[F-FT] RMS delay question/comment

wrote on 4/7/05 11:21 PM:> You're assuming too much.

the
"tool to modify delay times" is not a stange concept to rocket scientists, or even those of us that just fly rockets
"not having TMT involved" is also not a stange concept, as JI talks about it every 5 minutes, it seems, and Kaplow claims they never were involved.......
What have I assumed?
You let the cat out of the bag Gary, and therefore, "you got some 'splainin to do"... (tell me again how the ellis production of the j350 didn't result in a motor that required user mods not to Cato?)
And then there was the good old "red liner" thing..........(Newbies, google this one...)
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Well, they were involved, just not in doing their stated duty.
NAR actually tests what it says it tested. That's why it actually has the data to publish on motor firings and delays. TMT does not. Read the tea leaves.

He was clearly wrong on that one and it seems he is not "publicly admitting" it either.

Ditto
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I have no direct first hand info so I am free to speculate.
It is an electronic device that is adjustable with a pot or something and not a pyro delay at all.
How am I doing so far Gary?
Watch out for rmr!
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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IIRC, the reason TMT requested the discrete steps from CTI is that they DID test every one of the options. I'm sure Mike can enjighten us on what CAR testing did, but it seems to me that they'd also need to test every combination.
    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
    Homeland Security Administration: The Gestapo of the 21st Century
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kaplow snipped-for-privacy@encompasserve.org.TRABoD (Bob Kaplow) wrote:

That rule needs to be changed since it is being widely ignored anyway (by TMT).
Jerry

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When we introduced the adjustable delay tool with the Pro38 motors, there were no procedures in place with any of the motor testing committees to handle the concept. Therefore a plan had to be developed on the spot. Obviously with finite adjustment as per the Pro38 tool, which has 4 delay reduction settings for a total of 5 possible delay times, one could simply require three tests of each delay. And that is exactly what was done in the first run of TMT tests, 15 of each reload were provided for test, from the G60 to the J360, i.e. 90 reloads.
Note that we did initially want "infinite" delay adjustment on the Pro38 line - however, this was apparently too much of a paradigm shift for the TMT committee at the time, and they wanted us to provide preset stops instead. Thus the genesis of the current design of the ProDat tool for the 38's, which also appears in relabelled form by another manufacturer. Had the issue been less contentious at the time, we might have had an infintely adjustable tool for 38's instead of the current design. However, quite frankly, who needs delay settings between integer values in seconds? Reality is not so precise. One second off is only 16 feet of altitude and 32 feet per second in velocity, which is no problem for any properly constructed rocket and recovery system. Also, the molds are really, really expensive and a new tool is just not worth it at this time.
With the increased confidence in the concept that developed after certification testing and subsequent consumer use in the field, a reduced number of firings have been used more recently, typically with three at full delay, three at minimum delay, and intermediate spot checks. The fact is that (a) if you have your full delay length properly dialed in, AND (b) you have the coasting burn rate properly characterized, AND (c) your delay adjustment tool is properly designed with respect to the coasting burn rate, then you can actually pretty much test the top and bottom ends of the delay spectrum and have confidence in the intermediate settings. If the full delay meets specifications, and the full delay reduction setting does as well, every setting in between will be accurate within those bounds. Assuming the full delay time is on spec, the full delay reduction setting has the potential for the largest error. Each incremental setting in between will have proportionally less error as you get closer and closer to the full delay time, i.e. small delay reduction settings. However, it is perfectly rational to expect the certifying committee to spot check the intermediate delays.
As anyone who manufacturers motors with delays will know all too well, dialing in delay times is a bit of a pig. No matter how good your formulating skills and manufacturing methodology and quality control, typical cast composite delay systems vary all the time. Luckily, they tend to stay reasonably consistent within a window of error that presents no tangible risk to the vehicle in practical use. But for example [and I've done this before to get a handle on the variablity] when I cut a number of delay columns for a particular motor and fine-tune them to precise length tolerances with sandpaper (i.e. +- 0.002" or so across the center of the column), and use matched weight grain sets in the motors, I still see variability. There are myriad small variables not to mention chaos theory to contend with.
With the Pro54 system of "infinite" adjustability between bounds, it would literally take forever to test every delay three times... so the above system was used for those. The full delay was tested three times, the shortest delay was tested three times, and intermediate settings were spot checked. Jack Kane from NAR S&T was present for the first certification run of a Pro54 motor - the J210 - and was perfectly comfortable with the procedure and the rationale behind it.
I would tend to think that the first time a manufacturer brings an adjustable delay motor to market, they may be subject to a few more tests than perhaps strictly necessary, in order to put the system to the test. After that, with a confidence level established in the minds of the certifying commitee they might relax total number of firing requirements for later motor tests. That, however, is strictly for the certifying body to decide. It is what we had to do, and we had no major issue with the process.
Mike Dennett Cesaroni Technology Incorporated

there
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-----snip-----

TMT
issue
adjustable
tool
Allow me to quibble, please. The sims for my 5.5x Streak show that with a ten second delay (achieveable with the DAT) motor ejection occurs before apogee, at a velocity of 36 FPS introducing the possibility of a zipper. If an 11 second delay were available, the ejection comes within a foot of apogee at a velocity of 5 FPS. Guess which one I like better :-)
What is really troublesome to me is the concept that the TMT committee has trouble over a 'paradigm shift' and as a result MY choices are restricted so they can feel "all warm and fuzzy". I have other issues with Tripoli which I won't go into here but I believe we need to move away from having NAR and TRA setting all the rules.
I think the time has come for a truely independent testing and certification authority whose testing results would be acknowledged and accepted by all the national rocketry associations in the US. NAR and TRA each have their own agendas. For myself, I say a pox on both their houses when they artifically restrict our abilities to build and fly rockets which are *fully* optimized. When I design a rocket which requires an 11 second delay when flown with a 260 N motor I should be able to adjust the delay grain, legally, in the same way I can use 1.1 grams of BP for the ejection charge, not having to choose between 1 gram or 1.5 grams because a 'national organization' can't make a 'paradigm shift' to accomodate newer, more versatile motor technologies.
Even though I shudder at the thought, perhaps an international FAI standard would be a better solution. AIUI the CAR has accepted infinitely adjustable delays ?
As for the testing process its self, I think three rounds for each motor would suffice. Test at: 1) full delay with no modification, 2) miminum delay possible following the manufacturer's modification instructions and 3) at a randomly selected value, again following the manufacturer's modifications. If all the results are within <fill in the blank> percent of the published values the motor and delay adjustment process are certified.

Thanks, Mike I appreciate the background information you provided.
John<==maybe the UN could certify our motors ?
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The current TMT crew have no issue with an infinitely adjustable system, as I mentioned this was under prior rule, and was one individual's opinion on the situation. We were a little annoyed at the time, for sure, but have since gotten over it...
At this point both CAR and NAR have been involved in the testing of infinitely adjustable delay systems (Pro54) and all three agencies are okay with them. The only reason TMT wasn't involved in the testing was that by the time the 54's came out CAR had formed its own motor testing committee, so rather than ship motors stateside it was and still is far more practical to do it up here through CAR. That way, for example, certification testing can go on concurrently with our application for Competent Authority approval at the DOT, perhaps saving a month's delay in going to market. Besides, TMT has several motor manufacturers to deal with and it is a volunteer assignment, so in a sense CAR is also lightening the load for them. Jack Kane of NAR S&T was involved in the J210 certification testing since he was going to be in town anyways to discuss motor certification reciprocity and other issues with CAR personnel.
I don't think we have a big problem with certification of new technology at the moment, at least not from my perspective anyhow. IMHO the TMT staff over the last while have been very open minded and accomodating. After all, we just went through another "new" technology in that we certified cross-brand compatible reloads. They had no issues with the concept in general, although there was much discussion about procedures etc. which is to be expected with yet another "paradigm shift" being thrown at them. They got both opinion and flak from many sources, and there were of course some dissenting opinions offered as well as agreement, but in the end TMT waded through all that and decided there was no problem with the concept within the "jurisdiction" of a rocket association motor certifying committee. And the consumers of said products certainly seem to have no objection...
The problem with only testing one motor of any delay time as suggested is delay variability, see my prior post. One point tells you nothing, two points leave you guessing, three points is a minimum to infer any trends. It is very common for two of three to test really close to each other, while another sample sits close to the limits. If you test the full delay time and it is 14.1 seconds, then you test a -10 setting and the delay is 6.8 seconds, what can you infer from that? Nothing. Which one was off? Who knows? You need more data points, or what's the point of having a certification process at all? (some may chime in with agreement on that one, I am sure)
While it would be nice to only have to fire three examples total using three different delay settings, realistically that process would not be doing the consumer any favors at all. The system as it has been implemented so far [though it is not in stone] is IMHO a reasonable compromise between testing three of every possible setting, and not testing enough.
I suppose one way of separating the delay time from the certification process is to do it with an electronic timer, but integrate it with the motor in some manner or as an add-on module! Interestingly, note that there are no certification processes for avionics, so even inaccurate el-cheapo timers can make it onto the field in theory.
Hmmm..
Mike Dennett

But if my rockets zippered at that speed I'd work on fixing the zippering problem. Deployments 1-2 seconds from apogee are not uncommon.

choose
Well, you could do so if the manufacturer of that motor provides instructions on how to do so, and has the adjustment process verified through certification testing. I can still see the certifying bodies being involved.

standard
adjustable
All agencies are cool with the concept.

randomly
See above. IMHO not enough data points for confidence. Convient and economical however? No argument.

No prob.
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Out of curiosity how much did CTI invest (molds, samples, labor) to overcome this TMT "opinion"?
I am guessing several tens of thousands of dollars.

No point if you don't even publish the results.
At TRA, certification has been treated as a wide-band go-nogo for many years. Whether that is good or bad is a matter of opinion.
It is certainly non-compliant with the very rules they insisted on authoring and adding.
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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-----snip----

It
and
one,
three
the
testing
In an ideal world, you'd want to test 7 to 9 examples of each unit to minimize the measurement uncertainty. I was inadvertently factoring in the sticker shock at how much the reloads cost :-)
Thanks for the great post Mike ! You are sure teaching me a lot about how the motor certification process works and I appreciate it !
John<==n we use my Level 1 certification flight as a 'test' ?
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You are quite right, ideally (cost and PITA factors notwithstanding) there would be more samples per type. But as the goal of the certification process is to not to define motor performance to the last decimal place, but rather to ensure that the products function nominally and the pertinent performance parameters are reasonably close to the manufacturer's data/claims so the consumer gets pretty much what they think they are getting, this small number of samples does the job adequately.

Luckily manufacturers don't have to pay retail for their own products... ;-)
Mike D.

is
trends.
while
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Relabelers do.
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Jerry Irvine wrote:

products... ;-)

Poor Jerry.
a
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writes:

IIRC (my brother absconded with my good statistics book) you really want a sample size of 30 or so. Which is affordable for Estes type motors, but not for HPR. 12 is probably a reasonable compromise.
    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
"I tell you, freedom and human rights in America are doomed. The U.S. government will lead the American people in and the West in general into an unbearable hell and a choking life."
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wrote:

I haven't seen you post any questions in the TRA list which TMT does monitor. If you are a member of TRA, I suggest subscribing to the list.
Concerning the 'paradigm shift, ' I don't know what you're talking about. TMT tests what is provided by the manufacturers. To my knowledge, no manufacturer has presented what you are looking for. Most of the manufacturers monitor this list intermittently. If I'm wrong about this hopefully they'll chime in and correct me.
Also, you are notlimited to NAR and TRA rules. You are free to go anywhere and do anything you want. Although I suggest that you keep it legal.
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Everybody else did.

Not if they "lose" it.
Not if the manufacturer is not required to get an ATF permit by ATF, but TRA insists on one anyway.
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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wrote:

Poor Jerry. It really sucks to have to follow the same rules as everyone else when you're "Special."
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Jerry Irvine wrote:

ATF...
Really? Quoting from your own website: "ATF "knowingly and falsely" claimed PADs are not exempt..."
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In a lawsuit.
Not in my experience in the field.
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Jerry Irvine wrote:

You've been asked to prove that claim before, and failed to do so. All it would take is the name of the agent who told you that you don't need ATF permits.

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