack welded some stops onto the core so the ring wouldn't shift, then we heated the ring with a home brew torch that burned propane and compressed air - it was just a ring of 1" pipe that we bent around the ring, then drilled 3/32 holes in it for flame ports. We rigged up an extension to one of the forklifts so we could do the heating without affecting the forks. We ran the math so we knew how hot we had to be, then I used an infrared thermometer to monitor temperatures. Once we had it at the right temperature, we let it sit for about 10 minutes, then heated it again so the ring temperatures had time to stabilize. We lined up the forklift extension even with the top of the center, and slid the ring off using several men with pipe push poles. They held it position for a few minutes until the ring had shrunk enough to stay in place. Once it cooled, we removed the temporary stop blocks, and we were done.

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    Roll suitable flatbar

    Weld 2 angle iron dogs to fb.

    Use your math skills to determine exact length and bevel.

    Do trial fits.

    Heat fb weld remove dogs

    Drill and tap several small (1/4,5/16, 3/8) cs screws into the broken gear teeth

    If there is a substantial taper in the gear put an appropriate taper in the fb prior to rolling ie take as little of the gear as possible.

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    How long has the existing patch been holding the gear together. If bolts are broken replace them the old rings have a lot of slack ant the existing repair seems to have worked for decades. My two bits. Noun

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    enginebill is correct. roll a band,weld and machine inside to fit taper of ring gear. Then shrink on and if necessary put in a few bolts similar to the original repair.

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    Metal stitching might also be an option. Frank Casey in MA is the man who would be able to stich it back together.

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    Quote Originally Posted by enginebill View Post
    Metal stitching might also be an option. Frank Casey in MA is the man who would be able to stich it back together.
    This true - but - metal stitching likes to have "mated" surfaces. I.e. newly machined or newly broken.

    To replace an FD fan casing damaged when the impeller exploded, we bought a new cast iron fan casing which had been made by the original maker "split" to be assembled around the shaft of the FD fan. This to remove the necessity to totally remove the fan impeller, motor, bearings, everything. We cut the old casing away (used jack-hammers to break it up also) and then assembled and stitched the new casing in place. But this new casing was designed from the ground up for this installation method.

    The stitch pieces were most interesting. Special portable milling machine to form the slots and then the stitches were hammered into place and created a force to bring the two mated pieces together. Resisting this force (and preventing misalignment being created) is why a metal/metal joint is required.

    We cleaned the metal/metal joints and then used epoxy and the stitch pieces to bring and hold everything together.

    To my knowledge, the fan casing is still there. Now 33 years later (my how time flies!)

    Joe in NH

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    Due to all the wear in the gear teeth, make an impression of a good section of teeth and cast a piece long enough to replace all those cracked pieces, then fit it in, the gearsr will not care a small amount of excess lash after all these years. Then add that ring around the whole gear.

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    Insted of of rolling a ring, machine a long piece of rack and roll it into a new inside gear. Would be a great shaper project. You would have to work out the change in profile for the teeth.

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    It appears that the ring gear is bolted to the face plate.If that is true you could make another one.Those teeth appear to have been created from drilled holes not by a gear cutting tool.The holes themselves could then be set on a jig with pins to align the gear blank while the shaper opened them up with a straight cutter.A single pin jig could even be used if there were a cradle to match the od.Also if the flange can be eliminated and the bolts put through the whole cross section the gear would be stronger.Repairing primitive things sometimes calls for primitive methods.Just another .02


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