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How to Fit a 54mm Motor into a 38mm Motor Mount

The Big Daddy Akavish has flown several times on 38mm I motors. Each time it only reached about 300' in altitude. In order to allow it to reach a higher altitude, I decided to upgrade it to use a 54mm motor.


Unfortunately, 54mm to 38mm motor mount adapters are in short supply, so I had to remove the current motor tube and replace it.

I used a hacksaw blade to cut a slit in the old motor tube then peeled it out layer by layer. Then I used a Forstner bit in my cordless drill to enlarge the motor mount hole to about 2 1/2 inches in diameter all the way through the rocket's body. I had to drill through the fiberglassed foam body, a lot of expanded expanding foam, two 1/4" plywood centering rings, and the ends of dowels that form the Akavish's legs.


One problem we had with the Big Daddy Akavish is that the ejection charge weakened the coupler where the two parts of the spider's head connected. So, I beefed up this part.


I created a coupler that also transitioned from the 54mm motor tube to the 38mm tube used in the top half of the Akavish's head. I started with a PVC coupler. A wrap of tape wrapped around a short length of 38mm motor tube fit perfectly inside the PVC coupler.


I cut a section out of a short length of 54mm motor tubing and glued it on the outside of the other end of the PVC coupler. This made the whole thing fit perfectly in a 54mm motor tube.


In the top half of the Akavish's head, I replaced the paper coupler tube with a piece of metal tubing. I also moved the altimeter (mounted in a presciption pill bottle), to a new location to make room for the 54mm motor tube.


Finally, I centered the new motor tube in the hole and filled in the gaps. I also cut another hole for the launch rod and glued in a tube to use as a launch lug.


The Akavish is now ready to fly on a 54mm motor! Unfortunately, we won't be able to attend a launch until December. And, I'll have to certify Level 2 before I can fly the Akavish on a long-burning J motor.

[Posted: 2007-10-21 | Updated: 2007-10-21]


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