[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 ) 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
Reply to
David Erbas-White
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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
Reply to
David Erbas-White
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')
Reply to
AZ Woody
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:
Reply to
David Schultz
NO. The line remains if you are launching at a site that has a Model Rocket limit in the land use and/or fire authority permit.
F101 motors are not model rocket motors. More than 80 Newtons of average thrust.
That is why FSI renamed their F100 as the F80 near the end of their existence. They never were 80 or 100 Newtons of average thrust, but they thought it sounded "cool" and "marketable". At some point the legality of shipping or certifying them came up and they changed them.
-Fred Shecter NAR 20117
Reply to
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.
Reply to
Jerry Irvine
david: it looks like you didn't get any clear answers so I will try:
from the NAR MR Safety Code:
Size. My model rocket will not .... contain more than 125 grams (4.4 ounces) of propellant or 320 N-sec (71.9 pound-seconds) of total impulse.
IF your model rocket has >113 g of propellant it becomes a LARGE MR and FAA notice is required.
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The TRA Safet Code is NFPA 1127 .It has nothing to do with model rocketry so they have no line
NFPA 1122: 4.5 Model Rocket Power Limits. A model rocket's installed motor(s) shall produce a total impulse of no more than 320 N-s (72 lb-s).
4.8.2 Type G motors with an installed total impulse of more than 80 N-s(18 lb-s), but not more than 160 N-s (36 lb-s), shall be permitted to be used by individuals 18 years old and older.
NFPA 1125: Model Rocket Motor. A model rocket motor that has a total impulse of no greater than 160 N-sec, an average thrust of no greater than 80 N, and a propellant weight of no greater than 2.5 g (2.2 oz).
(ii) Contain no more than 62.5 grams (2.2 ounces) of propellant material and produce less than 80 newton-seconds (17.92 pound seconds) of total impulse with thrust duration not less than 0.050 second.
12520. Model rocket engine
"Model rocket engine" means a commercially manufactured, non-reusable rocket propulsion device which is constructed of a nonmetallic casing and solid propellant, wherein all of the ingredients are self-contained so as not to require mixing or handling by the user and which have design and construction characteristics determined by the State Fire Marshal to provide a reasonable degree of safety to the user.
12565. Classification as model rocket engines
All fireworks or toy propellent devices containing pyrotechnic compositions examined by the State Fire Marshal and found by him to come within the definition of "model rocket" or "model rocket engine" in Section 12519 or 12520, respectively, shall be classified as model rocket engines.
6) Model Rocket Motor. The same as a model rocket engine, as defined in Health and Safety Code Section 12520. Model rocket motors shall not produce more than 160 Newton-seconds of total impulse power.
Perhaps somebody can devise a table showing what is a MR according to whom?
shockie B)
Reply to
It's been around a lot longer than that.
The safe distance for H hasn't been 50' since the original interim / draft NFPA 1127. And their reason for changing it from 50' to 100' was nothing more than the reason that the BATFE uses to decide what's onthe explosives list. They made it up.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Reply to
Bob Kaplow
IIRC the 62.5g limit came from CPSC.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Reply to
Bob Kaplow
slow day phil?
from nfpa 1127: 1.3.6 This code shall not apply to the following: (1) Model rockets as specified in NFPA 1122, Code for Model
3.3 General Definitions. Model Rocket. A rocket that (1) weighs more than 1500 g (53 oz) with motors installed; and (2) is propelled by
one or more model rocket motors having an installed total impulse of no more than 320 N-sec (71.9 lb-sec); and (3) contains
no more than a total of 125 g (4.4 oz) of propellant weight.
This is all thats said about model rockets in NFPA 1127. NFPA 1127 is teh TRA Safety Code. If TRA has some TRA specific "model rocketry" rules or regs I am not aware of them, other than the fact that they sometimes CERT model rocket motors in the EFG class, which doesn't make a whole lot of sense to me, other than the fact, that TRA motor Cert requiremenst are probably more lax than the equiavlent NAR requirements. Although I would welcome a TRA model rocketry program.
shockie B)
Reply to
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
Reply to
David Erbas-White
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
Reply to
David Erbas-White
Slow week. Next week too. Also, thanks to a pit bull, I can't do rocket stuff for a week or so.
Anyway, TRA's MR rules are NFPA 1122.
Reply to
Phil Stein
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.
Reply to
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.
Reply to
Alan Jones

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