[F-FT] Where is the line regarding G motors

I'd like to hear the input from folks here about where the 'line' is regarding a G motor as a model rocket motor and a mid- or high- power
rocket motor.
I've seen several posts in the past that state that certain 'G' motors aren't really allowed for model rockets, but as I understand the NAR Safety Code, if it's a 'G' motor it's allowed.
I've also heard some discussion about motor with more than 62.5 grams of propellant not being 'allowed' for model rocket motors, but I'm not sure where this is called out, and/or why, if the size of the motor is governed by the total impulse (and not the propellant weight). For example, if I have a really crappy propellant, I might have a 125 gram 'A' motor, but it's still an 'A' motor.
Tied into this is the fact that the Aerotech motors have propellant grains that are all less than the 62.5 gram size, so one could argue (at least I'd try <G>) to say that I was using a 'vertical cluster' when assembling the engines (vertical because the grains are stacked together, cluster because they're ignited simultaneously). This (IMHO) allows a way around the 62.5 gram limit for a 'G' (if there really is one), since clusters are allowed.
One more monkey wrench -- some folks have told me that certain 'G' motors may or may not be CSFM certified, and I'm not sure where to find out that information -- so if you know of any 'G' motors that specifically AREN'T certified, I'd appreciate hearing about it (and where to find out such information).
David Erbas-White
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NAR TRA NFPA CSFM
each have different "lines".

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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Jerry Irvine wrote:

Yes, that's kind of my point. I'm trying to determine where each is drawn, so I can kind of have a cross-reference chart for these.
David Erbas-White
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For G's (or f's for that matter) it has to do with the total propellant weight and impulse. Some motors below H are considered High Power due to this.
Also, some clusters of non HP motors are considered HP. For example, a cluster of 5 g80's would probably be considered HP!
The NAR safety code kind of "skims" over this issue, as it was probably adopted before there were G's which fell into the HP category. Read 1127 as that's what the NAR and TRA codes are based on - you'll get a copy with the TRA handbook, with TRA additions (e.g notify the TRA BOD for a flight over 25k')

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It is really quite simple. NFPA 1122 and 1127 (and probably 1125 but I don't own a copy) define model rocket motors as having:
1) No more than 160 N-sec total impulse, and 2) No more than 80N average thrust, and 3) No more than 62.5 grams propellant mass.
The NAR safety code is based on the NFPA codes but a lot of detail has been left out to make them short and simple. Perhaps too short.
The TRA has adopted NFPA 1127 as its official safety code.
So NAR and TRA are theoretically in line with NFPA.
Examples of motors that you might think are model rocket motors but aren't:
The Aerotech G33 reload is a High Power Rocket Motor because it has more than 62.5 grams of propellant.
The Aerotech G104 reload is a High Power Rocket Motor because it has more than 80N average thrust.
The Aerotech G75 reload is a High Power Rocket Motor because its propellant mass is greater than 62.5 grams.
Those are the few examples that I can think of off the top of my head. I believe that there is at least one Pro38 G motor that is HPR and perhaps some Ellis Mountain as well.
The 62.5 gram restriction was added in the 2002 round of revisions to the NFPA codes. Why? I have no idea.
TRA sent me a copy of the TRA safety code (basically a copy of NFPA 1127) several years ago when I was still a member. I do not know if they have ever mailed a version to their members based on the 2002 revision but the HPR safety code posted on the TRA web site still lists the minimum safe distance for an H impulse rocket as 50 feet. Which was changed to 100 feet in the 2002 version of NFPA 1127.
Is TRA using an outdated version of NFPA 1127 as their safety code?
David Erbas-White wrote:

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wrote:

This is worth researching. Who proposed the change? Who voted on the change? What was the vote?
Perhaps it is time to propose a rules change BACK.
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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IIRC the 62.5g limit came from CPSC.
    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
We need to ensure that actions by our government uphold the principles of a democratic society, accountable government and international law, and that all decisions are taken in a manner consistent with the Constitution.
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Bob Kaplow wrote:

Then, to follow up on this, what exactly is the authority of CPSC and how does it relate to model rocketry?
In other words, obviously motors larger than 62.5 grams are available, and obviously other AHJs claim 125 grams as the limit, so when/where/how does CPSC have jurisdiction? And when do they not?
David Erbas-White
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It relates to minors.

You ask as if there IS a definite answer.

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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Jerry Irvine wrote:

If this is truly the case then the 62.5 gram limit for a G motor would relate only to minors, would it not?
David Erbas-White

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N.F.P.A. 1122 clearly states a 62.5 gram limit for Model Rocket Motors. So does N.F.P.A. 1125.
This limit has existed for decades at the CPSC and it's predessessor agency and is simply reflected in the N.F.P.A. code because everyone complained about how different codes had different limits and their brains hurt trying to keep track of it.
It is really extremely simple.
;)
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No.
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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shreadvector wrote:

If the 62.5 gram limit came from the CPSC, then for consistancy, the impulse limit should be 80N-sec and the maximum average thrust should be 1600N.
Obviously there is a breakdown in the logic somewhere.
If someone had a copy of the ROP or ROC, or even better, was actually at one of the meetings for the 1998 revision cycle, we could see who submitted the request for change. Then we would know.
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this same topic was discussed here in this forum several years ago. the original NFPA Model Rocket Code 41-L in 1968 had the 62.5g limit. In 1978 in support of the manufacturers the NAR helped determine that 62.5g was the right size as far as DOT packaging requirements to get 1.4S shipping status.
I would gather that the CPSC probably got it from the NFPA in the early 70's...
shockie B)

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The CPSC limit came from the ICC limit. But it was NAR in its infinite wisdom that applied a minor limit globally. CPSC and ATF didn't do THAT to us.
NAR did.
Jerry

I might have mentioned that before :)
Like at a NFPA meeting!!

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Email and ask Bruce. he was the committe member
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On Fri, 01 Jul 2005 13:54:18 -0700, David Erbas-White

I don't think G motors of any propellant mass are to be sold to minors. The CPSC limits sale of motors to minors up to F, with less than 62.5 g. of propellant.

I don't think CPSC is a model rocket AHJ. They are a consumer protection agency, and in that role they limit the size of motors that can be sold to minors. CSPC "jurisdiction" is commerce, not model rocketry.
However, AHJs like NFPA often incorporate rules from peripheral groups. I think the 62.5 g. limit came from the CPSC, and the 80N limit came from the NAR. :( Effectively tail wagging the dog.

Right. Even judges may disagree, and some related things are in a state of flux. "The Economist" has his definitive answer. My answer above is least definitive of all.
Alan

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But NAR ALSO restricted model rockets, even to adults, away from 62.5g+, despite the MR limit of 125g and the FAA limit of 125g.
Jerry told THEM so.
Jerry
Anybody remember where 125g came from?
JUST Jerry

Wrong I do believe.

NFPA is not an "AHJ".
They are an authorizing "body" (room and books) for OTHERS called AHJ's.
Ie Fire marshals.
Testing agencies, etc.

And original DOT (ICC) ClassC.

That was a buttfuck supreme.
Thank Miller, Boles, Roberts and perhaps GH Stine for that.

:)
Jerry
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wrote:

Yes, but this was NAR conforming to NFPA, CPSC, etc., not NFPA, CPSC conforming to a restriction originating with the NAR.
At one point I think the NAR was even OK with Class B MR motors.

I am a bit fuzzy on the model rocket AHJ thing, and I'm not very familiar with the CPSC. Certainly they have some authority over the sale of MR motors, especialy wrt minors, but I would not put them in the same class as Fire Marchals, BATF, FAA, launch site owners...

Right. I was thinking Fire Marchals and others, who typicaly use or enforce NFPA codes.

Yes, but nobody says all MR motors must be readily shippable. Let's pray that 62.5 g. rule does not become the 30 g. rule.

Trip Barber

Alan
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