Originally posted by DynaSoar
WOOWOO! Now THAT is what I'm talking. That's a mighty fine hack. I was thinking of something like that, with drillings for a couple different sizes of rods/tubes so it could fit any size of vehicle. I'd thought of using solid rod, but with tube you could extend them if necessary.
What thickness of tubes would you suggest for mid- and large-size rockets?
I used 1/16" wall steel tubes, but the rocket was O powered and the tower was only used 4 times. I'd recommend 1/32" wall stainless for a tower you will be using for a longer term. Use fairly large tubes, they can be as large as the diameter of the rocket and still work well.
Was it necessary to have the top piece that large to prevent shimmy in the tubes, or was that over-built?
The cutout in the top piece is just large enough to clear the fins of the rocket no matter if it rotates. The cutout is shaped so the fins miss even if the rocket is rotated against the tubes in either direction. As you can see in the picture, the top piece is just large enough for the cutout. You need something to keep the tubes aligned so a solid edge around the top is required. I could have made the piece round but it wasn't necessary. Don't forget you need to clear the fins of the rocket with the greatest span.
I saw someone mention using PVC for stand-offs and found they were fairly flame resistant. Any thought on whether PVC would work for the guide tubes?
PVC is not very rigid, your tower would be quite flimsy. Also, there is quite a bit of blast at the base of the tubes. I expect PVC would work for a few launches before requiring replacement.