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  1. #821
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    I guess, I tend to run away with my thoughts, all kinds of stuff running through my head, what material is the shaft, could I reuse the spline from the old shaft perhaps, bore it out and thread it on the new shaft, etc etc etc.


    Gonna try and take it slower today, read a book, clean the shop.

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  3. #822
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    Best if you can remove the shaft intact. That way you will have a accurate model to make a replacement if needed.....
    Linear features will need to be accurately reproduced if replacement is needed. If the shaft is drilled out or cut some way
    your references will be compromised.

    Cheers Ross

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    Well in the above case, it should only be drilled to under the 3rd gear or a little beyond, so the geometry under the gears is not that complex and could probably be inferred from the intact gears themselves, rest of the shaft would be intact. I wonder if it could be doable to save the rear part of the shaft in that case and only machine a new part for the front. Perhaps the new part could be threaded into the old, or a press fit (cooling one part and warming the other for the actual fit).



    Anyway that's me running away again on a tangent. Last night I filed on the shaft, I modified a square file on the belt grinder so a safe side was made and put it against the gear face and ground away until I was sure there was no mushrooming on the shaft, instead a small reduction, that did not help in getting the shaft off.

    I guess I will have to proceed to drilling out the front of the shaft and remove the key and try and sand the inside of the 3rd gear now.

  5. #824
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    Quote Originally Posted by DennisCA View Post
    I guess I will have to proceed to drilling out the front of the shaft and remove the key and try and sand the inside of the 3rd gear now.
    Is your plan to drill down the 4x4mm slot with a 4mm drill bit? That's certainly what I would consider next. Is it correct that you can now reliably line up the key slots in the three gears?

    One other thought. Could you build a U-shaped puller which wraps around the machine? Referring to the drawing in your previous post #823, the right leg of the U goes on the right side of gear 3 (which is labeled "5" in the drawing). The left leg of the U goes to the left of the left end of the shaft. A pushing bolt passes through the left leg of the U and bears against the left end of the shaft. Then by tightening the bolt you can press hard on the shaft. The force is taken up by the U of the puller (welded from steel) and applied directly to gear 3, so there is no force on the machine casting. This would allow you to apply a few thousand Newtons of force to the end of the shaft and force the shaft through the gears.
    Last edited by ballen; 08-14-2019 at 10:52 AM.

  6. #825
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    The biggest problem there I believe is the amount of available space behind gear 3 and the casting, only very thin metal fits in there and I think it would all need to be made from thick box section in order to be stiff enough. On the other side of the cast iron webbing there is more space available. Then the cast iron rib would be supported though under pressure.

    I am not sure, the darn thing is so stuck I wonder if it would move even with a very strong pushing setup.

    I can reliably line up the slots now too.

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  8. #826
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    Quote Originally Posted by DennisCA View Post
    I can reliably line up the slots now too.
    That's very good, opens up many possibilities.

    On the other side of the cast iron webbing there is more space available. Then the cast iron rib would be supported though under pressure. I am not sure, the darn thing is so stuck I wonder if it would move even with a very strong pushing setup.
    As I recall, you are good at welding. So perhaps you could weld up a U "pusher" as I described, with the left leg of the U to the left of the left end of the shaft, and the right leg of the U on the right side of the case webbing. The rightwards pressure on the shaft would then be transmitted to gear 3 which would bear on the left side of the cast iron which would carry the force through to the right side of the cast iron and then onto the right leg of the U.

    This would give you a way to apply a very controlled force to push the shaft though. I suspect that a few thousand Newtons of force would easily overcome the burrs and damage to the shaft. It would take a day to weld up the pusher, but might then make the rest of the job straightforward.

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    I wonder if it could be made stiff enough myself given the size limitations

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    I'm not sure, if I followed the progress right.

    Is this the state:
    1. The first and second gear were moved to the left as much as possible.
    2. So the shaft can not move axially in the gear box.
    3. They (all three gears) don't slide on the shaft (in axial direction).
    4. The key is partially removed --> where do remain parts of the key and does the first (and/or the second) gear rotate on the shaft?
    5. The third gear does rotate on the shaft, but not slide in axial direction.
    7. The slots of the gears can be lined up reliably.

    Most probably, parts of the broken key made grooves in the inner bore of the third gear. Sharp edges or tips of the parts do grip inside the grooves, so that sliding the third gear in axial direction is not possible.
    While pressing the shaft out of the third gear, such a part of the broken key could grip harder into the bore of the third gear.
    Therefore I would not press too hard.
    If the third gear would not move with moderate force in axial direction, I would prefer Ross' suggestion (make the bore of the third gear larger with a sandig tool).
    To apply the sanding tool, the key would drilled off in axial direction.
    I wouldn't be surprised, if after removing all parts of the key out of the key slots the third gear will not slide (perhaps particles of the broken key stick in the shaft or in the bore of the third wheel all around).
    Last edited by CharlyDE; 08-14-2019 at 02:24 PM. Reason: corrections

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  13. #829
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    You have it mostly right, the two first gears are not rotating freely on the shaft either (nor axially), they still have the key under them and they are quite stuck to the shaft as well, but not as much as the 3rd gear. I am going to have to move them back again to provide better access for me to open up the key shaft, so I am going to have to weld up a bigger U-shape pusher, except this time in reverse to push the first two gears back. I plan to make a cylinder to push directly on the face of the first gear and on the shaft rom behind. It does seem all three gears are fitted on the shaft incredibly hard. I wold have thought a slip fit was the fit one wanted, but maybe this changed for some reason in this machine, though I don't see what. The reasons for the 3rd gear are obvious and I agree with your assessment on that.

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    Presumably, the first two gears could be moved to the left only because the nearby bearing has been removed, correct?

    In other words, I assume the the total cluster of three gears is normally held in place by the two adjacent bearings. Otherwise, they would need something to stop them from wandering axially. Now, if the bearings do not “bookend” the cluster of gears, then what does? One possibility - which seems unlikely - is that the cluster could have been shrink-fitted to the shaft. That would at least account for the force required to slide to first two away from the third.

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    You are right I believe, that is how it ought to work, retained by the bearings, that should be more than enough IMO.

    But on my machine, all three gears are stuck more than normally. The two first ones not to the same degree as the third one, but still beyond normal. The cause of this I am not sure since the key did not shear under them.

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    Is there enough meat on the right side of the gears smaller OD for a taperpin? If everyting else are working as they should and in good running condition. It could be the cure for now to get the machine running.

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    Something like that has been suggested and I think it could perhaps be doable, but I am worried it would make a weak solution and risk breaking again, and possibly leave me in a worse position if it breaks.

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    I have read this entire thread and I am very impressed with the work that you have done. Great job. Also, there are many great ideas about how to get the gears off the shaft.

    That said, I think you need to take a step back. At this point removing the gear will require destruction of some very important and hard to replace parts. I think, that if the bearings are in good shape, then you should simply focus on the problem at hand. That is, the gear is turning on the shaft. If you can devise a way to fix all 3 gears together then you can make the machine fully functional until the time at which you REALLY need to take it apart.

    I think you could build a collar that fits between the second and third gear drill a hole or holes parallel to the key and through the web of the gears, then put a bolt through the gear and the collar. Or, maybe just drill a hole through the hub of the gear and the shaft and install a shear pin.

    Problem solved. Clean it up and put it back together until you can find replacement parts.

  20. #835
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    Quote Originally Posted by Harri89 View Post
    Is there enough meat on the right side of the gears smaller OD for a taperpin? If everyting else are working as they should and in good running condition. It could be the cure for now to get the machine running.
    I think you are on the right track here.

  21. #836
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    It does sound like a tempting solution, though I am afraid it means the machine will be weakened in certain gears and might snap more easily, it would be like a cloud hanging over my head when I used it. And one day I think it will have to come apart regardless.

    I don't think I need to replace the shaft entirely though, I think the idea I mentioned earloer, of making it from two parts would work. Certainly I think a press fit like that would be stronger than a key or taper pin through the shaft so I doubt it would break there.

    At any rate my motivation has been down in the dumps and I'm working during day time again (no more vacation), weekend now though so I welded up a puller and used it to press the two front bearings back, oh my they where stuck good too, the puller wasn't able on it's own to get them back and I had to use my little sledge while under pressure to get them back, but I need to weld it more and reinforce it. The 3rd gear feels locked, probably just friction though and in a real operation it would come free.







    I only tig welded it for now, the front and rear needs a cap to stiffen up the structure, and I will go over all the weld with 7018 stick welds to beef everything up, as I think I will need this again.

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  23. #837
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    Think for a puller/press you would be better served to make the tool in double shear.
    Use the square tub as you have done already, but make it longer...long enough to reach the outside of the machine casting on both sides with some excess....
    Use threaded rod of ample size on each side with nuts to make the frame. This then will become two members in tension (threaded rod)
    then apply force using a pusher screw (large fine thread) I would use heavy pattern nuts on the pusher thread and use a hardened washer between the nut and the frame...
    The point here is to rotate the nut rather than the screw. Less chance of damage on the shaft and you will get better advantage having only one friction interface to overcome
    (washer).

    Good luck....
    Cheers Ross

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    I thought of that design but I do not have the material at hand to make such a version, and all this needed was to push the two gears back in place so I did not think I needed that much strength for this version, and they are back in place now.

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    Dennis, I like the press. What's your plan now? Cheers, Bruce

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    Ok, I think you can still save the shaft and gears. Since you don't want to put pressure on the center web of the casting, then put the pressure on the outer part of the casting.

    solution.jpg

    Drill 4 holes from the front of the casting all the way through the web of all 3 gears. Place the holes as close to the gear hub as possible so you can apply maximum force to the shaft. Put 4 long Grade 8 bolts all the way through the casting and the gears with nuts on the end after each gear. This will securely fix the gears to the case so you can then push or pull the shaft out.

    When you are all done, thread and plug the holes in the casting. If it works, you can reuse the gears and shaft with minimal cleanup.


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