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  #41  
Old 01-19-2014, 08:39 AM
Jerry Irvine's Avatar
Jerry Irvine Jerry Irvine is offline
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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
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  #42  
Old 01-19-2014, 09:29 AM
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blackshire blackshire is offline
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Quote:
Originally Posted by Fireman
Absolutely true, as some "basement bombers" found out, even back in the 1950s. The Jetex motors did what they were ment to do, and they did it very well. But they would not, should not, could not handle a more intense, "super-jetex" fuel.

Any homebrew Jetex tablets would have to match pretty closely the impulse and presure of the original.

About the Jetex stuff on e-bay... It would be interesting to know what the "shelf-life" of original Jetex fuel tabs might be. If you could get some of the old ones, at a premium price, of course, would they be "safe and effective" or not? Anybody here have any thoughts or experience on the subject?

The Fireman
Roger Simmonds includes information on this on the Jetex.org website (see: http://www.jetex.org/index.php ), which is functioning as I write this but has been offline intermittently because Roger is working on a new, improved version of the Jetex.org site. The old Jetex fuel works fine, although the fuel pellets must be used *only* in the motor(s) for which they were designed. For example, while the slow, end-burning pellets made for the aluminum Jetex 50B motors will also work in the same-size (but steel-cased) Jetex 50HT (High Thrust) motors, the fast, core-burning 50HT fuel pellets will melt the aluminum Jetex 50B motors. Also:

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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Last edited by blackshire : 01-19-2014 at 09:54 AM.
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  #43  
Old 01-19-2014, 10:39 AM
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Quote:
Originally Posted by Fireman
OK. You guys have done it again. I thought I knew the Jetex story pretty well... In days gone by, I have flown my share or more of Jetex powered craft. (Including the wonderful Jetex powered Dyna-soar that I built from plans in American Modeler or some such place.) But I never knew that there were Jetex verticle launch vehicles.

I do remember trying to build the Jetex powered Snark from plans in one of the "Modern Popular Scientific Illustrated Mechanics" type of magazines from the late 1950's or so. (I'm not sure, but that article may be on YORS magazine page.) It was a rather complex, catapult launched missle that used Jetex as a sustainer. It was beyond my model building skills at the time, and I never finished it.

The Fireman
Thou art in luck this day, O mortal, forsooth! (I think that's the way unicorns are supposed to talk...) Both of Paul Del Gatto's books (which contain the Jetex-powered Dyna-Soar model plans), "All About Jetex" and "Building / Designing, Maintenance & Care of Jetex Engines for Models" are available from Rocket Science Books (see: www.rocketsciencebooks.com ), who also offer these and other books of theirs on eBay. These are high-quality reprints on archival paper, *not* photocopies. Also, here is the article (with model plans) on the Jetex-powered Snark scale model, from the April 1958 issue of Science and Mechanics magazine (see: http://www.ninfinger.org/rockets/sn...ans/snark1.html ). Gift offerings of pomegranates will be accepted at your convenience... :-)
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  #44  
Old 01-19-2014, 10:50 AM
Jerry Irvine's Avatar
Jerry Irvine Jerry Irvine is offline
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Quote:
Originally Posted by blackshire
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.
I don't currently have listed certified motors so do not have a ready base of production for such a niche product. Either AT or CTI does, and have DOT approvals for igniter pellets, hybrid igniters and pyrovalves which most closely approximate them. They would be mailable however.

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
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  #45  
Old 01-19-2014, 11:46 AM
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Quote:
Originally Posted by Jerry Irvine
I don't currently have listed certified motors so do not have a ready base of production for such a niche product. Either AT or CTI does, and have DOT approvals for igniter pellets, hybrid igniters and pyrovalves which most closely approximate them. They would be mailable however.

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
Thank you for clarifying that. (If you could import Dr. Z's Rapier motors and sell them in the U.S., that would also be good. A Jet-Ex-Press Jetex/Rapier forum member was fairly close to getting the necessary UN, DOT, and USPS approvals, but this all stopped when he died.) Also:

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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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
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  #46  
Old 01-19-2014, 12:28 PM
Jerry Irvine's Avatar
Jerry Irvine Jerry Irvine is offline
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Quote:
Originally Posted by blackshire
A Jet-Ex-Press Jetex/Rapier forum member was fairly close to getting the necessary UN, DOT, and USPS approvals, but this all stopped when he died.)
I would be interested in getting a copy of the file from a survivor so it can continue to be processed. That would be the shortest path.
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  #47  
Old 01-19-2014, 12:51 PM
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Quote:
Originally Posted by Jerry Irvine
I would be interested in getting a copy of the file from a survivor so it can continue to be processed. That would be the shortest path.
I agree; I'll post a query about this on the Jet-Ex-Press forum!
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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.
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  #48  
Old 01-19-2014, 09:58 PM
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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
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  #49  
Old 01-20-2014, 12:13 AM
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Quote:
Originally Posted by Fireman
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
Thank you. In the meantime, while the Rapier importation matter is being sorted out, I have found an *existing* alternative to the Rapier motors (I'd still rather have the Rapier motors become available here again, but this is a workable interim solution), one which actually offers new flight profile options, as I will explain:

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.
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  #50  
Old 01-20-2014, 07:38 AM
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Jerry Irvine Jerry Irvine is offline
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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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