N3180 question

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JimJarvis50

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I recently acquired a CTI N3180 red. I decided to do some test fitting of it, and the liner seems shorter than it should be. When assembled as normal in Pro98 hardware (using the parts I received), the liner is about 3/8" short. Hmmmm. So, doing a bit of research, it appears that this motor was cross-certified in RMS hardware, and when using the RMS hardware, there was a special longer closure specifically for this motor. The nozzles for the RMS and Pro98 were also supposed to be different. Although the o-rings provided are for the Pro98 nozzle, they don't fit the nozzle very well, and I suspect that the nozzle is the RMS version.

The pic below shows a nozzle for an O3400 on the top and my N3180 nozzle on the bottom. The shoulder on the O3400 is longer, and this fits the liner/motor for the N3180. Therefore, I suspect that the nozzle on bottom is for the RMS version of the N3180. Note the shorter shoulder and the wider o-ring groove. The Pro98 version of the N3180 nozzle would likely have the same longer shoulder as the O3400 nozzle. Can anyone confirm that the nozzle on the bottom in the pic is indeed an RMS nozzle?

Thanks.

Jim

IMG_0788.jpg
 
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dixontj93060

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I am no expert, so maybe tfish will chime in. But from what I have seen RMS nozzle designs utilize an aft nozzle lip that is compressed against an o-ring (see below) versus the o-ring channel as shown in your first picture.

Nozzle.jpg
 

JimJarvis50

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I didn't realize that the grains might be different too. Looking at the propellant boxes, I do indeed have the RMS grains. Not sure why the box says Pro98 as do the o-rings, but the price was attractive :blush:

Interesting concept, to cross-certify a reload, but then all of the reload parts are different. And I guess I'm still not sure if the nozzle I got with the N3180 is for the RMS or Pro98 reload?

Jim
 
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blackjack2564

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FYI:

I built a M-3400 [98-4-grain White thunder] it was ordered for AT case. I checked the fit of grains & liner before I glued it up.
After I built it [glued], next day went to install in case & discovered it was to long to get closures on.
A quick call to CTI & the discovery it was shipped with a CTI nozzle [error]. They offered to send correct nozzle, but I had already glued it in, so it flew in a CTI case. They sent a loaner, which I thought was very kind.

So according to them, for this motor, the difference was just the nozzle which was shorter for the AT case.

Lesson learned....to check entire fit before gluing anything. LOL

Edit: & O-rings [difference]
 
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JimJarvis50

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It would help me if someone has the Pro98 version of the N3180 and can post a pic of the nozzle.

Thanks.

Jim
 

jsdemar

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It would help me if someone has the Pro98 version of the N3180 and can post a pic of the nozzle.

Thanks.

Jim
I flew a red Pro98 6-grain with AT-sized parts and nozzle and liner. (See other thread). I made a 1/2" spacer ring that goes over the nozzle before tightening the closure. It was "manufacturer approved". I can make you one.
 

JimJarvis50

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I flew a red Pro98 6-grain with AT-sized parts and nozzle and liner. (See other thread). I made a 1/2" spacer ring that goes over the nozzle before tightening the closure. It was "manufacturer approved". I can make you one.
Thanks John. I may take you up on that. I thought I might be able to submerge the two closures and cover the gap, but it's still about an 1/8" short. More than I'd like. At the moment, I'm trying your packing tape trick. I have saved the O-rings for the RMS cases and I'm trying to install a nozzle into the case. Sure seems tight though.

Jim
 

JimJarvis50

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Success! I was able to pull the nozzle/O-ring into the case with a long piece of all-thread, and didn't damage the ring. Getting these rings into the Gen2 case is with the sharp edges is an interesting process. Now, I just need a spacer and I can use the motor.

Jim
 

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