Launchers

Intro:

I have 3 launchers, all based on the cable-tie release mechanism described by Ian Clark.  While the launch tubes on both are interchangeable, Little Joe is set up with a shorter 17″ tube and is used primarily for launching 2-liter bottles (or rockets with a 2-liter bottle as the bottom section), Big Hoss has a 48″ tube and is used for FTC rockets, and a Triple-Cluster launcher for rockets with 3 engines that fire simultaneously at launch.   All have schrader valves and can be pressurized using a bike pump but I prefer a CO2 Tank setup that is far easier.

Little Joe:

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:

Big Hoss:

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.

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