AdamG Posted January 21, 2017 Share Posted January 21, 2017 Hi all, i am just about our set up with the basics in my garage now, including the pneumatic hammer I have been working on for some time. It doesn't hit as hard as I expected though, so I thought I would check here and see if anyone has suggestions. have a look: Quote Link to comment Share on other sites More sharing options...
brianstucker Posted January 21, 2017 Share Posted January 21, 2017 From what I understand you have to have an air compressor putting out a minimum of at least 17cfm. I bought the plans. I like the design for simplicity. But I don't want to spend 1500$ on an air compressor. Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 21, 2017 Author Share Posted January 21, 2017 Hmmm. I did buy a big compressor... 5 hp 60 gal tank, but it might be a bit less than 17 cfm. I figured I should get at least a few good hits before it slows down, especially with 1" hose (until the final piping around the valves etc, which are 1/2". I might take the silencer off the exhaust to check if that helps. Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted January 21, 2017 Share Posted January 21, 2017 CFM is rated at different pressures, what CFM is needed at what pressure? The higher the pressure the less CFM you get. Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 21, 2017 Author Share Posted January 21, 2017 I'll have to look. I think it was 12-13 cfm at 90 psi. It's a 4-cyl compressor with 5 hp motor on a 60-gal tank. That pneumatic cylinder on my hammer is pretty wide... if I could have found one narrower, I'm sure it would be more efficient. I think the reason I went with this one was the shaft diameter (which was beefy). I might see if a smaller cylinder would fit, but I might have to make an adapter plate, as I drilled out a big hole for the actuator/shaft, and the bolt holes only have so much steel. I told myself that the cylinder would probably be the first thing to fail, so when it goes, I might try the other size! I couldn't figure a way to run that ram through a round bushing (I don't have a lathe etc). The plate-bolted-on design probably doesn't win any awards, but at least holds it roughly aligned vertically, and should keep the ram from flopping off, but it isn't a precise kind of system. Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted January 21, 2017 Share Posted January 21, 2017 Figure out the volume of the cylinder, and compare that to the compressor. That compressor should do far more than 12-13 @90. A couple off things to check. Is the ram binding at all in either direction, and can the air exhaust fast enough so as to not create a cushioning effect. Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted January 21, 2017 Share Posted January 21, 2017 I just watched the video, and I think you may not be fully exhausting the air from the lift side and that is cushioning the downstroke. I would think that you would need a way to leave a big exhaust port open on the downstroke until you are ready to lift, then have it close as the air comes on. Any air trapped on that side slide of the piston will act as a cushion unless it can get pushed out fast enough. Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 21, 2017 Author Share Posted January 21, 2017 I think you have nailed it. Even though I have a needle valve regulator on the up hose, enough air gets trapped in there that I can hardly contact the dies at full throttle. But if I power the second valve any further, stock wider than 1" will make it stick closed like in the video. I was going to go back to the single valve, but this is the reason I went to two. The hoses, threads and barbs are all 1/2", which is the biggest I could find for the 6-port valve and cylinder. Do you know how to avoid this cushioning? I could also extend the exhaust and branch it (in place of the silencer) but I'm not sure the issue is exhaust, or this air cushion. As for binding, it does shudder a bit, but not terribly. Maybe I'll make a new video today. Just in case, I will increase the pressure going to the co trip valves and make sure they both leak a bit so that the shuttle inside the main valve gets moved back and forth properly. That's part about the original plans that didn't make sense to me; you may send air to one side or the other, but unless the other side can vent somehow, the shuttle won't see differential pressure and move! Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 21, 2017 Author Share Posted January 21, 2017 Wait a minute... I think the issue is with trying to use this 'balanced' system as in these diagrams: I need to ensure that the exhaust of the up stroke goes to exhaust when moving down (i.e. not to a sealed dead end), and vice versa. I thought it did, but I'll have to check. If on the 'down' stroke the air can't vent, I need to rearrange the P and EA/EB approach for exhaust. I see bleeding knuckles in my future (hose clamps always seem to bite me). Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 21, 2017 Author Share Posted January 21, 2017 Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 21, 2017 Author Share Posted January 21, 2017 Just in case, I will increase the pressure going to the co trip valves and make sure they both leak a bit so that the shuttle inside the main valve gets moved back and forth properly. That's part about the original plans that didn't make sense to me; you may send air to one side or the other, but unless the other side can vent somehow, the shuttle won't see differential pressure and move! Muhahaha! Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 22, 2017 Author Share Posted January 22, 2017 ...going to the control valves... Quote Link to comment Share on other sites More sharing options...
Anderson G. Phillips Posted January 23, 2017 Share Posted January 23, 2017 Looks much better. With the hammer dwelling for a while at the bottom (We call this the finite delta time) you may just need to move the bottom trigger or mini valve up some so the hammer has to stretch to hit the material. The hammer never gets into a natural rhythm if the valves are two far apart. That natural rhythm where the head hits air cushion on either top or bottom will make it easier to use IMO. Great to see the videos, Thanks for posting them! Here a chart of what we shoot for as ideal form from a few years back. Quote Link to comment Share on other sites More sharing options...
AdamG Posted January 23, 2017 Author Share Posted January 23, 2017 This is amazing. Thanks for that chart. I have been planning to go back to the single valve, but being able to fine-tune my existing setup is also great. It would have been difficult without knowing this. In the end, I'll have a single valve that can be moved up/down based on where it pinches onto a vertical rib on that slide/retaining bar on the left side. I just replaced my garage door opener and the old one had a long acme threaded rod that I was contemplating using for this, but I think it's simpler to stick with my current design. One other thing... I think I have noticed that the bolt heads that hold the ram onto its back plate are grazing up against an unevenness in the slot I carved for them on the back side. This creates some lateral motion (elbow articulation at the clevis pin) that I don't like. Next chance I get I'll tear it down and grind out that slot to avoid this rubbing. Quote Link to comment Share on other sites More sharing options...
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