New Way Blade Runner, Part 2, Engine Mount

The 20/50 centering rings are laser cut from plywood.

I like to sand off the charring from the faces using 400 grit on a block. 

It's not necessary to do this, I want cleaner parts - especially when the surfaces can be seen on the finished model.

The motor mount tube is marked 1/2" from both ends for centering ring positions.

Slot the tube for the engine hook at 1/4" from the top and insert the upper bend of the hook.

The retainer ring ends up centered between the centering rings. Slide on, apply a ring of glue and into position. 

The fit of the rings was almost perfect! A hair tight.

For a smooth slide over the ends of the tube, a piece of 400 grit was wrapped around a finger and used to lightly "ream" the center hole.

Enerjet by Aerotech Strong Arm Build, Part 24, Engine Retainer

The inside edge of the motor retainer should be roughed up for better epoxy adhesion.

I used the back side of my knife to scrape off the paint. Using the back of the blade will rough the surface and not dull the sharp side of the knife.

The fit of the ring is tight.

To make an easier slide in and seat, the edges of the motor tube were slightly rounded with some 320 grit sandpaper.

Here's the ring slid in until the motor tube butts up against the raised ring inside. 

After the epoxy dries, the cap can be screwed on. 

The trailing edges of the fins are longer than the retainer cap so the rocket can stand on it's fins.