Pneumatic Hammer Control

Hello,
I am working on a science project that will pneumatically pound a
small nail into a piece of wood. I will be using a Basic Stamp to
control it. My question is what would you suggest for the actuator
and control mechanism (electrically controlled air valve?)? I have a
coleman bike/tire pump to 'power' the actuator. Any help will be much
appreciated. Please keep in mind that my budget is not huge for this
project.
Thank you in advance!
Reply to
NewB
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Maybe you can find some info about how rotary hammers work. I just bought a Bosch Bulldog rotary hammer. It has a hammer-only mode and from the lack of wrist pain after a 10 hour demolition project I assume it uses some kind of pneumatic action.
These things really rip. I was amazed that I could buy this tool for just over $200. With the variable speed it can hammer very gently but when fully pushing the trigger it sent a fist size chunk of concrete 10" up into the air.
Regards, Joerg
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Reply to
Joerg
--Howzabout adapting the mechanism in an electric stapler? They really whack pretty good and it's just a solenoid...
Reply to
steamer
Hmm... my experience is mostly with industrial parts, which are (naturally) priced for the kind of pocketbook that Ford or GM has. Pneumatic cylinders and electrically-actuated control valves tend to be expensive items. If there's an industrial facility near you that's junking any old equipment, you might be able to cannibalize some parts off of that. Alternatively, an automotive salvage yard might have something useable. But that's a crap shoot. And what parts you can find within your budget are going to impact your design. A bike tire pump? Is it electrically powered? Otherwise, your arms are going to get real tired, real fast -- those pumps are made to bring a tire up to pressure, not to provide volume. I'd strongly suggest looking into one of those small "emergency kit" electric tire pumps, the ones made to plug into a dashboard cigarrette lighter. Any Wal-Mart, K-Mart, or auto-parts store ought to have some. Chop off the cigarrette-lighter plug and wire it to a control relay on your board, and you can control the pump from the Stamp. That might allow you a way to get around buying/scrounging a seperate valve. With pneumatic actuators of any kind, volume and flow rate are the big items. To deliver a punch hard enough to drive a nail, you need to slam a lot of air into the actuator, fast, which means using good-sized tubing for your air. Small tubing just won't move enough air fast enough, even if you have lots of source pressure. And with a bike pump or even the electric pump I mentioned above, you're not going to have a great deal of volume *or* pressure available, unless you add more to your system. You could add a pressure tank that could be charged up slowly by the pump, and then release that pressure hard and fast through a valve. This is usually called a "surge tank" -- it lets you get big, short bursts of air when your supply pump can provide enough CFM (Cubic Feet per Minute), but *can* provide decent pressures. One problem with this solution, though, is that it adds cost and complexity. Tubing and valves to handle higher pressures can cost more. My first thought would be to use an actuator to raise a hammer over the nail, and drop it, letting gravity do the hard work. That way, you can deal with the low pressure and CFM of your air supply. One thing to watch out for is the size of your exhaust: once you've raised the hammer, you have to be able to let the air out *fast.* If your exhaust opening is too small, the hammer will "float" down rather than fall down. Even openings that seem like they ought to be big enough can provide a surprising amount of back pressure. A lot of pneumatic cylinders on the market have openings small enough to be a problem, and they can't be increased in size, because it's part of the cylinder's contruction. One way to get around *that* would be to build some kind of mechanical latch system -- once the actuator raises the hammer past a certain height, the hammer "disconnects" from the actuator and falls free. The hard part with something like this is setting it up so that the two re-connect when the actuator comes back down. You could maybe add some kind of solenoid-driven locking pin, controlled by the Stamp, but that would mean adding sensors to detect when the actuator and hammer were at the top or bottom of their strokes. That's probably how *I'd* do it, but I'm an electrical engineer -- I reach for my soldering iron when more mechanically-inclided people are reaching for a screwdriver. I'm sure there are ways of doing it purely mechanically that would work just as well. What you end up doing will probably be strongly influenced by what kind of parts you can find, and what kind of help you can get locally. Hope this helps some. Good luck.
Reply to
SkyeFire
Electric lawn sprinkler valves might be a reasonably priced alterantive.
Reply to
Si Ballenger
Check out:
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They have solenoid valves for as low as 99 cents and pneumatic cylinders for Hello,
Reply to
Scott McDonnell
Also, don't forget to put a weight on your actuator. Nails like to be driven by something massive hitting them.
Reply to
Guy Macon

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