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6.11 Rocketry: Improving on the Estes Shock Cord Mount




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This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.

6.11 Rocketry: Improving on the Estes Shock Cord Mount

There are a number of ways to improve on the old paper-and-rubber-band
shock cord mount used by Estes for the past 35 or so years. The
following suggestions have been repeatedly made in r.m.r.

1. Replace the rubber band or short elastic in the kit with sewing elastic
at least twice the length of the model. This will help to avoid
tube zippering or ripped out shock cord mounts when you have a 'hard'
ejection.

2. Epoxy the shock cord mount to the inside of the body tube rather than
using white or yellow glue. Thirty minute epoxy works best for this.
Be sure and lightly sand the inside of the tube where the shock cord
mount is to be placed. Also be sure and 'cover' the entire mount with a
very thin layer of epoxy. This method works best for models with BT-60
or larger body tubes.

3. Use a 'Quest-style' kevlar-and-elastic shock cord mount. This type
of mount uses a length of 50 to 150 pound test Kevlar (such as Stren
Kevlar fishing line or Kevlar kite string). The Kevlar is tied and
glued to the motor mount (motor block, centering ring, or around the
motor tube). It is sized to end just shy of the front end of the
body tube when a length of elastic shock cord is tied onto the free
end of the Kevlar. This method eliminates any shock cord mount on the
inside surface of the body tube. Estes-style shock cord mounts have
been known to interfere with parachute deployment. You can used this
method on any sized rocket. Size the Kevlar appropriately.

4. You can also use a 'LOC-style' shock mount for body tubes in the
1.5" and up range. With this you take a short length of Kevlar line,
fold it in half, and make a 1-2" loop in the closed end of the folded
line. You then epoxy the loop to the inside of the body tube in such
a manner as to have the end of the loop extend a little past the open
end of the body tube. A shock cord is tied to the loop. The advantage
of this technique is that is allows damaged shock cords to be easily
replaced. It tends to work better on body tubes greater than 1.5"
in diameter.

 

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