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  1. #1
    BobL is offline Member: Blue and white apron brigade
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    Default Removing a large flatbelt pulley from a 7.5HP motor

    The Mens shed has a 7.5HP motor with a 3 step (large diameter is 265mm) flatbelt pulley on it and they asked me If I would sell the motor. I thought it would be more saleable with the pulley take off so I said I would do it.

    I removed the bolt that was holding the key in place and the key just fell out Great, I though this is going to be easy
    As you can see I had good side access to the pulley so I got my biggest wooden mallet made of Rock Oak and gave it a number of fair whacks while rotating the pulley.
    The striking sound was like a large gong, but ZERO movement, AND I completely destroyed the mallet head!
    Original.jpg

    So I decided to make a puller using some 12mm steel plate and 1/2" all thread rod.
    Also Poured some diesel into the cavity above the shaft and left it ON.

    Pulley.jpg
    BUT again not even a squeak of movement.
    Heated it with a MAPP and propane torches - nothing.
    One issue I identified was that the big pulley is hollow and the main boss is inside that so it was very difficult to get heat direct onto the main boss.
    I could just poke the MAPP torch up between the back of the pulley and the motor but didn't want to leave it in there too long as I was worried about overheating the motor.
    What that photo doesn't show is how mangled/bent the all thread rod ended up - basically unusuable.

    At this stage I decided to use my press.
    Now the stand on my press is too short to fit the whole motor under so I firstly had to lengthen it.
    Fortunately I had some HD 2" galv water pipe handy.
    I set it up so the edges of the big pulley sat firmly on those wooden blocks and cranked on the pressure.
    At around 8 tons and heating with the MAPP and propane torches the outside of the big pulley emitted a mild crack and snapped off the boss.
    SNappedPulley.jpg
    Well I thought, now I can at least apply heat direct onto the boss.

    I rang my Al boat builder Boilermaker/Welder BIL and he came around with an angle grinder with a 125mm tungsten carbide tipped saw blade especially made for chewing Al and he cut some vertical slots in the boss but of course he could not cut them all the way through to the shaft or down to the base of the boss. It's slightly terrifying to watch him use it as tiny shards of very sharp Al go everywhere. He was fully PPEd while doing it - he uses this sort of gear all the time at work.

    This morning made a custom boss/pulley support (S in photo below) from some 125 x 75 x 12 mm angle.
    Support.jpg

    At around 9.5 tons after heating with the MAPP/Propane torches for about 15 minutes there was a medium BANG and the motor moved down a couple of mm.
    Then after that about 2 tons was need to fully remove the boss.

    Below you can see how clean the shaft is - so not corroded.
    It even looks like some diesel got down there.
    The chewed side of the boss was done so the boss could nestle closer into the side of the support and be more directly under the press.
    Boss1.jpg

    Here you can see how large the Boss is.
    The bore size is 35mm
    Boss2.jpg

    I reckon I've spent 20 hours on this.

  2. #2
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    Default

    Were you able to get this red hot with your torches?

  3. #3
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    Default

    Thanks for the pics and report of the efforts that you had to go through.
    To grow old is mandatory, growing up is optional.

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Default

    Quote Originally Posted by pipeclay View Post
    Were you able to get this red hot with your torches?
    Not the large pulley, but managed to get the bottom of the boss a dull red (could see it with the shed lights off) but didn't leave it too long as I was worried about over heating the motor itself.

  5. #5
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    Default

    Spot heating on the small pully under your press may of worked without breaking.

  6. #6
    BobL is offline Member: Blue and white apron brigade
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    Default

    Quote Originally Posted by pipeclay View Post
    Spot heating on the small pully under your press may of worked without breaking.
    The shaft did not extend up past the big or even intermediate pulley and was inside a boss covered by the big pulley.
    Screen Shot 2020-10-24 at 7.02.32 pm.png

  7. #7
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    Default

    I think the pulley was doomed because of its configuration, but not a great loss.
    It didn't need to be such a tight interference fit on the shaft, but that's how they sometimes are found.
    Well done.

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    Default

    This morning I took a closer look at the motor shaft.
    It has distinct circular ridges on it.
    The ridges are easy to feel with a fingernail.
    I've never seen one like this.
    I wonder if they were put there deliberately during a turning process or maybe the previous pulley was loose and scored the shaft?
    Either way it was probably a significant contributing factor as to why it was hard to remove and even once loosened continued to need 2 tones of pressure to keep moving it.

    shaft.jpg

  9. #9
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    Default

    I feel your pain Bob.
    Pulley was probably shrunk on originally. If it wasn't, then whoever fitted it should have used some anti seize. That would have made it a lot easier to remove.
    Back when I was on the tools for real, not using anti seize on couplings, bolts (basically everything ) was a sure fire way of getting your backside kicked so to speak.
    Peter

  10. #10
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    Default

    Another way is to lay a nice high current arc weld along the length of the boss. That shaft definitely looks like a previous pulley has spun on it especially as you noted the keyway fell out.

  11. #11
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    Default

    I wonder if it mightn't have been quicker to use an angle grinder with flap disc to sand the boss down to the key slot? Then there wouldn't have been as much left holding the boss to the shaft and it would have pulled off easier. Still your struggles were entertaining but I doubt the 20 hour effort was recouped by the cost of selling the motor. But the satisfaction of beating it is priceless.

    Pete

  12. #12
    BobL is offline Member: Blue and white apron brigade
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    Default

    A number of things would have been possible in hindsight.

    A couple of positives is I now have a 750 mm taller press and a HD boss support that should come in hand for a number of processes,

  13. #13
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    Default

    An interesting tale - that contains a warning - "Don't be so keen to offer your services."
    The story qualifies you for the "blue and white apron" award with oak leaves!
    Wear it with pride!

  14. #14
    BobL is offline Member: Blue and white apron brigade
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    Default

    Just as a follow up I've had the motor running on a 3HP VFD using a 10s start and it runs very nicely and only draws 600mA when free running.

  15. #15
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    Default

    Quote Originally Posted by A J in WA View Post
    "Don't be so keen to offer your services."
    I need to print this out and hang it up in my workshop. I keep falling into that trap. I've got a bloke coming over this arvo to utilise my services because I opened my big mouth. It's a job HE volunteered to do for someone else, but he's bitten off more than he can chew. That's my afternoon gone.

    Nice work Bob. I hate jobs like that.
    Chris

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