MMX Engines - Friction Fitting

It seems I've been flying many MMX rockets lately - for good reasons.

1. I can fly early in the morning before the Florida Summer heat gets unbearable.
2. I can fly them at the (small) nearby schoolyard.
3. It's something to do between monthly NAR section launches.
4. I had too many of these engines just sitting around.

Through the many launches I'm friction fitting the engines differently now.

Carded rocket (hand rolled) body tubes are not as strong as machine made tubing. After nearly crimping some carded tubing when installing MMX engines, I had to find another way to do a friction fit.

Micro models don't have engine hooks. Most others don't have body tubes extending past the fin's trailing edges for an outside wrap of tape.

So now instead of simply doing full wraps of tape, I've been tearing tape pieces into triangle shapes and laying them over the nozzle end as shown.

This gives the engine a "wedge fit" in the body tube. When inserting the engines using this method, the friction tightness increases the farther the engine is pushed into the mount. After you get the right amount of tape pieces applied, cut off the overhanging tape from the nozzle end.

This friction fit (nozzle end application) is for MMX engines and models with easy, simple nose blow or small streamer recovery. This is not recommended for 13mm or larger engines. Like anything else, experience will tell you what a reliable friction fit engine feels like. At ejection, I've yet to lose an engine out the back doing this.

For easier engine removal in MMX rockets, always design your rocket so the engine sticks out the back of the main body tube by at least 1/8". After a flight you can actually crush the MMX casing and nozzle with small pliers and pull the engine out easily.