Weird issue with e-matches.

At Red Glare, I used my standard DD set up on two rockets. I use the Billuscon/Amazon/Ebay orange e-matches, and have for years.

At this particular launch, I had a weird occurrence, not once, but twice! Both on my MAC Performance kits.

On my Radial Flyer, I have a redundant set-up; so four e-matches. All four tested for continuity and good resistance when prepping.

My Scorpion has a single alt. set-up, but again, both e-matches tested for continuity and good resistance (I get anywhere from 0.8 to 1.2 Ohms, generally).

On the Scorpion's flight, the e-match for the main did not ignite, and the rocket came down fast and needs major repairs. When I checked the e-match, it had no continuity. I was unburnt, but I could no longer get a continuity beep.

Then, when I checked my Radial Flyer, one of the four e-matches had not ignited. Same thing. Unburnt, no continuity.

Anyone got any ideas? :confused2:

I had this happen on a few ematches I got from Wildmans a few years ago. Luckily, I had backup/redundancy. My guess is that there was a small air bubble over the filament so the pyrogen did not light. I have not had any issues since. I did let Tim know of the issue, but it seems to be isolated at this point. Maybe just a statistical coincidence for you? Do you know if they are from the same lot?

I assume so, since they all came together. I've been working through them for about two years. These guys don't use filament, though, I don't think. They seem to be chip-based.

What "on" time is set on your altimeter? What voltage level do you have driving your e-match? And what battery type?

dixontj93060 said:

What "on" time is set on your altimeter? What voltage level do you have driving your e-match? And what battery type?

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The voltage and amperage will definitely effect the ability to fire the match.

I have not seen this myself except with homemade ematches. Personally, I had the similar issue to what you have describe when I got the dip measurements wrong. The filament burned without igniting the pyrogen.

I have heard of a similar issue with commercially made products on two occassions. The pyrogen reportedly was made with a substandard or an incorrect chemicals. You can see how all white powders look alike.

I cannot see how Chinese made would be any different than homemade or US made. Pyrotechnics is pyrotechnics whether it is made in China or the US.

dixontj93060 said:

What "on" time is set on your altimeter? What voltage level do you have driving your e-match? And what battery type?

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Each rocket was flown with a previously successful configuration. In both cases, the failed match was fired from an RRC2+. Mains set to 500' (Scorpion) and 300' (Radial Flyer back-up). I use 9V alkaline batteries, single e-match per channel.

9V battery should not be a problem then when using the standard RRC2+ on time.

I have seen too high voltage/current pop the bridge wire (chip head still has a wire) without staying on long enough to heat up and burn the pyrogen.

In fact, that is likely what happened, but not due to your setup, probably just faulty e-match heads.

What brand of 9v are you using? Have they flown before or was this the first time (for the batteries, not the rockets)?

They were Energizers, and the flights were not high G. Of the three batteries, two were used before and one was new. The Scorpion definitely had a used one; the Radial Flyer may have had a new or a used one, not sure.

Here is my take on your ematch issue and I'll use the analogy of a home made dipped igniter that just "pops". Made a bunch of those. I like the idea of perhaps a micro bubble across the element that Crazyrocket mentions as a possibility too.
I have another explanation. Depending on nichrome wire size, resistance and the condition of the battery, if there is an uneven heat flux in the filament, there can be a rapid buildup of combustion gases close to the surface of the bridgewire that
blows out the surface and breaks the wire in the process. That results in the "pop" and since there wasn't enough energy transmitted to other parts of the pyrogen, it fails to catch since the wire is broken from the shock to impart anymore energy.
The end result is the same, a dud. Use a partially depleted 12V battery that can't zap it with a pile of amps and the wire heats up more evenly and slowly allowing enough flux to be imparted at several points of the pyrogen.
Like yeah, that's easy to put in practice! NOT!

Or to be practical and salvage a "bad batch" of motor igniters, I gently crack the pyrogen along the length of the head in several places. The idea there is to allow any built up gas to vent safely and give the wire more time to get the pyrogen going. If any one has this problem with home made igniters, try this trick or give 'em to me and I'll use 'em

I haven't had a dud for a long time since doing this routinely. Especially with the igniters that have a big honking pyrogen head on them. The head can usually be cracked without having the pyrogen fall off.

Now, this won't help with the ematch issue but one usually has a very fine and relatively more fragile bridgewire as opposed to a 24ga. honking wire wrapped nichrome. I believe the theory would apply there also.
Another thing that comes into play is how neatly is the bridgewire soldered to the chips? With a commercial ematch one can't see. Heck if they are sloppy, the solder could go all the way out to the end of the bridgewire!
Ummmmm, kinda hard for the wire to impart heat if it's insulated by solder for cry'in out loud! Might just be that .020 to .032 thickness where the bridgewire goes from the topside to the bottomside of the chipboard!
And sheesh, if some of the solder goes along the bridgewire over the edge of the board? Ah dud city may result EVEN though there is continuity!

I experimented A LOT with commercial chips and quite frankly I believe all the good ones go to the ematch makers and the dud chips go to the hobbyists. I couldn't get consistency until I made everything and controlled the quality myself. But then again, I don't bother with it anymore because it's a lot of work and the commercial ematches are still pretty reliable. Jim Hendrickson has an extensive post on ematch reliability here somewhere that is reassuring.

Bottom line is backup when you can and expect anomalies when you can't. If you wanna catch fish, you gotta expect you'll snag and lose fishing lures!! Kurt Savegnago

The explanation is simple. Poor quality control on the ematches, high variability. You did nothing wrong. Use 2 of those ematches per channel in series if you are flying with a single altimeter.

There was quite a thread on this just a short while ago. Your recent experience is good timing and support of that discussion.

jderimig said:

The explanation is simple. Poor quality control on the ematches, high variability. You did nothing wrong. Use 2 of those ematches per channel in series if you are flying with a single altimeter.

There was quite a thread on this just a short while ago. Your recent experience is good timing and support of that discussion.

Click to expand...

Yep. Lesson learned.

jderimig said:

The explanation is simple. Poor quality control on the ematches, high variability. You did nothing wrong. Use 2 of those ematches per channel in series if you are flying with a single altimeter.

There was quite a thread on this just a short while ago. Your recent experience is good timing and support of that discussion.

Click to expand...

So that is a question I've been asking myself but scared to test in flight. Single perfectflight alt with two matches in drogue and two in main for redundancy as I also have a batch of the orange amazon ones. All ground tests are great - but the gentleman advising me at the field recommended j-teks on my cert flights, so I've not flown them yet. Is there issues wiring two into a single output on a single alt? I dont want to mess up the alt; but want to be assured of ejection as much as possible.

kcobbva said:

So that is a question I've been asking myself but scared to test in flight. Single perfectflight alt with two matches in drogue and two in main for redundancy as I also have a batch of the orange amazon ones. All ground tests are great - but the gentleman advising me at the field recommended j-teks on my cert flights, so I've not flown them yet. Is there issues wiring two into a single output on a single alt? I dont want to mess up the alt; but want to be assured of ejection as much as possible.

Click to expand...

You really need to read the other thread on this. It's quite extensive. If you use 9V batteries, wire two in series (not parallel). If you are using LiPos, see first sentence.

I used orange ones exclusively on the six DD flights at red glare. No issues. Jtek are great, but i wouldn't skip flying over them.

Yeah, this is the first time I've had one let me down. And it was on back-to-back flights. So strange.

Bat-mite said:

Yeah, this is the first time I've had one let me down. And it was on back-to-back flights. So strange.

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How do you store them? Is there a chance they got dinged in your range box somehow? How SHOULD things like this be stored?

I test and then insert immediately. My rockets go to the range ready to fly. No chance something got dinged inside the AV bay.

Another way to protect matches is use the micro-centrifuge canisters available from a variety of sources. Drill a sized hole and thread the lead wires through and secure with a dollop of epoxy. Can zip-tie to a long screw through a bulkhead to avoid
blowing the wall out of a cardboard rocket. Test the ematches first with a continuity tester. https://www.oda-ent.com/Continuity Tester 2.html Kurt

Kurt, I don't understand how that would have solved this problem. :confused2:

soopirV said:

How do you store them? Is there a chance they got dinged in your range box somehow? How SHOULD things like this be stored?

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Whenever I walk into a Jack in the Box and place an order, I grab a handful of straws. I cut the straws in half and use them to slide the pyrogen side of my igniters inside the straw. My igniters are folded in half so that there's a bow in them that will add friction inside the straw so they don't slide out.

Bat-mite said:

Kurt, I don't understand how that would have solved this problem. :confused2:

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I think it might have been in reply to my question- about protecting them in storage. I use the centrifuge tubes (3 sizes) for this too, but so far have only had a few ground tests. It's good to know this is a common practice. I like the screw idea, as I'm currently using charge caps, and just broke a CPVC cup.

soopirV said:

I think it might have been in reply to my question- about protecting them in storage. I use the centrifuge tubes (3 sizes) for this too, but so far have only had a few ground tests. It's good to know this is a common practice. I like the screw idea, as I'm currently using charge caps, and just broke a CPVC cup.

Click to expand...

Yeah good point. I should have made it clearer. If the ematch is epoxied in the base of a centrifuge tube, it will protect against physical damage to the pyrogen head. If the match is defective in the first place, won't fix that Plus if the head is defective but shows continuity, won't fix that either.

I blew out the sides of two cardboard rockets with unrestrained centrifuge tube charges. Heck, I blew out the side of a tired old rocket with a restrained charge by a cup holder: [video=youtube;hMvT9BKzbUg]https://www.youtube.com/watch?v=hMvT9BKzbUg[/video]
I've posted this before. That is a beeper that comes out in the slipstream and I forgot why I put it on. Fincan is salvageable. I just need to epoxy a tube to the coupler and make a new upper bay. The nosecone and ebay are fine.

Thing I liked about this rocket is it never had a fast spin to it and made a nice camera platform. Flies on 38mm motors and the J510 gives a really nice flight. I will get it rebuilt again. The original iteration was single motor deploy that was rebuilt after a wreck. The fincan is hard to kill. It's a 3 fin iteration of the rocket in the avatar. I pulled up Rocksim 5 and did the 3FNC with stock tapered fins years ago and as a single deploy, drop in a J350M and perfect L2 flight will be had. Kurt

I have even blown out body when the side of the centrifuge tubes let loose. So it is good to both secure them and "direct them." My typical prep is to:

1. Drill hole in bottom of tube
2. Apply hot glue to bottom of e-match chip
3. Pull wire down to seat e-match and fill bottom hole
4. Let hot glue set (a couple of seconds)
5. Fill with BP
6. Pack tight with dog barf
7. Cover top (open end) with blue tape
8. Wrap laterally (sides) with a piece of aluminum tape
9. Secure and hook up to altimeter and/or bay terminals

The aluminum tape seems to provide more tension/holding force than the blue tape helping to always direct the ejection out of the centrifuge tube in the right direction.

dixontj93060 said:

I have even blown out body when the side of the centrifuge tubes let loose. So it is good to both secure them and "direct them." My typical prep is to:

1. Drill hole in bottom of tube
2. Apply hot glue to bottom of e-match chip
3. Pull wire down to seat e-match and fill bottom hole
4. Let hot glue set (a couple of seconds)
5. Fill with BP
6. Pack tight with dog barf
7. Cover top (open end) with blue tape
8. Wrap laterally (sides) with a piece of aluminum tape
9. Secure and hook up to altimeter and/or bay terminals

The aluminum tape seems to provide more tension/holding force than the blue tape helping to always direct the ejection out of the centrifuge tube in the right direction.

Click to expand...

I like the aluminum tape method of wrapping the centrifuge tube.

dixontj93060 said:

I have even blown out body when the side of the centrifuge tubes let loose. So it is good to both secure them and "direct them." My typical prep is to:

1. Drill hole in bottom of tube
2. Apply hot glue to bottom of e-match chip
3. Pull wire down to seat e-match and fill bottom hole
4. Let hot glue set (a couple of seconds)
5. Fill with BP
6. Pack tight with dog barf
7. Cover top (open end) with blue tape
8. Wrap laterally (sides) with a piece of aluminum tape
9. Secure and hook up to altimeter and/or bay terminals

The aluminum tape seems to provide more tension/holding force than the blue tape helping to always direct the ejection out of the centrifuge tube in the right direction.

Click to expand...

I blew out a few too. Stuff a coupler inside, push back together, glue / epoxy / fill the body tube. I often had the chute / dog barf push the tube against the sidewall. I taped them to the harness's quick link to direct mine a bit.

jderimig said:

The explanation is simple. Poor quality control on the ematches, high variability. You did nothing wrong. Use 2 of those ematches per channel in series if you are flying with a single altimeter.

There was quite a thread on this just a short while ago. Your recent experience is good timing and support of that discussion.

Click to expand...

I've never used two in series. If 1 is bad, it may pop quickly and then open, then none work.
I prefer 1 on each altimeter.
While on that subject, at $50 a piece I would NEVER fly anything with 1 altimeter unless it's 38-54mm, but I do not fly those much anymore.
At least it doubles your chance of firing a charge.

Dave A said:

I've never used two in series. If 1 is bad, it may pop quickly and then open, then none work.
I prefer 1 on each altimeter.
While on that subject, at $50 a piece I would NEVER fly anything with 1 altimeter unless it's 38-54mm, but I do not fly those much anymore.
At least it doubles your chance of firing a charge.

Click to expand...

That's a good point. I'm still at 38-54 and everything has worked well so far with a single and only room for one alt...but I know my days are numbered. I'm just hoping to learn from you all the best ways I can keep that from happening. No question that bigger endeavors down the road will use more than a single alt.

Here's what I do

1. Drill hole in bottom of tube
2. Apply hot glue to bottom of e-match chip
3. Pull wire down to seat e-match and fill bottom hole
4. Let hot glue set (a couple of seconds)
5. Fill with BP
6. Fill space with dog barf
7. Close top, trim tabs and hinge off with knife
8. Insert top down into pvc charge cup, wrap with tape
9. Secure and hook up to altimeter and/or bay terminals

This way, the blast always happens in the charge cup and any plastic shrapnel is contained.

Banzai88 said:

This way, the blast always happens in the charge cup and any plastic shrapnel is contained.

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I really only use the centrifuge tubes in rockets of small diameter and/or ones that are built light for performance so no room and/or desire for charge cups.

BTW. I stopped using the plastic caps on the tubes and just went to blue tape because in much ground testing the caps seemed to be a significant contributor to lateral blow outs.