Jump to content
I Forge Iron

Recommended Posts

Hi everyone,

I saw this idea in a rough sketch on pinterest about 5 years ago, and only recently managed to get around to trying it out. 

Hopefully this will start a new type of cheap power hammer for us novices I like to call a "Diff hammer". Basically, you power the tail shaft on an open rear vehicle diff, then brake the opposing wheel to send force to the hammer drive. Made exclusively from free parts, excuse the welding of a few novices. 

  • This is powered by a 3hp DC treadmill motor, using the treadmill front drive roller as the drive wheel for a V belt, but a flat belt would also work.
  • The plans were to link the two brake levers together, so the hammer was actively braked as soon as you lift your foot, but I haven’t found this necessary.
  • The hammer spring is offset by an opposing counterbalance on the wheel to prevent additional vibrations and noise.
  • I used an opposing spring mechanism as I only had access to trampoline springs for free at the time, and it made the spring rate highly adjustable
  • It is a very quiet unit to run, and bearings are all available at local auto parts stores should they need replacing. 
  • The anvil is a big 130kg round of cro-molly I got for scrap prices, with a bit of rail line welded to the top sitting on a 100mm thick 300mm round I got for free from a local laser cutting place

Video of it working hopefully to come on Thursday. 


any advice would be thankfuly recieved. 








Link to comment
Share on other sites

I remember seeing pics of one years ago and have read the plans. The version I liked best shortened the axles way down and mounted the motor vertically below the Diff.

Take a look at a Little Giant type mechanical. Your crank and link arms are hopelessly complicated and almost none of it is necessary. Besides multiplying the number of failure points and making it significantly more dangerous in a failure it really increases the reciprocating weight without adding to the weight of the hammer. 

You can have a fine working power hammer but you need to clean up your design. I'm not trying to discourage you I just don't want to see you injured if I can help it. I'd much rather see you succeed to show off a hard hitting hammer, some beautiful forgings and tell us a bunch of bad jokes and tall tales. 

Frosty The Lucky.

Link to comment
Share on other sites

I had a hammer based on this at one point.  I was told it came from a blacksmith shop in Carson City, NV.  I sold it years ago when I knew I was going to be moving several times.  It was a pleasure to use and hit hard.  It was around 60 lbs if I remember right.  Mine was driven from a flat belt to a large wheel.  I will try to post photos if I can.




Link to comment
Share on other sites

I think I figured out how to post photos.  One is from before I refurbished it and one from after.  I dont have many pictures of the hammer, but you can sort of see how it worked.  The treadle applied a brake to the off side which engaged the hammer.  It was quite controllable and very simple.  I regretted selling it for years.





Link to comment
Share on other sites

Oh awesome! I like the idea of shortening the axles. Would make for a much more compact hammer. 

Yeah, I'm aware that the spring mechanism is far more complicated than it has to be. And will be updating it eventually with a heavier hammer and lighter rotating mass. Along with a lot more panels covering the moving parts. For starters I wanted the spring tension to be easily variable though and free is good to start with too. I wonder why they had so much rotating mass in the flywheel on the front of the hammer there. 

The next project is a pneumatic hammer and forging press. The log splitter I recently picked up seems to work quite well, but I might substitute in a larger cylinder as it perhaps moves too quickly and could do with a little more force. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...