CTI M1590 Build difficulties

I had a little trouble today with the assembly of the CTI M1590 motor I'll be flying soon. Right off the bat the grains had to be pushed in, where normally the grains almost fall through,... on the CTI L910 motors I usually fly. Then after all the grains were in it took a lot of persuasion to getting the loaded liner into the case (yes, the case was lightly greased and it is new). And THEN,.. like a kid telling you about what the neighbor kid did to him ,... with a lot more of muscle, the fwd and rear closures were screwed in. Final result looks like the grain at the nozzle end is about 1/2" short of bottoming out against the nozzle. I don't think that's normal, speaking from building about 7 to 8 CTI L910 motors... and the one CTI M1101 that I did my last year's cert. flight on.

Thoughts? (I would gladly included a pic if I could get the uploader to work!)

Does you grain packaging and liner label have an "AT" suffix on them? The grains for some of the AT-compatible CTI loads are shorter than the native CTI loads. I had this problem with an CTI N load and had to make a spacer ring on my lathe to fill in the spacing.

jsdemar said:

Does you grain packaging and liner label have an "AT" suffix on them? The grains for some of the AT-compatible CTI loads are shorter than the native CTI loads. I had this problem with an CTI N load and had to make a spacer ring on my lathe to fill in the spacing.

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None that I noticed. I'm going to delete this post because I think that I got all excited over nothing. The internal shape of the nozzle is making it appear that the final grain is too far up when it is not. I just remembered this......

Right, I was going to say that if you got it to fit snug and did not skip O rings you are probably good. I am hoping to fly one of these later this season too.

I gave up on uploading pictures long ago, and now add them via imgur links.

jsdemar and watermelonman, Thank you for your responses! Watermelonman, good luck on your flight. The rocket I'm flying will hit near 27K with this motor... I hope. Moderator, you can delete this thread; I can't seem to find a way to do that.

No need to delete the thread. Might help someone else who has the same question.

Walldiver7 said:

None that I noticed. I'm going to delete this post because I think that I got all excited over nothing. The internal shape of the nozzle is making it appear that the final grain is too far up when it is not. I just remembered this......

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In my situation, once everything was put together and the closures bottomed out all the way, there was a good 1/2" of space left. I could push the nozzle in and out 1/2". If you have that situation, don't fly it!

Where and when are you launching the rocket? I'm in So. NM. We have a 75Kft waiver.

jsdemar said:

In my situation, once everything was put together and the closures bottomed out all the way, there was a good 1/2" of space left. I could push the nozzle in and out 1/2". If you have that situation, don't fly it!

Where and when are you launching the rocket? I'm in So. NM. We have a 75Kft waiver.

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That is not the situation... Forward closure is flush and the rear 1/16" from bottoming out against the case. It's tight and looks good.... now that I remembered about the nozzle inside convergence. I'm up here in Farmington. On May 28th our waiver is to 18K and on May 29th our waiver is to 53K (of course if the weather goes bad, we won't be activating the 53K waiver on Sunday). Please join us if you can! When is your 75K waiver active?.... I might head your way some time.

jsdemar said:

In my situation, once everything was put together and the closures bottomed out all the way, there was a good 1/2" of space left. I could push the nozzle in and out 1/2". If you have that situation, don't fly it!

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Did you ever talk to CTI about this? As far as I know, all CTI Pro75 loads are usable in both AT and CTI hardware, there aren't two versions of everything. Maybe this was a long time ago?

mikec said:

Did you ever talk to CTI about this? As far as I know, all CTI Pro75 loads are usable in both AT and CTI hardware, there aren't two versions of everything. Maybe this was a long time ago?

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This was a Pro98-6G, which has different loads for AT and CTI, as well as liners and aft closure on some.

Good to know; I was under the impression that only the O rings changed between versions of Cesaroni reloads.

Well, that and the XL nozzle being completely incompatible with Aerotech hardware.

jsdemar said:

This was a Pro98-6G, which has different loads for AT and CTI, as well as liners and aft closure on some.

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Not any more. The loads include both sets of orings now. They removed the choice from the dealer order forms a few years ago.

tbonerocketeer said:

Not any more. The loads include both sets of orings now. They removed the choice from the dealer order forms a few years ago.

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I bought it this year. Thought the same thing, but there it was with "AT" suffixes staring at me the night before a major outreach launch for 100 students. Very surprised when the grains and liner were 1/2" too short for the CTI casing. Good thing I have a lathe!

jsdemar said:

I bought it this year. Thought the same thing, but there it was with "AT" suffixes staring at me the night before a major outreach launch for 100 students. Very surprised when the grains and liner were 1/2" too short for the CTI casing. Good thing I have a lathe!

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Interesting. How old was the date code?

jsdemar said:

I bought it this year. Thought the same thing, but there it was with "AT" suffixes staring at me the night before a major outreach launch for 100 students. Very surprised when the grains and liner were 1/2" too short for the CTI casing. Good thing I have a lathe!

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Hey John,
If the grains and liner were too short, what did you do with your lathe, shorten the case? I'm not trying to be a smartass.

Post #2:

...had to make a spacer ring on my lathe to fill in the spacing.

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Steve Shannon said:

Hey John,
If the grains and liner were too short, what did you do with your lathe, shorten the case? I'm not trying to be a smartass.

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Made a ring about 0.58" thick that fit around the nozzle expansion, about the same OD/ID as the threaded closure. Everything snugged down with about a 1/16" extra.

jsdemar said:

Made a ring about 0.58" thick that fit around the nozzle expansion, about the same OD/ID as the threaded closure. Everything snugged down with about a 1/16" extra.

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Thanks! That's apparently what Viking was trying to tell me too, but the embedded quote was confusing.