Spark Plug E-Match

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Arpak

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I was wondering if anyone has ever tried igniting an ejection charge with a spark gap like a spark plug makes, it would essentially be a reusable ematch if it worked. I'm imagining it wouldn't work because it's not creating an open flame, thoughts?
 

kuririn

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It would have to be a really small spark plug to fit in the nozzle. :D
Sounds like a static test is in order.
Let us know the results.
 

cerving

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The Aerotech Electronic Forward closure used an R/C glow plug. It probably did a pretty good job of tranferring heat to the BP because it takes a bit of time to heat up, a spark plug fires very quickly and might not be so good for that.
 

Arpak

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The Aerotech Electronic Forward closure used an R/C glow plug. It probably did a pretty good job of tranferring heat to the BP because it takes a bit of time to heat up, a spark plug fires very quickly and might not be so good for that.
I thought about a glow plug approach but I think the slow warming time would be... less than ideal for ejection charges.
 

rcktnut

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Fouled plugs don't work well, spark or glow, and after the first use with BP they will be pretty well fouled.
 

Arpak

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Fouled plugs don't work well, spark or glow, and after the first use with BP they will be pretty well fouled.
Maybe just a simple gap igniter like a pair of wires, wouldn't really hurt to mess it up if it was cheap to replace. Although, now I feel like I'm reinventing the e-match.
 

ksaves2

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Fouled plugs don't work well, spark or glow, and after the first use with BP they will be pretty well fouled.
......or the element would break and it would be single use. Kinda pricey proposition if you ask me. I think a delay and BP is the most economical way to go with trying to come up with a "reusable" ejection charge ignition simply an academic exercise to absurdity.

Get a new delay grain and BP charge with each commercial load one buys.

Say this over and over again...... "It's only a hobby. It's only a hobby. It's only a hobby." In that regard, K.I.S.S. ing it (Keep It Simple Stupid) with ejection charges is the way to go. Delay grain and BP or electronics and BP is the simplest way to go. ;)

(Errrr, ummmm, in my humble opinion electronics is the way to go as apogee detection is so much better than a fixed delay grain that one might screw up on the drilling. Get a good, low energy deployment at apogee and avoids zippers with cardboard tubed rockets.)

Yeah, yeah, yeah. Run a ton of simulations in different wind conditions on ones rocket and one get a half way decent delay time to drill a grain but what a PITA. I could spend an hour on a rocket doing a sim. Go to the field and take a wind reading with a hand held anemometer (though winds aloft can be totally different than what they are on the ground) and thank you Kestrel instruments for that. Push the button and get a nominal flight with no zipper.
What a pain. I have to admit though due to the lower mass of modrocs and the rubberband shock cords, zippers are not as much of a problem in that realm.

A subtle "trick" for a low energy deployment is to point the rocket on the pad a few degrees "downwind" as the rocket will have a tendency to weathercock into the wind and have a curving path to apogee with a low energy deployment. Run a sim and will get an idea of this phenomena. Rocksim has the video simulation mode and that's where I got the hang of it.

I vaguely remember the offering of a glow plug ejection charge system back in the day when I first started out with HPR around 2004 or thereafter. Slick website but I thought I was "too" young and stupid to try something like that. Probably a lot of folks felt that way and the site (and product) disappeared.

Oh for the uninitiated, drilling a delay grain is using a drill bit of manufacturers recommended size and drilling a hole of a certain depth to shorten the delay time. I've done that a lot with research motors that fit the small AT cases and pack a kick. I usually have to buy the longest delay grain and drill accordingly to what the simulation suggests.

Kurt Savegnago
 

RobertH3

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Lightning bug altimeter has flyback transformers and replaceable wire to the charges. Have one, just have to finish my DD fiberglass rocket to fly it.
No e-matches 😃
 

ksaves2

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Lightning bug altimeter has flyback transformers and replaceable wire to the charges. Have one, just have to finish my DD fiberglass rocket to fly it.
No e-matches 😃
I think I vaguely remember that product. When did you buy it? Did you get it when it first came out or used? I think that was the product I saw in the past and they had a slick website.

Access and cost of ematches became manageable so I didn't bother.

Actually, I learned to make ematches but gave it up as they were a PITA to make. The commercial blanks were so poor it was ridiculous. Many wouldn't fire at all. Had to make my own chips with PC board, wire wrap and silver solder. Two different pyrogens to make too although with ematches just a small amount needed to be mixed to minimize risk.

It's doable but a real pain. Like knitting. I spent 4 winters perfecting my technique but like I said, it was cheaper and easier to buy than making them eventually. I'd rather be building rockets than making ematches.

I will say my matches were the best. Instead of simply "popping" like the commercial matches (which is perfectly fine and works with BP) mine would instantaneously "flare" like a sparkler most of the time besides those I made that "popped". I had an Ohm meter as one wanted as low a resistance as possible with an ematch. Those that read high, I made into an augmented primary motor igniter with a 3rd pyrogen! (Just for fun!)

Again, I gave it up as it was too much work and a source of matches became more "easily" available.

My advice: "Don't try and make ematches." Not worth the effort as one wants 100% success. That's why dual electronics are advisable if possible. Don't get me wrong. I don't think it's all that "dangerous" to do. Certainly on par with mixing ones own research motors. But it's too tedious to make them with close to 100% fire rate. Again, a PITA to make reliable ematches.

Oh as an aside. I once took a dried toothpick that I used to mix the primary pyrogen for ematches put on my safety glasses and hit it with a sledge hammer! I read where the pyrogen was "shock sensitive". I was greeted with a "pop" like from my cap gun days as a kid and the smell that matched that when I fired a cap gun! I discovered what they used to make caps in the "olden" days! :)

Motor igniters? That's another story and if one is interested I encourage careful experimentation with primary ignition. If an igniter fails, one just puts another one in the motor. Staging igniters are a different proposition though and is a subject in its own right with the limited voltage and amperage that the onboard electronics can provide.

Kurt
 
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RobertH3

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Bought from Apogee, also contacted the company and chatted. They're planning a version with data extraction. Requires twisted pair wiring as the spark generates some RF noise though that's easy. Looking forward to trying it out.

Cheers / Robert
 

AllDigital

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I was experimenting with different ways to do HEI, so I bought some tiny spark plugs to play with. In my case, I was only looking for a better through hole bolt and wasn't actually going to use the spark gap to ignite anything. I was able to successfully solder leads on both sides of the plug to connect an ematch, but ultimately decided not to use the spark plug as the through hole bolt. While the spark plug is built to withstand high pressure (not sure how much), the extruding top and the fragile soldering outweighed the benefits. That said, a rocket motor with a spark plug sticking out the top looks really bad ass.

IMG_6534.JPG
 

Bat-mite

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I think a lot of these ideas spring from "I have more time than money." Also known as, "My way might not be better, but it's cheaper."
 

kuririn

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so I bought some tiny spark plugs to play with.
I like it.
I'm thinking the spark plug can ignite an air/fuel mixture in the gap but not sure if it can ignite BP.
Wouldn't the spark have to contact the BP? And if solid grains of BP are in the gap would it still fire?
Maybe the OP can do some testing.
 

manixFan

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I remember making BP canisters that used a filament based Christmas tree light as the ignition source. They worked well as I recall. I know one of the altimeter makers (Perfectflite) suggested them as an alternative to e-matches.


Tony
 

prfesser

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I think I vaguely remember that product. When did you buy it? Did you get it when it first came out or used? I think that was the product I saw in the past and they had a slick website.
I have a Lightning Bug. Haven't had a chance to try it yet but I've seen it used at the last LDRS, and it looks to be a pretty slick device. For those who don't want to mess with ematches it's a darned good solution.

My advice: "Don't try and make ematches." Not worth the effort as one wants 100% success. That's why dual electronics are advisable if possible. Don't get me wrong. I don't think it's all that "dangerous" to do. Certainly on par with mixing ones own research motors. But it's too tedious to make them with close to 100% fire rate. Again, a PITA to make reliable ematches.

Oh as an aside. I once took a dried toothpick that I used to mix the primary pyrogen for ematches put on my safety glasses and hit it with a sledge hammer! I read where the pyrogen was "shock sensitive". I was greeted with a "pop" like from my cap gun days as a kid and the smell that matched that when I fired a cap gun! I discovered what they used to make caps in the "olden" days! :)

Kurt
I'll second Kurt's advice. Two bucks for a couple of the unregulated type of ematch (like Chris Short sells, I don't know who else has them) is a small price to pay for reliability. Especially when you consider that the price of failure is a rocket, motor case, altimeter...

The stuff used in cap-gun caps is one of the most dangerous mixtures to handle in commercial quantities. Sensitive to friction, impact, spark, flame, and probaby to my ugly face. My understanding from discussion with a guy at PGI is that the stuff once ignited merely by unscrewing a lid from a container.

Best -- Terry
 

heada

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$0.60 each when you buy 80 of the 1 foot lead version. $0.95 each when you buy 40 of the 7 foot lead version. More expensive than the cheap orange-wire ebay versions but supposed to be BAFTE blessed.

1 +/-0.2 ohm test, 600 mA all-fire but recommend 1A. I don't know of any modern avionics that can't source 1A for 1second.

I used to make my own from soldering 40AWG nichrome wire to soldering lead wires to chips and just dipping pre-made blanks in pyrogen. I stopped all that because its cheaper and easier to just order a bunch of these. $48 gets you 40 dual-deploy flights or 20 redundant dual-deploy flights.
 

Arpak

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Great link dh!
So the answer seems to be lengthening the duration of the spark with resistors.
Somebody going to put together some hardware?
Might be my next time sink after.... Boy I have a lot of projects going, huh.
 

sl98

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Interesting topic. In addition to the Lightning Bug altimeter, they show an "Electronic E-match" as coming soon. Estimated availability is listed further down the page as May 2021.

I found the Arc Ignition Technologies website here:

 

Arpak

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Interesting topic. In addition to the Lightning Bug altimeter, they show an "Electronic E-match" as coming soon. Estimated availability is listed further down the page as May 2021.

I found the Arc Ignition Technologies website here:

Wow! That looks exactly like the solution I was looking for, guess now is a waiting game.
 

ksaves2

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I have a Lightning Bug. Haven't had a chance to try it yet but I've seen it used at the last LDRS, and it looks to be a pretty slick device. For those who don't want to mess with ematches it's a darned good solution.



I'll second Kurt's advice. Two bucks for a couple of the unregulated type of ematch (like Chris Short sells, I don't know who else has them) is a small price to pay for reliability. Especially when you consider that the price of failure is a rocket, motor case, altimeter...

The stuff used in cap-gun caps is one of the most dangerous mixtures to handle in commercial quantities. Sensitive to friction, impact, spark, flame, and probaby to my ugly face. My understanding from discussion with a guy at PGI is that the stuff once ignited merely by unscrewing a lid from a container.

Best -- Terry
Yup,

That's why I worked very hard to just mix up enough that I needed to dip. If I had leftovers, I should'a poured it on a wood burnpile but didn't. I did take pains to wipe the lid extremely carefully and when I did a dip session the next week, all was well. That said, once they became easier to purchase I figured it was better time spent building rockets than making ematches.
Retired now so I gotta get back to flying and building. Only problem is I'm widowed so I gotta take care of myself now! :)
Takes time to get chores done the beloved use to do! ;)
Kurt
 

rcktnut

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The Electronic E-match looks pretty nice, but for me that is adding to many links to the chain of things that can go wrong. I'll stick with conventional e-matches.
 
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