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  #11  
Old 08-22-2019, 09:23 AM
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Quote:
Originally Posted by blackshire
Guess what? (I'm not being sarcastic, as I just came across the following this morning.) A new Jet-X product line--including kits and motors--*is* being developed (see: https://jetxus.wordpress.com/ ). Their paper-cased, single-use J-1 motor is 1/2" in diameter and 2-1/2" long. Videos on the above-linked Jet-X website show the motors and models in action, and there are also photographs, as well as descriptive text.


Donít hold your breath that site has been out there for years. And it ironically says the previous venture failed because there is no market. Be aware the there is an Aerotech C3 and D2 in 18mm with a 10 second burn time so there are alternatives to jet-X vaporware.
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  #12  
Old 08-22-2019, 09:30 AM
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Quote:
Originally Posted by astronwolf
That's nice, but it kind of side-steps my point. You suggested "one of the model rocket manufacturers" take up the torch for Jetex.
So? I only mentioned them as possible producers of model jet motors because they already produce not terribly dissimilar products, single-use paper-cased black powder model rocket motors. I don't care *who* produces model jet motors; I just want to be able to purchase them (and kits, too, although they are of secondary importance, since replica Jetex kits are already available elsewhere) from a manufacturer.
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  #13  
Old 08-22-2019, 10:08 AM
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Quote:
Originally Posted by jadebox
Maybe someone can develop a really tiny and lightweight thrust-vector control system for those motors. :-)
I was thinking about that, too. (The jet motor mount tube could also--in some model configurations, such as ones in which the motor mount was inside a larger-diameter pod [as in this Veron Fouga Cyclone model: https://www.vintagemodelcompany.com/fouga-cyclone.html ]--be angled in pitch and/or yaw, in order to tilt the thrust vector accordingly.) Constantly-immersed (in the exhaust plume) jet vanes should be feasible, because the exhaust temperature, while high, isn't too high to use metal, or coated metal, or maybe graphite. Also, the burn time, while longer than that of a typical model rocket motor (it's approximately 12 seconds), isn't long enough to burn vanes away. Also:

"Tap contact" jet vanes (whose flat sides would intermittently contact the exhaust plume--Goddard's later rockets used these), or "jet tabs" (they're on shafts parallel to the motor axis, which intermittently rotate, bringing the jet tabs into contact with the exhaust plume--BAC planned to use these on the Skylark sounding rocket), would have even briefer exposure to the jet motor's exhaust plume. Jetavators (gimbal-mounted, rotating circumferential rings--a jetavator is a short length of an open cylinder, surrounding a rocket nozzle) could also be used, for example, in a scale model of a Polaris missile. The Polaris first stage had four fixed nozzles, each with a jetavator surrounding it. As well:

A jet model plane equipped with a micro R/C system could use servo-actuated jet vanes or jet tabs to steer the model during its period of powered flight. One lightweight possibility that I'd thought of could be used in Vintage Model Company's reproduction Veron Fouga Cyclone jet sailplane kit (see: https://www.vintagemodelcompany.com/fouga-cyclone.html ). It could utilize jet vanes or a movable motor mount tube to provide thrust vector control during powered flight. (Axion makes two-channel motorglider models that work similarly; they use rudder control for left-right turning, while a throttle-able, fuselage top-mounted electric motor/pusher propeller [with a slightly raised thrust line] provides pitch control.)
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  #14  
Old 08-22-2019, 10:29 AM
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Quote:
Originally Posted by 5x7
Donít hold your breath that site has been out there for years. And it ironically says the previous venture failed because there is no market. Be aware the there is an Aerotech C3 and D2 in 18mm with a 10 second burn time so there are alternatives to jet-X vaporware.
Unless the videos on their website (at least one of which dates only to last November) were shot using models powered by Rapier motors, the Jet-X J-1 motor is already in existence, although not in quantity production yet. Also:

Depending on how much those long-burn Aerotech C3 and D2 18 mm motors cost, I'd be perfectly happy using them. (After World War II, especially in England, many large Jetex-type target aircraft were available as military surplus. It wasn't terribly different from the Aerotech Phoenix R/C rocket glider. The target had, if memory serves, swept wings and tail surfaces, a pod-and-boom fuselage [the boom was a dowel or an arrow shaft, I think], with a circular opening in the rear of the pod fuselage, into which a large Jetex-type motor had been fitted.)
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  #15  
Old 08-22-2019, 10:48 AM
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  #16  
Old 08-22-2019, 10:54 AM
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Quote:
Originally Posted by stefanj
The Jetex revival page that Blackshire points to mentions a crowdfunding effort.

Who would be onboard? I'm wavering.
I will be. Jet-X plans to produce their own kits (and they've already tested them, as their website's videos and still photographs show). Also, since Vintage Model Company already sells "Retro-Repro" duplicates of classic old (Veron, Skyleada, etc.) Jetex model kits, there are already such models that could use Jet-X's J-1 motors. Their J-1 motor is similar in size to Dr. Z's Rapier motors (which are no longer made, although some are still in stashes here and there), whose motor mounts, in turn, are easy to retrofit into Vintage Model Company's Jetex kits (and Jet-X's J-1 motor mount is very similar to the Rapier motor mount). Also, speaking of very small jet motors:

Sam's Models, from whom I bought Rapier motors years ago, carries Derek Knight's tiny (32 mm, 24 mm, and 18 mm diameter) EDF--electric ducted fan--units (see: http://www.samsmodels.com/electric-flight-ducted-fan ). One model rocket-related application of these that comes to mind is a small-scale model of the Harpoon cruise missile, using an 18 mm EDF in the missile and a 13 mm or 18 mm model rocket motor in the booster, which could be parachute- or streamer-recovered (as could the EDF-powered missile as well).
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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
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Last edited by blackshire : 08-22-2019 at 12:25 PM.
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  #17  
Old 08-22-2019, 11:51 AM
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Also, Roger Simmonds' Jetex.org website (see: https://www.jetex.org/ ) sells several new-design Jetex/Rapier model kits, which could also use the Jet-X J-1 motor (they also sell a hand-held electric igniter [which is a veterinary device]). His site also contains numerous old and new articles, images, and model plans.
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http://www.lulu.com/product/cd/what...of-2%29/6126511
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  #18  
Old 08-22-2019, 12:01 PM
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Thank you--I helped Dr. Edward Jones (he's deaf) get a supply of parallel-wound paper tubes for Rapier-type test jet motors several years ago. His propellant formula at the time even included red gum from a particular Australian tree (I forget which species), but he achieved long, smooth, even-thrust motor burns. He and others have been tinkering to optimize the thrust-time curves, for a family of motors (Dr. Z. had also developed a family of Rapier motors of different sizes, thrust levels, and burn times).
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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
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  #19  
Old 09-17-2019, 07:40 AM
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Quote:
Originally Posted by blackshire
Also, Roger Simmonds
could also use the Jet-X J-1 motor (they also sell a hand-held electric igniter [which is a veterinary device]).



ooooh poor ol' hoss !
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  #20  
Old 09-17-2019, 10:35 PM
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Quote:
Originally Posted by britroc
ooooh poor ol' hoss !
Judging by its size (it's a roughly fountain pen-size device, with batteries sealed inside its plastic case; the folded-wire heating element protrudes about half an inch or less [the one I ordered with my Rapier motors is stored away at the moment]), I think it's used on rams and/or billy goats.

Gelding of horses is done with a crimping device that is applied to the spermatic cord (as well as removing the testicles), which is not always done--even today--under anesthesia, instead using only sedation and a lip twitch for restraint, with the horse standing. (Only the English-speaking world seems to have a "stallion behavior problem." In France, Germany, and other countries, stallions aren't kept in isolation except when bred; they are ridden and driven, and they also pull farm implements [including with geldings and mares, sometimes even when the latter are in season], instead of living alone--it's no wonder that those secluded stallions are so poorly socialized. People in the English-speaking world, assuming that "stallions have one-track minds," keep them in a manner which ensures that they will become that way.)
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
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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
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