Launch Towers

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I like almost all of Giant Leap's products, but not this one. Our club got that tower and it is really flexible, on top of being heavy, large and hard to transport.

I made a cheap, transportable and stiff tower with the following from Home Depot:

3 shower rods, 1" aluminmum, $5 each
2' x 2' piece of 3/4" plywood $5-$10
3 1/4" lag screws
About a dozen 1/4" T-nuts
18" x 18" galvanized sheet steel
15-minute epoxy

The basic idea is to glue the lag screws into the ends of the shower rods, glue down the sheet steel on top of the plywood, and then screw the rods onto the base using the T-nuts on the back side of the plywood. Why this works is that the shower rods are straight and pretty large diameter, so they're reasonably rigid on their own. The bolts preload them onto the base, and the sheet steel on top of the plywood makes a good metal-metal contact with the ends of the tube, so you can screw them into the base pretty hard. You can make several different hole patterns for different sized rockets. If you work out the math, rods tubes a little over an inch are the largest that can still work with a 13mm tube.

Stabilizing the tube ends at the top is optional, but recommended. I made an elaborate adjustable ring holder to keep the tube ends in just the right spot, but then forgot it when I went to the field the first time. I cut out a cardboard stabilizer and used 24mm coupler sections to fit into the ends of the tube, and it worked quite well to keep the tube ends all in the right spot. I'll post some pictures next.
 
Here is the tower, used to set a Tripoli F-impulse record (pending) last weekend:
DSC00708.jpg


And a closeup of both types of stabilizing rings for the top:

DSC00709.jpg


I used a PVC pipe coupler for the top stabilizing ring so that I could slip on a pipe on the bottom to turn this into a tube launcher, or put a pipe on the top as an additional wind screen. I haven't really been motivated to try out either of those options, however.

The things hanging off of the eyebolts on the outside are to attach guy ropes. I made the round plywood things on the inside ends of the eyebolts using a drill and a belt sander at the same time, since I don't have a lathe.

And the all-important T-nuts:
DSC00711.jpg

The large hole in the base makes it a lot easier to carry.

I attached the lag bolts to the inside of the tower rods by using a hole saw to cut out some round plywood inserts, kind of like centering rings. The lag bolts went into these, and then the lag bolts + plywood inserts were glued into the tower rods with a lot of epoxy.
 
My design was very similar but a larger scale. 4' x 4' plywood base, 2.5" tubes, and a plywood top piece. Steel plugs were bolted to the base and top, they slipped into the tubes. It can be scaled to any size, this was for a 4.5" rocket.
 
Everyone
Thanks for the ideas shared, this was exactly what I was looking for.
 
The tower that I made uses three 3' lengths of 1/2"emt conduit to connect two 10"x4" pvc pipe sections together. For the launch tubes I used 4' long 1/2 emt conduit. they are sloted to connect to the adjusting bolts and have spring loaded ends to keep the tubes on tight. The adjusting bolts are 6"x3/8" all thread with on end drileed and taped to accept a 10x24 flat head machine screw with the springs and washers on them to hold the launch tubes.
I also sloted two of the areas on the 10" pvc that the adjuster bolts go through so it is adjustable for either a 3 or a 4 fined rocket, with the addition or removal of the 4th tube.
I have two sets of three legs, one thats 12" long and one thats 24" long. Both sets have 45 deg bends in them to spread out the base and can be swaped end for end for a wider base. The reason for the 24" legs is for a piston set up. They attach to the tower supports using union collars.
 
Here are few pics of the tower that I built.
travel/ storage modetravel mode.jpg
Launch tube adjusters and retainers tube retainers.jpg
Set up for 3 tubes 3 tube close up.jpg
Set up for 4 tubes after 4th tube.jpg
Tube adjuster bolt adjustment slots for either 3 or 4 fin rockets adjustment slots.jpg
 
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