Power hammer build

[arftist]

Cut to the chase and change it to a flat belt. While you are at it, eliminate the speed reducer, it is way too slow to do any work at all. 350-400 blows per minute. 

I would also rearrange the geometry of the entire top of the hammer, balance out the spring so it has a chance to whip. The spring should come near the bottom of the stroke and still have 1-2" of free space between the dies. 

 

[Ted Ewert]

I've decided that the crank, pulleys and clutch are not the most optimal mechanism for this application. I'm going to rebuild the whole drive system using a cam instead of a crank. I like the cam because it is a constant load through 98 percent of the cycle. I've mostly worked out a "clutch" mechanism, but it's still in the planning stage. Stay tuned...

[Ted Ewert]

After pondering a cam system for a week or two, I decided to give the crank one last try. I ordered some larger diameter (6 in) pulleys which would fit a B size belt, and got a BX belt to match. This works far better than the little 4L belt I had before.

Consequently, I found that my crank was too long for this particular configuration, and shortened it to roughly where it was before (2 1/4 in). This was due to the spring over flexing and pulling the hammer out of the guide and throwing it halfway across the room. These are the types of effects you just don't get on paper (or in a model).

I had some trouble with the hammer sticking in the guide. The lateral force of the rollers wanting to slide off the end of the spring when it's bent is fairly high. This occurs during the first part of the lifting cycle. Having tight tolerances between the guide surfaces and the hammer minimizes the amount of cocking the hammer can achieve, but any little amount of friction can cause sticking. Since the material I'm using is resistant to oils, I sprayed some light grease on the surfaces and solved the problem.

I had to clamp the springs together for added stiffness. It's not a proper floating spring clamp, but that will come later. Reversing the direction of 35 lbs of hammer takes a fair amount strength. Adjusting this clamp to the optimal position will still take some fiddling.

I also modified and mounted a motor adjustment plate so I can adjust the motor position if the belt stretches.

I think I can still get some more travel out of the hammer so I'll try that. Otherwise I'm pretty happy with the overall operation at this point. The hammer hits hard, and I think with the right dies, I may be able to shape some steel. The anvil is relatively quiet (no ringing) and has held up quite well.

[Benona blacksmith]

I don't mean to be a party pooper but my hammer would have blown that board apart in one swift blow!!!

[Ted Ewert]

Well, good for your hammer. 

[Ted Ewert]

I hope at least a few of you enjoyed this thread.

I built this hammer not purely for my own benefit, but also to show guys who want to build one that it's not that difficult. I also built it for under a thousand dollars, which could be further reduced with some more creative scrounging. That's fairly cheap in the world of power hammers. 

It not the biggest, and certainly not the best, but it works and will adequately serve my modest needs. It will also save my aging arm a lot of wear and tear. 

Most importantly, it was fun to build.

Learn to build

Build to learn

 

[anvil]

Great post! Keep it going.

[pnut]

I second that thought, Anvil.

Pnut

[GolFisHunt]

I have enjoyed it thoroughly! 

Not being afraid of failure is quite liberating. However, a 35 lb. hammer flung around the room would be a bit disconcerting.

[Ted Ewert]

OK, I'll be happy to update any changes I make, and maybe even a video while I learn how to pound metal with it. 

Failure is only when things go south and you give up. The hammer learning to fly was a bit of an eye opener. Fortunately I was standing off to the side and out of range and no damage was done. That was the clincher for shortening the crank though.

[anvil]

No mistakes, just learning experiences.

[arftist]

This is a good example of why reinventing the wheel is a waste of time for most people.

For the best possible geometry the spring should lie flat...the rollers can be much tighter and the possibility of flinging the hammer out of the guide is nil.

[Ted Ewert]

I mentioned earlier that I was going to try a cam instead of the crank, so I finally got that built. The reason I went to a cam is that a crank only accelerates the hammer for 90 degrees of rotation. The other 90 degrees is slowing down. With a cam I get full acceleration through 180 degrees of rotation.

This cam is a double action cam where it drives the hammer both up and down. This is accomplished through having a roller above and below the cam, so when the cam is finished pushing in one direction it immediately starts in the opposite direction.

To do this I have four rails, two on each side of the cam, which straddle the drive shaft and ride against bearings mounted right next to the cam. This arrangement allows the the cam to drive the rollers while also keeping the rollers constantly aligned in a vertical plane.

Here's a short video I made for illustration...

[Judson Yaggy]

The video doesn't work.  Put it on youtube and post a link here.  

[Ted Ewert]

9 minutes ago, Judson Yaggy said:

The video doesn't work.  Put it on youtube and post a link here.  

Works for me, anyone else?

Here are a couple of pics

For the cam I'm using a 8" X 1" disc which I had from another project. I offset the hole 2.25" from center which gives me a total of 4.5" of travel. I'm also using 1" wide by 2" high nylon rollers. 

I was thinking that a cam might work better than a crank for those who are using a VFD. It's much smoother and doesn't have any slowdown in the cycle.

[Buzzkill]

37 minutes ago, Ted Ewert said:

Works for me, anyone else?

I get "video playback aborted due to a network error."  I get that with some other videos posted on here as well.

[Chris Williams]

I can see the video. 

[Kevin Olson]

Vid works for me. Sure looks like it hits harder. I wonder if your getting more whip from the spring with this settup. 

[Ted Ewert]

17 minutes ago, Kevin Olson said:

Vid works for me. Sure looks like it hits harder. I wonder if your getting more whip from the spring with this settup. 

It does hit harder, I noticed that right off the bat. I don't think it's whip as much as it is straight drive. It goes back to a crank slowing down (vertically) during the last 90 degrees of rotation, while a cam actually speeds up during this portion of the cycle.

The cam assembly is a little more difficult to make than a crank, but it works a whole lot better. It doesn't shake the bolts loose either like the crank did. 

Just a note, you don't need a solid round to make a cam. You could use a steel ring with a vertical bar for the axle.

I'll try uploading the vid to Imgur and attaching it that way to see if it works better for you guys.

[Goods]

I have never been able to get the uploaded videos to play. The thing that seems to work the best is YouTube, but not sure if everyone likes having to setup accounts with them...

David

[Ted Ewert]

OK, I posted the video on YouTube: 

I'm curious if anyone now, or in the future, would want to try a drive system like this. A cam can be used in place of any crank, but there are a few things to take into account to make it work properly. I can post what I learned if anyone is serious about it. 

[Benona blacksmith]

It seems to hit much harder and faster than before! Well done!!!

[Steve Shimanek]

That looks like it hits well, with a decent rate; is there a way to secure it better so it doesn't vibrate from the cam action, and have the ram in  the up position when you start? Good job.

[Ted Ewert]

Thanks guys, I appreciate the support.

The vibration is due to small support column. If I did it again, I would use at least a 5 inch square tube. Scrounging is cheaper, but you pay the price in other ways. Since that video I have installed some support to minimize the movement. 

I don't know any way of stopping the thing with the hammer up Steve. It just stops wherever. It's not what you would consider a sophisticated piece of machinery. The speed reducer has a worm gear which doesn't lend itself to any slop. I'm sure there's some way to do it, but it's not that big a deal to me. 

I'm still trying to figure out how to use it properly. I plan on forging something with it tomorrow, so we'll see how it goes. 

[Ted Ewert]

I've been practicing a bit on the hammer. I figured simple tapers were a good place to start so I made some hooks. 

The closest hook was made from 5/8" square stock, and the hammer made short work of flattening out the finial. I actually shortened the hammer stroke for the smaller stuff because I don't have fine control of the stroke and it was over squishing the thinner parts. The "clutch" is more of an on /off control. 

I saw a video where a guy was making feathers with 3/4" angle iron. I made a hardie tool with a slot in it for the raised portion, and it worked pretty good. I textured one and chiseled one, and the chiseled one took a whole lot longer. I like both styles.

I beefed up the center column with some 3" angle iron. The outer edges of the angle fit perfectly on the "fins" of the I beam, so I welded it on one side and it's quite stiff now. Looks a bit odd but it did the trick. I also found out that bolts like to come loose unless tightened hard. 

The only thing which has worked flawlessly from the start is the anvil. I got a lot of grief over that design, but it has performed beyond my expectations. No deformation of the steel and no cracking or spalling in the concrete whatsoever. In fact, everything I have made with concrete (two anvil stands and a swage block) have never shown even the slightest failure of the concrete. Reinforced concrete is a whole lot tougher than people realize. Heck, they used it for bunkers and pill boxes back in the day and it held up well, even against artillery.

The only other thing I should have done is to make an isolated pad for the anvil. When I run the hammer it shakes stuff off the shelves in the shop and you can hear and feel it all over the house. The wife isn't real happy about it. I may have to rent a concrete saw and dig out a good sized hole for a new pad. I think I'll be good if I can get the anvil separated from the slab.