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I Forge Iron

Started Power Hammer Project


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  • 2 months later...
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I ordered a shop air kit from Northern Priority Mail 3 months ago...it got misdirected and ended up on ocean mail, finally got it about a week ago. The compressor is installed and wired already. I still need to get my valving, but the project is still alive.

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I got a chuckle from "any decent spring shop should be able to help".....no such thing around here. Do you see a problem with the geometry of my machine in progress?

The problem with Northern Tool is that they use Fedex for ground delivery in the mainland US and apparently Fedex is not consistently able to then transfer to the USPS. Somehow what should have been 2 to 3 weeks by air turned into 3 months by ship. I do buy from them every now and then anyway. I haven't bought my valving yet, but have spec'd the parts from McMaster-Carr. I can dig up the part numbers if anyone wants to review the list i came up with.

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  • 1 month later...

So the air piping from Northern is installed, and the parts I ordered from mcMaster-carr came as well. I opted to get a dual air solenoid operated main valve, Norgren MN01CGA23A000, actuated by two Mead Fluid Dynamics LTV-20 mechanical air solenoid valves. I looked for some simpler solenoids, but couldn't find what I was looking for. The LTV-20 has 5 ports, so i am a bit confused as to how to plumb in the valve. As far as i can tell, port 1 is for the air supply from the compressor; 2 and 4 are for supply from the solenoid to the cylinder; and 3 and 5 are exhaust ports. The LTV-20 is actuated mechanically in only 1 direction, as it has a flipper lever that allows the ramp to bypass it without actuating it in one direction.  It may be simpler to run the hammer with only one solenoid valve, and fix the lever to actuate in both directions. otherwise, I will need to figure out the plumbing arrangement for two of them.

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This link allows the ram to travel up farther than the spring eye, and whips back when the cylinder retracts. I am going to make another piece with "ears" that will wrap around the yoke of the rod end to limit the movement; the effect may be due to the testt lacking the solenoids to control the  extent of travel, but it seems a prudent fix to make.JPG00003.JPG

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Since I have never built anything like this I hesitate to chime in, but I do have an observation/question regarding the spring orientation.

The way that is mounted it appears as though at the end of the downward stroke of the hammer (when it impacts) that will cause the leaves of the spring pack to separate (or attempt to) rather than the shorter leaves supporting the longer one, which will then concentrate stress on the upper leaf at the first weak spot - most likely where the leaves are fastened together.  Since this will happen in the opposite direction of the curvature of the spring it seems likely to me that the spring will fail fairly quickly under heavy use.

In general though I'm enjoying the thread and learning all I can with the idea in mind that I may attempt such a build myself some day.  Please keep the pics and updates coming in.

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Buzzkill, you may want to look at the pictures at the beginning of the thread and rethink your hypothesis. When the cylinder is retracted, the ram is up, and vis versa. Also, the limit switches/solenoids will help control the cycling and how far the cylinder travels in each direction.

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Those are the pictures I was using.  It's still the same.  When the cylinder ram is up the hammer is down.  When the hammer hits it will flex the spring in the opposite direction of the curvature of the spring and since the shorter leaf does not extend between the rollers on top of the hammer assembly it will not provide much additional resistance to flexing when the hammer hits.  All the stress will be on the top spring back to the point where the leaves are fastened together, which is a likely point of failure since normally there is a rivet through the individual leaves at that point.  Assuming you want the hammer to strike with some force, the cylinder ram will have to extend up slightly beyond the point where the hammer will touch the steel on it's downward stroke.  Once the hammer makes contact with the anvil, or whatever is on it, the spring will flex upward on both ends compared to the pivot point, but more on the hammer end since it is further from the pivot point and that will result in the top leaf attempting to separate from the bottom shorter leaf.

It's entirely possible I'm missing something here, but based on the pictures you've posted I can't see where I'm looking at this situation incorrectly. Maybe I'm wrong or maybe it will turn out to be inconsequential.  Either way I'm looking forward to seeing it in action.

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If you think about how a leaf spring operates on a vehicle, the arrangement is the same as is on the hammer, with the exception being the pivot point is not centered. The shorter section of the leaf spring bundle serves to limit the flex. edit: looking again, I think you are looking at the thick section at the bottom of the spring pack, which in auto use would be at the top....that piece has no function other than as a spacer in my design. it is so thick that it would provide no flex with the forces the hammer will generate.

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On a vehicle the leaves are stacked with the longest leaf on top to the shortest on the bottom with the force on the spring pressing down opposite the direction of the curve.  That way the more the top leaf is flexed the more support it has.   For your configuration the spring will most likely flex in both directions, but need to absorb the most force as the hammer strikes whatever is on the anvil.  When the spring is flexed that way there will be no support behind the main leaf in the direction of the flexing.  It may be a moot point if the spring is strong and durable enough that it doesn't need any additional support. 

If your spacer is several feet long and ends shortly before the rollers on the top of your hammer assembly then that's what I'm looking at.

I've never used a pneumatic cylinder for a rapid cycle.  How many beats per minute are you anticipating with your setup?  What do you see as the main advantage to using an air powered ram over the typical eccentric shaft on some form of wheel or a camshaft setup?  I'm still gathering ideas at this point and am nowhere near ready to start a build, but I do like to know why people choose the various options.

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As to the cycle rate, i do not know; maybe 120 bpm? I have not seen any home made mechanical hammers that match what air hammers with appropriately sized cylinders do; also some tend to be a bit unstable due to the eccentric motion. The air hammer arrangements tend to be linear in 2 directions; also it seems they hit harder than just the falling weight and speed of the ram generates. I chose the helve style for ease of build since i am using scrap iron; also i have limited overhead room. These are just opinions, backed by experience with a 100 Little Giant mechanical hammer, a Bull air hammer and a Phoenix air hammer, plus watching other builds on video.

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In this orientation of the spring, there is a tendency for the ends or eyes to get a little more separated by the extra pivoting or slop from the flex. you could shrink a collar onto the whole bundle ends or feather them out with lock collars..  Or use it and see if any of it needs to be done.  

I for one am looking forward to seeing the hammer in action. 

 

Steve,  well done and thanks for sharing the journey.   Please show how you mounted the limiting switches. 

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I did some additional testing using one switch; it seems I can run the system with one valve, as the ones i bought were 5-2s instead of 3-2s. If I do, I need to figure out a control mechanism to actuate and control the stroke. I was able to get reciprocating action and the ram alignment was pretty decent. More to come......

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from what I have read on my own studies of building such a hammer.  the 5-2 or 3-2 valves can use a micro switch at both ends of the travel. this can come in handy for one strike function as well as fast cycling.  this can also make it so there is less time wasted on the recovery stroke. 

because the exhaust port can be triggered by the complete movement of the inner piston of the control valve (activator) one side can be vented to ambient and it still will cycle. 

Looking forwards to the video.. :)

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 Steve, the tup doesn't just fall from the weight and speed of the ram; rather it is hurled downwards by the force of the springs. 

Not sure how this is going to work for you, normally you would use a solid helve since you are driving it with a spring anyways. As to your geometry problem, you already solved it. 

So...the point of this post is just for clarity.

A well tuned mechanical hammer can hit hard. 

FYI, Litle Giant was the low end of factory built mechanicals.

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