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Questions on design issues...work in progress

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Hey folks,
I'm in the process of building a power hammer (helve type). Been studying those I have spotted on line to develop design that will work for me.
A couple of questions...
On the linkage between spring and hammer shaft, the ones I have seen seem to allow the spring to slide between two round bars on the end of the shaft.

Is this slide method necessary? How much clearance between spring and bars?

Why not use 2 rod ends mounted to the hammer shaft, linked to the spring by one bar? This would allow rotation as the hammer shaft moves up and down.
Pretty much that is the same type linkage on the other end of the spring.

Speaking of spring.....is it a problem to use curved vs straight? I have a set of 69 Camaro springs that I parked the tractor on for days.....still curved.! I have seen a couple examples with curved....just the majority have flat. Safe to assume concave up/concave down should matter little?

Any thoughts/advise??? Other than to build a tire hammer....I'm too far into this now! HAHAHAHHA
Appreciate the help....

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Hey Brian,
Thanks for the link. Perhaps I misspoke when I used the term helve hammer. (?) I am building a medium sized (about 40-50#) power hammer in the style of Jerry Allen and others. Uses flat springs for the 'helve'. The blueprints are 'similar but different'. However, I did pick up some good ideas for construction and welding techniques, so I do appreciate it!

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Okay so more like a rusty/krusty hammer then. here is a link that might be of more interest then.

FERRUM D GENTILE - Forge - Know How ( Krusty the mechanical powerhammer )

He has photos of his build as well as pdf plans. he is in Europe so the plans are Metric. Hope this helps you.

I am thinking here and have no proof but if you curve up the springs instead of facing down, you will not need to increase the height of the pivot post.

Good Luck with the build and post some pictures. We always love to see what others have done.

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You could use a link setup at the hammer end. I have not quite worked out the geometry yet, but it can be done. However, using two rod ends and a link between them will not work, since there is nothing stopping the link from just folding up against the spring, unless I an not understanding your design. If you had a solid mount on the spring and just a pivot on the hammer head, it might work if the link were long enough. You would have to cycle the hammer to see if it would run without binding. The one hammer I have seen done this way was over 100 years old and the pivot on top of the mast had a link to make up the lateral movement of the spring as it arcs through its radius. Straight springs make set up easier, but you can use curved ones. I would not use 40 year old springs though. Way too dangerous. Go to a spring shop, buy some leaves, not a whole pack, and have the spring guy straighten them with his press.
If you do end up using rollers, the way to determine the distance between them is to move the hammer to its highest and lowest positions. The spring and both rollers should be in full contact with each other only at the extreme ends of the stroke. That makes setting the roller gap one of the last things to be done on a spring helve.

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Brian: Thanks once again. Actually, that site I had spotted early on in my wanderings. It was indeed quite helpful. I will see if I can manage some pics along the way.

Arftist: I was not clear with my rod end concept. I would mount a bar perpendicular to the axis of the springs and offset somewhat from the under face of the spring. The 2 rod ends would be mounted on the upper end of the hammer shaft somewhat like a clevis arrangement with the bar running through them. I thought using the 2 might help stabilize any 'lateral' movement, while the rod ends would allow for the angle changes as the spring moved up and down in an arc. Some of my 'mechanical' concern was whether there was significant 'forward/aft' movement as the spring end moved up and down that required the spring to be able to slide between the two fixed bars. My comment that 'there's a rod end on the pittman arm side of the springs' may not hold water. That end might be able to handle 'forward/aft' movement better since the lower end of pittman is going round and round, not straight up and down like the hammer shaft.
I also thought having the concave of the springs down might trace an arc with less fore/aft movement and have better chance of not binding the hammer shaft.
Does any of this make sense? My poor old brain is close to melt down..:o

Might just have to go with the tried and true.

Definitely appreciate you folks sharing your thoughts!

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