This is a very inexpensive, easy-to-build, and reliable
launcher made from 3/4" PVC. The 17" riser, launch tube, is threaded
into the base using 2 wraps of teflon tape on threads to seal it well -
don't glue it in, it's nice to be able to swap out different length launch
tubes on occasion. Cable ties are used to hold down the rocket during
pressurization, based on
Ian Clark's design.
A Shrader valve accepts air via most bike pumps. Alternatively, the
red hose shown has a quick-connect fitting that attaches to an air hose from
the CO2 setup. I use plastic tent
stakes to firmly secure the launcher to the ground. Notice the nylon
cord attached to the PVC collar through a pulley - a ~40' length of nylon
cord is attached (implying how far away I am when I launch). NEVER,
ever launch a rocket by pulling down the collar by hand! I learned
this the hard way, unfortunately, and ended up with a broken hand a couple
years back. The pressure gauge, purchased from Home Depot, reads to 150psi.
Here's a closeup of the cable-tie hold-down mechanism:
Click to enlarge
Big hoss is based on the principle that the larger the
volume
of air in the launcher, the less the pressure will drop as the rocket
accelerates up the launch tube on lift-off. This gives 48" of
acceleration for virtually free. The launcher is made from 2"
PVC, with the base 28" x 28". The launch tube is constructed
identically to that of Little Joe, just longer. The Schrader
valve was purchased at True Value hardware, has 3/8" threads and is
connected to the PVC cap via another metal coupler.
There is some
extra
plumbing for convenience. Click on any of the photos to enlarge.
In addition to the shrader valve on the left, there is a built-in
quick-connect fitting on the lower half of the "T", below the pressure
gauge. In the photo on left, the air hose is shown connected to the
quick-connect fitting directly.
I
prefer
the arrangement shown here. In this case I use the red hose adapter to
connect the air hose up to the shrader valve fitting, and attach a
quick-connect with compressor tank drain valve on the fitting below the
pressure gauge. The drain valve serves to give a quick/safe way to
de-pressurize the launcher when needed. Leaving this fitting
unconnected to anything gives a good "hole" to drain the launcher of any
water that gets in.
Of
course there's always the good 'ol bike pump method that works for
pressurization as well. For those that prefer to pump, I recommend
this Blackburn model.. it's kind of spendy ~$50 but is relatively easy to
pump up to over 100psi. However, I do NOT recommend pressurizing a
rocket from this close to it (as shown in picture), and if I did, would
limit pressure to 50 psi max. A bike pump can be used from far away,
although takes extra work to pressurize the extra volume of the hose. Works okay on Little Joe, but still takes a
lot of time (and work) to pressurize Big Hoss so I use a
CO2 setup.
Triple Cluster
This is a specialized launcher built for one particular
rocket configuration. Read more about it
here.
