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Thread: Pole lathe with mechanical advantage

  1. #1

    Pole lathe with mechanical advantage

    Iím unaware of anyone using pulleys for mechanical advantage on a pole lathe in the Neanderthal days, but I saw a youtube video of a guy with some pulleys doing SOMETHING other than just redirecting the rope. The problem was he never showed the whole setup. After watching every one of his pole lathe videos (no talking, more just selfie videos turning) I found him confirming in a comment that the pulleys were for mechanical advantage. If youíve ever used a pole lathe you know that possibly the two most important factors are a) turning speed and b) number of revolutions per treadle stroke. So I was off to the home center!

    My pole lathe is powered by a bungee since I don't have the ceiling height necessary for a real pole (which would also be a pain in the butt). Originally my power cord was tied to the treadle, wrapped the stock, redirected by the pulley at the soffit and then connected to the bungee (a single bungee; not a double) strung across a very heavy and essentially immovable utility bench. This would be your normal pole lathe scenario (just with redirecting the power cord because of the low ceiling combine with a tall operator). With this setup, on a typical 1.5Ē diameter piece of stock I could easily get 7 or more revolutions per stroke.

    Now, instead of being tied to the treadle, the power cord is tied to the lathe itself and hits a pulley on the treadle before wrapping the stock. This gives me (theoretically) double the cordage to turn the work for the same treadle travel. The problem is that would require the bungee (pole) to travel twice as far, which it obviously canít do. So instead of tying the cord to the bungee it goes through another pulley that is attached to the bungee and comes back and is tied to where there redirect pulley is. This makes sense if you look at the pictures. So my theoretical 2:1 at the treadle is inverted 1:2 at the bungee and Iím back where I started, just with double the cordage travel and double the speed. Thereís no free lunch of course, and the bungee suddenly had half the strength required to bring the treadle back up. Simple solution Ė something you canít really do with a pole very easily Ė I just cut another length and doubled the bungee power. Now I get double the turning speed and double the number of revolutions and everything feels and functions like normal. In reality itís not really double because things donít work that way in the real world. But itís close. In fact, I sometimes have found I need to treadle more slowly because the speed of the spindle can get ridiculous.

    Iíll explain a few confusing things in the photo. There are a series of nails in the soffit Ė thatís because when Iím turning something longer, I may need to move the redirect pulley. If I had a pole up 10 feet in the air it wouldnít be such a big deal. But that redirect pulley is only a few feet above the lathe and the angle can get kind of tight. Some people simply flip their stock around, but that sounds like a pain. Originally I had three, but then I worked on a really complicated piece and putting in a could more nails for some more options really helped. The other thing is that on a normal treadle, if you need to take up slack (as your stock gets smaller in diameter) you simply give the cord another wrap around the treadle. Thatís not possible for me now, so I take it up at the opposite end where the power cord ties onto those very same nails. Now I can take up slack just by giving a wrap or two around a couple nails.

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  2. #2
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    Cleaver

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  3. #3
    By using pulleys you increase the speed, but decrease the power. It is like a car in high gear that cannot go up hill. The great advantage of a pole lathe over a treadle flywheel lathe is much greater power. I learned turning on a treadle lathe and a big Delta variable speed lathe. When I first tried a pole lathe in 1980, I couldn't believe how much power there was. There was a very positive feel when you put in the tool.

    Pole lathes are also negatively affected by too long a cord. If you have the pole too high up or too far away, the action gets a little spongy. It is a little like planing on a shaky bench, because some of your effort is used in stretching the cord. It is better to have a crisp action and tight response. And there is a little loss of energy with the pulleys as you suggest.

    You could certainly put a pole in your shop. Although a lot of old illustrations have the pole over the turner's head, it also works with the pulley coming from the other side of the lathe or from the side. I have used a 13 foot hickory pole for 39 years.

  4. #4
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    Youtube fellow would be The Renaissance Woodworker?

  5. #5
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    You could certainly put a pole in your shop. Although a lot of old illustrations have the pole over the turner's head, it also works with the pulley coming from the other side of the lathe or from the side. I have used a 13 foot hickory pole for 39 years.
    There is no rule that says the pole has to be flexing in a vertical plane.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  6. #6
    The trade is force for distance, however it is only a momentary trade as it is traded back, distance for force, getting me right back where I started. Because the force is the same, the increased distance results in speed. Ordinarily, the increased distance is the cost of a block and tackle system, but in the unusual case of a pole lathe, thatís actually desirable. Itís like having your cake and eating it too because nobody else wants to eat it. I find no difference other than the faster turning speed. The increased friction from the pulleys and the stock is negligible. Thereís no trade in power. The key is inverting the ratio at the bungee to get me right back where I started. By going 2:1 at the treadle and 1:2 at the bungee everything equals out; I just have a doubling of the speed and a corresponding doubling of the rope in-between the two - I just don't care about extra rope and the speed is desirable. It's like being able to buy that cake with pocket lint that you didn't want in the first place.

    Hereís a link to the youtuber. This is the video where you can see more of the pulley system than in his other videos. https://youtu.be/rZIT7Td0gCA


    It would be fun to use a pole, but the nature of my basement makes it too difficult in any configuration and incredibly inconvenient. I sometimes think in good weather I might take the whole thing outside on the patio, in which case I could use a pole.

  7. #7
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    I saw a lathe that was set up using a compound bow (overhead) in place of a plain bow or spring pole. It seemed to work quite well.

  8. #8
    [QUOTE=chris carter;2972124]The trade is force for distance, however it is only a momentary trade as it is traded back, distance for force, getting me right back where I started. Because the force is the same, the increased distance results in speed. Ordinarily, the increased distance is the cost of a block and tackle system, but in the unusual case of a pole lathe, that’s actually desirable. It’s like having your cake and eating it too because nobody else wants to eat it. I find no difference other than the faster turning speed. The increased friction from the pulleys and the stock is negligible. There’s no trade in power. The key is inverting the ratio at the bungee to get me right back where I started. By going 2:1 at the treadle and 1:2 at the bungee everything equals out; I just have a doubling of the speed and a corresponding doubling of the rope in-between the two - I just don't care about extra rope and the speed is desirable. It's like being able to buy that cake with pocket lint that you didn't want in the first place.

    Here’s a link to the youtuber. This is the video where you can see more of the pulley system than in his other videos. https://youtu.be/rZIT7Td0gCA
    [/QUOTE}

    I watched the video that you referenced, Chris. Caspar Labarre has a very well made lathe, reminiscent of lathes around 1700. He has pulleys similar to yours that double the revolutions per stroke at the expense of power. His turning technique leaves something to be desired. He makes a chair rung from an already rounded blank in about 21:30. This afternoon, I turned a similar rung from hickory in 7:20. I used a pole lathe without pulleys and I started with a blank that was a little rougher. I think that the difference in time can be attributed in part to a difference in power and a tighter system with less stretch in the cord.

    I had not turned anything for quite some time so I was a bit out of practice. I think someone doing this regularly would be under five minutes.

    Three hundred years ago turners knew about pulleys. Turners were the ones who made pulleys. It is somewhat laughable that someone thinks they can improve on the pole lathes from the seventeenth century.

  9. #9
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    [QUOTE=Warren Mickley;2972600]
    Quote Originally Posted by chris carter View Post
    The trade is force for distance, however it is only a momentary trade as it is traded back, distance for force, getting me right back where I started. Because the force is the same, the increased distance results in speed. Ordinarily, the increased distance is the cost of a block and tackle system, but in the unusual case of a pole lathe, that’s actually desirable. It’s like having your cake and eating it too because nobody else wants to eat it. I find no difference other than the faster turning speed. The increased friction from the pulleys and the stock is negligible. There’s no trade in power. The key is inverting the ratio at the bungee to get me right back where I started. By going 2:1 at the treadle and 1:2 at the bungee everything equals out; I just have a doubling of the speed and a corresponding doubling of the rope in-between the two - I just don't care about extra rope and the speed is desirable. It's like being able to buy that cake with pocket lint that you didn't want in the first place.

    Here’s a link to the youtuber. This is the video where you can see more of the pulley system than in his other videos. https://youtu.be/rZIT7Td0gCA
    [/QUOTE}

    I watched the video that you referenced, Chris. Caspar Labarre has a very well made lathe, reminiscent of lathes around 1700. He has pulleys similar to yours that double the revolutions per stroke at the expense of power. His turning technique leaves something to be desired. He makes a chair rung from an already rounded blank in about 21:30. This afternoon, I turned a similar rung from hickory in 7:20. I used a pole lathe without pulleys and I started with a blank that was a little rougher. I think that the difference in time can be attributed in part to a difference in power and a tighter system with less stretch in the cord.

    I had not turned anything for quite some time so I was a bit out of practice. I think someone doing this regularly would be under five minutes.

    Three hundred years ago turners knew about pulleys. Turners were the ones who made pulleys. It is somewhat laughable that someone thinks they can improve on the pole lathes from the seventeenth century.
    Yep. No doubt that technology reached its zenith in the 17th century.

    The pole functions as a return spring. So does the bungee cord. You could use a garage door extension spring or various other things including a leaf spring from a car as a direct substitute for the pole. The power comes from your leg. The travel length desired of the foot pedal is a key input to the design. This is not 17th century rocket science.
    Last edited by Pat Barry; 12-10-2019 at 7:19 PM.

  10. #10
    [QUOTE=Pat Barry;2972617]
    Quote Originally Posted by Warren Mickley View Post

    Yep. No doubt that technology reached its zenith in the 17th century.
    I think Isaac Newton understood mechanics in the 17th century. Not so sure about some posters in this thread.

  11. #11
    Warren, I don't think much stumps you. But don't forget Newton was a complete failure at making gold !! I know it's not
    always easy to find pics ,but I know many would enjoy seeing your pole lathe again.

  12. #12
    Quote Originally Posted by Warren Mickley View Post

    I think Isaac Newton understood mechanics in the 17th century. Not so sure about some posters in this thread.
    Maybe we can have this conversation without throwing insults around.

    There are plenty of good reasons why pulleys for mechanical advantage in a pole lathe wouldnít have taken off in the 17th century (although I have no doubt that some people probably tried it). It could be because without the machining and the use of plastics and PTFE dry lube there was too much friction in the pulleys. Or maybe itís because twisted rope stretches horribly and does not run very smooth through pulleys while braided rope stretches less and runs much more easily through pulleys (braided existed then, but was uncommon because it was considerably more difficult to make). There are plenty of reasons. I think itís going out on a limb to assume that just because something was done a certain way for a few centuries, centuries ago I might add, it MUST have been the absolute best possible way to do it and thereís no way to improve upon it today.

    I made a matching pair of candlesticks and figured out the pulley system between the two. The second one was considerably easier and faster to do with the faster spinning stock. The difference was obvious. So either this thing works or Iím somehow breaking the laws of physics.

  13. #13
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    Question for you polecats (no insult intended) Why not use a counterweight?

  14. #14
    Quote Originally Posted by Tom Bender View Post
    Question for you polecats (no insult intended) Why not use a counterweight?
    A pole lathe takes about two up and down strokes per second. A counterweight will not move that fast. If you raise the weight, it takes time for the weight to slow down from its upward momentum and start going down again. Meanwhile the cord is slack and the weight will bounce when the cord is taut again etc.

  15. #15
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    Warren Produces excellent turnings that are finished equivalent to that of a brightly planed surface right off the chisel. I think it wise to heed his advice. The information he provides is hard won and accurate. Warren’s advice has served me quite well over the years, I’m thankful to have received it.
    Bumbling forward into the unknown.

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