trying to come up with new Jetex fuel and fuse (or igniter)

[lincoln]

I bought a Jetex 50, and have been trying to figure out suitable fuel and reliable, convenient ignition for it. I'm still in the 99 percent perspiration phase. For instance, the best ignitor I've had so far is passing current through about a quarter inch of carbon tow. But it's a bunch of work to set up even one, and I'd been hoping to use less exotic materials. Fuel pellets are probably going to be epoxy, potassium nitrate, and iron oxide, or maybe will have sugar instead of most of the epoxy. Have had one test run with mostly sugar based. It ran for almost a minute, didn't seem to have much zip, and left behind a very fragile, pellet shape leftover of carbon. So I gather that one was a bit rich. I'm hoping to press on until I find something that really works.

[PB_guy]

According to this site ( https://www.airplanesandrockets.com/motors/Jetex-Motors.htm ) :

ICI, based in Scotland, manufactured the Jetex fuel pellets* from a measured blend of guanidine nitrate, 2,4-dinitroresorcinol, potassium nitrate (aka saltpeter), iron oxide, kaolin, and asbestos.

ian

[lincoln]

Interesting. I'd have gotten back sooner, but the software here doesn't list any replies to my posts.

I'd heard about the asbestos, though I think I'll avoid it. I'm kind of surprised by the kaolin. I continue to try things.

[PB_guy]

The asbestos may have been used as a binder to keep the pellets from breaking apart. Any fiber, like cellulose, could be a useable replacement.
ian

[lincoln]

I've made some progress with fuel, I think. It's made with stump remover (potassium nitrate), finely ground sugar, and a little bit of epoxy. It's fairly sturdy stuff. However, I haven't come up with a good fuse yet, and I haven't been able to yank electric ignition wires out of the exhaust hole yet, either.

[lincoln]

By sturdy, I mean that last night, when it was stuck in the mold because I only used one coat of wax, it mostly survived a lot of hammering on a rod trying to push it out of the mold.

BTW, I'm guessing that the asbestos may actually have helped with combustion in some way, but that's not my field.

[aerotrope]

Not that I've tried this, but it looks like it can be made into a reliable ignition method.

[aerotrope]

No idea where that first bizarre picture came from; just ignore it.

[PB_guy]

Good research aerotrope! It seems like an excellent idea for a re-useable ignition system. My ancient experience with Jetex 50 back in the 60's was having the pellet refusing to ignite three or four times before a successful ignition.
ian

[lincoln]

After having my previous, aluminum Jetex 50, which was a little tired when I got it, blow out the side when I  used some fuel that maybe was a bit too hot, I'm averse to making notches. However, I slipped a couple of 30 gauge magnet wires in anyway, sort of the way it's shown in the drawing. I find the best igniter seems to be a short piece of carbon fiber between two pieces of magnet wire, zapped with a 3S lipo capable of tens of amps. One time, at least, the wire didn't get shorted, but that was the run that burnt out the motor. The carbon fiber is kind of a pain to set up. I don't know if it's really necessary to put a bit of pyro stuff on it to insure ignition, but I do. I've also used little resistors, including surface mount resistors, as the heating element. Those work best if zapped with a little less vigor. And I think I even managed to make some conductive glop with graphite and rubber cement, but I can't seem to make that be sufficiently conductive consistently. I wonder what those guys were using for gaskets?

I'd prefer to use a fuse. At lest if it could be reliable. Maybe sprinkle a bit of rocket candy or black powder in there.