Positive Motor Retention

With bigger rockets and bigger motors you often run into the problem of holding your precious motor or reload casing in the model during ejection. You can't simply scale up the (in)famous Estes motor retainer hook.
Here is the description of my method, which can easily be added to already built models.

What you need:
A piece of threaded rod of aproppriate size,
two nuts and a piece of scrap PCB, G10 or similar.
How it fits together
Cut two pieces of appropriate length from the threaded rod and make a retainer plate from the PCB/G10/whatever material.
A test fit should look like this.

Prepare the rocket
Drill two holes for the threaded rod into the lower centering ring.
..now test fit the parts...

Now glue it!
First protect your motor or reload casing with some tape. Then pour some epoxy (15 to 30min) through the holes in the CR, fit the holder, fix it with some tape and add generous fillets to the bolts. Rotate the rocket until the epoxy sets. Voilá!
There it is: positive motor retention!

I suggest to use threaded rods that are longer than actually needed. Normally the rocket will come down rods first and occasionally it will hit a stone and damage the thread. One can then cut off the damaged part and is fine again. The longer rods allow to use adapters (eg. 38->29mm) too.

Addendum (05/98): Bob Crowley suggested the use of cap nuts to fasten the locker plate and to protect the thread simultaneously. A very good idea IMHO.

This method is of course only one of several ways to achieve motor retention.
Click here to see Jeff Gortatowsky's implementation of the "Kaplow Klips"

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Last edited: 04/20/98 by wsw

What you need: A piece of threaded rod of aproppriate size, two nuts and a piece of scrap PCB, G10 or similar.	How it fits together Cut two pieces of appropriate length from the threaded rod and make a retainer plate from the PCB/G10/whatever material. A test fit should look like this.
Prepare the rocket Drill two holes for the threaded rod into the lower centering ring.	..now test fit the parts...
Now glue it! First protect your motor or reload casing with some tape. Then pour some epoxy (15 to 30min) through the holes in the CR, fit the holder, fix it with some tape and add generous fillets to the bolts. Rotate the rocket until the epoxy sets.	There it is: positive motor retention!