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I Forge Iron

Alternative to Fly Press?


Purple Bullet

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At one time a little over a year ago I was all ready to buy a new fly press. I couldn't find one locally and when I called one of the importers he said he wanted to wait and see what the economy did before ordering any more. It got me thinking about trying a build, but although I have a lathe that might be capable, my skills are not up to cutting multiple thread screws. I also kind of question the design.

I've never used one, but I've heard of bumped noggins from the handle or counterweight. Also, the force you are putting in is horizontal while the force delivered is vertical. Not the most efficient, but then again, I don't know. Maybe its easier to develop a horizontal pull than a vertical.  I started to think of how to do this with commonly available materials. I remember as a kid growing up down Bayou Lafourche, seeing boats lifted up out of the water with two windlasses made of wire rope wrapped on pipe and a large hand wheel. These were ~20 ft skiffs with inboard engines. I don't know how heavy they were, but I'm pretty sure they were multi-ton. I made a trial run with something made from a truck tire with half axle. I turned the axle down to fit pillow block bearings that I mounted on a stout frame. I used two lengths of wire rope to pull two 3/4" rods through guides welded to the cross piece that held the bottom die. This was attached to the movable cross piece (or ram?) that would hold the top die. I made a lightweight frame with springs to lift this pressing part.

It worked after a fashion. I could cold bend 1/4 in square mild steel in an angle iron die, but too much energy was wasted in coiling the wire rope so tightly on the shaft.  Now I'm trying for a re-design and would like some advice before I go buy the materials. Especially I'd like to know if I'm figuring these forces right, but if you see anything that doesn't look right or safe about this, I'd appreciate the input.

One big caveat! THIS IS EXPERIMENTAL! Don't take this as a "how to" to build your own. I'm not saying "Don't build this." I'm saying there are no guarantees here. That's why I'm soliciting input from the experienced and knowledgeable folks on this forum.InertiaPress.thumb.png.648179b1ce0ed9288baebed864321cf8.png I

BTW - speed of 5 ft/sec is just a guess. I'm thinking that is reasonable for a speed you could accelerate to before the press die hit the object. 

 

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PB, very interesting and a concept I haven't seen before to convert the radial inertia of the rotating tire to vertical force on the ram.  Is there a stop at the end of the motion of the ram to halt the vertical motion?  Could you use something other than a tire as a flywheel which has more mass nearer the rim?  That is why the weights are on the end of the bar on a fly press and are sometimes adjustable in and out to vary the pressing force. 

This may be overthinking but could you incorporate a clutch mechanism where you could spin up the tire and the engage it into the ram to increase the pressing force?  I'm thinking spinning it by hand, not using a motor which might give too much oomph.

Anyway, I look forward to seeing how this works out.  I like the idea of using inertia, like a fly press, rather than hydraulics.

GNM

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Thanks, George. The tire was just my first available thing to use. I thought of filling the tire with concrete, but that would be WAY too heavy. Currently, I'm thinking of rolling or segmenting a three inch pipe into a 30 in circle and weld that onto the tire rim instead of the rubber.

Do the force calcs look reasonable? I thought of having different sized sprockets for faster but lighter strokes. Not sure that would be worth the effort. 

As for a clutch, are you thinking something like a derailleur on a bike? The chain could be on an idler sprocket and swapped to the drive sprocket?

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Your concept isn't unlike one I had for a log splitter I never built though there are similar versions available for sale now. My idea was a spinning wheel, concrete filled tire in the case of the splitter, not as heavy just means less momentum to convert. Spinning flywheel on a shaft with a rubber "drive" wheel on the shaft. The linear motion was caused by a contact "board" that was lifted into contact with the small "drive" wheel. The contact "board" was driven by the "drive" wheel and forced the wood block into the splitting wedge. To prevent slippage between drive wheel and "board" wrapping the wheel with a cogged belt teeth out and the other half glued, screwed and tattooed to the drive "board" drove the wood block into the maul. When the drive board hit the limit of it's travel it lifted out of contact with the drive wheel.

The above concept doesn't have the leverage advantage a screw provides as in a screw press, however the operator can crank the fly wheel up to a higher rotation speed and have more momentum to convert. The "engine" has more torque to make up for not having low gears. A fly press has less momentum but the lower gear ratio provides comparable impact force. A rotating flywheel converts greater momentum to comparable force through higher gear ratio.

I was going to drive the log splitter with a gas engine but drew up a 10 speed bicycle drive because I like options. The flywheel press doesn't need to be spinning very fast, for a partial revolution even. However a simple coaster brake bicycle pedal drive and a hand crank within easy reach makes the machine. You even have a coaster brake to stop it if you wish.

Hmmmm?

Frosty The Lucky.

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Frosty - Thanks for the input. My aim is to make something comparable to the fly press, but with easily available materials. Too much momentum will make it difficult to get to speed (the other third of the equation - weight X speed X radius) Your idea sounds great for a log splitter because you want one great stroke to do the job. The way I've seen fly presses used, looks more controlled. Again - I have no experience, just trying to think it through.

I decided on 50 pitch roller chain because one strand tensile is nearly the same as I calculate the force generated (but I'll have two strands) AND its the largest easily found at Tractor Supply. I don't think that bicycle chain would stand up to the stress very long. I don't know if I could adapt a derailleur to 50 pitch and that might prove something to pursue for greater flexibility. For now I'll be happy if this thing will put out anything close to what I calculate. Almost 3.5 tons/ft^2 concentrated on a die with an area less than 2 in^2 should be useful.

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Have you looked at a board hammer for another take on how to do it?

My screwpress has a ring that provides the mass with two dependent handles.  They are removable and you can use a strap attached to the ring for the "pull".  OTOH if I'm giving a big pull my head is outside of the danger zone anyway. If I'm giving a small pull---a bump, my hand is on the handle and I know where my hand and head are at. Now making adjustments to the dies the screwpress can autorotate down if you don't set the stop on it and thwap you.  I slide some pipe insulation on the handles when I expect that may happen. (And try to use the stop all the time!)

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The description sounds more complicated than it is, it's certainly simpler than your chain block system. The drive "board" is  shaped like a tuning fork so when it bottoms the drive board shifts so the other side contacts the drive wheel and it returns to the rest position. No spring return to suck energy from the blow.

You don't have to turn the flywheel any faster than you need, you aren't splitting wood, you're striking single controlled blows. however if a person wanted to spin the fly wheel up it could be used like a low bpm power hammer.

Yes, Thomas it drives like a board hammer but it's not a free falling weight. It's the same mechanism of conversion from rotary to linear motion.

Frosty The Lucky.

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I had to look up board hammer. I've never seen one work and the only drop hammer I've ever seen was massive. 

Thomas, I never meant to imply that fly presses were any more dangerous than anything else you find in a smithy, just that having the flywheel on the side made it a little more safe for the head and MAYBE a little more efficient (remains to be seen). 

This design is really borne of the desire to have something you can make (and repair) with easily available OTS materials. I haven't heard any challenges to the calculations so I'm going to order the parts and get started. I'll take pictures of the build as I go. Thanks guys.

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I think you are underestimating the side forces the pressing of a piece of stock may have on your frame and guides.  There is a good reason for those heavy weight guides on fly presses, hydraulic forging presses and power hammers.  I would be careful of the potential for off center force, the guides binding, and the whole thing wracking.  Just the offset of the chain from the center of the axle may cause you trouble.

Still, best of luck with your build.  I'd love to be proved wrong.

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Thanks Latticino. I had that problem on my first try using wire rope without a pulley. I can't say I solved it, but the way I got around it was to have my anvil "float" on the top of the frame. The anvil and ram were made from heavy duty truck springs. I used the center bolt hole to mount my dies. The two draw rods were not connected. 

The cable would wrap unevenly and it would move as it wrapped. The small movement up until the instant that everything came together was easy to compensate for in a test, but wouldn't be acceptable in a production machine. That is one of the reasons I'm going with roller chain. My hope is that the pull will be consistent enough that I can place the anvil where it will always pull straight through the guides before i weld it down.

I'll give your advice some more thought. Perhaps static rod guides ABOVE the anvil that the ram will ride down? And I'll try to be more careful to center the loads than I was in the drawing.

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Minor change - I ordered 13 tooth instead of 12 tooth so I wouldn't have to bore out the hub sprocket to 1.25".  I also realized that the last sprocket that takes up the slack with a counter weight doesn't need to be a sprocket. Just a rope pulley large enough to fit the chain in to hold it straight. Cost for 2 hub sprockets, 2 idler sprockets and 10 ft of #50 roller chain - USD $76

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