Using a foot-powered lathe for large work

discussion of the niceties of turning on a bow, bungee or pole lathe.

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Using a foot-powered lathe for large work

Postby danny may » Mon Nov 21, 2011 4:47 pm

I am making a large heavy timber-framed lathe which can be used by either pole, treadle or electric power method.
It is an experiment in constructing large work outdoors.It is intended to turn work up to 12' in length.
How likely is it that I will be able to turn large objects using foot-powered methods?
My initial thought was that the pole method would not be able to cope with the inertia of a large piece, the piece would be too heavy to recipricate easily?
Also I thought that the treadle method would not have enough torque to cope with heavy work and would jam often?
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Re: Using a foot-powered lathe for large work

Postby gavin » Mon Nov 21, 2011 5:27 pm

danny may wrote:How likely is it that I will be able to turn large objects using foot-powered methods?
My initial thought was that the pole method would not be able to cope with the inertia of a large piece, the piece would be too heavy to recipricate easily?
Also I thought that the treadle method would not have enough torque to cope with heavy work and would jam often?

I'd build a small version first e.g. a bowl lathe or pole lathe and get an idea of what is feasible - your own legs will tell you. You could reach out for some basic engineering input on mass, inertia and human power for some theoretical answers to your questions above.

But more importantly WHY? Why attempt to turn items 12 feet long? You do not specify how many kilos a 'large piece' may be, or how long that may be. If you build a reciprocating lathe, the upper weight limit is restricted - I'd guess roughly to 10 kg max. But if you have a continuous-motion flywheel lathe (sometimes called a 'treadle lathe' ) , then you need to be capable of far better engineering to cope with the large amount of stored energy you'll build up in the work spinning on lathe, and you could then turn heavier objects. I have only seen these lathes made with a metal bed. I suspect a wooden-bedded continuous-motion flywheel 12 foot lathe will not last long before shaking itself to bits.
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Re: Using a foot-powered lathe for large work

Postby SeanHellman » Mon Nov 21, 2011 9:36 pm

Years ago I met a chap who turned 6 foot on a lathe, could have been 6 inches dia. He held the tool and someone else used the treadle. The way our ancestors turned large stuff was to use a `great wheel`, a very large wheel with a belt running from it to the lathe. From all accounts it was not a favourite job to turn the wheel.
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Re: Using a foot-powered lathe for large work

Postby danny may » Tue Nov 22, 2011 12:59 pm

I have already experimented with a smaller pole-lathe and turned spindle work up to 5' * 3'' diameter. Thats no problem. the relative ease of this made me think it is possible to pole-lathe much larger, heavier work. I wondered how large work was turned in pre-motor days, mostly it seems by big-wheel method or by water wheel, producing the same effect, loads of geared-up power. There are many examples of American big-treadle machines, but none that are specifically big pole-lathes. And yet the treadle machines have some lesser qualities to the pole-lathe. I am aiming to make a wood-frame machine that can work in all 3 ways, but would appreciate any advice

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Big wood-frame Lathe
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Re: Using a foot-powered lathe for large work

Postby gavin » Tue Nov 22, 2011 10:16 pm

danny may wrote: And yet the treadle machines have some lesser qualities to the pole-lathe.

What specifically are the lesser qualities?
And how do you define a 'treadle machine' - for a pole-lathe has a treadle. Perhaps you mean 'continuous motion' when you write 'treadle machine' ?
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Re: Using a foot-powered lathe for large work

Postby HughSpencer » Wed Nov 23, 2011 1:23 pm

Thinking about this, I reckon that using a reciprocating action like a polelathe would get exciting when the revolving mass gets over a few kilos. If you want to use this action I suggest a freewheel or ratchet drive would be needed otherwise you are starting and stopping a large mass every second or so. This would make the belt/rope slip and wear out in short order.

In a moment of madness I considered the following for a big lathe drive. Old pickup truck. Remove back wheels, put separate parking brake levers on each drum. Use one drum as a faceplate and leave the other one free to rotate. To run it you apply the faceplate brake and release the other brake. Start the engine and put it in gear. The free drum will start to revolve. Now release the faceplate brake and slowly apply the free drum brake. The diff will transfer the drive to the faceplate. To stop it you switch the brakes. Of course this would all have to be bolted down and would be pretty scary but you could turn some big stuff if you were mad enough. You can hardly call this greenwood work other than you might want to do it deep in the woods away from the Health & Safely police :D
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Re: Using a foot-powered lathe for large work

Postby danny may » Wed Nov 23, 2011 3:09 pm

Hi Hugh. Yes I agree that a big lump is not easily going to spin back and forth without slipping and wearing out, though if the belt is strong enough the slip is not neccessarily bad, it just means that the work doesnt reciprocate.
I have also heard of and seen pictures of lathes attached to the PTO of a tractor or Landrover which seems to work well enough, but like you say not very peaceful or ..safe.
I find the flywheel-treadle method awkward due to the fact that the flywheel tends to run-away with the rhythm, therefore you end up chasing it and finding the balance is difficult and inevitably the rhythm collapses and the cam sticks. Maybe it is easier to control with a very heavy or big flywheel?
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Re: Using a foot-powered lathe for large work

Postby Brigstock Bodger57 » Wed Nov 23, 2011 6:19 pm

I was asked years ago to turn some copies of early table legs out of 4inch square green oak, 3 feet in length. I managed to do it but it was hard work and the weight was a problem, as was getting it centered and keeping it there. Once I had turned a section of it round it became much easier and the string didn't wear as much. I have turned stuff up to 4 feet in lenght but this was all square section pine and so not very heavy, though it was seasoned. I found that even on this length there was a lot of whip in the centre, so I don't think that long stuff would work with the normal centres used on most pole lathes.
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Re: Using a foot-powered lathe for large work

Postby jrccaim » Fri Dec 02, 2011 5:10 am

Hmmm. Twelve feet? Say four meters. You don't specify the maximum diameter. The first lathe I ever met was a 16" screwcutting machine with a bed about 4' long. WWII vintage. Frame cast iron. Weight at least two tons. Beautiful machine. But even that monster would whip a bit on long turnings (over 2'). If you really wanted to turn four meters of stuff you would require, I think, a cast-iron frame. There is a reason wooden lathe frames went out in the industrial revolution: cast iron is much, much more rigid. Also you can get the centers aligned to within .01mm -- an important factor in avoiding whip. Then you would require steady-rests spotted along the frame, say every half-meter or so. 2' is considered marginal without a steady, even on a powered lathe. Then I do not think you could do say 4m x 15cm by muscle power. Even with a continuous-motion arrangement, there are limitations to human muscles. And finally, I am sure you could not do it at all with a reciprocating lathe. Stopping/starting shock. Just too much mass for humans. Unless you are turning balsa wood:)

Now I know that people have turned far longer things than 4m. For instance, naval weaponry in the 1880-1950 era. A 300mm naval cannon, for instance. But the size of the machinery they used boggles the mind. And the cost of that machinery boggles the pocketbook. And they were steam powered. I hate to be negative, so let me offer a suggestion. Somewhere in some junkyard in the UK there is doubtless some neglected piece of equipment lurking; perhaps it was used to turn greek-style columns for upscale yuppie houses; If you could find such an animal it might be adapted, or rebuilt. I think that trying to build such a monster out of wood is a losing proposition. Many people think junkyards are eyesores. I regard them as treasure houses.

This post is already much too long, but might I suggest that this fascinating thread is misplaced? It sure does not belong in "Indexed Pages of Interest." I think "Pole Lathe Turning" is its true home.
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Re: Using a foot-powered lathe for large work

Postby danny may » Thu Dec 05, 2013 7:48 pm

I completed the lathe some time ago, and have been using it since. I made it capable of being powered by belt, be it from treadle / mill / continuous motion etc, but in the end bolted on a 3 phase motor, controlled by an inverter. Works great, though large pieces have to be .. started slowly.. http://www.dannymay.co.uk/blog
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