A local TARC team I am working with is using Estes E12-6s this year, and on Saturday (in the rain) they put up a flight that went up nicely then proceeded to arc over and streamline in. After the wreckage was retrieved we found that the clay cap over the ejection charge was intact.

Has anyone else had this issue with E12s? I know about the occasional more energetic CATOs (and have experienced two personally in the years E12s have been available) - no need to go there in this thread. I'm just looking for other instances of no ejection charge occurring, and if you have had this happen, did you file a MESS report and/or contact Estes?

Thanks.

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Was it only one engine that malfunctioned or an entire package of engines?

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OUCH !
I have heard of plenty of E9/E12 catos, and in the past plenty of "overly energetic/shotgun blast" Estes ejection charges, but never a "ZERO" ejection charge in anything but an intentionally plugged motor. Almost sounds like an E12-P motor production anomaly.

While I find Prangs, Powr-Prangs, Core-Samples, and Lawn-Darts at sport-launches hilarious, I hate to see that happen to TARC teams or any sort of competitors.

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Jeff,

We haven't tried any of the others yet. The reason I posted the query here (and on that other forum) is because the good folks at Estes said they'd not had this reported before. They actually advised us trying another to see. I have a saucer-type thing that I made from a dollar store candy dish with a 24mm mount in it that I can offer up as a test mule.

The team (and parents) are worried as to whether or not they can use the rest of the dozen or so they've purchased from AC Supply (which all have the same date code).

GH,

I've never looked closely at -P motors - do they look any different at the top? The failed one looks just like any other E12 with respect to the clay cap. But I actually framed my query to Estes that I sent exactly the same way - suggesting that this might have been a -P motor that was mismarked or some such.....

The kids were pretty bummed about it Saturday....I appreciate the sympathy.

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Bernard Cawley
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I've seen intact and mostly-intact clay caps on D12 motors over the years. I haven't seen enough E12s at our launches to see the same thing. Given that it is an Estes 24mm motor, it doesn't surprise me that someone crashed a rocket due to a wimpy delay or overly thick clay cap. No shocker here. I'm sorry that the kids had to experience this and have their project crash.

I usually check the clay caps after loosing a couple models. If you lightly scratch the surface of the clay cap, you can at least verify if there is black powder there. No telling how much.

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Did the delay charge ignite? Did you see tracking smoke? It may be worthwhile to use your hobby knife to cut it lengthwise on opposite sides and open it up for an internal inspection.

This happens, but very infrequently. Use the remaining motor on a recreational rocket you don't care for, or use it educationally by putting it on a test stand to let the students see the full burn/delay/ejection (or lack of), within a close but reasonable safe distance.

The various incarnations of Mabel motor making machines work like a rotary assembly line and the delay charge likely just didn't drop on that individual motor. I usually look at motors in a pack to see if the depth to clay is consistent within that particular pack, but the amount of BP is so thin that you'd probably never be able to tell. You also can't compare a motor with motors from other batches because the propellant volume vs total impulse between batches varies, causing the propellant slug length to vary.

I have had everything from shotgun ejections (mostly 13mm and 18mm A motors) to ejections so weak the clay is mostly in tact (mostly D12's), but I can't think of a total failure to even crack the clay on any of my flights.

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As I told Mike at Estes in a follow-up note last night I didn't think to look for tracking smoke as we just expect it. It was raining and this turned out to be the last flight of the day. In other words, I can't really answer that question.

tbzep - lots of good thoughts. There is a little discussion about thick caps over in the other forum in my thread there. I don't recall ever having issues even with D12s. I do recall getting a 29mm BP Estes motor with an incomplete cap once (opposite situation) and it worked fine.

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Bernard Cawley
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The caps for -P motors are much thicker to prevent blow-thru.
I would use a straw or rod to measure the distance from the cap to the top of the casing.
That would identify any 'extra thick' ones. This clay is typically very soft compared to that used for the nozzle. I would not worry about a 1mm variance, but if you find much more than that from high to low, I would suspect those that measure 'short' on distance from the clay cap to top of casing.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !

1mm is well within spec when it comes to different batches of propellant. I've seen it vary as much as 1/8" if not more and still have a total impulse within normal tolerances.

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