What would be the huge problem for Estes is the new marketing that would have to be done, including a revamp of the entire mini-fleet. Instantly all the old models would be useless, or they would have a customer service problem with un-informed customers who tried to use the longer motors without dealing with the stability and motor retention issues.

You might compare this to the D -> E issue (and to some extent, to the E15 -> E9 issue), but I think that there are enough differences in quantity to make it less likely that Estes would ever want to make that sort of change.

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Roy
nar12605

I never said that I didn't think it would work--I'm just not on FaceBook and don't ever want to be on it again, but I suppose someone I know is a member, and if so I imagine he or she would let me contact Estes through his or her FaceBook account.

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NAR #54895 SR

The later Centuri 13 mm mini motors (which used the same 13 mm X 1.75" case as the Estes mini motors, see: http://www.ninfinger.org/rockets/no...a/79cen042.html ) might present some possibilities for longer-delay Estes mini motors. The Centuri 1/2A4-5M had a maximum liftoff weight (including the motor weight) of 1.5 ounces, and the A4-6M had a maximum liftoff weight of 2 ounces.

An "Estefied" version of the 1/2A4-5M could be a 1/2A3-5T, and this motor should have sufficient volume inside the existing 1.75" long case for all of the powder and the clay cap. An "Estefied" A4-6M (the A3-6T) has an available case volume problem, but a 3/4A3-6T should be able to use the existing mini motor case. It could use the same delay charge black powder as the C6-7 motor. (This blend of black powder appears to take up *less* "space per delay second" than the delay charge in the C6-5, judging by the relative depths of the C6-7 and C6-5 ejection charge clay caps.)

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NAR #54895 SR

I never had any problem with any of the 13mm Centuri B4M motors like some had; Also flew many MPC 13mm B-motors as well without any CATOs.
I'm pretty sure the Centuri B4M's were full 5n-sec B motors but the MPCs were a little less.
All the Centuri B4M's I had were made of the goofy blue or green dyed engine casing paper.
Were those originally made by Estes ? If that is the case, they have in the past made longer mini-motors.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !

What I've read (here) is that the delay times (ie, burn rates) vary with batch and thus the amounts (lengths) are adjusted with each batch of motors. So you can't extrapolate too much from the observed differences you noted.

Doug

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YORF member #11

My take on this is that Estes was trying to make their new minis cover their existing shortie line so that they could avoid excess product types. (Hence the need to make them 1.75" long.)

As you're aware, the shortie was killed off upon introduction of the mini line.

If the new minis had been longer, Estes would have had a 3rd, different form factor, overlapping the impulse range already covered by the other motors, which would have surely proved problematic in trying to differentiate their products. And their resellers would have been hard pressed to add that extra shelf space. So making the minis 1.75" long enabled them to compete with the MPC minis while providing a reasonable replacement series for their shorties.

At least, that's how it appears in my retrospectroscope

Doug

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YORF member #11

Exactly!

My take is that, if they really need a longer delay A3-xT, then do it ala the D11-9: cheat a little on the propellant to make a little more room for the delay. And don't do an A3-6T, but do an A3-5T. The A8-5 seems well suited for a long delay A, so I'd think an A3-5T would suffice for making an equivalent mini motor (ie, in the same impulse class).
...
My engineering instincts are to do away with 18mm A's and half-A's, and instead do only 13mm minis for those impulse classes. The minis can always be adapted up. I know the nozzles are mostly smaller (except for the A10), but that has never been a problem for me staging. This way, there could be a wider variety of thrust/delay combos while keeping the overall number of product types under control.

For me, it's a no brainer adapting 13's into 18mm applications. Alas, I understand it's a marketing challenge for Estes to sell such substitutions to 10-thumbed dads, and hence would cause a similar "huge problem for Estes" as Roy has cited.

But having A8's and A3's which are virtually identical in capabilities (other than form factor) strikes me as being inefficient. I'd much rather have a wider variety of minis and forego the 18mm A's. For example, I would add an A3-2T to the mix, for gliders. However, I know this is very unlikely.

Doug

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YORF member #11

I totally forgot about that fact! Thanks.

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Roy
nar12605

I was just about to comment about the possibility of extending the delay the old D11-9 way, but Doug beat me to it. "Cheat" a little by getting rid of a little propellant.
I can however see the need of an A3-6T over even an A3-5T, which would be better than nothing.
The A8-5 IS the right/optimum delay for min-diameter light rockets using the BT-20 tube, but a -5 delay is not so for min-diameter BT-5. An A3-5T or A10-4T would be better than the A3-4T though.
I really don't understand the need for an A3-2T ever...what rocket could possibly have a 2 second delay be correct with an A motor ? Seems an A could not be enough impulse to reasonably fly anything that could need a 2 second delay. I would like to see that motor retired and replaced with something useful, just like the B4-4 could be.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !

I think Centuri made their own mini motors, at least initially when they first introduced their mini motors in 1973 through the full B range. I think that at some point after they had dropped their full B and had shortened their motors to the now more traditional length, those minis were then made by Estes along with all the other Centuri motors once they shut the Centuri motor plant down sometime in the mid 70s approximately.

Earl

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Earl L. Cagle, Jr.
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Rocket-Brained Since 1970