Manufacturer: Cygnus Rocketry
(Contributed - by John Lee - 11/09/08)

This is a motor mount to accommodate a 29mm motor in a BT-60 body tube. It is 5 1/4" long.

Cygnus motor mount

The package consists of simple instructions, 2 centering rings, a thrust ring and a motor tube. Construction of the motor mount was simplicity itself.

The motor tube was marked 1/4" from one end. The two centering rings were then test fit around the tube. One fit just fine and the other needed a good bit of sanding to fit around the motor tube. Once they fit, I placed one even with the 1/4" mark and the other flush at the end. The rings were then epoxied in place with 5 minute epoxy. A thrust ring was provided and epoxied into the end with the flush centering ring. When the epoxy on one side was set, I turned it over and painted it on the other, building up a good fillet on the aft ring and sealing together the thrust ring, motor tube, and centering ring on the forward end. After that, it was just a matter of waiting for the epoxy to cure.

Cygnus motor mount

The mount was tested on two different flights. It handled a Roadrunner F60 and an Aerotech G77. I had planned to use a Roadrunner G80 for the second flight but could not because it would not fit. The Roadrunners have a built in thrust ring aft but, forward of that, are of uniform diameter. The AT SU motors do not have a thrust ring aft. They are also necked down to a smaller diameter where the ejection charge is stored. This allows the "skinny" part to slip through the hole in the motor mount's forward thrust ring.

As long as this fact is taken into consideration at design time, I can heartily recommend the mount.

Overall Rating: 4 out of 5

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