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I rcould really use my help with this best. I took the design off of ones I saw on You Tube. But Im getting so little force with the hammer and I don't know why. Does the hammer shaft have to be heavier? Does the bottom anvil need to be beefier? does my pivot and spring mechanism look correct? help?

PS- I'm not doing forge work. I Need to make a thousand of the items pictured- Hammered 1/8 bronze rod.

IMG_1275.jpeg

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I would tighten the spring and shorten the ram accordingly. If your sabot (the anvil) is now hollow tube, you can pour it full of concrete, weld flat metal right over and make your lower die fixed on that. The ram is probably too light. If its a hollow jackel, you can either change it for full square rod or again, you could pour concrete inside and weld over. Once you tighten the spring and shorten the ram, you need to make it turn about 3X as fast as now, that means either making the secondary pulley smaller (probably easier) or the primary bigger (more costly option) accordingly. I would want the ram to be at least 20# .   I have just built mine, which has 50# ram, but its very sturdy machine, which weights about 1300# whole. It took me about year to make it.

Edited by Jaro Petrina
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From what I can see from the video, the motor is way too slow, the spring isn't doing anything at all (it's supposed to be a large compression spring that pushes the arms apart with great force), and the ratio between the arms and the toggles is way off.

 

Not trying to be a downer, but that needs some work.

 

Edit: Jaro posted as I was typing. He just built one of these that works, so listen to him!

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Well, I copied some things from Alan´s hammer and it was lots of work to make it do what it should. It runs very nice now, but its one of the machines that cannot be done halfway and expected to work. If I was really low on technology, I would just make single straight spring hammer - just the ammount of things that turn and need to be greased, all the pivots and everything are just not there in comparition with something like little giant. Even the ram guides do not be very precise and it will work. Like the scrap machine on this picture, thats far less work than properly done tyre hammer with dupont ram mechanism. 

spring hammer.jpg

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Thank you Jaro and Alan!! You're NOT being a downer- this is what I need. But when you say the ratio between the arms and the toggles is way off - Can you give me better idea of what this means? Thanks

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3 hours ago, jonkessler said:

Thank you Jaro and Alan!! You're NOT being a downer- this is what I need. But when you say the ratio between the arms and the toggles is way off - Can you give me better idea of what this means? Thanks

First, you dont seem to have an understanding that the spring is supposed to be arranged. Yours does not do any work. For the lenght of the toggle arms you would do good to study some dupont mechanism machines on youtube, one thing - if the bones and toggles are too long, the hammer hits limp.  Notice that on yours they are kind of badly angled, because the spring is not pushing them from each other. Which it should I think.

Edited by Jaro Petrina
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The arms, the sort of vertical parts, should be longer and the toggles, the short horizontal parts, should be much shorter.  The spring needs to be strong enough that it pushes the arms apart with enough force that the toggles are horizontal when at rest.  Your spring looks like a loosely wound 1/8" diameter wire?  On a 25lb Little Giant the same spring wire is about 3/8" diameter and is coiled very tight.  The spring is what makes this type of hammer work.  The only thing the toggles do is keep the ram from hitting the pitman at the top of the stroke.  Speaking of which, a second look at your video shows the ram hitting the guide at the top of the stroke.  This is a Bad Thing.  The ram should be free-floating.  I know you just want a fast light hammer to texture small-diameter bronze, so you don't need a heavy ram.  You do need it to work, however.  The leaf spring hammers Jaro showed are far easier to build and tune.  You can use the tire drive to run them as well.  They are a little slower than a DuPont linkage, but since your current linkage doesn't work, it's something to think about.  

 

This guy's hammer shows the geometry, but his progressive-rate spring is also not the best, plus it's mounted too low between the arms.  It should be near the top: 

 

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This is the video of mine. I have spring, rather than the dupont mechanism.  I think youll do best really to start a new and built appalachian style straight spring hammer, they are not super efficient, but much much easier to build.

 

 

 

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As has been mentioned, a hammer like that needs to be about 300 bpm. You have no real mass in the ram, so need to get some velocity into it to get forging energy.

 

Spring rate is wrong, among lots of other things, but get it wound up to a decent speed, then address the other issues as they will make themselves known.

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I do have a couple of insights from my own build in 2000.

You would like the anvil to be a single piece of solid stock.  That said, mine is two pieces bolted together (a 12 inch round bolted to a 1" base plate, with an 8 inch round sitting on that with welded tabs and bolts holding it).  Mechanically it would be better if it were one piece, but that's what we could salvage.  To be honest, it seems to work fine.  According to the engineers you would like to have between a 10:1 and  a 20:1 ratio of anvil to tup. 

 

Concrete is a bad idea, for a couple of reasons.  First, it's just dead mass.  It acts like a dead blow hammer.  A good anvil reflects energy back into the system, aiding the return stroke.  A concrete anvil absorbs energy.  Second, concrete will disintegrate under the repeated blows of the tup, leaving you with what is effectively sand.  Sand is even worse in terms of energy return.  It's why sand filled frames are used to kill the resonance of noisy machines. 

 

Lead, if you were thinking that way is worse in many ways.  It's dangerous to you and everyone around you to work with, and, it acts as an energy dampener (think dead blow hammer) and, over time it will deform.  Steel shot is as bad as sand, for the same reasons.

There were small powerhammers (up to a couple of hundred pound tup weight) that used an anvil (often a broken anvil) and a wood base.  Many of the water driven helve hammers were built this way.

The tup needs mass, a hollow tube is not a good idea.  One of the things I learned looking at old hammers, sometimes the tup was made up of discrete pieces.  The reason this works for the moving mass (top die) and not for a stationary one (anvil) is in the nature of kinetic mass.  At the moment of impact, all of the moving mass acts like a single piece.  It's like pool balls that are in contect in the rack at the instant the cue ball strikes.  Energy is transmitted through the contact points pretty well.  There are losses, but not on the scale of large stationary masses resting against one another.  What I'm trying to say is that I think you could fill a hollow tube with a die on the end of it with loose stuff ( ball bearings come to mind, but a bunch of rebar on end would do the job) and it would act as a mostly solid mass in action.  Best would be to replace the tup with a solid bar.

When the tup is at rest the dies should be about 2 inches apart.  That gives the spring some space to work.  You want the toggle arms close to horizontal when the tup is at rest.  This is a pretty silly video, but the hammer is moving slowly enough to see the action.  Notice that the A frame arms are hardly moving, and the spring is only moving a tiny bit.  Also, notice where the eccentric pin is in relation to where the tup is.  As the connecting rod goes over TDC, the tup is still moving up, compressing the spring.  As the pin reaches BDC, the tup is lagging behind.  As the tup come down the spring is extending, adding power to the stroke.

 

In your video, the spring is flopping.  It lags behind everything.  You don't have enough spring (it's not stiff enough) and it doesn't have nearly enough preload on it.

 

If all you want to do is texture (or draw out, I'm not sure) the brass/bronze rods, maybe what you want is some sort of an Oliver or Grasshopper hammer.

See the source image 

 

See the source image

 

You might also look at a DaVinci Hammer design.

Just my .02

 

 

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  • 2 weeks later...

Nice build.  I love those Rusty style hammers (that's what they are called here in the USA).  I think I would add one more leaf to the spring, it's got a bit too much whip for my taste.

 

g

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34 minutes ago, Geoff Keyes said:

Nice build.  I love those Rusty style hammers (that's what they are called here in the USA).  I think I would add one more leaf to the spring, it's got a bit too much whip for my taste.

 

g

 Not mine, but an interesting chap here in my country. Does lots of things on his youtube page. 

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