Weird issue with e-matches.

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cwbullet said:
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.
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I don't know about e-match manufacturing but I know a bit about manufacturing differences between the US and China. When it comes to China as a contract manufacturer it is not uncommon that you provide specifics, they send back an acceptable sample, you come to a contractual agreement, but once it goes into production the runs are not on par with the sample. This is fairly well known and if you are not around or have a representative on-site to inspect as they go, and who cannot be bought, then they will cut corners at every chance in an effort to shave a fraction of a penny per unit. Of course there may be exceptions however this is a not uncommon.
 
You don't say what voltage the batteries read before you used them. Do you routinely re-use batteries? The fact that you mentioned you were unsure if you had used one of the batteries before is one reason why I don't reuse them. It's just too hard to keep track of how long each battery was used, etc.

It would be useful to know the starting voltage of each battery. Not sure if a low starting voltage could cause that kind of misfire but that would be a good project.


Tony
 
mpitfield said:
I don't know about e-match manufacturing but I know a bit about manufacturing differences between the US and China. When it comes to China as a contract manufacturer it is not uncommon that you provide specifics, they send back an acceptable sample, you come to a contractual agreement, but once it goes into production the runs are not on par with the sample. This is fairly well known and if you are not around or have a representative on-site to inspect as they go, and who cannot be bought, then they will cut corners at every chance in an effort to shave a fraction of a penny per unit. Of course there may be exceptions however this is a not uncommon.
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Interestingly, we (just this week) have some anecdotal evidence of that happening with some stainless steel swing bolts we organised to be manufactured in China. Doesn't happen all the time, but it does happen from time to time.

Regarding Ematches, a few years ago now I was chatting to someone who worked with professional pyros - putting on displays and whatnot. He mentioned the reliability of Ematches did vary considerably depending on the manufacturer. Some of their cheap Chinese offerings would fail 1/200 whereas some of the high quality (US made I assume) would be 1/multi thousands.
 
mpitfield said:
I don't know about e-match manufacturing but I know a bit about manufacturing differences between the US and China. When it comes to China as a contract manufacturer it is not uncommon that you provide specifics, they send back an acceptable sample, you come to a contractual agreement, but once it goes into production the runs are not on par with the sample. This is fairly well known and if you are not around or have a representative on-site to inspect as they go, and who cannot be bought, then they will cut corners at every chance in an effort to shave a fraction of a penny per unit. Of course there may be exceptions however this is a not uncommon.
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That is probably what happened to the companies that ordered the ematches. I just rationalized it to my own mistake. It is easy to measure wrong or grab the wrong bottle.
 
dixontj93060 said:
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.
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Ditto, One layer of duct tape or use masking tape on the end. Kurt
 
I must be doing something wrong because I have used a lot of centrifuge capsules and never blown out a body tube. I haven't done anything special either. No tape around the capsule or attach it to anything.
 
The only time I have damaged a body tube with canisters is when I use the lid. The lid fragment put a hole in the tube. I just remove the lids.
 
manixFan said:
You don't say what voltage the batteries read before you used them. Do you routinely re-use batteries? The fact that you mentioned you were unsure if you had used one of the batteries before is one reason why I don't reuse them. It's just too hard to keep track of how long each battery was used, etc.

It would be useful to know the starting voltage of each battery. Not sure if a low starting voltage could cause that kind of misfire but that would be a good project.


Tony
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I get different voltages depending on which meter I use. My digital multimeter always reads about 0.1 higher than the altimeters. I believe the voltages were about 8.9 or 9.0 on the meter, but beeped out about 8.8 from the altimeter.
 
Bat-mite said:
I get different voltages depending on which meter I use. My digital multimeter always reads about 0.1 higher than the altimeters. I believe the voltages were about 8.9 or 9.0 on the meter, but beeped out about 8.8 from the altimeter.
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Most of mine are 9.2-9.5 on the harbor freight volt meter.
 
cavecentral said:
Most of mine are 9.2-9.5 on the harbor freight volt meter.
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When I get the cheap batteries at Home Depot, they usually measure at 9.4 V. But I ordered a bunch of Energizers on ebay. They are still within their good date, but none of them has measured over 9.0 V when fresh out of the package.
 
I don't trust the e-match knockoffs enough to use them for charges.
I use them only for ignition.

JD
 
Bat-mite said:
When I get the cheap batteries at Home Depot, they usually measure at 9.4 V. But I ordered a bunch of Energizers on ebay. They are still within their good date, but none of them has measured over 9.0 V when fresh out of the package.
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Hmmm. I won't use a battery that doesn't measure at least 9.1 volts. The Duracells I buy at Costco measure 9.4 when new and I date them when bought and retire them if I don't use them within a year or so. I don't think the date code on the battery is nearly as important as the voltage. 9 volts or less sure doesn't sound very fresh.

New 9 volt battery - less than $2, cost of rocket and electronics - $$$

Not sure if the used batteries are related to your issue but just something to think about. It seems possible that low voltage/amperage could slowly burn the bridge wire without igniting the pyrogen. Maybe someone out there has some empirical data one way or the other on that. Occams razor - chance of 2 bad e-matches or 2 batteries with known low voltage.


Tony
 
I'm waiting for general availability of a Lithium Iron Disulfide ( Li-FeS2 ) 9v.

I see pictures of packaging for Energizer Ultimate Lithium 9v, but I can't find an MSDS or Technical Information sheet.

Anybody have a pack laying around and can rattle off the MN/PN?

It is -not- L522 , that's "Advanced" AKA Lithium Manganese Dioxide ( Li-MnO2 ); most online vendors are unwittingly selling you this.
 
UhClem said:
I must be doing something wrong because I have used a lot of centrifuge capsules and never blown out a body tube. I haven't done anything special either. No tape around the capsule or attach it to anything.
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Same here, and I use a lot of wimpy 2.6" LOC tubes for my airframe. I just fill the vial with BP, pack the remainder with dog barf, and snap the lid closed. Done. No damge.

I think the lateral blow-outs are caused by excessive BP charges and laundry that is packed too tightly.
 
I've routinely lit cheap ematches with a single cell AA during ground tests without issue over 30ft of cable, I have a hard time believing that a 9.0V+ battery would fail to ignite... Then again, odd failure mode.

Then again, cheap batteries could still be an issue. Alkaline battery chemistry can be a strange thing. Batteries that are old can hold bizarre characteristics during discharge, even when the voltage seems okay. Batteries tend to drop voltage fast and then brown out. Even a AA reading 1.3V would seem usable, but if it has already discharged once or is old, can brown out within 30 seconds under use.

Basically, alkaline batteries lie to you with their voltage, it's not a good representation of how much charge is left.

When viewing discharge graphs for alkaline batteries it looks like it should be a good representation of total charge, but you need to consider that once the battery is no longer under load, that the chemistry will rebalance and the voltage will rise, often back to near initial voltages, but the total capacity is now lower. Upon re-use the voltage drops faster to the plateau point. The old batteries will have a lower capacity from being old fuddly batteries, and when a volt meter is attached appear usable, but the total capacity is not really known.

I would suggest for a cheap lot of batteries to complete a discharge test with an electric load that can discharge the battery at a certain current and you could log the voltage and used current over time to verify before flight, or stick to some lipo chemistry or reputable sourced alkaline.

The EEVblog had an interesting video along these lines. He's Australian and kind of difficult to listen to (his voice is rather annoying) but his YouTube channel is pretty awesome.

[video=youtube;8Ur9gM4DRdA]https://www.youtube.com/watch?v=8Ur9gM4DRdA[/video]

But again, your batteries might be fine, and the failure still likely to be an ematch issue, but it's weird, and I've never had that failure with over three orders of 100 piece matches
 
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Buckeye said:
I think the lateral blow-outs are caused by excessive BP charges and laundry that is packed too tightly.
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This is my guess too. I trashed one that I had a 54mm DD I accidently a put 2g charge in. Had a 3/16 wire eye bolt and bend it out straight such that I though I never hooked it up. Lesson learned.
 
Jeffmhopkins said:
I've routinely lit cheap ematches with a single cell AA during ground tests without issue over 30ft of cable, I have a hard time believing that a 9.0V+ battery would fail to ignite... Then again, odd failure mode.
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Agreed that most 9V should fire, but there is the powered altimeter between them. With the capacitor, it should fire anything, but might not send a signal at all if it dies or the battery is fiddly and it reboots during flight. Energizers are known to be 6 smaller batteries inside without soldering. Duracell are soldered. Rayovac had a black mud like substance, not sure on other brands. Energizers are generally not advised for the lack of soldering. I never had an issue, but have been warned by several members.
 
manixFan said:
Hmmm. I won't use a battery that doesn't measure at least 9.1 volts. The Duracells I buy at Costco measure 9.4 when new and I date them when bought and retire them if I don't use them within a year or so. I don't think the date code on the battery is nearly as important as the voltage. 9 volts or less sure doesn't sound very fresh.

New 9 volt battery - less than $2, cost of rocket and electronics - $$$

Not sure if the used batteries are related to your issue but just something to think about. It seems possible that low voltage/amperage could slowly burn the bridge wire without igniting the pyrogen. Maybe someone out there has some empirical data one way or the other on that. Occams razor - chance of 2 bad e-matches or 2 batteries with known low voltage.


Tony
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I think I will be mending my ways.
 
cavecentral said:
Agreed that most 9V should fire, but there is the powered altimeter between them. With the capacitor, it should fire anything, but might not send a signal at all if it dies or the battery is fiddly and it reboots during flight. Energizers are known to be 6 smaller batteries inside without soldering. Duracell are soldered. Rayovac had a black mud like substance, not sure on other brands. Energizers are generally not advised for the lack of soldering. I never had an issue, but have been warned by several members.
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The soldered internals is why I only use Duracell. I also use the same battery for at least the season, or until the altimeter reports less then 9.0V. The flight that worries me the most is the first one with a new untested battery. If there are internal connection issues, that first flight is the most likely time they will show up.
 
Handeman said:
The soldered internals is why I only use Duracell. I also use the same battery for at least the season, or until the altimeter reports less then 9.0V. The flight that worries me the most is the first one with a new untested battery. If there are internal connection issues, that first flight is the most likely time they will show up.
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Before this thread it hadn't occurred to me to think about battery internals, but I could see under extreme G loads how deformation might be not completely impossible.

Does anyone have a documented failure to share? I'd be interested to do further reading / research.
 
dhbarr said:
Before this thread it hadn't occurred to me to think about battery internals, but I could see under extreme G loads how deformation might be not completely impossible.

Does anyone have a documented failure to share? I'd be interested to do further reading / research.
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I only heard stories. Problem is that when they lawn dart, there often isn't much left to say exactly what was to blame.
 
dhbarr said:
Before this thread it hadn't occurred to me to think about battery internals, but I could see under extreme G loads how deformation might be not completely impossible.

Does anyone have a documented failure to share? I'd be interested to do further reading / research.
Click to expand...

I don't know if this could be considered a documented failure, but the battery is the only thing I can attribute the loss of my L1 rocket to. The HiAlt45 and battery was on a sled I moved between rockets. On about the third flight, it had a hard landing when the main fouled and it came down on drogue only and the av-bay hit pretty hard. The battery checked good and the altimeter was still reading 9.1 v so I put it in my L1 rocket. The voltages checked right, the altimeter beeped correctly and the rocket was launched.

After the lawndart caused by neither charge firing, both charges were checked and both matches fired with a single AA battery. The HiAlt45 was undamaged, tested extensively in a vacuum chamber, and has almost 20 successful flight on it since the lawndart. Of course the 9V battery was poured out of the remains of the av-bay in about a dozen pieces.

Since the altimeter and both matches were good, I figure it had to be a bad power connections, either between the altimeter and the battery, or the battery itself. I still fly batteries until the altimeters read less than 9V, but I always replace them if there is any type of mishap that cause a hard impact. I haven't had another battery issue like that in the last seven years.

As I said, I don't know if you could call that a documented case, but I believe the failure was because of a loosened connection internal to the battery cause by the previous unusually hard landing and it worked while on the pad but failed under thrust.
 
Handeman said:
The soldered internals is why I only use Duracell. I also use the same battery for at least the season, or until the altimeter reports less then 9.0V...
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I have a threshold of 9.1 volts. But what altimeters and e-matches are you using? I don't think any of my batteries read even 9 volts after a single flight with dual deploy. Maybe they sit longer on the pad and I'm slower to recover? But I can't imagine using the same battery for more than one dual-deploy flight.

If it works for you, that's great, you've got more intestinal fortitude than I do.

An important point about AA's vs. 9 volts: AA's have about 2000mAh capacity vs. 450-500mAh for 9 volts. So a AA has far more capacity to set off e-matches that can be fired by low voltage. And don't forget that battery chemistry allows them to regain voltage levels that read high but drop quickly under load, so if not tested under load they can give a false sense of confidence.

Finally, a check of prices of Duracell 9 volt (only ones I've ever used) shows just under $2 each at Costco, but a whopping $3.50 in a blister pack at Walmart. I won't by batteries over the internet - read some of the reviews in this example:

https://www.amazon.com/Duracell-Coppertop-9V-Size-Pack/dp/B0074M2J88/ref=sr_1_4_a_it?ie=UTF8&qid=1461280143&sr=8-4&keywords=duracell+9+volt

Batteries are like the motors, if it fails the results are rarely good.


Tony
 
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