What the heck am I doing wrong? Aerotech makes a wrench for the aft end but the front end is where I need a wrench!

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Swimsuit Model
TRF Supporter
Apr 5, 2013
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The back end sometimes unscrews without the need of a wrench but the front end (delay and ejection side) sometimes gets STUCK and I've needed plyers which just scratches the hell out of the case.

What am I doing wrong?
I have a couple of pieces of leather that are strapped to my vice so I can flip them down to cover each jaw. That way I can still get a good grip without marring the surface. I'll use that to hold the closure, then while wearing a pair of nitrile gloves I can usually get a good grip and unscrew the closure. But I'm always very careful to not over tighten the vice jaws on the closure to avoid distorting it.

I did just buy a strap wrench for larger cases, but as @Buzzard mentions, I'll wrap the case with blue tape before using the wrench to avoid scratching it. I've also started making sure the threads are really clean before assembly, and then greasing them up before I build the motor.

What kind of grease you using for the threads. Most turn to glue when they get to hot. I use super lube without any problems. Only grease the orings and threads. If the oring comes in contact with BP don't grease it. Most cases do not grease the liners. It's much easier and cleaner removing liners without the grease gluing then to the cases ( there are some motors where greased liners are required for a good seal).
Maybe it's just that the threads are dirty. I make sure there's no dirt on the threads and use a light greasing with Super Lube. When assembling I install the forward closure first and snug the rear one with the wrench last. When disassembling I remove the rear closure first with the wrench, and the forward one unscrews with no tools required. As long as there is no tension on the threads they always come right off, 18mm - 29mm. Is the case distorted around the threads?
I've always used 2 strap wrenches.

"Cannon plug pliers" ...a tool that I didn't know existed until today but could have used many times in the past.
Thinking of the number of times I've wrapped slip joint plier jaws with paper towel and electrical tape because I didn't know about these...
Maybe I'm just doing it all wrong, but starting with a clean case, I burnish in either powdered graphite or moly d. until I see the shine. Then I use super lube or a German synthetic high temp bearing grease designed for racing brake systems. Sorry, on the road, forgot the name. I ordered a six pack over a decade ago, gave at least three tins of it away, rebuilt/restored a couple of classic Mustang and still have enuff to last way beyond my life span. Gloves only when the case is hot. My three cents.
Rubber jar openers.
They sell these little rubbery grippy things for opening pickle jars.
That usually works on the ejection end of my 29/40-120, and doesn't scratch the hell out of the case. Give it a try.
Never had a problem with any closures not coming loose by hand only. After use I drop the closures in a little container with vinegar, let for about 10 minutes and then into the soap water, and use a tooth brush to clean the threads. After drying I grease the threads with Super Lube.
Loosen your closures immediately upon recovery of your rocket. Or at least ASAP. I'm talking while still warm. I'm not sure I have ever used a wrench on Aerotech closures 29mm through 75mm. I use plenty of either red grease or Super Lube on closure threads. None or minimal on liners.

Under no circumstances would I use Dow 111 on anything other than o-rings - that shat is impossible to cleanup.

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Since you mentioned the wrench, I’ll assume you’re referring to HobbyLine cases with the smooth forward closure. They certainly would benefit from some form of knurling like the RMS-Plus cases. I clean the threads very carefully after each use, using alcohol wipes and a fingernail, until it threads on smoothly. Usually light grease threads with Super Lube before storage. Never had one seize.
I bought a used 24/40 case off of Ebay. Forward closure was stuck on really tight. I gave up and put it on my workbench.

Then a couple of weeks later, I thought I'd give it another try. Put an ice cube on the counter and ran the case under hot running water, trying to avoid the closure. Sat the closure on the ice cube for a moment, and it twisted right off.

No damage that I could tell, I threaded the closure onto another tube, and threaded a new closure onto the used tube just to see if there was any looseness in the threads. I've used it several times.

Just do a search now that you know what they look like. Amazon has a set made by Crescent for about $29. They call them connector pliers.