Instructables

Step 6: Bend Launcher Arms


In this step we will build a bending jig, and use it to bend four launcher arms to a specific angle. Make sure annotations are turned on when viewing the video.

  • Launcher arm supplies
4 13" lengths of 1/2" pipe
2 1/2" PVC caps DO NOT PRIME OR GLUE THEM
Sand, at least two cups worth
Heat gun, propane torch or candle
Wood scrap and 3 2" screws to make bending jig
Leather gloves

Assembly
  • Choose a launcher tube angle. A 17 or 19 degree angle will give you longer range but you may need the high performance tractors. A 21 or 23 degree angle will give you quicker opening shorter range netting, a safer bet if you are going to use soda bottle tractors. Choose and print out one of the PDF templates below. They should be printed in landscape mode on 8 1/2" by 11" paper at 100% scale.
  • Build bending jig. My example bending jig is built on a scrap of 2x4 wood. Hold the template to the surface and put a screw in the pivot position Fig 1. Hold one of the arms against the pivot screw and sink screw #2 using the edge of the pipe as a guide Fig 2. Again, with the pipe held against the pivot screw, sink screw #3 using the pipe edge as a guide Fig 3.
  • Cut four 13" lengths of 1/2" pipe, these are the launcher arms. Measure and mark, with permanent marker, 3" in from one end of each arm. This mark, the pivot mark, will indicate where to heat the pipe for bending, and indicate the point to line up with the pivot screw of the bending jig.
  • Bend the launcher arms. Tap in place, but DO NOT GLUE, a 1/2" cap on end of the arm. Fill pipe with sand, and tamp to get as tightly packed as possible Fig 4. Fill the second 1/2" cap half full with sand and tap on the open end of the arm. The sand keeps the pipe from kinking. With both caps on the pipe the sand shouldn't slosh when shaken, if it does, add more sand. Put on leather gloves and heat arm as locally as possible on the pivot mark. Rotate the pipe rapidly for even heating and to prevent blistering the pipe. The arm is ready for bending when it will sag under its own weight held horizontally. Align pivot mark with pivot screw, the remaining short length should be captured by screw #2, immediately bend longer length of pipe over and lodge against screw #3. Allow to cool on the jig, if PVC is removed while it is still warm it will begin to straighten and lose the correct angle. Once PVC is room temp, remove from jig, remove both caps, and pour out the sand. The heating can also be accomplished with a candle, have a look at robert's instructable step #3. Both tk4717 and ome33 had good results with the candle technique.

  • Repeat for the remaining three arms.
17 degree.pdf(612x792) 201 KB
19 degree.pdf(612x792) 172 KB
21 degree.pdf(612x792) 210 KB
23 degree.pdf(612x792) 216 KB
 
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hey if i dont have sand what else could i use? Would water work?
tj123675 years ago
does the net you order come with the things on the corners?
which angle did you use? a 17 or 19?
tk47175 years ago
thanks, the candle worked like a charm! Anyone who doesn't have a heat gun - don't go buying one unless you'll use it otherwise... just buy a candle!
tk47175 years ago
okay, so I don't have a heat gun, and I don't see much of a need to buy one (likely wouldn't use it for anything other than this project) who thinks heating the launchers over a flat top stove would be a terrible idea?