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Thanks Buzz, I'm looking forward to pounding some metal too. This design is a conglomeration of several different hammers. I'm still trying to decide if I want to use square tubing lined with plastic, or a T slot for the hammer guide. I'm leaning towards the T slot because it would be fun to build. 

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That build is looking great. This is very random but you mentioned the woodpecker motif back on 7 Oct and that got me thinking back to a small hammer bench top hammer I saw on Youtube. This thing was like a sewing machine  with a 10# or 15# needle. I had just competed some of the Allan Quatermain books and one of the main characters was a Umslopogaas, a Zulu Chief who for no fault of his own needed to take his act on the road. Umslopogaas used his axe, Inkosi-kaas, to peck at his enemy like the Picador with his lance or the Banderilleros with their darts during a bullfight. This style of getting stuck over and over. That how Umslopogaas got his name of 'Woodpecker' that according to the author translates to "woodpecker" in Zulu. 

 

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In one aspect you are correct in your assumptions Ted. You can indeed adjust the stroke length by adjusting the drive side distance from the fulcrum. Levers and pullies are the same thing where the physics are concerned, a pully is a lever that goes all the way around.

However, there are a couple other concerns with adjusting the torque vs distance ratio on the helve the way you plan: First is stress, that close to the fulcrum will require a lot of torque. I don't recall the length on the other side of the fulcrum or I'd post the ratio. There is a huge moment of torque against the motor. 

You will get the stoke and hard blows but it'll be at lower BPM with more wear on the machinery. 

You can get the stroke and speed at a higher BPM with less stress and wear by increasing the crank radius and pulling the connecting rod back from the pivot to match the change. 

Frosty The Lucky.

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Thanks eseemann for the interesting history tidbit. The Zulu's are great warriors. 

I got my hammer mostly assembled and it came out at just over 30 lbs. The main body is 3" x 3" x 12", and is made up of nine 1" x 1" solid bar pieces welded and pinned together, with the center bar longer and used as the connecting rod. 

I decided to go with a rectangular steel tube as my hammer guide. For the bearing material I bought some UHMW (Ultra High Molecular Weight). This stuff is supposed to be better than PTFE (Teflon) as it is specifically designed as a multipurpose bearing material. It is self lubricating and engineered to work with metal surfaces. Sounds good on paper anyway, so we'll see how it holds up.

Frosty, we're on the same wavelength. I just wrote the following and then your post popped up!

It was mentioned earlier that most cranks are 3.5" inches, whereas mine is only 2". Theoretically it shouldn't make any difference as you can adjust the position of the drive point for any desired hammer throw. However, there is a catch. The closer you get your drive point to the fulcrum, the stiffer the spring is. This affords less shock absorption than if your drive point is further out on the spring.

This is more of a concern with a speed reducer in the drive line than it would be with just pulleys. The armature in an induction motor will take a lot of shock load without damage. A worm gear speed reducer is a one way device and much more susceptible to shock damage. I may have to build a new crank.

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The more flex in the helve on the driven side the more energy you loose for no good reason. The hammer side needs the spring for a couple reasons: First it provides the give upon impact that prevents the mechanism from breaking outright. Secondly, it isolates the rest of the mechanism from the impact shock inherent in a hammer. This is arguably the same as reason one but less immediate. Thirdly it provides "snap" to the stroke same as a spin casting fishing rod does to the lure, if the hammer side doesn't have spring you lose velocity for the same energy/velocity input. Spring in the helve here stores mechanical energy and accelerates the hammer to a greater velocity than just the crank speed. A large part of this energy comes from the mass continuing beyond the top of crank and helve stroke.

Were I building this hammer there wouldn't be spring on the linkage side, only on the hammer side. Being able to adjust the ratio of leverage is attractive and would be worth the experiment. With the top die at rest and bottom of it's stroke it needs to be out of contact with the bottom die or it can't take advantage of the snap the spring imparts. 

Frosty The Lucky.

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Matching the right amount of spring to the weight is going to take some fiddling. Getting the maximum amount of snap at just the right moment is going to take even more fiddling. 

I did manage to make a longer crank today. I'm trying to get in as much shop time as I can before #@&**# PG&E turns my power off! It's about 70 degrees with no wind here and they're threatening to turn the power off! Crazy times...

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Getting the desired snap is a matter of treadle control, it needs to be real time control to be effective. This is why so many variable speed power hammers don't get talked about much except in disappointment. You need the speed control under your toe, honestly.

It'll take a little while, surprisingly little, to get a working handle on using a power hammer and you'll be taking raw stock, say 1" sq. isolating sections in the hammer, forging leaves, stem and from hard slamming rough preform to fine plannishing sometimes in one heat. Believe me you just can't shape a leaf and SOR the stem without changing BPM and the power of the blows. 

If you watch videos of the old water wheel tilt hammers you never see the smith reach up and change the gate in the flume to change the BPM of the tilt. Nope you see rough to preform work and the finish work done with hammer and anvil or on a different power hammer.

A throttle is a BIG deal.

Frosty The Lucky.

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Thanks for the info Frosty. I've started to build the foot control mechanism but I'm still working out how high I want the fulcrum position. I spend a lot of time staring off into space trying to figure out how I'm going to build one part of the hammer or another. Been a fun build so far. It's never a bad thing to build something which stretches your abilities a bit. 

Power was out all day yesterday, but supposed to come back on today. At least there haven't been any fires in my immediate area. 

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Got a little more work done on the hammer. I built the hammer guide and attached it. 

N68tjcF.jpg

I also go the hammer finished, as you can see. I built it out of 1" solid square stock which I cut to 12", with the middle piece being used as the attachment rod. I welded a pre-drilled and tapped face plate on the end. This was made from 3/4" plate. I also added two 1/8" sheet metal pieces to the sides of the hammer for the primary wear surface. 

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I made the roller assembly with a couple of nylon rollers. They seem to work pretty good. 

9vsFQwG.jpg

I have a piece of 4140 coming to make the dies out of. It's 1" thick by 2" wide by 12". I should get a few good dies out of that. 

I just have the foot control for the clutch to finish, and a few other odds and ends, and it will be ready to test. 

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I do a lot of space staring off into myself, graph paper drawings and maybe modeling. When working on fine details like just where to put the connecting rods and pivot on your hammer I go to a good fashioned erector set.

Frosty The Lucky.

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I find designing mechanisms in my mind to be rather relaxing. It's my form of meditation. 

I'm hoping to get the electrical done today, then it will be time for a test run. I still have to build some dies for it too.

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It is meditation to me as well but I've built too many things to think I can trouble shoot a complex device sufficiently during little mental trips. Modeling shows up little deal breaker details that aren't intuitively visible. And a lot of things that can be done mentally are too tedious to follow to the logical conclusion. That's close enough to actually work properly. 

A good example is the crank linkage on your hammer. You've compensated for not being able to refine distances mentally by making the device overly adjustable. Once you've modeled it by using it the linkage isn't likely to move until the kid who buys it at your estate sale decides he knows where it SHOULD be. And the learning curve is reborn. 

Frosty The Lucky.

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