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
When Fascism comes to America, it will come wrapped in an American flag.
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)
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 !
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
-----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
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)
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.
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
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
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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
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
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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.
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.
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
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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