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cerving

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If the liner doesn't slide all the way in (assuming your case in clean...), doesn't that indicate that the case is damaged, possibly out of round?
 

OZRoc

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Hi Cris,
I had / have 3 reloads. First one slid in perfectly. Last 2 slid in half way and jammed. Sand down the liner with an orbital sander and all good (Thanks to advice by @TOM C). Will double check next year B4 launch once out of this covid crap.
Cheers, Mark
 
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Rocketjunkie

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Tolerances are pretty loose on phenolic tubes. I had to sand the previous batch of 98 mm tubes to fit all my cases. (2 5120, 2 7680, 2 10240, 1 15360, 1 CTI 6GXL, 2 20480.)
 

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Cameron Anderson

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If the liner doesn't slide all the way in (assuming your case in clean...), doesn't that indicate that the case is damaged, possibly out of round?
Potentially, but the QC is tighter on case manufacture than the current supply of liners. I don't know of a CTI 75 or 98 liner that I have flown or a friend has flown this year that didn't require significant sanding. And that isn't just trying to find a liner in one case, we passed them around and the liners didn't fit any cases.
 

cerving

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Wow... I don't think I've ever had a 75 not fit, both in the 3G and the 5G cases that I have. I HAVE had some tight 54's, however.
 

phyzzld

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Hi,

I am building my first N motor for Midwest Power and have a quick question.
It is an N2600 6G 98mm.
Four of the six grains look like this:

grain_face_1.jpg


but two them each have a face that looks like this:

grain_face_2.jpg


I wasn't sure if this is something I need to remove or everything is ok as is.
Anyway I thought it best to check before completing it. I do appreciate any help.

Thanks,
Jeff
 

Cameron Anderson

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Hi,

I am building my first N motor for Midwest Power and have a quick question.
It is an N2600 6G 98mm.
Four of the six grains look like this:

View attachment 484036

but two them each have a face that looks like this:

View attachment 484037

I wasn't sure if this is something I need to remove or everything is ok as is.
Anyway I thought it best to check before completing it. I do appreciate any help.

Thanks,
Jeff
The first 4, that's just slight oxidation...you can lightly scuff it off if you want but it's fine to fly.

I would be more worried about the second pictured grain and the grain pulling away from the casting tube.
 

rharshberger

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The first 4, that's just slight oxidation...you can lightly scuff it off if you want but it's fine to fly.

I would be more worried about the second pictured grain and the grain pulling away from the casting tube.
Is it oxidation or where the propellant stick was cut into grains, the pattern appears to be circular, oh and yeah the gap between casting tube and grain had me wondering too. The smooth faces are I am guessing from the casting jig end caps (?).
 

phyzzld

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How old is this motor? Is there a date code on the packaging?

If you have not already, show this picture to your motor vendor so they can either render an opinion themselves, or they can reach out to CTI on your behalf:
The date code is Apr 3 2019. It was purchased from Wildman's in Nov 2019. I received it in March of 2020. I haven't reached out to Tim yet. I just opened it a couple of hours ago.

I checked the faces of all the grains. Only the two grains with the "smooth faces" show a gap.
 

mikec

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Wow... I don't think I've ever had a 75 not fit, both in the 3G and the 5G cases that I have.
I had an M1101 reload bought last year that took an hour+ of sanding before it fit my Aerotech case. Same case, two Aerotech reloads, fit perfectly normally. Something up with CTI 75mm liner tolerances, no question.
 

Banzai88

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I had an M1101 reload bought last year that took an hour+ of sanding before it fit my Aerotech case. Same case, two Aerotech reloads, fit perfectly normally. Something up with CTI 75mm liner tolerances, no question.
It's several issues across the product line, and they're not getting any better
 

manixFan

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How old is this motor? Is there a date code on the packaging?

If you have not already, show this picture to your motor vendor so they can either render an opinion themselves, or they can reach out to CTI on your behalf:
View attachment 484041
Just in case you are wondering what will happen with the gap, the flame front will very likely find its way into those gaps and start burning the grain from the outside in. You now have a lot more surface area burning than intended or designed. I've seen it happen and the result is not pretty.

Tony
 

Cesaroni Technology

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How old is this motor? Is there a date code on the packaging?

If you have not already, show this picture to your motor vendor so they can either render an opinion themselves, or they can reach out to CTI on your behalf:
View attachment 484041
Definitely DO NOT fly that motor. The debonding between the propellant and casting tube will certainly lead to a failure. Return the reload to your vendor for a replacement.
 

cerving

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Seeing that gap between the grain and the casting tube gives me a new item to add to my motor building checklist... inspect all of the grains. It's real easy with the motors that come with the grains shipped in the liner to just leave them in there and not look at them.
 

bobbyg23

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Seeing that gap between the grain and the casting tube gives me a new item to add to my motor building checklist... inspect all of the grains. It's real easy with the motors that come with the grains shipped in the liner to just leave them in there and not look at them.
Great point.
 

phyzzld

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Definitely DO NOT fly that motor. The debonding between the propellant and casting tube will certainly lead to a failure. Return the reload to your vendor for a replacement.
I will return the motor. Thanks for the heads up.

Jeff
 

WILDMANRS

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Definitely DO NOT fly that motor. The debonding between the propellant and casting tube will certainly lead to a failure. Return the reload to your vendor for a replacement.
You can not ship that reload back to me unless you are hazmat certified.

The first thing you have to do is fill out this form.
That's the first thing Sandi is going to ask me for.
I will be happy to forward the form to CTI and then its Up to them as to what happens and how soon it happens .
We will have an order coming for MWP .
 

phyzzld

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You can not ship that reload back to me unless you are hazmat certified.

The first thing you have to do is fill out this form.
That's the first thing Sandi is going to ask me for.
I will be happy to forward the form to CTI and then its Up to them as to what happens and how soon it happens .
We will have an order coming for MWP .
Thanks Tim. Will call tomorrow to see what else I need to do.
Jeff
 

rcktnut

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A question for the experts- Could storage issues like temp/ humidity cycling cause this, or is this defect due solely to the manufacturing process?
 

3stoogesrocketry

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A question for the experts- Could storage issues like temp/ humidity cycling cause this, or is this defect due solely to the manufacturing process?

Yes , but I'm not even a minor league player yet.
 

Cesaroni Technology

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A question for the experts- Could storage issues like temp/ humidity cycling cause this, or is this defect due solely to the manufacturing process?
Temperature cycling is more likely to cause de-bonding than humidity. I have seen that in the past but it's been quite a while.
 

cbrarick

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It's really hard to humidity cycle grains left in their sealed bags until you are ready to use them. Just sayin' it's in the instructions......
Having said that I've built a 75/ 6 grain motor, put blue tape over the nozzle (what else would a rocket guy use??), let it sit for 4 years then flew it, and it was ok. No humidity cycling because it got sealed up with the tape. In my basement so temp cycles were minimal.....
 

yo3ict

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Pro38 J150 6GXL has an extended charge well.

I have it ordered but I'm planning additional ejection testing this weekend and I need to secure the motor retaining hardware inside the airframe at the correct position to account for the extended well. The extension length is what I'm interested to find out and it is not documented on Cesaroni's website.

Does anyone know exactly how much it pokes out compared to a standard Pro38 ?
 

Cameron Anderson

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Pro38 J150 6GXL has an extended charge well.

I have it ordered but I'm planning additional ejection testing this weekend and I need to secure the motor retaining hardware inside the airframe at the correct position to account for the extended well. The extension length is what I'm interested to find out and it is not documented on Cesaroni's website.

Does anyone know exactly how much it pokes out compared to a standard Pro38 ?
This is a J150 charge well.
 

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