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
Thank you in advance!
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
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.
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
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
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
Hope this helps some. Good luck.