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Pneumatic Chisel

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Pneumatic Chisel

Unread postAuthor: daccel » Sat Apr 12, 2008 11:42 pm

The last project I posted never ended up getting finished, so this time I thought I'd finish one and then post!

This isn't a cannon, but uses many of the same principles, so I thought it might be interesting to those on this forum. It's a single impact air powered chisel. Air chisels already exist, but they have many small impacts, instead of one controlled large one. My dad needed something like this for use in his rock quarry for shaping rock, as people that can wield a sledge hammer all day are few and far between.

The diagram and pictures should be self explanatory, but basically it consists of a chamber, main piston valve, barrel, 4lb sledge hammer sleeved in bondo w/o-rings, chisel and guide, small piston valve for barrel venting and pressurizing, and 4 control valves (1 pressure washing gun and 3 blow guns).

Unfortunately I don't have a compressor to test it here, but I'm shipping it to my dad soon - I'll update when he tests it.
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Unread postAuthor: Blitz » Sat Apr 12, 2008 11:50 pm

Very nice, I really like your design.

How hard do you expect it to impact?
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Unread postAuthor: hi » Sat Apr 12, 2008 11:50 pm

its more like a small jack hammer than a chisel. i think you should try to finish it.
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Unread postAuthor: elitesniper » Sat Apr 12, 2008 11:54 pm

beautiful job, maby you could convert it to a full auto piston :lol:
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Unread postAuthor: daccel » Sun Apr 13, 2008 12:11 am

Thanks guys.

I did a small scale test with an old solenoid valve cannon and compared that to what I could do by hand, and it needed to be about 5x more powerful, which is what this is. So it should be equivalent to using the same sledge hammer by hand. It can be adjusted relatively easily though by extending the barrel and/or chamber.

It is finished I just disassembled it to show the components.

Full auto eh? Let's see if this works first! Actually, auto is why commercial ones won't work for this application, so I don't think that's on the drawing boards.
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Unread postAuthor: miskaman » Sun Apr 13, 2008 12:30 am

Looks beastly. Except I'm kinda lost on how it works. Does it recycle its own air?
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Unread postAuthor: daccel » Sun Apr 13, 2008 4:22 pm

No recycling, the used air is vented. Essentially, on the down stroke you first trigger the pilot for the piston valve at the bottom, then the main piston valve. As the hammer travels down it pushes the air ahead of it out of the lower piston valve. The hammer transmits virtually all of its force to the chisel and stops. There is a rubber ring at the top of the chisel that seals the hole it travels through. To move the hammer back up, the air behind the hammer is vented and the space in front of it is pressurized through the pilot of the lower piston valve. When the vent above the hammer is closed it creates an air lock which holds the hammer in position. Then the pilot of the lower piston valve is triggered, which de-pressurizes the space ahead of the hammer. And repeat.
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Unread postAuthor: DYI » Sun Apr 13, 2008 4:43 pm

That chamber looks like 3" pipe to me, and the one on the GGDT model says 2". Try it with unregged CO<sub>2</sub>, and you'll get an hour's worth of hammering done in one shot.
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Unread postAuthor: daccel » Sun Apr 13, 2008 5:07 pm

The chamber is 2", the barrel is 3" with 2.5" pvc sleeved inside, because I couldn't get seamless steel pipe easily. Haha, yes, and then you can use the remaining 59 mins to nurse your sprained wrists.

But mentioning CO2 gives me an idea, reg'd down to 120psi a 10lb bottle would give you 400 shots if my calculations are correct. That could potentially be useful for places where you couldn't get a compressor to or didn't want to run air lines.
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Unread postAuthor: Sergeant Dotson » Sun Apr 13, 2008 5:09 pm

Very nice design. I don't see much you can improve on. Maybe you can get a patent? This is beautiful. Now all you need to do is make or have someone make yourself a casing or shell.
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Unread postAuthor: XxtriviumxX » Mon Apr 14, 2008 8:24 am

Thats one big chisel :o ... I like it very much, creative, s=xy design
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Unread postAuthor: paaiyan » Mon Apr 14, 2008 9:54 am

You know, this actually makes me think of a way to possibly make a small automatic chisel. Anyone seen the Tippmann A5 with the response trigger?
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Unread postAuthor: daccel » Thu Apr 17, 2008 9:18 pm

I did think about a patent, but just don't see a large enough market for it. And manufacturing on a small scale would push the price too high for something you can make out of some parts from the hardware store. If it helps make my dad's business more efficient that's good enough for me. Plus, I got to play with epoxy and make valves with all materials paid for 8).

A casing is a good idea, it would help keep the fittings and hoses from getting wrecked. Any ideas on a good material? It can't be that heavy as the whole thing already weighs a lot, but would have to be quite strong, as it will inevitably end up getting banged into rocks all day.
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