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This picture of the "bulbous payload section" 1340/20 (see: http://www.oldrocketplans.com/enerj.../enj1340-20.pdf [its main body tube--to the rear edge of the fin unit, the drawing seems to show--was 12.0" long]) shows the protruding motor pretty well; it looks like it's protruding 1" or so behind the rear edge of the fin unit (there's also a short length of motor tube, or body tube, just behind the rear edge of the fin unit). Here (see: http://www.ninfinger.org/rockets/ca.../72ejetcat.html ) is the 1972 Enerjet catalog, which shows the big motors the 1340 Sounding Rockets used. |
In addition to the Centuri Phoenix Bird (see: http://www.ninfinger.org/rockets/no...a/79cen010.html ) and the Enerjet 1340 Sounding Rocket (see: http://www.oldrocketplans.com/enerj...340/enj1340.pdf ), the Estes Discovery (see: http://www.ninfinger.org/rockets/ca...6/86estcov.html and http://www.ninfinger.org/rockets/ca...87/87est10.html ) and the Estes Challenger II (a 24.25" long, "D"-powered launch vehicle for the AstroCam 110, although it came with the regular BT-56 nose cone, see: http://www.ninfinger.org/rockets/ca...84/84est54.html ) also used the Phoenix Bird/1340 Sounding Rocket plastic fin unit and nose cone. I don't think (although I'm not 100% sure, having never had them) the Discovery and the Challenger II had payload sections, but simply ejected their nose cones, to which their parachutes and shock cords were tied.
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Gee, guess I had an upscale Enerjet 1340 without realizing it. Will look into resizing and repainting my Eliminator XL bird. Or maybe Phoenix Bird XL?
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By process of elimination, the length that the motor tube protrudes is .6" ( Overall length minus nose cone length, minus payload tube and main body tube with fin can length, minus coupler length). I have doubts that an Estes E2X rocket can handle a 24 or 29mm composite propellant motor, however. |
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Jason- I glanced through the thread somewhat quickly (and possibly you've already noted it), but the 1340 used heavy walled tubing that was thicker than the standard Centuri ST-13 tubing (Semroc/eRockets would have it). The 29mm motor mount tube (also heavy walled) is a "glove fit" inside that tubing. The O.D. of this heavy walled ST-13 tubing is the same as the regular ST-13 tubing, but because it used a thicker tube, the nosecone was different than that used in the Phoenix Bird, Eliminator and other kits that made use of that similar looking plastic cone. I think the cone profile was the same; what was different is the 'shoulder' had a smaller O.D. to account for the thicker tube wall. That said, the nosecone and fin unit from an Estes Eliminator can be used to make a nice clone...it just won't be as 'beefy' as the original 1340. The fin unit is the same between all kits that have used it off and on now for 46 years. It holds up well under F power from what I understand, but I think Jerry Irvine has reported fin flutter/fin breakage under G power. Earl |
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Funny you should mention that. Just received Frank Burke's Pegasus X R/C rocket glider kit. https://dynasoarrocketry.com/?page_id=1640 Would have loved to build the TMRK Pegasus kit, but they went defunct, plus it's a tad out of my budget ( Okay, more than a tad). http://tmrk.rocketshoppe.com/pegasus.htm Looked into cloning it, but the wing to body transitions look very difficult. |
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I hadn't known that the 29 mm motor tubing "sleeve fits" into that thick-walled body tubing--that is good to know! I have relayed your information to Bruce Levison ('teflonrocketry1'). Thank you also for passing along Jerry Irvine's report about the fin unit's "F-power limit" (for avoiding fin flutter and breakage under G power). F power is plenty strong for me, but maybe (for those who'd like to use G power safely) a somewhat "beefier" duplicate of the fin unit could be 3D printed (slightly thicker gauge, perhaps?)--or maybe the fin unit in the Estes Eliminator might be strengthened with Kevlar veil and epoxy--to withstand the stresses from G motors. |
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I pulled out my original Centuri Phoenix Bird while at home for lunch. I brought the upper section back with me and can tell you the following: The visible adaptor has a coupling 1.5" long with 1" to hold onto the lower tune. The remainder is a .5" cone with a eyehook for connections. I assume the upper coupling is the same, but since its been glued together for 39 years, I can't tell. The middle part that is the same diameter as the tube is .875" long. The upper tube is 7" long. I didn't bring the lower half so I can't give you a length on that.
Mike |
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