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Thread: Mechanical Power Transfer???

  1. #1
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    Mechanical Power Transfer???

    I’m trying to figure out “power transfer” using drive belts, probably serpentine, possibly cogged.

    If you have a primary drive belt that comes forward from say a 25Hp motor to power a secondary serpentine belt. The thing I can’t figure out is this. The second belt goes around a line of say five, seven, nine, etc. pulleys, causing each one to counter rotate. Then at either end you would have two idler pulleys completing the circuit or route. The simple thing would be – in say a five shaft configuration; you would simply put a second pulley, drive pulley, on the center of the five individual shafts (shaft number three), right? The problem is – those five shafts that the second belt is on – needs to move (altogether as one continues unit) side to side (linearly) approximately three inches, approximately two hundred forty cycles per minute. It would almost seem like the action of a wigwag that you would see in a standard washing machine. Incase you need it, each of those other shafts represents about .25Hp +/-. And one more thing, their (as a collective whole) rotational speed would be variable, 400 – 1200RPM.

    How can I energize that second set of shafts while they are moving back and forth, side to side?

    Thank you in advance.

    Wes

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    Hi Wes, you paint a really complicated verbal picture. Is there any chance of a sketch, drawing or picture?

    If I understand the problem, and I am not sure I do, the five sideways moving shafts could be mounted to a frame so that all five stay in a firm and fixed relationship with each other. No belt racking. On one shaft, you could have a spline and on that sliding pulley for the incoming drive belt.

    That pulley stays fixed with the incoming drive system and the "frame" (five shafts with their own belt) slides the spline back and forth in the drive pulley.

    I think I just muddied the description even more.

    Ooops, the red lines on the shaft indicate the splines. Forgot to Label. I'm old I forget stuff, you will too eventually.
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    Last edited by PinkertonD; 05-03-2012 at 05:35 PM.

  3. #3
    Technical Fellow jboggs's Avatar
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    Check out "ball spline bearings". They transmit torque while allowing linear motion.

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    Hi Dave, thank you for your reply along with the picture. Jboggs also responded elsewhere but I wanted to post back to you as well. Unfortunately I didn't explain myself correctly I think. I'm currently working on trying to put a picture together, let me try this verbal illustration for now though.

    Imagine a lawn mower that has its engine at the rear, from that comes forward a primary drive belt to the cutting deck/s. This mower is "goofy" in that it has two decks, one directly in front of the other (not side by side). Each deck has a row of five shafts that penetrate the deck, going from side to side, a pulley on top of each shaft and a cutting blade on the bottom of each shaft. Each shaft is counter rotating because all five of those shafts run off of one serpentine belt. That's two decks with a total of ten shafts, each deck having its own belt for its five shafts. Here's the challenge -

    It would be no big deal to power each deck with their five shafts but the problem is that these decks move from side to side at about 240 cycles per minute. As the front deck goes right, the second deck goes left. And they continue to go back and forth linearly for the duration, at that speed. Yes I did say it was one "Goofy" mower.

    The way I understand a ball spline to work would allow the pulley to move up and down the shaft at a right angle to the drive belt. Whereas with this scenario the primary drive belt would come forward parallel to the ground and all the other belts would also be parallel to the ground.

    I hope that makes more since and thank you again for your help.

    Wes

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    Wes, I'll wait for your picture.

  6. #6
    Technical Fellow jboggs's Avatar
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    I'm just trying to picture an entire mowing deck with 5 spinning blades in it all moving together horizontally back and forth several feet in each direction at a rate of 240 cycles per minute. Something tells me I don't have the right picture.

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    Lead Engineer RWOLFEJR's Avatar
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    I'm guessing this isn't literally a mower with goofy decks but maybe the best way he could give a description of what he has going on...? If it is for the purpose of mowing I not seeing any advantage over a conventional deck design.

    I'm pretty sure I have a grip on what you're trying to do... and my nature has me asking why... only because I always want to know so I can consider other ways of skinning the cat etc... But I won't ask why and just go with it. Maybe you need some violent shaking to keep things... shook up?

    Anywho... Forgetting about driving these two units for a moment... I'm hoping that whatever means you are considering for the side to side motion is a pretty stout set-up. Sounds like you're going to be reversing direction of some pretty heavy things... pretty quick... and in straight lines parallel to each other?

    Simplest thing coming to mind right off would be a spring loaded belt tensioning pully on both sides of the belt driving the two units. As one side of the back of the belt would begin to loosen the other side would be tightening and I'm guessing it should give you a pretty even belt tension across the range Full spring tension on one side and next to none on the other when all the way in one position... opposite scenario when all the way the other direction and half and half when the units are lined up.

    You might also be able to eliminate the tensioners by having your drive pulley set up like a 1-1/2" throw crank... or a pair of throws 180 apart... timed to the other two driven pulleys... but I haven't thought that through all the way...?

    Oh wait... I just figured out what you're building...
    Remember those old things that had a belt on them that you could put around your waste and they'd shake you back and forth and were supposed to jiggle the fat off of folks? You're making a ten person group fat jiggler-offer aren't you... How cool is that...!!

    I can see it now... Ten chunky chicks all gabbing away and all the while shedding those unwanted pounds.

    Sorry... not sure how that popped into my head or why I'd think anyone else would find that funny... or why I decided to share it. Must've spent too much time in the sun today.

  8. #8
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    It's the Fat Jiggle machine, you nailed it. Aint gett'n noth'n past y'all.

    No honestly, I think you got what I was trying to describe RWOLFEJR. The "mower deck" was only for illustration purposes.

    For this contraption the "deck" would only be about 15" +/- long w/ five shafts OR about 27" +/- long w/ nine shafts and about 3"-4" deep, front to back. It would need to be as stout as possible but no more than an overall height of about 2.5", maybe three inches at the extreme overall height. Remember - there's two of these decks, one in front of the other, each shaft going through each deck is counter rotating. The side to side throw would only be about 3".

    Your idea of using a push crank is spot on I think. To me, that would seem to give the most consistent results and be the most trouble free. I thought about a cam as well or using something (I don't know the name of it) like an offset bearing that works like a cam but doesn't need the spring resistance pushing it back. But I still think the push rod is better.

    For driving the shafts I thought about going with two spring tensioners like was mentioned but I don't think it will work, here's why. Let me know if this makes since please. The shaft speed on those five shafts has to be as consistent as humanly possible. The dwell/lag time - albeit slight - at the end of each throw might be a problem I think. More so, as the deck leaves TDC and starts to accelerate the other direction (essentially being pulled along the drive belt) I think that would have a bearing on the shaft speed. Wouldn't it in a sense, slowdown say the clockwise shafts and speed up the counter clockwise shafts and then as it went back the other direction do the same thing but in reverse? IF any of that's true, it would seem to make since to have each set of five shafts powered by their own belt in place of one belt running all ten shafts - I think.

    Which brings us back to - One drive belt coming forward to power two individual decks, each one having its own belt turning five or nine shafts in a counter rotation direction, each deck moving side to side at about 240 cycles per minute, each shaft turning 400-1200 RPM with one deck about 4-6" behind the other.

    To address a few preemptive questions - Yes, it would make life much easier if I could power each deck w/ its own standalone electric motor w/ a VFD but overall, amperage probably wont allow that. Also, the electric power source will be an issue. This will probably be powered via a 25-30Hp water cooled propane motor. That being the case, powering each deck hydraulically wold be nice but due to the work environment there can be absolutely no leaking at all at anytime.

    Wes

  9. #9
    Lead Engineer RWOLFEJR's Avatar
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    Hi Wes,
    I read this over again and gave it more thought and it came down to this...

    I can't see what you're seeing and don't understand exactly where you need to be. Also don't know what the work envelope will allow. I still keep coming back to a crankshaft which spins and throws might be worth looking at closer for this. If you have two cranks timed exactly same then the belt tension will remain the same. The crank throws are your spinning pulleys that drive the spindles??

  10. #10
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    Article is good,but little bit confused..Iam new to Forum,would anybody Explain me Clearly????

  11. #11
    Technical Fellow jboggs's Avatar
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    angelina, look at the dates. We all left this one a month ago. I'm not sure any of us clearly understood what the poster was trying to accomplish.

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