Does anybody remember thin, black wire-like "fuse" from 50 years ago?

[Grant_Edwards]

In another thread I mentioned buying Estes kits, motors, igniters, and (not-Estes) fuse at the neighborhood Rexall Drug store in the early 70s. Before we had electrical launch controllers, we used fuse. [Don't do this. It is a bit dangerous, didn't work all that great, and launch controllers are cheap.]

One of my friends had what most of us think of as fuse (fireworks guys call it "match cord"), it was thickish (2-3mm) cotton string soaked in some sort of black powder slurry then dried. It burned, hissing and sparkling, at about an inch a second or so (I think it came in various speeds and colors, my friend's was red). I don't know where he got it.

But, the fuse I remember buying at Rexall drugs wasn't the stiff cotton string stuff. It was much thinner and looked and felt more like black wire (similar to maybe 26-28 awg solid wire w/o the insulation). When you bent it, it stayed bent. I don't remember it having visible strands. It burned without any sparking or hissing, there was just an orange glow that burned slowly down the "wire". It was slower than any of the cotton stuff I've ever seen (IIRC, several seconds per inch). It came in a small round "tin" about 2 inches in diameter with a removable lid — sort of like the tins some tiny, expensive mints come in. Each tin contained a coil of 2-3 feet of the stuff.

Does anybody else remember that sort of fuse?

Does anybody know what was it called or what was it made of?

I've asked a friend of mine who knows a lot about fireworks and has seen and worked with many types "match", and it was unfamiliar to him. He's going to ask about it on a fireworks mailing list, but I suspect it's something that wasn't used for fireworks.

I'm sure there's probably info about on the interwebs, but I haven't been able to come up with the right combination of search terms in Google...

 

[Kelly]

Could be you're thinking of Thermalite?

 

[BEC]

That sounds like Jetex wick to me. I never used it with rockets but I had two or three Jetex motors for model airplanes back in the very late 1960s/early 1970s. Low thrust, long burn time rocket motors with metal cases and one or two or sometimes three pellets of fuel. There were three diameters of the fuel pellets/motors as I recall.

I had a Jetex 50B and a Jetex 150 as shown here http://archivesite.jetex.org/motors/motors-jetex.html back then. I also vaguely remember some rocketry uses of the wick for either clustering in the very early days or even staging before the simple tape-the-motors-together direct staging method appeared.

Here’s the page with the wick/fuse: http://archivesite.jetex.org/motors/fuse.html I remember those little round tins.

 

[Grant_Edwards]

Could be you're thinking of Thermalite?

I don't think so. The descriptions I've found don't sound like it, and the photos don't look right.

 

[Grant_Edwards]

That sounds like Jetex wick to me. [...]
Here’s the page with the wick/fuse: http://archivesite.jetex.org/motors/fuse.html I remember those little round tins.

I think that must be it.

I don't remember the wick/fuse looking that lumpy, and I thought the color was darker than that photo. But, somebody's description of it being thin copper wire coated with something sounds right. Google found another photo of a bunch of wick and some fuel pellets, and the wick looks darker in that photo (I remember it being almost black, but it was a long time ago).

 

[BEC]

I don‘t remember it being lumpy either, but it did separate into segments on the wire if you didn’t handle it carefully. I recall it being reddish brown, not too different from the Jetex fuel pellets themselves. But I don’t think I have any around to verify one way or another….though I did look a little.

 

[Grant_Edwards]

I found a couple more photos of the Jetex wick. The tin was smaller than I remembered. I said 2" diameter, and it's barely over 1".

From https://amablog.modelaircraft.org/amamuseum/2012/07/17/jetex-100s/:



Here's a listing on worthpoint that came up once, but now refuses to open https://www.worthpoint.com/worthopedia/powermax-jet-atom-35z-jetex-engine-1814821555:

 

[BEC]

I had never heard of the -35 until I found that page I linked to in my first post above. I remember the 50(B), 150 and 600, but none of the others on that page. I never had a 600 but did have one of each of the other two. I remember doing several models for the -50, plans and kits and one Jetco kit for the 150.

 

[Grant_Edwards]

I'm 99% certain the Jetex wick is what I remember buying at Rexall. I think I probably only bought 1 (maybe 2) tins before my dad and I built a launch controller. I think we burned more of the wick doing timing measurements and experimenting with it that we did actually launching rockets with it. I don't remember it working very well with Estes engines.

 

[kevin.mcgee]

Jet-X. Bought mine at small hobby store.

 

[cerving]

Jet-X's were very cool... the first reloadable rocket motors IMHO. I don't think any of them put out enough thrust to lift themselves, but the 50 was a lot of fun (and a bit scary) in a small glider.

 

[Joekeyo]

My initial reaction was Jetex; brown not black. Other responses seem to confirm this. I remember this and a thicker waxy fuse. Like that on an M80 firecracker, if you know what that is. The thicker fuse was more durable, but the Jetex fit in small nozzles better. We soon switched to electrical methods as per the NAR safety code.

 

[davel]

I remember this and a thicker waxy fuse. Like that on an M80 firecracker, if you know what that is.

Waterproof (or underwater) cannon fuse. From Wiki: "Cannon fuse is a visco fuse that is most often thicker, steadier burning, and often extra coated to be more waterproof. Most cannon fuses of high quality can burn while under water. Cannon fuse is normally red or green in color."

 

[user 35280]

https://www.jetex.org

 

[Trident]

Jetex was great for clusters. You would put a short piece in each motor, and tamp in a small piece of wadding to hold it in place. Your igniter would wrap around the pieces of Jetex, to ignite them. Or, as the guy at the hobby shop told us, just light it with a match.

 

[bjphoenix]

There were some rocket companies that used Jetex, FSI I think. I remember when we discovered 21mm FSI C motors long ago, before Estes made a C. The FSI motors have very small nozzles and you couldn't put a normal igniter in there. I believe they put a piece of jetex in the nozzle and wrapped nichrome around the end that stuck out of the motor.

 

[beeblebrox]

There were some rocket companies that used Jetex, FSI I think. I remember when we discovered 21mm FSI C motors long ago, before Estes made a C. The FSI motors have very small nozzles and you couldn't put a normal igniter in there. I believe they put a piece of jetex in the nozzle and wrapped nichrome around the end that stuck out of the motor.

The smallest FSI nozzle throats are the 21mm end burners. C4, E5, etc. about 0.085" (Note I measured an old E5 I have in stock...), they just fit the thermalite. An old style Estes igniter worked in them as did the Sure Shots, if you left them straight, they would not fit folded in half. FSI used red thermalite fuse as their igniter starters. Thermalite has five nichrome wires wrapped around it like a spiral with fiberglass thread wound in the opposite direction to old it all together. Thermalite was made in three burn rates. Red was slow, about 1"/sec. Yellow was medium about 2"/sec. green was fast about 3"/sec. AeroTech used 1" pieces of fast thermalite as their standard igniter supplied with two pieces of stripped Kynar wire that you assembled yourself.

Thermalite is about 50-70% larger in diameter than Jetex wick. They are similar. Both types do not age that well. I have a few feet of thermalite left and it is very brittle. I have seen old Jetex wick that had "grown" tiny white crystals all over it and it was also very brittle.

Another wick type igniter was the original Centuri Sure Shot igniters. They included a piece of wick that looked similar to Jetex but was larger in diameter. Looked like thermalite without the external wire and fiberglass overwrap. EnerJet motors included a long piece of that same wick. You folded one end of it twice to make a 1" long bundle of four strands, The end stuck out of the nozzle and had nichrome wrapped around it.

 

[Tractionengines]

Green waterproof canon fuse worked well for me years ago for Estes motors. Hobby store in the the local mall recommended it to my dad when he wad trying to ask for help with igniters not working. I was about 10 years old at the time. My dad was NOT into rockets, electronics, or mechanically inclined; fishing was his hobby. (I like it too.)
Later I went to summer church-camp and one of their areas of interest was rockets....I got read the riot act when I pulled out my spool of fuse...it was then I learned how to get the igniters to be a little more reliable.
Mike

 

[bad_idea]

Jetex was great for clusters. You would put a short piece in each motor, and tamp in a small piece of wadding to hold it in place. Your igniter would wrap around the pieces of Jetex, to ignite them.

Ignition via a normal igniter sounds similar to what a fellow rocketeer at a local club launch yesterday described to me about using a standard Estes igniter to light a long piece of fireworks cannon fuse that itself lighted smaller fuses for clustered motors. The idea was this satisfied electric ignition requirements. Seems no more dangerous than the flash pan ignitions many LCOs okay for big clusters.

 

[Joekeyo]

The sure shot igniters were the bomb! I preferred them to the pretty good estes igniters. Both much better for low current situation than what we have today. Yes, I know why.