CTI Pro 75 O Rings

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cerving

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I'm doing an AT M1500G crossload into a CTI P75/5G motor, and in doing the test assembly it occurred to me that CTI uses a few O rings that AT does not in their 75-5120 hardware. Does anyone know the size of the two O rings that go in the forward closure and the nozzle holder? Thanks!
 
I'm doing an AT M1500G crossload into a CTI P75/5G motor, and in doing the test assembly it occurred to me that CTI uses a few O rings that AT does not in their 75-5120 hardware. Does anyone know the size of the two O rings that go in the forward closure and the nozzle holder? Thanks!

Are these the ones you are interested in?

IMG_1079.JPG

If so, I'll mail them to ya so you can get measurements you need.
 
Thanks, but I need them for next weekend. I expected more of them... the CTI instructions show two orange O rings for the forward closure and the nozzle holder, generally that means they're silicone for higher temperature use than the buna O rings.
 
I'm doing an AT M1500G crossload into a CTI P75/5G motor, and in doing the test assembly it occurred to me that CTI uses a few O rings that AT does not in their 75-5120 hardware. Does anyone know the size of the two O rings that go in the forward closure and the nozzle holder? Thanks!

I have done a handful of AT reloads in AMW hdw and one in CTI Hdw.
The same ones that work in the fwd and nozzle in the 75mm reload sin snap-ring motors.
The ones for the fwd are #230.
The inner o-ring for the nozzle holder is #228


McMaster-Carr Part #: (can be delivered within 48 hrs, std shipping)
#230-- 1283N103 10 pack
#228-- 1283N101 10 pack
They are nice to have in the toolbox.
The 230 is in the AT, AMW, LOKI, most all of the 75mm reload hdw.
 
Thanks! Mc Master is 10 minutes away from my day job... I go there all the time during my lunch hour to pick up little hardware bits. FYI, they're also a good source of shear pins, too.
 
I'm doing an AT M1500G crossload into a CTI P75/5G motor, and in doing the test assembly it occurred to me that CTI uses a few O rings that AT does not in their 75-5120 hardware. Does anyone know the size of the two O rings that go in the forward closure and the nozzle holder? Thanks!
You don't need them, use the ones with the aerotech kit, you need the 75mm seal disk, and use this video
https://youtu.be/d0xjmJ-Yur8


Sent from my Pixel XL using Rocketry Forum mobile app
 
You don't need them, use the ones with the aerotech kit, you need the 75mm seal disk, and use this video
https://youtu.be/d0xjmJ-Yur8


Sent from my Pixel XL using Rocketry Forum mobile app

It's now making sense to me now why the CTI nozzle holder has an "extra" relief cut at the front end... it's to accommodate an AT-style O ring between the nozzle and the nozzle holder. So Chris, does this mean that when you use AT loads you only need the one O ring at the forward end of the nozzle holder, but when you use CTI loads you use both the #228 inside O ring and the #230 outside O ring in the grooves of the nozzle holder? Thanks.
 
It's now making sense to me now why the CTI nozzle holder has an "extra" relief cut at the front end... it's to accommodate an AT-style O ring between the nozzle and the nozzle holder. So Chris, does this mean that when you use AT loads you only need the one O ring at the forward end of the nozzle holder, but when you use CTI loads you use both the #228 inside O ring and the #230 outside O ring in the grooves of the nozzle holder? Thanks.
You will use the forward oring on the closure like normal, the aft oring goes between the carrier and the nozzle, with the carrier installed backwards. The oring groove on the outside should be closest to the nozzle, and the oring is sitting on the nozzle directly but not in the carrier. The carrier acts as a spacer, and must be installed this way to compress the oring properly.

Sent from my Pixel XL using Rocketry Forum mobile app
 
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