The system of choice for medium to medium large rockets is the ProRail® system from blacksky. (Now called the "High Power Rail.") These rails have been popular from their inception several years ago and have become almost ubiquitous since blacksky gave 100 of them away to rocket clubs. Many clubs and individuals have also purchased their own rails as a much superior alternative to launch lugs. Many individuals, myself included, use ProRail buttons on all their new rockets (except the very largest ones).
The ProRails come in 6' sections which can be joined to make longer rails. A single 6' section suffices for smaller rockets, but a 12' section made of two rails is better for larger rockets and can handle all but the very largest projects. (The ProRails come with joiners which allow the sections to be mated together into longer rails.)
Blacksky also makes an adapter which fits into a standard launch pad. This bolts to the bottom of one of the rails and has a 5/8" round section which can bolt into a base made for a large rod. However, this adapter is too short for most large pads, not to mention that most pads meant for rods aren't stable enough for a 12' tall rail and the rocket likely to need it.
What is really needed is a dedicated base for the ProRail which can handle the torque from a 12' section of rail and the rocket on it. Scott Bartel has been talking about making such a base, but hasn't yet done so. This has driven several people to making their own bases and what you see on this page is yet another of those.
I wanted a base which would have a large footprint for stability, yet be reasonably portable (all pieces 8' long or shorter). This would allow the base to fit into the back of a Suburban or pickup truck. The frame would need to fold up and be made of aluminum tubing to be light enough for one person to lift.
See the drawings of the base legs and mast (PDF) on the right.
Below are various pictures of the completed base and the ProRail. Two of these bases have been made and used successfully at several AERO-PAC launches. Thanks to Bob Fortune for the great photos.
From Kent Newman:
1) I extended the stainless steel plate at one end of the base leg to provide two points of connection for each of the folding legs. It really firmed up the stability of the stand. I toyed around with making the plate big enough to be used as a blast plate but opted for a deflector discussed below.
2) I welded a bracket on the stainless steel mast connection point to limit any tendency to rotate at that point. I'd like to play with that connection point some more but it's pretty stable as is.
3) I put a small standoff near the base of the rail to avoid dragging around a 2" X 4" or whatever to hold up the rocket. And, even at that, depending upon what's flying, I may still have to use something other than the standoff but it currently takes care of most of the rockets our group flies.
4) What I didn't get a picture of is a blast deflector that cradles the mast just below the rail, extends down at a 45 degree angle, then angles out horizontally again to provide two 1/2" holes for staking down the plate.
I suspect that most of the changes made to tighten up the launcher are due to the fact that I used 2" square tubing versus 3" but, nonetheless, it is sturdier.
Above you can see Kent's base with the two bolts for each leg. Below left, you can see the stand-off for the rail. Below right, you can see his rail assembled and upright.
Very nice work Kent and thanks for sharing!