explosives, the big
boom is really what it’s
Of course, our
with this project is
safety. We wanted to
ensure that every
rated. With respect to
the steel pipe fittings,
that meant we would
be using schedule 80.
Given the challenges
we faced in tracking
PVC for our previous
efforts, we undertook
the search for the fittings with some trepidation. Would we
be hamstrung by the lead times for specialty parts right
from the get-go? The anticipation would be torturous, like
having to wait to open the present under the Christmas
tree that was clearly in the distinctive shape of that Razor
scooter that you had been waiting patiently for all year.
However, we were as pleasantly surprised as a shopper
emerging from Black Friday without getting trampled at the
entrance to Best Buy in the wee hours of the morning. All
of the schedule 80 fittings we could ever want were
available at good prices through the McMaster-Carr catalog,
and they arrived at our door mere days later. We picked up
all of the elbows, tees, nipples, and end caps we needed, in
addition to a few other smaller fittings.
We would need a new setup for the input valve — a
Schrader valve like on a bike tire wouldn’t work for
something we wanted to pressurize up to 3,000 PSI. We
opted for a Foster straight-through quick disconnect fitting
that would allow input through a manual ball valve. The
ball valve would allow us to reliably open and close the
tank, and McMaster even had a great selection of small
high pressure ball valves. We placed our orders and eagerly
awaited our presents.
Making a Parts List, Checking it
Thankfully, the wait wasn’t long because we didn’t
even have advent calendar chocolates to count down the
days. The heavy duty boxes arrived at our doorstep, and we
must say that it was a different experience than with
smaller scale projects. Don’t get us wrong — we like a
bright red SparkFun box just as much as the next roboticist,
With the fittings in hand, we could begin to lay out the
cannon and get a sense of the scale. Given the smaller
diameter pipe than our PVC versions, we were concerned at
first that the cannon might look too small and thus lose
some valuable cool factor. Fortunately, laying the fittings
out like a really heavy jigsaw puzzle didn’t disappoint us at
all. It was a lot more like putting the first ornaments on a
freshly cut and fragrant Christmas tree — an exciting
preview of even more exciting things to come.
One of those exciting things would be the pipes for the
tanks and barrel. The barrel would be the heaviest part of
Twin brothers hack whatever’s put in front of them, then tell you about it.
SERVO 12.2016 55
HIGH PRESSURE FITTINGS. THE 6,000 PSI DYNAQUIP VALVE.
THE SOLENOID VALVE FROM CLARK COOPER.