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#11
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Tandem type engines. The simplest to understand would be to epoxy an A3-4T inside of a C6-0, to get a wimpy D. In the case of D12’s, those were end-to-end D12’s, the lower would be a D12-0 and the upper a D12 with a time delay, to get a 35-38 N-sec “E12”. When I saw him doing some of these at NARAM-19 in 1977, I think he used a short length of BT-50 across the joint for some added reinforcement. Maybe he later added fiberglass, I just remembered the BT-50 collars. Around 1978, Estes informed the NAR that they considered tandem engines to be a modification of the engines, so the NAR could no longer allow them under the Safety Code. There were also some practical issues. The D12 to D12, or C6 to C6 type tandems often had burn thrus of the sides of the casings, just above the nozzle of the lower motor. It was due to the burning/erosion of the paper casing inside, being exposed to at the least was twice the normal burn time, and the casing were not designed for that. Also, I do not remember anyone removing nozzles from the upper engines (which definitely would be an illegal mod), so the erosion was made even worse by the upper engine “spraying” its exhaust plume down inside of the lower casing. The erosion would have been significantly reduced if the nozzles had been removed, but the erosion problem probably not eliminated since paper casings can only handle so much (some of the AVI E11.8 and D6.1 engines had that issue). Now, a tandem of an A inside of a C6-0 did not have this burn-thru problem, maybe a mini-B3 in a C6-0 might have. But there were some occasional burn-thrus when using a C6 epoxies inside of a D12-0. For some of my R/C R/G’s, where I needed to do some practice boosting with more power than a D12, but could not afford to fly E6’s that much, I did some D12/C6 tandems. And every once in awhile, one would burn thru just above the D12 nozzle. Of course this was not a very efficient way to use them either, the D12 nozzle throat was a lot larger than a C6 so there was a significant thrust performance downgrade. Possibly the C6 only add a B’s worth of extra power when burning thru the D12-0. Maybe say like going from a D12 to a B4? But for the R/C boosts it was OK since it was another 1.5 seconds of some thrust for the boost practice, for a total burn time of about 3 seconds from liftoff to burnout Fortunately, Aerotech came out with E6 reloads, and D7 reloads, whose cost per flight (and thrust curves) totally eliminated the reasons to mess around with D12/C6 tandems for R/C boost practice. - George Gassaway |
#12
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Doug .
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YORF member #11 |
#13
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Have you ever been to one of his manufacturer forum sessions?
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I fought the law, and the law LOST! |
#14
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Or one of the Imagination Celebrations! They're both quite enjoyable!
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Roy nar12605 |
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Ace Rockets was the first HPR company. He's famous for the first consumer hybrid company, Hypertek. I think I remember pics of him warming his hands to a burning motor in some Tripolitan ads back in the late 80's/early 90's. Seems like it was a Plasmajet ad. BTW, his "real" profession was/is r&d engineer in the explosives ordinance industry.
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I love sanding. |
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I might have been a little nervous, sudden fame and all... |
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You're digging thru threads that are way too old Seriously, glad to have you here. I look forward to seeing the new stuff you come up with. BTW, where are you? UK? Let me add a challenge - you need to design a 2-stage or 3-stage shrocket Doug .
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#18
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How about a 24 stage rocket with one hour duration motors?
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Doug .
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YORF member #11 |
#20
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Just about everyone who I have ever met in rocketry is a bit askew in one way or another. Whenever you become a dedicated hobbyist in any field, it takes you out of the mainstream, and that is especially true of rocketry, which is very non-mainstream. Perhaps it could even be more true if you take it to the level of designing and producing your own line of rockets. Every manufacturer that I have met so far, though, has seemed to really have his or her head on straight. I could say that each one was very "grounded," but that would be the wrong word to use here. I'm sure that you get the idea, though. The process of starting a business and keeping it up as a going concern keeps the owners very much in touch with reality, I guess. I haven't met all that many in person yet, so I might have to modify that assessment in the future. I have corresponded with quite a few more online, and although I am reluctant to draw any firm conclusions from that, my online experience so far has been consistent with my real life one.
Some people (actually, quite a few, now that I think of it ) think that I'M more than a little bit weird and off-base, but I am neither a designer nor a manufacturer. MarkII
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Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic • Advice Unsullied by Erudition • Rocketry Without Pity
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