"Plugging" my 98mm closure

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utahrc

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I've got an older (serial #36) Aerotech 98mm casing with an open forward closure. I realize that I can fly it without using a charge, but having a true plugged closure eliminates one of the failure modes of the motor - delay blow-by.

I'd like to find a good way to seal the touch hole on the forward closure rather than spend ~$120 to buy a new plugged enclosure. My initial thought is to Dremel off the anodized coating in the well and fill it with JB Weld, but I'm not sure the JB Weld would hold if combustion gasses got to it.

It's supposed to be able to take 600F for 10 minutes so I'm guessing it can handle 1000+ for the few seconds that it might be exposed to combustion gases in the event of blow-by, but that's just a hunch.


Thoughts?
 
I've seen 38mm ones plugged with epoxy filled with fiberglass balloons. He filled it from the inside and then the outside.


Edward
 
I machined an aluminum plug with an o-ring to seal the forward closure. The plug has blind 4-20 threads from one side so a bolt can be used to remove the plug and an o-ring groove cut for the same o-rings used for the delay elements.
I've seen or read somewhere that other simply take a wooden dowel of close diameter and epoxy it into place. Both method allow removal (sort of) that could permit delay charges to be used in the future.
Attached is a picture of my plug that I use in both the 38 mm and 29 mm forward closure.

John Wagner
 
Cast a dummy plug out of Durhams water putty. Use High Temp silicone and glue it in. Cast it into a cardboard tube. If you can't find a cardboard tube the right size, roll your own out of craft paper. It's not that hard.

The Red silicone, RTV???? Not sure of the name. It works great and can be removed if needed, a pain in the arse but possible.

This is the way we seal our EX motors that have a smoke well in the forward closure.
 
Drill and tap it for a 1/16" NPT pipe plug and seal it with Teflon thread sealer. Been there, done that.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
https://www.cesaronitech.com/
(905) 887-2370 x222 Toronto
(941) 360-3100 x101 Sarasota
(410) 571-8292 Annapolis
 
I didn't think of tapping it - if you can't find an 1/16 NPT tap I've usd a 1/4 28 tapered zerk tap for pressure. Drill a 7/32 hole, then tap it and you can find zerk plugs at auto stores.... Good idea!

Edward
 
I don't want to eliminate the smoke/delay well. I just want to cap off the touch hole/black powder well on the outside of the motor.
 
Originally posted by Anthony Cesaroni
Drill and tap it for a 1/16" NPT pipe plug and seal it with Teflon thread sealer. Been there, done that.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
https://www.cesaronitech.com/
(905) 887-2370 x222 Toronto
(941) 360-3100 x101 Sarasota
(410) 571-8292 Annapolis

Ooh, I like that idea. Unless, you're giving me a way to blow up my Aerotech so I can buy a Cesaroni. :)
 
Originally posted by utahrc
Ooh, I like that idea. Unless, you're giving me a way to blow up my Aerotech so I can buy a Cesaroni. :)

Funny but no. AT makes a good product and I've flown a lot of it. It just happens that I've made that mod to a few RMS motors for various reasons.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
https://www.cesaronitech.com/
(905) 887-2370 x222 Toronto
(941) 360-3100 x101 Sarasota
(410) 571-8292 Annapolis
 
I think I'll go the tapping route. 1/16" taps do seem a bit hard to come by(and they are pricy), but I think I can pick up a 1/8"-27 locally.
 
An 1/8-27 Tap takes a 11/32 (or 3/8) hole drilled - I don't have the dimensions of the closure but think the smaller the hole you have to drill the better.


Edward
 
It is just a 1/4 -28 tapered tap. Uses a 7/32 drill. I found mine at a local machinist tooling place. NAPA or Autozone might have them also. If you can't find a zerk plug, they also make a 1/4-28 to 1/8NPT adapter that you can put a regular 1/8 NPT plug...I'll get pics tonight.

Edward
 
I've got a 1/16 NPT tap and a matching SS plug on the way from www.mcmaster.com. It was about $22 shipped, which is quite a bit less than a new enclosure. Thanks for all the tips everyone.

Anthony,

I apologize for my Aerotech/Cesaroni comment. Stuff like that has got to get old after the first few hundred times. For what it's worth, I tried to buy a set of Cesaroni casings yesterday from a local guy that was getting out of the hobby but someone else beat me to it. I'm looking forward to seeing the 1:16 N1 at Plaster Blaster in a couple weeks flying under the power of 42(!) Cesaroni motors.

Matt
 
I once saw someone at a local launch plug a 38mm closure by filling the ejection charge well with Play Dough, and taping over the top of it. Don't know if it'll work on a motor as big as yours, but it worked great on his.
 
Originally posted by utahrc
I've got a 1/16 NPT tap and a matching SS plug on the way from www.mcmaster.com. It was about $22 shipped, which is quite a bit less than a new enclosure. Thanks for all the tips everyone.

Anthony,

I apologize for my Aerotech/Cesaroni comment. Stuff like that has got to get old after the first few hundred times. For what it's worth, I tried to buy a set of Cesaroni casings yesterday from a local guy that was getting out of the hobby but someone else beat me to it. I'm looking forward to seeing the 1:16 N1 at Plaster Blaster in a couple weeks flying under the power of 42(!) Cesaroni motors.

Matt

Just make sure not to run the tap too deep. You don't want the plug extending too far into the delay chamber. Tap it in increments until it's where you want it. Good luck.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
https://www.cesaronitech.com/
(905) 887-2370 x222 Toronto
(941) 360-3100 x101 Sarasota
(410) 571-8292 Annapolis
 
The tap and plug arrived today. It worked like a charm! Thanks again.
 
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