the project. At 10. 25 pounds per foot, our two foot
long/three inch diameter barrel would clock in at 20. 5
pounds. That’s as much as a pug dog. Or, way more than
enough LEGO kits to completely fill up the bottom of a
Christmas tree.
McMaster, unfortunately, doesn’t stock large diameter
high pressure steel pipe. We would have to find another
source. Googling around led us to Southern California
based Totten Tubes. Totten has a wide selection of tubes,
including the schedule 80 steel pipe we needed. Totten was
able to cut the pipes to the length we required, and cut
threads onto the outer edge of the tubes so that they
would play nicely with our fittings. They even delivered right
to our door.
On that day of Bot-mas, we were delighted to see that
the threads on the tubes were beautifully cut, and as we
hauled the tubes onto our work bench we were amused to
think that the weight of the tubes far exceeded the weight
of some of our other entire robots (like our Featherweight,
Twibill Trouble).
High Pressure Parts are Coming to
Town
In addition to the pipes and fittings, our high pressure
cannon would need a variety of special parts to operate
safely and effectively. The heart of the cannon, of course,
would be the high pressure valve. Just like one of our PVC
models, we wanted to use a large diameter ball valve to
avoid pressure drop over the valve. This one required a lot
of research. After the fact, it’s easy for us to write down
that we found a great valve from DynaQuip: a two inch
VAJ2.AR series forged steel body ball valve. However, that
doesn’t capture the hours of research that went into the
search — sifting through lots of valves that looked promising
but then ended up having the wrong specs, or were
prohibitively heavy or expensive.
At times, it seemed as hopeless of an errand as
tracking down a Turbo Man action figure on Christmas Eve.
Finding the right valve was a real team effort, but we
ended up with a valve that we were really happy with. The
DynaQuip valve was rated for 6,000 PSI and was one of the
lightest weight high pressure valves we looked at, clocking
in at only 13. 5 pounds. It was a bit pricey, but safety is
priceless.
Why 6,000 PSI when we only want to pressurize the
chunker to 3,000 PSI? We wanted to go with higher
pressure parts in some areas that were really vital to the
functioning of the device to ensure that the safety of it was
beyond reproach. It would always be the best way to stay
on the Nice List.
Another critical safety feature was to ensure that we
had a way to purge the tanks in case something happened
that prevented us from opening up the main valve and
firing it off like normal. This was another challenging
search, and we eventually decided on a solenoid valve from
Clark Cooper. The solenoid valve — an EH30 series — was
56 SERVO 12.2016
BEAUTIFUL THREADS.
THE 6,000 PSI REGULATOR FROM HARRIS.
THE 5,000 PSI TRANSDUCER FROM TRANSDUCERS DIRECT.