Diy E-match or igniter

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Reading about rocket starters there is all kinds of discussion of secret pyrogen recipes, friction sensitivity, regulated materials, etc. I've also read about people dissolving ping pong balls in acetone. I don't want to get into anything questionable, I just need a few igniters for some leftover motors. I found that I can dissolve a bit of smokeless powder in acetone and blob it on the nichrome wire. It dries hard and doesn't seem to be sensitive to friction or impact. It burns about as violently as a wooden match. This seems like the most innocent engine starter that there could be. Am I missing something here? Do some motors require more exotic mixtures to create enough heat for reliability? For my use I would be using these in D through G motors starting with a couple of G Econojets I have left over.
 
What you need for a starter is very dependent on what you are trying to start. Blackpowder is very easy to start. APCP a bit more difficult, some mixtures quite a bit more difficult. Motors with large internal unfilled volume might require enough 'starter' to bring the casing up to operating pressure before the propellant kicks in.
The main use of NC lacquer ("ping pong balls in acetone") is as a binder for other stuff, not as the pyrogen itself. Nichrome wire with an NC dip would be fine for BP motors. Your Econojets might require a bit morethan that, but I don't have a specific recommendation as I've not personally tried that combination.
 
bjphoenix said:
Reading about rocket starters there is all kinds of discussion of secret pyrogen recipes, friction sensitivity, regulated materials, etc. I've also read about people dissolving ping pong balls in acetone. I don't want to get into anything questionable, I just need a few igniters for some leftover motors. I found that I can dissolve a bit of smokeless powder in acetone and blob it on the nichrome wire. It dries hard and doesn't seem to be sensitive to friction or impact. It burns about as violently as a wooden match. This seems like the most innocent engine starter that there could be. Am I missing something here? Do some motors require more exotic mixtures to create enough heat for reliability? For my use I would be using these in D through G motors starting with a couple of G Econojets I have left over.
Click to expand...

From the start I had a deep disliked for Aerotech Copperheads, they are the reason I began making my own starters. Here is the method that has worked for me for the last two decades, some details are sketchy as it has been a while since I dipped any.

Strip your double strand wire (can't remember the gauge) about an eighth of an inch, keep the leads as straight and as possible. Mix a small amount of powdered graphite in Sig butyrate dope. Dip the stripped ends in the mixture leaving a smallish "blob" covering the leads. Try not to make the blob too large as the starter may pop and fail to ignite properly. Hang to dry.
These made with a smaller gauge wire work great for BP motors, but for APC I re-dip in one of the three pyrogen kits that have accumulated over the years.
 
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Pem Tech said:
From the start I have disliked Aerotech Copperheads, they are the reason I began making my own starters. Here is the method that has worked for me for the last two decades, some details are sketchy as it has been a while since I dipped any.

Strip your double strand wire (can't remember the gauge) about an eighth of an inch, keep the leads as straight and as possible. Mix a small amount of powdered graphite in Sig butyrate dope. Dip the stripped ends in the mixture leaving a smallish "blob" covering the leads. Try not to make the blob too large as the starter may pop and fail to ignite properly. Hang to dry.
These made with a smaller gauge wire work great for BP motors, but for APC I re-dip in one of the three pyrogen kits that have accumulated over the years.
Click to expand...
Do not use conductive pyrogen starters in clusters. Too much variation.
 
Pem Tech said:
From the start I had a deep disliked for Aerotech Copperheads, they are the reason I began making my own starters. Here is the method that has worked for me for the last two decades, some details are sketchy as it has been a while since I dipped any.

Strip your double strand wire (can't remember the gauge) about an eighth of an inch, keep the leads as straight and as possible. Mix a small amount of powdered graphite in Sig butyrate dope. Dip the stripped ends in the mixture leaving a smallish "blob" covering the leads. Try not to make the blob too large as the starter may pop and fail to ignite properly. Hang to dry.
These made with a smaller gauge wire work great for BP motors, but for APC I re-dip in one of the three pyrogen kits that have accumulated over the years.
Click to expand...
Hi, sounds like what i may be looking for. Is the gauge 30AWG by chance for BP ignitors?
 
Years ago, a housemate ignited something I'd rather not discuss by applying 115V AC to a tiny diode. I think I saw him try this with just the diode first, which promptly exploded. Of course, that kind of voltage outside could be a problem.

Not quite as far back, I saw a carbon composite thing*, which will remain unidentified, fall across some high voltage wires. There was the most amazing 60 cycle hum, and then a little mushroom cloud. A lot of the epoxy just vaporized, but a lot of the carbon fiber survived, some even intact. So it was natural that I thought of carbon fiber when I wanted to make my own motor igniters. I want them with tiny leads that can go through a 1 mm hole, so I have been trying different things, all with 26 gauge magnet wire or smaller leads. A quarter inch long piece of carbon tow can have several ohms of resistance and withstand lots of current. (It may be that different types vary.) If the current source can put out enough amps, I suspect that no pyrogen at all would be required. If you're using tow, wrap the wire around it. The fibers are so rigid that if you try to wrap them around the wire, they break. I have some old uni prepreg that expired and cured on its own that is much easier to wrap wires around, since it doesn't flex all over the place.

In my particular application, I want to be able to yank the wires out, but for a normal rocket, I don't think that's relevant, so wire wrapping ought not to be all that much of a problem. Soldering two pieces of 26 gauge or smaller wire in a lap joint, so they can be pulled apart when hot, is a bit fiddly.

How much current can the usual power source at rocket launches put out? If it's a reasonable number of amps, I suspect that carbon makes a superior bridge wire. And maybe doesn't even need pyrogen in many cases.

With the lithium batteries and super capacitors we have these days, I should think an on-board, powerful 12V ignition current ought to be possible even for the ejection charges.

When I had an Estes type rocket I'd built some years ago, I used a gel cell and a piece of an extension cord to apply voltage to one strand plucked from the same cord. No pyrogen. It worked ok, though it was probably critical to have the wire actually touching the propellant.

Nakka-rocketry.net has several discussions of several types of igniters, some of them requiring very little current. As in, refrigerated, tired 9 volt battery. I'm kind of in favor of high current and 12 volts. Recently, in tests on my Jetex motors, I've been using a 3 cell, 1400 mAh lipo. Plenty of current and more than 10 volts. Doesn't weigh much, either. If I was going to buy something just for that, I might get lithium iron phosphate, as I think they're supposed to be a little safer.

*Not mine. And I was fortunate enough to be a couple of hundred yards away.
 
Pem Tech said:
Learn something new everyday. Guess we got lucky when we launched the Medusa on a double D years ago.

What would you suggest for clusters?
Click to expand...

Orestes Mayo said:
Hi, sounds like what i may be looking for. Is the gauge 30AWG by chance for BP ignitors?
Click to expand...
I recommend the bp motor starters from electricmatch.com or csrocketry.com. The leads are standard ematch 22 gauge. Use as is for BP motors and dip in ProCast for composite motors. If the nozzle is big enough, use regular fireWire ematches. For tiny nozzles like Q-Jets, you may have to DIY. This is a B4 Q-Jet and the leads are 30 gauge.
18mm igniter in B4-4 4.jpg
 
Update on the starters. I found much cheaper alternatives to the gold plated tungsten and kynar wire wrap. This unplated tungsten wire requires soldering and yields a starter with 1-2 ohm resistance. Do not use values outside this range in clusters and make sure the starter is secured to the motor it's inserted in.
Tungsten get the .05 mm https://www.amazon.com/RINGGLO-Tungsten-0-01mm-1mm-Machinery-Manufacturing/dp/B09J2CD7ZN/ref=sr_1_2?crid=2FMZ3S1GRD86&dib=eyJ2IjoiMSJ9.P9WU_S9PvXBHE41bv6HzPff6xODbdkWh1dVkraC--xVZ95XZ81kspHnBhsSTHB3aelqXJv3WhSdZtdcGioIFPoDd7OMOf6c3exCQe8yaCjOJmmL7nIzfa6iUbbJxvRcHQacnMDauaJxep7WayR2yRZ7hKnvi90ke_s0zoMLpFE2jwmpkLeBiBKlbwb3i4h20bgLolMKeNYiUrdW-PBWN8Ygggj_ZrkacCrwDWNmDTnseBd2LDxvaE-9Y2JAh7cY6JFLKAIe2TPHVgkuxoO6SmZs1uVpjO6YmhEJoFfetnPw.wdvUWSc3nk-vcqL_RlkHHf-Du6tyhv3CCpeVEaN6aPo&dib_tag=se&keywords=ringglo&qid=1710467943&s=industrial&sprefix=ringglo,industrial,99&sr=1-2&th=1
30 gauge wire wrap PVC insulation https://www.amazon.com/dp/B083352WFF?psc=1&ref=ppx_pop_dt_b_product_details
 
Sounds promising. Can you even work with wire of 0.05 mm? I know that wire that's maybe a quarter of that diameter can be hard to see. They use it for bracing very light indoor free flight models, though using tungsten for that sounds backwards. The models, or at least some of them, have wire bracing. The ones with mysterious little sticks perpendicular to their motor sticks definitely have wire bracing, though you can't see it in the video.

--------------
I just did a little experiment. Last night, I pulled a loop of AWG 30 magnet wire around the back side of an Xacto knife to make a narrow loop. I stripped the loop with a flame and some steel wool, but only the loop. Globbed on a mix of Beacon 527 (nitrocellulose glue) and graphite. My voltmeter couldn't make heads or tails of it, so it wouldn't pass a continuity check. Coated it with a bit of newly mixed RNX thinned with a little dope thinner. Or was it acetone? With the thinner, it took quite a while to cure. Despite the voltmeter's misbehavior, when I connected a 3S lipo (11 volts, tens of amps possible), I got a nice, persistent fireball, which eventually fell off the wire and onto the ground before it went out. Normally, RNX isn't so easy to light, BTW. I haven't done this particular mix with this particular glue before. I've had problems with inconsistency using other glues, though, so it's not definite yet.
 
lr64 said:
Sounds promising. Can you even work with wire of 0.05 mm? I know that wire that's maybe a quarter of that diameter can be hard to see. They use it for bracing very light indoor free flight models, though using tungsten for that sounds backwards. The models, or at least some of them, have wire bracing. The ones with mysterious little sticks perpendicular to their motor sticks definitely have wire bracing, though you can't see it in the video.
Click to expand...

The tungsten serves as the bridge wire. 0.05 mm is .002" and is about as thick as my head hair. 30 gauge wire is .010" thick. I use tungsten as is doesn't burn through like thin nichrome does. You have to size the nichrome to the voltage/current of your launch system while tungsten can operate on any voltage. I wind the bridge wire over a white surface so I can see it.
18mm igniter making 11 crop.jpg
 
Rocketjunkie said:
The tungsten serves as the bridge wire. 0.05 mm is .002" and is about as thick as my head hair. 30 gauge wire is .010" thick. I use tungsten as is doesn't burn through like thin nichrome does. You have to size the nichrome to the voltage/current of your launch system while tungsten can operate on any voltage. I wind the bridge wire over a white surface so I can see it.
View attachment 635582
Click to expand...
That's the way I wrap 34 ga nichrome on shooter wires. I don't have any issues with any of the 12V systems at any launches.
Where i have issues is with long term storage. I've found that if you don't use the igniter in the first 6 months or so, something in the pyrogen causes the resistance of the igniter to climb from 1 - 2 ohms to 50 - 100 over time. Usually at 6 months it's getting near 6 - 10 ohms, which is about the highest it will still be reliably useable on a 12V system.
I tried dipping them in nitrocellulose lacquer right after wrapping, but that almost instantly sent the ohms to the 6 - 10 ohm range.

I suspect it's the oxidizer in the pyrogen that limits the shelf life. It's really hard to solder the nichrome to copper. Is it easier or harder to solder tungsten to copper? What flux would you need.

Edit, updated wire ga.
 
Last edited:
Handeman said:
That's the way I wrap 32 ga nichrome on shooter wires. I don't have any issues with any of the 12V systems at any launches.
Where i have issues is with long term storage. I've found that if you don't use the igniter in the first 6 months or so, something in the pyrogen causes the resistance of the igniter to climb from 1 - 2 ohms to 50 - 100 over time. Usually at 6 months it's getting near 6 - 10 ohms, which is about the highest it will still be reliably useable on a 12V system.
I tried dipping them in nitrocellulose lacquer right after wrapping, but that almost instantly sent the ohms to the 6 - 10 ohm range.
Click to expand...
With nichrome, they must be soldered for a long shelf life. I've had soldered ones for at least 10 years without any increase in resistance. The one you see in the picture I posted is gold plated tungsten. Unplated ones must be soldered. The ones Wildman sold were soldered and they still were reliable even after banging around in your range box for years. I do have a couple hundred soldered ones and the makings for more.
 
Handeman said:
I suspect it's the oxidizer in the pyrogen that limits the shelf life. It's really hard to solder the nichrome to copper. Is it easier or harder to solder tungsten to copper? What flux would you need.
Click to expand...
Easy peasy soldering nichrome. Just use a flux similar to Baker Soldering Fluid. There must be a similar product over there. And I use the bridgewire igniter guide.
 

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Handeman said:
I suspect it's the oxidizer in the pyrogen that limits the shelf life. It's really hard to solder the nichrome to copper. Is it easier or harder to solder tungsten to copper? What flux would you need.
Click to expand...
Rosin won't work. I use Rubyfluid (ZnCl2) Tungsten is harder than nichrome but the Rubyfluid works and solders nichrome just fine.
 
I wonder how long the wrapped wire igniters would last if the wraps had a tiny bit of ACF-50, Corrosion-X, or other anti-corrosion substance applied? Maybe even just oil? Vaseline?
 
Handeman said:
That's the way I wrap 34 ga nichrome on shooter wires. I don't have any issues with any of the 12V systems at any launches.
Where i have issues is with long term storage. I've found that if you don't use the igniter in the first 6 months or so, something in the pyrogen causes the resistance of the igniter to climb from 1 - 2 ohms to 50 - 100 over time. Usually at 6 months it's getting near 6 - 10 ohms, which is about the highest it will still be reliably useable on a 12V system.
I tried dipping them in nitrocellulose lacquer right after wrapping, but that almost instantly sent the ohms to the 6 - 10 ohm range.

I suspect it's the oxidizer in the pyrogen that limits the shelf life. It's really hard to solder the nichrome to copper. Is it easier or harder to solder tungsten to copper? What flux would you need.

Edit, updated wire ga.
Click to expand...
I have had one fail in 3 years (out of at least a thousand). I am not sure the oxidation is that significant.
 
Handeman said:
That's the way I wrap 34 ga nichrome on shooter wires. I don't have any issues with any of the 12V systems at any launches.
Where i have issues is with long term storage. I've found that if you don't use the igniter in the first 6 months or so, something in the pyrogen causes the resistance of the igniter to climb from 1 - 2 ohms to 50 - 100 over time. Usually at 6 months it's getting near 6 - 10 ohms, which is about the highest it will still be reliably useable on a 12V system.
I tried dipping them in nitrocellulose lacquer right after wrapping, but that almost instantly sent the ohms to the 6 - 10 ohm range.

I suspect it's the oxidizer in the pyrogen that limits the shelf life. It's really hard to solder the nichrome to copper. Is it easier or harder to solder tungsten to copper? What flux would you need.

Edit, updated wire ga.
Click to expand...
Mine have not degraded quite that fast, but they do degrade after a year or so. Though they seem to be usable on a 12V system for a couple years afterward. I don't solder at all. And I wrap the nichrome at least 8 times around the copper, usually 10 or more times, tightly, for maximum contact.

Yes, I suspect the oxidizer corrodes one or both metals and reduces the contact between nichrome and copper, increasing the resistance.
 
Thanks @cwbullet and @prfesser. I will have to retry and retest. I'm thinking the NT lacquer I've been using might be contributing. Originally I dissolved ping pong balls in acetone to make the NC lacquer. Then I bought some guitar lacquer which is NT lacquer, but doesn't seem to work quite as well.

I'm thinking the NKO3 is pretty old and maybe needs to be vacuumed to eliminate moisture, if that would even help.
 
Rocketjunkie said:
I recommend the bp motor starters from electricmatch.com or csrocketry.com. The leads are standard ematch 22 gauge. Use as is for BP motors and dip in ProCast for composite motors. If the nozzle is big enough, use regular fireWire ematches. For tiny nozzles like Q-Jets, you may have to DIY. This is a B4 Q-Jet and the leads are 30 gauge.
View attachment 635472
Click to expand...
Thank you. A picture helps a lot.
 
Orestes Mayo said:
ematch has an outrageous shipping cost, as much as the 20 ematches. Any other source?
Click to expand...
Part of the cost was the permits and licensing of being able to cut out fedex(saving the $50 hazmat fee and signature required) however, it is pricey for smaller orders. we did run some free shipping coupons in the past for rocketry forum customers, but there are none currently available. Maybe in September/October they will come back, but advertising that on the forum is a little difficult without paying for a higher tier membership. I had a hard time asking MJG administration to pay money to offer free shipping.
 
Handeman said:
Thanks @cwbullet and @prfesser. I will have to retry and retest. I'm thinking the NT lacquer I've been using might be contributing. Originally I dissolved ping pong balls in acetone to make the NC lacquer. Then I bought some guitar lacquer which is NT lacquer, but doesn't seem to work quite as well.

I'm thinking the NKO3 is pretty old and maybe needs to be vacuumed to eliminate moisture, if that would even help.
Click to expand...
Send message with how you are using it and I will help you. I use the same stuff with great results.
 
prfesser said:
As for motor starters/initiators, the most common type is wind-and-dip. Some say this takes too much work/time/something else. My view: I can make enough starters for a season's flying and testing in a single evening. And as (I think) I've said before, what is a hobby but a way to waste time and money? The product is happiness.....and I do enjoy making these.

Anyway, these should be fairly clear:
View attachment 461436 View attachment 461437 View attachment 461438 View attachment 461439

These images show so-called "shooting wire", but CAT-5 or whatever style of network cable (twisted pairs) is handy works fine. This batch used 32 ga nichrome but 36 ga has been quite successful. Some workers solder the nichrome-copper connections. My experience has been that if at least eight or ten tight turns are used to anchor each end of the nichrome, the starter is good for a year, possibly longer. I start with a length of nichrome a meter or so long, and snip off the end with scissors after the second winding.

Use your favorite dip. We don't discuss formulations except in the Research forum but a search of the web should land a dozen or so dip-mixtures.

Best -- Terry
Click to expand...
Completely agree with the purpose of a hobby.
 

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