Model Rocket Launcher

Introduction

When the club grew, and in contests we co sponsored, it became apparent that the single three pad launcher we used was not suffient, we built two more 6 pad launchers. This was over 20 years ago, and the connectors, launch button and control box have been replaced several times.

While I now live more than 3000 miles from the club, when it was mentioned that it was acting flacky, I decided to replace all the wireing and control box to eliminate any problems. In the process I decided to add an automatic count down sequencer, and a few other bells and whistles.

If your club would like to build one of these and you need more help than is described in this page, please feel free to email me.

General Construction hints

• A Simple Elevated launch platform can be built from
  1. A Saw Horse bracket Set.
  2. A few 2x4, 4 about 30 inches for the legs, 1 about 4 feet for the top.
  3. A 1x6 or 1x8, the same length as the top of the platform.
  Space the platforms about 8 inces apart. Note: the 4 feet quoted above will allow for 4 inches on either side and 6 pads spaced 8 inches apart. You can vary the spacing and number of pads to your liking, our club had three platforms of 6 pads, A typical launch only used one of the platforms, but a big meeting or contest would drag them all out.

  Attach the legs into the saw horse brackets, Nail the 1x8 centered on the top of on edge of the 2x4 to form a "T" when viewed from the end. The legs can now be clamped on to the platform using the brackets. This allows the legs to be removed for transport or storage. This will be easier to see when I add a picture!

• A remote Launch Button can be built from
  1. 1/2 inch Schedule 40 PVC pipe about 6 inches long
  2. A replacement door bell button
  3. 10 - 15 feet of low voltage lighting cable
  The Choice of low voltage outdoor lighting cable is better than "zipcord" or Lampcord" since it is quite fexible, has a thick insulation to stand up to the abuse it will take over the years and is typically heavyer guage than your hardwarestore will carry in lamp cord. Since the cable is quite heavy crimp small ring lugs onto the cable and connent to the puch button. Thread the unconnected end through the pipe and press the button into place. The replacement door bell button should fit snughly in one end of the pipe. If it is too tight, The pipe can be softened with heat and the button can be pressed in.
• Blast deflectors can be made from a piece of sheet steel. The easyest way to do this is to get a short piece of duct or stove pipe from the harware store.
• Launch Rod Supports, Estes used to sell a nice swivel that would hold the launch rod and needed only a sigble wood screw to attach it to the platform described above. I was told they no longer sell this, So I made some launch rod supports from:
  1. 1/4 inch fender washers, these are the ones that are 1 1/2 in outside.
  2. 1/8 inch wire rope clamps, These are about 1/2 x 3/8 x 1 metel with two screws, they are for clamping the end of a wire rope.
  3. 2 small "L" brackets
  4. a 1/4 20 bolt 1 inch long
  5. a 1/4 20 wing nut.
  Dissassemble the rope clamp. File out most of the blockages so that it tightly grabs a launch rod when you hold it closed. You might want to file the second side of it to hold a different size launch rod, so the clamp will hold a 1/8 or 3/16 launch rod depending on which hole you slide it into. Drill out one of the screw holes so the 1/4 bolt will fit through. Drill out the angle brackets so the 1/4 bolt will fit through. Weld the two angle bracktes to the washer. Use a wood screw to attach the washer with the brackets to the platform, assemble the clamp with bolt and wingnut.
• Electronic launch controller
  1. Parts List PDF file
  2. Main Schematic PDF file
  3. Countdown Sequencer schematic PDF file
  This is the design I built for the YMCA launcher. It was designed to use off the self parts and to with stand years of use. The design uses ancient but still avalable 4000 series CMOS components. It cost me about $250 to build, but most of that was in the wire and connectors.