38 CTI motor fail this one is a mystery. Help

SpaceManMat said:

Not sure I agree with you there. As far as I can tell the second picture shows the pellet and has the remains of the forward seal embed in it. So I would interpret this as the grain being forced upwards during over pressurisation, no doubt the forward closure lost the oring as it was forced through the spacer and then the grain ran into the oring and spacer resulting in the oring being embed into the top of the grain.

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The second picture is the top (fore end) of the forward closure mangled where he was attempting to drive is out of the case before cutting the case into two parts.

Jared,
If you’re still around, and I hope we (myself included) haven’t scared you away by looking for things you did wrong.
After seeing several other posts recently about single grain Pro38 motors which have over pressurized, I believe that you did everything just right. You should seek replacement from your vendor.
I’m sorry I assumed it was something that you did at first.

On a hunch, is it possible you used the XL spacer instead of the longer one? Seen it happen before...

Check out the "Another CATO" thread, Wildman posted a statement by CTI. The 38mm 1-grain motor CATO issue has been identified and is due to the igniter pellet burning faster than formulated and overpressuring cases.
https://www.rocketryforum.com/index.php?threads/151751/

There is a new bulletin published by CTI just recently (April 15, 2019) strongly recommending a modification trimming the “ignition pellet” in half (actually 40%) because their 3rd party manufacturer made the pellets incorrectly. I’ve got 3 G60s that I will need to modify at the range before launching. It sort of defeats the “ease of assembly” that CTI had over AT. See “https://www.pro38.com/pdfs/Pro38_Pellet_Modfications_v1.2.pdf” for further detail.

slothead said:

It sort of defeats the “ease of assembly” that CTI had over AT.

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It's not as though it's the entire range of their motors. As per their press release from Wildman, it's not even really necessary for the 2g, but they are recommending it out of an abundance of caution. EVERY manufacturer has issues from time to time, this is just the most recent for CTI.

Either way, dropping out a grain (which you're going to be looking at anyway when you pull the forward closure to adjust the delay), popping out the pellet, cutting it, putting it back in the grain, and putting the grain back in the liner is STILL orders of magnitude less complex than any part of an AT motor.

slothead said:

There is a new bulletin published by CTI just recently (April 15, 2019) strongly recommending a modification trimming the “ignition pellet” in half (actually 40%) because their 3rd party manufacturer made the pellets incorrectly. I’ve got 3 G60s that I will need to modify at the range before launching. It sort of defeats the “ease of assembly” that CTI had over AT. See “https://www.pro38.com/pdfs/Pro38_Pellet_Modfications_v1.2.pdf” for further detail.

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Thanks Tom!

Anyone know why would this only apply to 1 and 2 grain? And how could the purchase date matter for identification?

jahall4 said:

Thanks Tom!

Anyone know why would this only apply to 1 and 2 grain? And how could the purchase date matter for identification?

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It's in the bulletin and the update that Wildman posted.

A 3rd party makes the pellets now, and their formulation of the lot burns faster than spec, causing a pressure spike in the 1g motors. Every 38mm motor uses the same pellet, but the volume of the case in the larger cases is able to mitigate the spike effectively enough to render it harmless.

Purchase date relates to the lots that they've sent out to the vendors.

jahall4 said:

Thanks Tom!

Anyone know why would this only apply to 1 and 2 grain? And how could the purchase date matter for identification?

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The volumes of the 1 and 2 grain cases are the least and thus quickest and most highly pressurized by the pellet.

Steve Shannon said:

The volumes of the 1 and 2 grain cases are the least and thus quickest and most highly pressurized by the pellet.

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Thanks for the quick reply Tom and Steve. That would have been my guess too, but the bulletin is not explicit about why 3G and up is NOT affected and the purchase date does not make any sense unless they are referring to when my vendor purchased the motor, which sounds like what Tom is saying.

So now if you are flying Pro38 you have to check for 2 issues the ignition pellet AND the forward closures.

jahall4 said:

Thanks for the quick reply Tom and Steve. That would have been my guess too, but the bulletin is not explicit about why 3G and up is NOT affected and the purchase date does not make any sense unless they are referring to when my vendor purchased the motor, which sounds like what Tom is saying.

So now if you are flying Pro38 you have to check for 2 issues the ignition pellet AND the forward closures.

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Should be well past the forward closure issue, unless you have some deep stock and haven't been checking up until now. The dealers all got replacement forward closures and have made the appropriate substitutions.

Banzai88 said:

Should be well past the forward closure issue, unless you have some deep stock and haven't been checking up until now. The dealers all got replacement forward closures and have made the appropriate substitutions.

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It's been less than 3 years. Most all of my stock is older and I'm still buying motors from my vendor that are pre-fire so if you are using 38s w/o checking you are rolling the dice. Both checks will be in my checklist going forward regardless.

jahall4 said:

It's been less than 3 years. Most all of my stock is older and I'm still buying motors from my vendor that are pre-fire so if you are using 38s w/o checking you are rolling the dice. Both checks will be in my checklist going forward regardless.

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It’s always a good idea to check. A vendor told me he first saw this over pressure problem about September 2017. That agrees with the date codes for some of these reports also. That shouldn’t overlap with the forward closure problem, but why not check.

@Steve Shannon Is there some type of notification "service" for bulletins like these? I still encounter folks at the RSO table flying these 38s who have not heard about the forward closure problem.

jahall4 said:

@Steve Shannon Is there some type of notification "service" for bulletins like these? I still encounter folks at the RSO table flying these 38s who have not heard about the forward closure problem.

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The manufacturers notify the vendors and place notices on their websites. Typically the vendors then copy those notices to forums like this. All people flying motors should track the manufacturer notices.
A lot of times the manufacturers don’t even notify the testing organization that certified the motor. That’s something I think should change.
When TMT originates a notice, we should put it on our announcements page: https://www.tripoli.org/TMTAnnouncements. We haven’t had such a notice in a while. It would be great if we had a volunteer with the time to take Manufacturers notices and put them there also.
Announcements of newly certified motors go to the Tripoli Prefects Forum, the NAR/CAR/TRA email list and to TRF and ThrustCurve.
I’m open to suggestions how to make this better and more consistent and also to get flyers to consistently check.

Steve Shannon said:

The manufacturers notify the vendors and place notices on their websites. Typically the vendors then copy those notices to forums like this. All people flying motors should track the manufacturer notices.
A lot of times the manufacturers don’t even notify the testing organization that certified the motor. That’s something I think should change.
When TMT originates a notice, we should put it on our announcements page: https://www.tripoli.org/TMTAnnouncements. We haven’t had such a notice in a while. It would be great if we had a volunteer with the time to take Manufacturers notices and put them there also.
Announcements of newly certified motors go to the Tripoli Prefects Forum, the NAR/CAR/TRA email list and to TRF and ThrustCurve.
I’m open to suggestions how to make this better and more consistent and also to get flyers to consistently check.

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Flyers shouldn't have to check. In an ideal world the vendor would notify the purchaser, but IMO that could be rather onerous for the vendor and private sales would fall between the crack. So, instead there should be a centralized repository for motor bulletins/notices ran by the associations (e.g,. NAR and TRA) where flyers could sign up to be notified via email/text when new notices are issued. This has the potential to be a safety issue and the manufacturer should be responsible for submitting the notice. All it would take would be one high-profile injury and a statement by the flyer that they were not advised. One lawsuit would cost far more than setting up the website and having manufacture personnel take few minutes to submit a notice.

As I said, manufacturers don’t notify TMT of problems.
If they did, we could probably place their notifications on a read-only forum on the Tripoli website and flyers could subscribe to receive emails whenever a notification was posted.
Or each manufacturer could create a notification mailing list for people to subscribe to. Only for problem notices, no advertising.

Then the root problem is the manufacturer stop certifying their motors if they won't participate. Its simply not that much to ask of them.

Steve Shannon said:

...we could probably place their notifications on a read-only forum on the Tripoli website and flyers could subscribe to receive emails whenever a notification was posted.

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Good idea, but TRF might be better since it would be not be assoc. specific.

jahall4 said:

Good idea, but TRF might be better since it would be not be assoc. specific.

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I agree that it should not be specific to an Association specific. That’s the only one I have much influence over.
Any way it’s done the flyers must ultimately take the responsibility of signing up for notices.

Steve Shannon said:

I agree that it should not be specific to an Association specific. That’s the only one I have much influence over.
Any way it’s done the flyers must ultimately take the responsibility of signing up for notices.

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Yep, and if they are notified of the service when they join an a assoc and/or buy a motor, neither the assocs or the manfs would have reasonable liability (incl for warranty which is the way to sell it to the manfs).

I fail to see how a private for-profit forum ( which I dearly love ) would be a good choice for manufacturer-association-vendor-customer notification.

An email list jointly moderated by the chairs of TMT & S&T?

dhbarr said:

An email list jointly moderated by the chairs of TMT & S&T?

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I'd like to see something like to go to all the clubs. Most of the clubs are aware of the VMAX issues (for example), but would be good to know what open issues there are for RSO's to check.

djs said:

I'd like to see something like to go to all the clubs. Most of the clubs are aware of the VMAX issues (for example), but would be good to know what open issues there are for RSO's to check.

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That’s why TMT posts in the Prefects forum. All Prefects receive a copy of the post in the email address they have registered with Tripoli. There’s no good reason your Prefect should not be receiving notifications.

Steve Shannon said:

That’s why TMT posts in the Prefects forum. All Prefects receive a copy of the post in the email address they have registered with Tripoli. There’s no good reason your Prefect should not be receiving notifications.

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I like this, but I'm also thinking of NAR clubs too

djs said:

I like this, but I'm also thinking of NAR clubs too

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We talk frequently. I’ll keep this in mind.

Banzai88 said:

Should be well past the forward closure issue, unless you have some deep stock and haven't been checking up until now. The dealers all got replacement forward closures and have made the appropriate substitutions.

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Hey Tom Keith, I too am considering making a L2 attempt with MDRA some time in May or June. Perhaps we’ll see each other at the Sod Farm.
Later,
Tom

djs said:

I like this, but I'm also thinking of NAR clubs too

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...and UKRA, and CAR, and IMR, and RSA....