Brief:
I wanted a cheap easy way o' nay loosin' me reload cases, so I made a trip t' hardware store, and came back with this. Ya scallywag! This is enough parts t' make 4 retainers. Avast, me proud beauty! I spent $1.99 for t' smaller unit and about $2.50 for t' larger one.

Construction:
T' top one is a ¾" compression fitting, while t' bottom one is a ½" compression fitting. Well, blow me down! Which one you use depends on how large o' cap you want showing, me hearties, or will fit inside t' end o' your rocket. I use both. Ahoy! T' ¾" for larger rockets and t' ½" for smaller, and ones that I do nay want it t' be as noticeable. Begad! Now gettin' these t' work takes just a little bit o' work. Begad! I will start with t' ½" unit as it takes a little more work.

Motor Retainer from ½" compression fitting. Avast!

Above be t' picture o' t' ½" unit before I start (bottom one). Avast! Blimey!

T' first thin' I do is cut off t' threads from t' fitting.

This leaves me with these parts t' work with.

One other step with t' half is that thar be a “lip" in t' cap that restricts how far it goes on over t' motor. Avast, me proud beauty! This may cause a problem for t' escapin' engine exhaust, arrr, so I modify it as follows. Cuttin' t' cap down, thus removin' t' “lip".

T' depth is hard t' see but you can see t' finished cap, arrr, and notice t' difference. Ya scallywag! I then take a dremel with sandin' drum and sand out t' inside o' t' threads unit until it fits over t' 29mm tube.

After epoxin' t' threads on, matey, and epoxin' t' cap back together you end up with somethin' like this.

Motor Retainer from ¾" compression fitting.

T' ¾" unit is a little easier, once again start by cuttin' t' threads. Begad! This should leave you with t' parts shown.

Next take t' dremel and sand out t' inside o' t' threads until they fit over t' 29mm tube. Ahoy! Then epoxy in place.

Then just screw on t' cap that is it with t' ¾" unit you do nay have t' modify t' cap at all.

I used this on me Certification Level 1 flight with me 36" Crayon on an H128. Blimey! Here is me Crayon with t' larger 3/4" compression setup on 29mm. It has seen a number o' flights, me bucko, it is chared on t' outside from "blast deflector blow back", me bucko, but still fine on t' inside and still works great. Begad!