First Scratch Ignitors

[rbeckey]

I got some pyrogen from Rocketflite and using some scrap cat5 cable, made E-F-G ignitors. I had some 32 ga. nichrome and made solderless ignitors from instructions found online. I made 16 and tried 3, and all three lit ASAP and burned big.
What is the shelf life of an assembled ignitor? I will store them in a ziplock EMD bag, as I understand they are more impervious to moisture.

 

[swimmer]

rbeckey,

I also dipped my first dozen tonight. I will test fire several tomorrow.

I've had some purchased ignitors for over two years and they fire just fine, no problem.

I've heard of ignitors that will fire under water.

I haven't made my own wires yet but I'm waiting on nichrome wire from edwardw. You know that wire you get with a garage door opener for the control wiring? I bought two large rolls at a garage sale and the twin conductor will make fine ignitor wires.

 

[rbeckey]

Cat5 cable is what is used for computer networking. It can be purchased by the foot at Lowes, etc. It has four twisted pairs of bell wire, perfect for ignitors. I am sure the garage door control lines are similar stuff. Actually making the ignitors is a little tedious and time consuming, but it seems worthwhile compared to the cost of store bought.

 

[swimmer]

rbeckey,

Bought 12 pre-made Magnelite wires.....$10.99. I think I can do better than that..............

They do look tedious to make but the cost savings are worth it and I kinda like that "doing it myself" feeling.

How much is CAT5 wire per foot?

 

[rbeckey]

Cat5 cable probably costs pennies per foot. Certainly no more than 10-15 cents. I am not sure because I got mine as scrap from a buddy who networked his house. If you buy two feet and make them eight inches long, that gives you 12 ignitors for about 30 cents. I made mine about 10 inches long.
I cut the business end with one lead about an inch shorter than the other and stripped about a quarter inch off each lead. I used a wire wrap tool to wrap nichrome around the longer lead, then in a spiral around the insulated part of the longer wire, then around the stripped part of the shorter wire, which I had bent out at 90 degrees. I then bent the stripped ends in half on themselves and crimped tightly with pliers. I made sure before I dipped that the bent ends were all lined up to present a thinner profile for smaller motors. Follow the pyrogen instructions from there. Don't forget to strip about a half inch for attaching to the launch controller.

 

[swimmer]

Got a pic of the wire wrap tool?

 

[BlueNinja]

You know, if I ever get into making my own igniters, the CAT5 stuff should be good. I've seen something like it used before, and I like how small it is, if I am thinking of the same stuff in the pic. Can you describe the wrapping process with pics?

 

[rbeckey]

THis page is better than I can explain, and pics are supplied.

https://www.info-central.org/support_igniters.shtml

 

[Stones]

As far as nichrome wire, is this what to use?

 

[rbeckey]

I believe that is exactly what I have, though I bought a smaller quantity on Ebay. It works well in my tests. I wouldn't mind finding some a little thicker, like a Solar Igniter.

 

[BlueNinja]

Wow! That nichrome's cheaper than I thought. The CAT5 stuff is more expensive then I thought though, at like 30 dollars for 100 feet. Swimmer, I saw a underwater igniter once, I'll try to find the link.


Blue

 

[Stones]

Oops...
I see I posted the McMaster-Carr link to .032 wire and not 32 guage which is .008.
After I looked at it for awhile, I thought, something's not right here...seems a tad too thick.
This is the correct link. The smallest spool they sell is 660' long. I would guess that would make more than 2 igniters.

 

[KermieD]

Ninja, 100' of CAT-5 wire adds up to 400' of ignitors. I doubt you need that much at one sitting!

You can go to Radio Shack and get smaller amounts for far less. You can also use standard telephone wire and split that to get pairs.

 

[BlueNinja]

Yea i know, i just like to have extra sitting around so i don't have to go out and buy more. Went to RS today, just got back. I asked about cat5 and he said I could get 100ft for 15 dollars, so I think I'll do that. Better than 12 pre made wires for 11 dollars, that's for sure.

 

[Ryan S.]

wow nicrome is real cheap from mcmaster....might need to get some

 

[Batman]

For those of yopu who have already done this, what guages do you recommend for both the copper and nichrome wire?

 

[limd21]

For others who've used both the nichrome bridgewire and conductive dip primer, is there a good reason to favor nichrome over the conductive primer?

I used to build my own with nichrome, but since I started using a conductive dip, I find it a lot more convenient. Strip, dip. That's all that's needed for a good black powder ignitor. For other motor types, it's strip, dip, dip.

Is one reason nichrome is to be favored is that its electrical current requirements are lower? I use a hefty battery (from my cordless drill), so I've never had any problems with enough amperage capacity.

 

[jetra2]

Blue_Ninja,

I recently went to the Home Depot and bought 10 feet of CAT-3 cable (essentially the same stuff as CAT-5) for 12 cents a foot. I don't think it gets much better than that! It was 8 wires inside the outer coating, all perfectly sized for F motors and up. I have yet to try it in a E motor. Also, I e-mailed Rocketflite a while back and they told me that the nichrome they use is .056" diameter.

Jason

 

[BlueNinja]

Hmmm... haven't checked there, will try to get out and look. I'll probably just do the 110ft-$15 thing though.

 

[daveyfire]

What do you guys use for the conductive dip, besides what Igniterman (used to?) sell? I've been looking for a good conductive dip mix. I don't think the current requirement on a dipped igniter is any worse than the requirements of a wrapped igniter, since you're dealing with a lot of nichrome compared to the dip.

 

[jetra2]

Curious...

A conductive dip is basically the same stuff that's used on Copperheads? I would definately be most interested in getting my hands on some of it if it is. It would save me a lot of time. Then I might could make two different kinds of igniters, one with the conductive dip, the other the "normal way."

Jason

 

[BlueNinja]

yea it's gotta be, thats the only way to bridge teh copper unless there is some bridge wire... doubt that though.

 

[limd21]

I make conductive dip out of graphite powder mixed with clear nail polish. The graphite powder is sold in hardware stores as a dry lubricant (e.g. for locks). Most nail polish is nitrocellulose based, which is very flammable all by itself. I've heard of others using a powder called "conductive lamp black", but I cannot think of a cheap source of such material.

 

[llickteig1]

What is the shelf life of an assembled ignitor? I will store them in a ziplock EMD bag, as I understand they are more impervious to moisture.

I don't have any empirical evidence as yet, but I have been told that with the solderless ignitors there could be some corrosion between the conductors that could impede their ignition. A don't doubt this, particularly since the components are made from different materials (copper and nickel-alloy). I would say that a good 12v launch system would be a little more forgiving in this regard.

Storing in a moisture-proof bag is important. I personally don't make a lifetime supply at one sitting. I make maybe 50 and then share them as needed at launches and that'll last me about a flying season. When I get low, I make more and be sure to use the old ones first. If you have any doubts, fire a few to make sure they're still good. Also, handle your ignitors with care as the pyrogen is brittle and can flake off if it gets broken. One resource I have suggests storing your ignitors in small diameter mailing tubes for protection.

If you wrap your own nichrome and make your own pyrogen, you can make reliable ignitors for pennies. No more $1 or $1.50 ignitors from vendors.

Swimmer and Blue_Ninja_150: look me up at a launch soon and I'll show you a couple of tricks to making various sizes of wrapped ignitors for a range of motor sizes.

--Lance.

 

[Stones]

Originally posted by jetra2
...
Also, I e-mailed Rocketflite a while back and they told me that the nichrome they use is .056" diameter.

Those must be awful big igniters. That's like 15 ga. wire! I'm a little lost. Can we verify what most are using here for the nichrome? Either by decimal or gauge size. So far, 32 gauge (.008) sounds about right. At least for igniters in the E-G range.

 

[jetra2]

I would say you're right, Stones...I just checked the e-mail I got from them, and they told me they use .056 diameter wire for the element. Maybe he typo'd and meant .0056?

Jason

 

[aksarben10]

Originally posted by Stones
Those must be awful big igniters. That's like 15 ga. wire! I'm a little lost. Can we verify what most are using here for the nichrome? Either by decimal or gauge size. So far, 32 gauge (.008) sounds about right. At least for igniters in the E-G range.

I have tried several different gauges of wire for my ignitors and 32 gauge is my favorite for high current. 30 works great but I found it a bit to stiff and 36 was just too wimpy, fired great but was a pain to wrap. Smaller gauges are good if you are going to solder and make chips and low current matches.

My ignitors use the wire wrap technique as described on Info-Central.

Scott

 

[edwardw]

I use 36 guage for everything from G to M motors. The pyrogen I use just happens to be the propellant I use (KNCP) so some 36 guage and a slug of pyrogen light everything right up. I usually make the slugs round cylinders to fit the core, from 1/4" to 1" and about 1" long.

Edward

 

[jerryb]

Originally posted by Blue_Ninja_150
Hmmm... haven't checked there, will try to get out and look. I'll probably just do the 110ft-$15 thing though.

make SURE that the cat-5 your looking at is SOLID... and not stranded cat-5e not sure if the stranded will make good ignitors..

Cat-3 cable is a teensie bit smaller... but much cheaper... usually 2 pair per cable...


you could always do an Ebay search for Patch Cables...

I've bought 25 foot cables there for a buck a piece before.. you just have to pay the shipping...

 

[BlueNinja]

it is the CAT5 stuff, i asked to make sure it wasnt 5e.