#41
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Random thoughts
Jetex wick is what Centuri Sure-shots were made from IIRC. The vertical flight Jetex rockets required modifying the faster burning red dot pellet to have more surface area and burn a shorter duration according to the article where I got those photos. The time frame was closer to 1956-57 so did not predate our variant of model rocketry by much. The launch and rocket contraptions were complicated! An Apogee/AT 13mm B is so many times more efficient than either an Estes BP motor or the far less superior Jetex motor, it is ridiculous. APCP motors are a tremendous advance in performance, technology, and even storage and shipping safety. The cost to do a chemical analysis on a Jetex tab would be much lower these days. Anthony @ CTI could do it. I agree with Jstarstar's comments about the evolution of safe model rocketry and HPR being helped by prior events. In fact I only spearheaded it after softening the ground with a magazine, some proposals for rules similar to and thus compatible with NAR. NAR had a history of evolving their rules, once even allowing motor making, so I felt with the right conditions and leadership it would eventually at least increase the mass limits to make bigger higher mass lowwer altitude rockets allowed as well as allow motors up to the already slim propellant mass limit. The first change was to 1500g/125g total masses, albiet with a stupid 80N thrust limit, killing the venerable G125, but also a silly 62.5g per motor limit that didn't exist anywhere else of importance. Only recently has NAR increased the per motor limit to the 125g FAA limit, but also added a limit of 160N-s per motor making that limit moot on a single motor option where a 240H with current APCP would otherwise be possible. It also added a new confusing threshold set whereby a wide range of otherwise model rocket motors are treated as HPR, which wouldn't be so bad if the clubs that issued HPR certs would issue them for life. But tying them to continuous membership, they obtain "tithe" to maintain an achieved product access certificate. None of that is "consumer friendly", thus the anemic 3500 folks or so that are HPR certified and thus prospective customers for an entire industry nationwide. Needs fixin'. Jerry |
#42
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Jetex fuel pellets that have been stored in poor conditions are not dangerous; they either won't burn at all or burn less vigorously, producing less thrust (the fuel pellet's chemical reaction during Jetex motor operation is actually decomposition rather than combustion). The single-use, paper-cased Rapier jet motors (see: http://www.jetex.org/motors/motors-rapier.html ) made by Dr. Jan Zigmund ("Dr. Z") in the Czech Republic are "drop-in" replacements for the Jetex motors. In addition: There were several "imitation Jetex" motors and fuel pellets (see: http://www.jetex.org/motors/motors-imitators.html ), some of which--such as the Japanese "Tiger Rocketry" products--were very good. In the 1980s and 1990s, Powermax (see: http://www.jetex.org/history/rebirth.html ) sold original Jetex motors that had been found in a big "stash," and they made their own fuel pellets (and motors, later), which they labeled as "Jet-X" in order to distinguish them from the original Wilmot & Mansour (and later Sebel) Jetex products. The Powermax fuel pellets are rather variable in performance. As well: If someone (Jerry?) would make fuel pellets, there are a lot of Jetex and Jet-X motors still "in circulation" and use, whose owners would happily buy the new fuel pellets. And since the motors themselves can be made by a metalworking shop, producing new Jetex/Jet-X motors wouldn't be difficult. Plus, the large number of Free-Flight jet model kits that are made by several vendors (for Rapier or Jetex power) is a "ready market" for new Jetex motors and fuel pellets.
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR Last edited by blackshire : 01-19-2014 at 09:54 AM. |
#43
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__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#44
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I do have some DOT and HSE approvals but cannot be amended to such a different form of chemical. So the cost might be steep. The good news is I have access to the entire European market where they are more popular anyway. Pricing would have to be higher of course. I have never used Jetex myself but understand the pellets to be akin to aspirin tablets with the entire external surface exposed. Do any of them have an external inhibitor of any sort like reloadable grains? Jerry |
#45
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The Jetex fuel pellets don't have any inhibitors on them. They fit snugly into their motors, but the washers and the metal-mesh disc that are loaded along with the pellet(s) may serve as inhibitors (although the mesh disc is intended to keep the wick firmly in contact with the rear face of the fuel pellet).
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#46
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#47
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__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#48
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Keep fighting the good fight, guys. Rapier, Jet-X, or something similar would be great to have availible again. We could bring some old birds out of the closet and see them take to the sky again, and model builders, old and young, could start building some new craft, and new incarnations of old ones.
Will keep watch here for updates on the subject. The Fireman |
#49
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Some years ago, Bristol Aerospace in Canada developed a series of simple, low-cost rocket-powered targets, which were called ROBOT (for ROcket BOosted Target, see: http://cradpdf.drdc-rddc.gc.ca/PDFS/zbc79/p36614.pdf and http://www.secretprojects.co.uk/for...ic,10769.0.html ). The ROBOT targets used clusters of 70 mm (2.75") CRV-7 FFARs (Folding-Fin Aircraft Rockets); these are the tube-launched rockets that are fired from attack aircraft, helicopters, and (occasionally) fighter planes. The winged ROBOT-X used a cluster of 19 CRV-7 rocket motors, which could be ignited in various combinations to produce different flight profiles. Also: Quest Aerospace produces tiny (6 mm diameter X 26 mm long) MicroMaxx rocket motors (see: http://www.questaerospace.com/cgi-b...ion&category=TE and http://www.rocketreviews.com/quest-micro-maxx.html ), which are "1/8A" motors having 0.000 to 0.312 newton-seconds of total impulse, with a peak thrust of over 1 newton and a burn time of about 1 second (varying a bit between the MicroMaxx and MicroMaxx II motors). Now: As was done with the CRV-7 rocket motors in the ROBOT-X target, these tiny motors could be clustered to power Jetex and Rapier model jets; a 16-motor (4 X 4 MicroMaxx motors) cluster would be just 24 mm square. They could be ignited in any combination in order to produce any desired thrust/burn time profile. This versatility could be further enhanced by using catapult launching (10 feet of 1/8" wide rubber [the kind used in rubber-powered, propeller-driven model airplanes] and 20 feet of string, tied to a ground stake), as was used for the Folland Midge (see: http://www.jetex.org/models/plans/p...r-50.html#midge ) and Vulture (see: http://www.jetex.org/models/plans/p...50.html#vulture ) Jetex models (the construction of such catapults is covered in the Folland Midge and Vulture building instructions). For this jet model application, the MicroMaxx motors could be ignited with fuses (this fuse ignition could be done in accordance with the NAR Safety Code, as I'll describe below). Depending on how the fuses were set up, a total powered flight duration (with coasting periods in between motor firings) of any desired length could be arranged (this was also done with the ROBOT rocket-powered targets). In addition: While using clustered MicroMaxx motors to power model jets *does* go against the launch elevation angle rule (no launches more than 30 degrees from local vertical) in the NAR Safety Code, so do rocket cars--and Quest listed MicroMaxx-powered, string-guided rocket cars in their catalogs. (To make such jet plane catapult launches more nearly "NAR-Kosher" [or "NAR-Halal"... :-) ], a longer fuse--which would *first* burn through a catapult-release thread *before* it ignited the motors--could be electrically-ignited from the regulation 15 foot [5 meter] distance, using a standard model rocket igniter and launch system.) I hope this information will be helpful.
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR Last edited by blackshire : 01-20-2014 at 12:35 AM. |
#50
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I am not sure if the current safety code says it, but one specifically said testing not fully compliant with all rules could be conducted in isolation.
And if it and NFPA-1122 doesn't say that through the various "codifications", we have lost a right, not priviledge, we had and safely exercised for decades, in the name of "perceived safety". Last edited by Jerry Irvine : 01-20-2014 at 07:54 AM. |
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