[F-FT] Comments on motor decertification requested



The key parameter is the delta between max temperature they've been exposed to, and the internal temp when fired. So firing them in the cold also causes catos.
But take a cycled motor, warm it back to its max temperature, and fire it while warm, and it will probably work OK. I can't recall who did the R&D report (late 70s?) but someone actually did this and it works.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
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ok Bob, and how is any person supposed to know this magic max temperature....?
shockie B)
writes:

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Simple. Simply heat them to 700 degrees, then fire them... <G>
David Erbas-White
shockwaveriderz wrote:

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David Erbas-White wrote:

That's easy for You, You're a catalytic converter.
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whats needed is some kind of temperature sensitive strip embedded in the paper casing that would turn colors if its been temperature cycled....
shockie B)

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The problem is, the temperature-cycling cracking of a rammed BP motor can be caused through temperature excursions in either direction. I have motors purchased ten years ago which have never left the hobby den and are kept between 65 degrees (SWMBO starts to shiver) and 80 degrees (I start to sweat). More problematic is what temperatures they might have been exposed to during the truck ride from the distributor to the store. I tend to make motor purchases in the spring and autumn, but you never really know.
However, if I put them in my range box and took them out to the field on an nice sweltering South Georgia summer day they might heat up to over 120 degrees. Conversely, there were at least two days this winter when they would have gone down to below freezing.
So, you'd need TWO different strips. Or some kind of really inexpensive min-max recording thermometer :-) At the really, really large rocket factory I work at our motors are kept under controlled temperatures which are monitored and recorded from the moment they are cast until they are either launched or destroyed.
Personally I deal with the problem by careful storage, and always try to expend all the motors I take out on each trip to the range.
John<==unless I lose the rocket they fit in, of course !
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No.
Here is my standard BP motor failure explanation document cut & pasted here.
Here is why temperature cycling can cause Catastrophic failures (CATOs). The nozzle, propellant and the casing all expand and contract at different rates. Since the motors are so small, this is only a problem if the temperature that the motor "sees" swings between wide extremes. When this happens, we see several effects:
1) The propellant and the clay nozzle develop a crack at their interface. This actually results in *Lower* peak pressure and peak thrust because the motor can begin the end-burning earlier than it should (never forming the "big dome" of burning surface area that we should get at normal peak thrust).
2) The casing and the propellant can de-bond. They aren't really bonded in a "glue" sense, but the mechanical bond is weakened from the stretching and contraction. (For wet rammed motors, there may be a tiny glue-like "bonding", but the cycling will break that bond). The flame can propagate along the entire inside of the casing and propellant interface and result in a huge overpressure. This leads to a casing split (if the delay is still "grabbing" the casing tightly) or a "blow through" which is like a Roman Candle.
The two of these can combine to form different CATO scenarios:
a) Blow through at ignition or just after ignition (on the pad/rod). Clearly a sign of a nozzle/propellant interface crack allowing the flame front to reach the debonded casing to propellant interface at or just after ignition.
b) CATO above the pad (like 50 feet up). Clearly there was no crack along the propellant/nozzle interface and the flame front had to wait until it naturally reached the casing wall and then propagate up the de-bonded propellant/casing interface.
A final scenario is the cracked propellant grain. These can go BLAM (or KA-PLOW) quite spectacularly since they really overpressurize the casing big-time and can happen with a perfect casing to propellant bond. A defective tool used to form the centerbore of the propellant can cause these. The C5-3 had such a problem when a tool was mis-manufactured. I believe the root cause was a lack of radius on the tip, which formed a sharp edge, which led to cracking. Motors also could be cracked if any contaminant got on the tool or in the propellant during ramming, but dropping or rattling will not cause a crack!
As for the temperature cycling - avoid firing a motor at a temperature 75 degrees F lower than the highest temperature it has ever seen. If fired while too cold, the propellant will be contracted away from the casing and it will probably fail. Folks launching in cold weather can do so if they store their motors in their warm car or in their toasty parka inside pockets. (Is that an F100 in your pocket or are you just happy to see me?)
Why would a normally stable rocket fly unstable when using a motor that it flew stable with before? Did you look at the nozzle? We have had several VERY scary "flights" where the rocket had little thrust and/or veered into cruise missile mode. After crashing and putting out the brush fire, we examine the nozzle and find that it is either too wide (wider than normal at the throat) or it is eroded asymmetrically. The asymmetric erosion is bad and you can clearly see the exhaust residue all over the missing area of the nozzle indicating that it disappeared at ignition or shortly thereafter.
All unstable flights with Estes motors from years "A" and "B" and maybe "C" need to be inspected and if the motor/nozzle is the cause, a M.E.S.S. form filled out and the manufacturer notified. The least that will happen is a package of replacement motors and a kit. The most that will happen is an improvement in materials used in manufacturing and a product that performs like we remember for decades and decades.
I hope this info helps folks.
-Fred Shecter NAR 20117
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-----snip-----
Actually, I was carefully staying away from the insurance aspects of launching flaming pryotechnic devices into the sky :-) When I fly (most every weekend recently) I am by myself (rocketry isn't a big sport here in Camden County GA). Not being a member of NAR there is no way their insurance carrier would entertain a claim on my behalf if something bad occurred. I have my own private insurance coverage which includes a rider specifying my coverage when launching model rockets.
The verbiage can certainly be wordsmithed as required. My central point was when I show up at an NAR sanctioned launch and fly as a guest, any motor I want to use *must* be on the certification list.
What I do in my own time is up to me. Currently I'm tinkering with a titanium framed suger-fueled LEO capable 'Kitty Disposal Device' to send some company up to Laika (assuming that capsule hasn't deorbited yet).
John<==don't do the crime if you can't do the time
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From NFPA 1125:
7.9 Motor Shelf Life.
7.9.1 When the performance of a solid propellant rocket motor or motor-reloading kit deviates from the sample test criteria
and limits detailed in 7.8.6 within 5 years from the date of manufacture, it shall be withdrawn from commercial sale and
redesigned to provide reliable operation when ignited within 5 years from the date of manufacture.
7.9.2 If the expected shelf life of a rocket motor or motorreloading kit is less than 10 years, the manufacturer shall imprint
a "use before" date on the package or motor casing.
Since I have never seen a motor or reload kit with a Use before date, motor and reloads kits sem to have a shelf life > 10 years....
7.9.1 if taken literally seems to imlpy that if the motor/reload kit deviates from the (original test critera?) within 5 years from the date
of its manufacture, then its cert can be withdrawm, ie, it becomes decertified....
I don't beleive any of this testing is currently being done by NAR S&T... but as I pointed out in a nother post to this thread, NAR S&T and NFPA 1125 seems to contridict one another as to how decerts are supposed to take place, ie testing must be done to show that the old motor(s) are no longer safe for use...
shockie B)

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David Erbas-White wrote:

use
Suppose a line of previously certified motors had to be decertified, either because newer versions didn't perform as required or because the manufacturer failed to meet changes in the cert requirements. If the manufacturer was dishonest, he could continue cranking out new, backdated motors indefinitely. As it stands now, unless the manufacturer was dumb enough to let someone see him backdate the motors, he could only do so for up to three years past the expiration date.
I don't know if that's _the_ reason for it, but it's one possible reason that comes to mind. I'm not entirely convinced myself that it's even a big enough issue to outweigh the benefits of eliminating the expiration dates.

manufacturer
(i.e.,

Sounds ok to me.
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snipped-for-privacy@aol.com wrote:

What would be the realistic harm if this were to occur? I'm not advocating this, I'm asking an honest question. If the motors were found to be unsafe, they could be decertified immediately. If the manufacturer was found to be doing this, he could be prosecuted for fraud. If (as is apparently the case with Kosdon motors -- I'm going from hearsay) the organization didn't REQUIRE any date coding on the motors, that's an oversight they have to correct -- and would have to grandfather in for some reasonable time, as well.
I get real tired of having to do things in life based on what the 'bad guys might to' if they had a mind to. 'Reasonable' precautions are okay, but I just don't see the harm in the outlined scenarios.

Ditto -- I believe it might be an issue, but I think that the benefits of ALLOWING older motors to be used outweigh the possible downside. Eliminating this requirement would (IMHO) actually boost the hobby -- here's why (and this is real-life). I've heard recently that the C11-0 will no longer be made -- so, I bought a couple of extra packs.
Now, if I felt that I'd be able to use them at NAR launches over the coming years, I might have bought a BUNCH of packs, because I'd be assured that I could use them, or they could prove to be good as 'trading goods' that others would be able to use. My buying them and stashing them in my 'collection' no opens up pegs on the retailers shelf -- which he'll hopefully fill with more motors, and so on down the line.
David Erbas-White

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Very good point.
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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If the certs never expired there could not be a fraudulent claim of backdating.
The ONLY thing that could be an issue was actual product performance and under one suggestion I read here there would be a mandated 90 day compliance period.
Under those terms there would have been unlimited USR motors available after the AT fire.
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Jerry Irvine wrote:

Oh, this is rich...
The intent of dating motors (or anything else) is to allow for finding a 'lot' of motors if they are found to be defective.
Whether or not you actually backdated motors (and I obviously don't know and have no knowledge of it), that entire incident will have colored the industry as to whether or not the certification issues can be modified. It would be easy to point back to 40 years of spotless history and say "There's never been any problem, let's consider some modifications to make it easier", but with the (unfounded or not) accusations against you, and the fact that Frank didn't date the motors at all, there is REALISTIC concern about folks taking liberties with 'the system'.
David Erbas-White

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All the more reason why falsified claims by TRA (and there have been so many WRT so many people) have caused any industry damage.
I do not see people claiming errortech's foamy/recored J350 issue "damaged the industry" and it was far more widespread, recent, public, and witnesses as to truth.

Batch tracking is a manufacturer concern ONLY because if a "lot" is recalled (none ever were) and it is unclear what lot to recall it is a manufacturer risk that "all" motors might be recalled to catch the "bad lot".
In point of fact all legit USR motors (those not stolen and resold by Teeling for example, in a similar timeframe), were dated. Accurately.
I was seeking to (early) RENEW motors at the time the motors were decertified (I was never even informed of a backdating claim).
If the renewals were processed with the samples already tendered and ACCEPTED by Tripoli, this would have been a non-issue.
Between Teeling reselling stolen motors, Tripoli "losing" many samples they ACCEPTED, and the claims I never had FAA waivers (proven false), and the motor decert with NO NOTICE. I think it is clear there was something major going on and I for one had NO INCENTIVE to screw myself.
Teeling's partner in Powertech was on the TRA BOD and personally made the decision to remove me for FAA claims and was party to the decision to decertify USR and was also present and leader of the charge to certify Kosdon motors (yet another Powetech partner) in direct opposition to the partnership agreement (USR exclusive seller).
I got screwed and everyone familiar with the facts knows it.
Fine.
All l ask for now is a level playing field and it is NOT forthcoming.
Jerry

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Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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Jerry Irvine wrote:

jerry, I decided to help you out with your problem. I'll call Bob Lynch tomorrow and see if He can influence TMT motor testing to broaden their scope and to begin the testing of "model airplane parts" on regular basis. Also, I'll see if He has any recommendations or "tips" on solving your problems with the ATF. Just make sure all your current paperwork is ready to go, so we can get the ball rolling.
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Jerry Irvine wrote:

The playing field is level now. You just insist on playing a different game.
Submit motors and complete paperwork EXACTLY in accordance with the regs, and your motors WILL be certified.
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So let's be clear. You are suggesting I submit ATF LEMP paperwork (the only discrepency at issue) that the "manufacturer" (a subcontractor from my perspective) does not legally need (according to the ATF) and refuses to get, unnecessarily?
And how does that jive with YOUR position on ATF and the lawsuit?
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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Jerry Irvine wrote:

No jerry, you also need valid DOT papers with valid EX numbers in the same name as the LEMP, the name of the manufacturer.
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On Thu, 14 Apr 2005 18:22:27 GMT, Dave Grayvis

Who cares - let Big Fine prove his stupidity again if he wants to. Come on Jerry - live the life.
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