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REV 2.4 - Wed Aug 18 09:46:16 2010

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F.T.B.o.D.
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SPECS: MISSING
ROCKSIM FILE: MISSING - please submit here
SpaceCAD FILE: MISSING - please submit here
REC'D MOTORS: MISSING - please submit here

Contributed by - Mark Simpson

Flying Traffic Barrel of Death
F.T.B.o.D.
by Mark Simpson

As part of my Level 3 project, building and flying a full-sized orange traffic barrel, I decided to make a 1/6th scale flyable traffic barrel to test its dynamic flight stability.

I started with a 3" section of garden variety mailing tube, donated by an office mate. I scrounged a piece of 6" mailing tube from another office mate to use as a larger ring fin. Since the "real" traffic barrel, purchased for the L3 project, was sitting in my garage already, I got out my tape measure and went to town taking measurements.

Here's a summary of the major dimensions:
Height at top of barrel (flat surface) : 36"
Diameter at top of barrel : 18"
Flasher: 6" long, 4" high at top of battery pack.
Flasher dome: 8" in diameter

Now that I had the basic dimensions, I went to work creating the model.

Here's a materials list:

  • 6" of 3" mailing tube for the body
  • 1" of 6" mailing tube for the ring fin
  • 1 Stainless Steel Fishing Leader for shock cord anchoring
  • 1 small screw in eyelet for shock cord mount
  • 3' of nylon shoelace
  • Handful of politically correct steel bird shot mixed with non-hardening modeling clay scrounged from "the wife"
  • Scraps of wood cut into 1" x 2/3" _" blocks for flasher base
  • 4 small wooden 1-1/4 convex disks (scrounged from wife's Michael's Craft Store supplies)
  • 1/16" balsa wood scraps for centering rings and fin supports.
  • Aluminum foil
  • 4" of 29mm motor tube
  • Titebond II Wood Glue
  • 3" circle of basswood for barrel top
  • 3" X _" strip of basswood for (something or other, Mark you left this out - ed.)


Construction:

I started by cutting 6" of 3" mailing tube on my Miter saw, then cutting a 1" ring off of a 6" mailing tube, using an Exacto knife.

Using VCP I printed out a fin alignment guide using the following information:
# of fins: 8
Diameter: 3"
Fin Span: 1.5"
Thickness: 3/32"

I laid the 3" body tube on the alignment and positioned the 6" outer ring so that the radiating lines from alignment guide were even all the way around the ring. This ensures that the 6" ring fin is equidistant from all points. I then marked the inside of the radiating line so that I could measure the length of balsa needed to act as supports for the ring fin. (It was slightly less that 1.5") I cut out 8 supports from scrap balsa that were roughly 1.5" X 1", making sure that the grain was perpendicular to the body tube. I test fitted the 8 supports inside the ring fin, while sitting on the fin alignment guide. After some minor adjustments and sanding, I glued all 8 supports in place. (Getting them straight was easy since I glued them on top of the alignment guide.) Once dried, I filletted all joints to add strength and removed the assembly from the guide.

The motor mount assembly is made from a small piece of 29mm motor tube ~5" and balsa for centering rings. To strengthen the centering rings, I made four and glued them in sets of two with one of each pair having it's grain perpendicular to the other for strength. I glued both ends on and drilled a hole to pass the shock cord through.


A basswood sheet cut into a 3" circle forms the barrel top and a 3" strip of basswood acts as the flasher support. (see below for details). For the flashers, I cut two 1" x 2/3" _" blocks from scrap wood to serve as the battery pack (white base). The flashers were 1-1/4" one-sided convex "buttons" found in my wife's craft box. Gluing two together gave a nice convex lens assembly. Then I drilled through the center of the lens assembly and the middle of the flasher and inserted a small dowel to hold the lens on top of the base. (The dowels aren't visible in the photo, but are located at the glue joint) I glued the flasher support and both flashers to the top of the barrel at once so that I could ensure the support was perpendicular to the barrel top.

Now comes the shock cord attachment and weighting process. I used a small screw eyelet and screwed it into a _" by _" block of plywood which I glued into the underside of the basswood barrel top (see photo below) Then I added a _ thick plastic spacer from a brown paper roll endcap and punched out a section so that the launch rod could go through the rocket. I filled the _" circular gap with a mix of modeling clay and steel shot (estimated at ~2-3 oz). Attached to the eyelet was a stainless steel wire fishing leader. I tied the other end of the leader to 3' of heavy duty nylon shoelace.

{short description of image}

The shoelace is attached to the motor tube assembly. The aluminum foil-covered disk in the picture below is to protect the shockcord and upper portion of the barrel's insides. Since this is a rear ejection model the whole motor assembly should fit loosely in the body tube. The parachute is wrapped around the motor tube ( like in the Estes Sizzler). Care should be taken when test fitting the assembly so that holes can be drilled to allow the launch rod to pass through the rocket.

Since this was to serve only as a test vehicle for the real thing, I painted the rocket using water-based acrylics. The completed project is below.

Flight Report:
On Saturday, March 1st, I loaded up the rocket with an F50-4 and it flew perfectly to ~500'. Ejection was just about right on and the rocket landed within 50' of the pad.

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