Gonna’ ignite like the rocketeers of old

[Ladykate]

So, use regular 22 gauge wire for the leads but wrap some coils of nichrome around the ends of the leads you insert into the nozzle?

Wrap a coil on each wire so there is a space between the two copper wires that is bridged by a mm or 2 of nichrome. Don't just wrap the nichrome around both at the same time. The small length of nichrome between the two wires will heat up quickly. You still need a pyrogen of some sort. I use single base smokeless powder dissolved in acetone. Make a thimble full at a time. 1/4 powder to 1 acetone by volume. Let it sit overnight. Stir. Don't forget to solder the nichrome (it is a PITA but can be done).

You can do the same thing, though less efficient, by just using very fine copper wire instead of nichrome - much easier to solder.

 

[ksaves2]

Ohhhhhh man, There are a pile of igniter pyrogens out there. Believe me I've tried a bunch of them and they all work to start motors on the ground with a 12 volt system. I think powdered magnesium is a bit harder to get now but there are recipes out there that I believe don't need it. It pays to learn about igniters and making one's own as some of the commercial ones can be duds and one needs to have a backup. I liked working with MTV igniters but I suspect now getting raw viton is probably hard now. Magnesium too. Titanium bits and pieces probably not so hard.
Can always, very carefully crush "sparkler bits" into nitrocellulose lacquer and make a decent igniter. YMMV and as always be careful. 12 Volt igniters are not that much of a problem. Kurt

 

[brockrwood]

Tests completed. I created four igniters:

32 gauge nichrome wire dipped in Testor’s “steel” enamel paint

28 gauge nichrome wire dipped in Testor’s “steel” enamel paint

32 gauge nichrome wire dipped in Sally Hansen “silver storm” nail polish

28 gauge nichrome wire dipped in Sally Hansen “silver storm” nail polish

The results?

All of the igniters got white hot and broke in half rapidly with a 12 volt, SLA battery.

The igniters dipped in the silver storm nail polish seemed to “burst into flame” for a split second. The nail polish seemed to act like a pyrogen.

The igniters dipped in the Testor’s “steel” enamel paint seemed like they were “insulated” by the paint. The paint acted less like a pyrogen than the nail polish did.

Conclusion: Go with the nail polish. The 28 gauge and 32 gauge wire will both work if a 12 volt, high current battery is used. Also, people who apply nail polish to their fingers and toes are applying a very flammable, lacquer paint substance full of nitrocellulose to their body parts.

Pic:

 

[Ladykate]

You need a better pyrogen. Otherwise, your wire has to touch the propellant to be reliable. I like nail polish remover (acetone) mixed with single base smokeless powder (shotshell pistol or rifle powders). See my post for more. Ksaves2 mentioned a few.

 

[neil_w]

I had not heard that the steel paint works for this. It is specifically the silver, which does burst into flame.

 

[bjphoenix]

to 1 acetone by volume. Let it sit overnight.

What do you do to keep the acetone from evaporating? I've been trying to determine where I could get a small container that would hold the acetone.

 

[Ladykate]

I use a small bottle (actually an air brush bottle) with a cap. I've also used film canisters but those are not common now. Any small container with a cap will work. However, the acetone in the mix will evaporate even in well capped containers just from opening it and using it if nothing else. Only make a small amount.

 

[brockrwood]

I had not heard that the steel paint works for this. It is specifically the silver, which does burst into flame.

I was hoping any of the metallic Testor’s paints work that way. I just happened to have some of the “steel” color in the paint box. Sigh. Ok. I will go find the silver.

 

[brockrwood]

You need a better pyrogen. Otherwise, your wire has to touch the propellant to be reliable. I like nail polish remover (acetone) mixed with single base smokeless powder (shotshell pistol or rifle powders). See my post for more. Ksaves2 mentioned a few.

Once I go beyond putting some fingernail polish on a piece of nichrome wire, it gets too experimental for my competence. I am scared I will blow myself up.

 

[bjphoenix]

Once I go beyond putting some fingernail polish on a piece of nichrome wire, it gets too experimental for my competence. I am scared I will blow myself up.

If the silver fingernail polish worked then you don't need to experiment any further.
When I've used nichrome with a sufficient battery source I don't recall any problems with it. I think if it is touching the fuel grain then it doesn't matter how fast the wire melts, it will have enough time to ignite the propellant. The silver fingernail polish is just there to improve reliability.

 

[Big-Bob]

If you really want to fly like the old timers then how about using friction fit for motor retention and two slots in the body tube for shock cord retention?
Oh, and a folded coffee can for a launch deflector. And a launch controller with only a momentary launch button, no arm or continuity switch.
Ahh, the good old times. Nostalgic, yes. Better and more reliable? Meh...........

Sometimes "better and more reliable" does not equal more "fun". I'm pretty much a fan of vintage everything.

 

[brockrwood]

friction fit for motor retention

I resemble that remark. ;-)

 

[brockrwood]

The real world test is complete. With a 12 volt, sealed lead acid battery powering my launch system, no pyrogen is needed. A simple, short piece of nichrome wire, with a small loop in the middle, works just fine to ignite Estes black powder rocket engines.

I tried both the 28 gauge and the 32 gauge wire. Both worked fine. Reliable ignition each time.

I used the traditional method to hold in the igniter: a “spitball” of recovery wadding jammed in with a paper clip and small piece of masking tape to hold everything in piece.

Pics:









Caveat: I have only tried these nichrome wire igniters with single engine rockets, not with cluster rockets.

 

[waltr]

Of course this is the igniter my brothers and I used back in the '60s.

With a good 12V battery always ignited motor. Clusters sometimes worked correctly.