Light trip hammer evolution

Mecha

Mecha

Titanium Bladesmith
Knifemaker / Craftsman / Service Provider
Joined
Dec 27, 2013
Messages
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It didn't take long in the world of sword-making to realize I needed a lot more forging power than a mere human arm, especially for very tough beta titanium alloys. The result has been a slow evolution of a light trip-hammer design that's purely for making blade billets: The S.A.M. Hammer, or spring-action metalworking hammer!

The first prototype was a mechanism that could swing an 8-lb sledgehammer:

[video=youtube;C3wzBkxlIww]https://www.youtube.com/watch?v=C3wzBkxlIww[/video]

Pretty ghetto, but it worked well enough to inspire a more refined version that I liken to a mechanical striker, wielding an 8-lb sledge:

[video=youtube;uBGe3yMuU5w]https://www.youtube.com/watch?v=uBGe3yMuU5w[/video]

The hammer above forges smoothly but it was still way too weak, not to mention it has a few drive design flaws. Lifting the hammer under spring tension and dropping it sharply was not the answer. Thus comes the S.A.M. Hammer mark II! This latest design prototype pulls the hammer mechanism down against a spring instead of lifting it, and the hammer haft is made of leaf springs, giving the throw what my friend calls an "almost organic Irish whip." I think of this one as a mechanical arm. The hammer head is about 20 pounds of 4140, shaped like a rounding hammer, and it's much more powerful than the original versions.

[video=youtube;KMKQwZ3ls0A]https://www.youtube.com/watch?v=KMKQwZ3ls0A&feature=youtu.be[/video]

This design incorporates some sprung and flexible dynamics that make it a much more realistic tool. This prototype is rather spindly, and I have a few more advancements for future models that will make it much more compact and smooth in operation. All of these hammers can be easily lifted by two people. It's like a table-top trip hammer for knifemakers!

I'd love to see other people's home-made trip hammer designs!
 
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Very neat design. I wonder about the need for the coil spring at the rear of the helve. With so much flexibility in the helve, the spring really isn't absorbing anything and could be removed without any worry.
 
Glad you like the hammer!

The spring provides lift to the hammer that counters gravity, putting the action in balance. Because of the spring, the mechanism can be turned with just a fingertip, easily spinning it up to speeds that get the hammer slamming up and down: the solid portion of the arm contacts a rubber pad on the upright post that forces the leaf springs to flex and making the hammer head whip down, right at the bottom of the crank's travel. It's a strange feeling to get a 20-lb hammer head moving with so much force using so little input power...the beauty of mechanical systems! Without the spring, it would really be like lifting all that weight at the end of a long haft, and would put a huge strain on the little pushrod and the motor drive system.

If it turns just a bit slower, the leaf springs don't flex and the hammer doesn't whip down; a little bit faster and the hammer loses its harmony and starts to get a double-jiggle wherein it flops all over and may not even contact the anvil, as it starts to get lifted before it even has time to flex down. It has only one speed, a nice sweet spot that is easy to work!
 
I commented over in the sword subforum, but you have more videos here.

The first couple using gravity are basically small renditions of the old water-driven helve hammers that are still in operation here and there in Europe. A blacksmith buddy of mine saw one in Germany with a 2500 pound head, being used to forge church bell clappers. Those work because of the large scale on which they are built. A small version isn't going to generate enough force to do much, especially with a short stroke like you have the first couple of renditions set up with.

The longer stroke on your third rendition, plus the fact that it is a powered downstroke, makes for more power, but putting the ram on the end of the leaf spring with no guidance makes it wobbly, and makes for a very large footprint for a little power hammer.

Putting the spring between the linkage and the helve and either making it have a guided ram or mounting the ram solidly on the end of the helve is going to make it a lot more consistent in its hits. Looking at your clutch setup, you have the idea right, but I think it's engaging too well. If your clutch is able to slip, you can control the hits and feather it or hit flat-out. You might want to try a drive wheel without the splines/teeth. Mine has a piece of oilfield pipe for the drive wheel and has pretty good control for a mechanical hammer.

Again, Grant Sarver's Original Junkyard Hammer is a good starting point, though there are a few changes in approach I would make on a similar project.

[video=youtube;-tPTLwmxsWc]https://www.youtube.com/watch?v=-tPTLwmxsWc[/video]
 
Don't mean to be insulting, but I could forge that 7/8" alloy steel shaft faster by hand than your machine looks to be doing. At least, if by "alloy steel" you mean something like 52100.
Also, I'd recommend some real round-stock tongs- the vise grips are not optimum.
I do applaud your creativity, the machine does appear to function smoothly enough!
 
No doubt, Stormcrow, the hammer is a bit "under-engineered." You should have seen it whipping around before I added the second leaf spring and put a smaller pulley on the motor! It's the kind of thing Dr. Suess would like, but it gets the job done well for now! It certainly won't be forging on post anvils like any time soon, like Gunnhilda can. :eek:

I'm not sure what the alloy of the shaft is, Mr. Straub, it's pretty hard stuff though, just something someone dropped off one day. You noticed the vice-grips didn't work too well! :D The only tongs I normally use right now are one for square stock, and one for flat stock after the square has been flattened to the right thickness. I don't doubt you could flatten the shaft at the same rate as the machine, even I can squash it pretty fast by hand, but not for a long enough time, which brings me to the reasoning for the machine's seemingly gentle strikes.

It was sort of "optimized" for only one job: hammering the square beta titanium stock I've been turning into swords, which seems to only want to move a little bit per hammer hit even at high heat. If I try to move too much too fast, it can get damaged, developing strange cracks. The power hammer basically hits the metal as hard as I dare push it (but not sharply), and continuously. While the hammer could probably squash the round alloy shaft within 20 minutes, it takes several hours of continuous heats and draws to slowly stretch the titanium bar into a sword-sized billet, even with the machine, which I couldn't do by arm power alone.

It's pretty much just a giant arm that never tires, swinging a 20-lb rounding hammer in the same spot, with even force and at a steady rate. Trying to keep things focused and simple! Thanks for your interest. I'll be making more light power hammers, with better features like the ones you mention, Stormcrow.
 
Makes sense I suppose. I assume you've tried to find beta Ti in a more suitable shape, and been unable to? 'Cause even free stock gets very expensive if you have to draw it out that much!
 
I sure have, it's hard to find, and it was a great stroke of luck to have found the particular alloy of the square stock (89.5Ti 10Nb 0.5Fe), which has several qualities that make it especially good for forging into a large titanium blade. Using flat stock was that original plan, but as it turns out, forging the metal has been a crucial part of the puzzle:

The extent of my hammer-forging skills has been exclusively figuring out how to forge titanium alloy into a blade billet, as a single step in the making the best sword possible out of the stuff (titanium alloy sword). I can say that without the forging action, it's easy to see why titanium alloy (universally used to describe grade 5) is often considered too soft and malleable for blade use, but even grade 5 goes from 35 Rockwell C up to 45 or more reliably, staying flexible and getting much tougher just having been hammered out!

If it's heated a good bit above 2100 degrees F, it can definitely be moved faster say, under the force of a real trip hammer. But bringing it up to those temperatures causes a quick degradation of the metal, and the steady hammering at a lower heat, around beta transus of 1680 F, seems to greatly benefit the metal for use as a sword, a subject I would love to discuss with an expert blade blacksmith.
 
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One more thing to show, the machine in slow-motion, which really shows off that whip. I guess it's really a light-duty forging tool, but it's going to help make a pile of sword blanks and save me a lot of trouble. :)

[video=youtube;Wmm2YsXbaMU]https://www.youtube.com/watch?v=Wmm2YsXbaMU&feature=youtu.be[/video]
 
Sure thing, Mete.

This is what is observed in the beta alloy: At very high temperatures in the open air (2100 F+), the alloy rapidly develops a thick, powdery oxide and begins to form a hard surface layer that can sometimes crack and flake off in shiny "fish scales." The billet starts to get brittle, and soaking at high heat makes this contamination quickly dig deeper. The titanium is very reactive at those temperatures, and I believe in a normal industrial setting the alloy would be sealed in a layer of stainless steel before bulk forging into stock sizes.

I imagine the hardened layer is the Alpha case developing from reacting with the atmosphere, getting thick and gnarly. And what of mysterious and brittle Omega phase!

If the billet is heated to a lower temperature, around beta transus of 1680 or so between hammerings, it stays malleable down until all the glow is lost. The brittle surface layer stays micro thin, and the billet can be almost totally drawn out before the powdery oxide begins to form, and there will be stable malleability and no flaky cracks. From what I've learned, the niobium content should be shielding the metal from most atmospheric contamination at those temperatures, keeping most of it no deeper than the surface. This certainly seems to be the case! The metal inside stays really nice, it just doesn't want to be forced.

This is all done under an oxidizing flame, as I understand that a reducing flame will cause serious problems with embrittlement. Since it takes a while and a lot of heats to draw out a large billet via hammer, keeping the heat soak minimized and forging slower seems to maintain the quality of the metal until it gets forged down to sword thickness.

I'm still learning the reasons behind these observations, and if you have any light to shed on them, please do.
 
I wish I could help you there but I'm still learning. Certainly Ti will absorb O2 and N at high temperatures .I did see a reference to a 'glass" coating to minimize the problem but they didn' define 'glass'.Do you have a Ti-Nb diagram handy ? If so please post it or a link

http://cdn.intechopen.com/pdfs-wm/42424.pdf
I thought you might be involved with recrystallization, then I came across this .Ill have to take some time to read this one .Download the pdf and read at will !
 
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Thanks much, Mete! Very nice, the article helps a lot to explain the work-hardening effects, among other things. Here's one of my all-time favorites: "Evaluation of Dual-Hardness Titanium Alloy Armor," an EPIC wherein the metallurgists make beta ti ballistic armor plates with surfaces well over Rc 60 in hardness! You're gonna love this one! :D

www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0702238


I've been unable to finding a proper T-T-T diagram, just basic phase diagrams.
 
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