E-match shorting out in metal charge well?

[DHays]

Just a quick question.
I have always used aluminum charge wells that I purchase from a dealer for my drogue and main events. I have had excellent results with them over the years. So, as I am reading my altimeter user manual, it states that also avoid using metalized canisters to minimize your risk of shorts on an activated event output. Probably nothing to worry about since the match is on top center of well pressed in with dog barf and 4 layers of blue painters tape.
One of my ground tests that I did, I placed a match in a empty well in the bottom corner and it still fired off.
So, do I need to line the inside of the well with something non conductive (cardboard tube) or just leave as is and don't worry??
I would think that it is fine since the charge wells are made specifically for this situation?

Thank you!

 

[Kelly]

If there's ever any doubt I wrap a layer of tape around the base of the ematch to ensure it can't short to the well, other (redundant) igniters, etc.

 

[cwbullet]

Which altimeter? I have never seen it happen but guess it is possible.

 

[DHays]

It's the RRC2L. It has not happened. Just was worried that it could happen. Just didn't know if I needed to change my technique or not.

Thought about leaving the little red sleeve on the match head to prevent it from touching the side of the charge well?

Thank you Kelly I will try that.

 

[rharshberger]

I take a pair of sprue cutters and cut the red protective plastic sleeve shorter (most ematches seem to have them) so it still covers the exposed ematch blank, but the pyrogen is fully exposed.

 

[DHays]

Thank you everyone!

 

[cwbullet]

It's the RRC2L. It has not happened. Just was worried that it could happen. Just didn't know if I needed to change my technique or not.

Thought about leaving the little red sleeve on the match head to prevent it from touching the side of the charge well?

Thank you Kelly I will try that.

That should work. I have done this before. I often remove and save them so I have extra.

 

[Troy3003]

The anodizing on most of the charge wells out there does offer some protection against shorting as well.

 

[Handeman]

I've been using copper pipe caps as containers for the last 15 years. I fold the wire, just below the ematch head over the edge. The only time I had any concern was on a small rocket where I use 9mm brass as containers. They had a much thinner, sharper edge, but even then, I never had any issues with shorted matches because of the metal containers.

YMMV, but I consider shorting matches on a metal container to be one of those really small risk things that gets blowen up on TRF, but actually fall into the weeds when you consider all the other more high risk personal safety things within a rocket, like a motor Cato. Even a cato is low risk when you consider safe distances and look at what the risks are to people behind the flight line.

 

[DHays]

The anodizing on most of the charge wells out there does offer some protection against shorting as well.

Yeah true, I didn't think about that. Plus I would think that once the 4F and barf are packed in well, nothing should move?

 

[DHays]

I've been using copper pipe caps as containers for the last 15 years. I fold the wire, just below the ematch head over the edge. The only time I had any concern was on a small rocket where I use 9mm brass as containers. They had a much thinner, sharper edge, but even then, I never had any issues with shorted matches because of the metal containers.

YMMV, but I consider shorting matches on a metal container to be one of those really small risk things that gets blowen up on TRF, but actually fall into the weeds when you consider all the other more high risk personal safety things within a rocket, like a motor Cato. Even a cato is low risk when you consider safe distances and look at what the risks are to people behind the flight line.

Yes true, I really never gave it a thought until I was reading through the instructions again. I think that I will trim down the red sleeve just enough to protect the board and wires on the match. Then I will give it a couple of ground tests.

 

[OzHybrid]

If you know it might be an issue, do what you can to prevent it, tape on end of match, a bit of epoxy, hot glue, blue tac. There's lots of options to prevent it from happening. Pick one. Or 2.... Relying of something not happening to prevent it, like putting the match on top and hoping it won't move is bad.

 

[OzHybrid]

T

Yes true, I really never gave it a thought until I was reading through the instructions again. I think that I will trim down the red sleeve just enough to protect the board and wires on the match. Then I will give it a couple of ground tests.

That would work.

 

[OverTheTop]

I put a short piece of heatshrink tubing over the eMatch where it is likely to short out. Wear eye protection when shrinking.

 

[beeblebrox]

I put a short piece of heatshrink tubing over the eMatch where it is likely to short out. Wear eye protection when shrinking.

That is dangerous, the e-match could ignite. It would be much simpler to use a non metal charge well (I have used a cut off AeroTech SU motor casing (24mm) about an inch above the nozzle. Or you could simply pre prep dozens of e-matches by coating the exposed wire and the little pc board with epoxy to insulate...

 

[Handeman]

I've always used the copper water pipe caps in 1/2" and 3/4" sizes. I fold the insulated wire over the top edge and tape the wire to the outside. The match stays angled into the cup so its just on top of the powder. Some dog barf and two more pieces of masking tape over the top and it's good to go. I'm sure a shorted match could happen, but hasn't happened to me in 100s of flights over the last 15 years so I'm sticking with what works for me.

 

[David Schwantz]

Take a short chunk of your ematch wire, no ematch attached, and rub it on the inside of your charge well. See how long it takes to wear through. A flight will NEVER wear through the insulation.

 

[waltr]

I've always used the copper water pipe caps in 1/2" and 3/4" sizes. I fold the insulated wire over the top edge and tape the wire to the outside. The match stays angled into the cup so its just on top of the powder. Some dog barf and two more pieces of masking tape over the top and it's good to go. I'm sure a shorted match could happen, but hasn't happened to me in 100s of flights over the last 15 years so I'm sticking with what works for me.

That is what I have been doing. So far a dozen successful flights.

 

[FredA]

Instead of copper pipe caps, use PVC and problem solved.

 

[jsdemar]

I always put one wrap of masking tape over the exposed portion of the ematch head. No metal showing.

 

[Banzai88]

YMMV, but I consider shorting matches on a metal container to be one of those really small risk things that gets blowen up on TRF, but actually fall into the weeds when you consider all the other more high risk personal safety things within a rocket, like a motor Cato.

This! I've always had it explained to me that that little ball of plasma on the tip of the e-match when it ignites "could" short to the metal container and cause damage to the flight computer.

I've only been doing this (BAR) for 8 years now, have yet to see this happen, or even read a thread of it suspected of happening!

 

[RocketmanAleks]

I just shorten the little red plastic cap thing to the point where the metal of the match is not able to contact the well at all. I found the below picture saved in my phone because one of my friends had asked about it when I showed him some aluminum wells I use.

 

[cwbullet]

I just shorten the little red plastic cap thing to the point where the metal of the match is not able to contact the well at all. I found the below picture saved in my phone because one of my friends had asked about it when I showed him some aluminum wells I use.

View attachment 552112

I have never seen this issue. Interesting.

 

[jdsmith39]

I've always use 3D printed wells. They have a built in 4-40 hole at the bottom of the well.
https://www.printables.com/model/267864-avionics-bay-black-powder-well
I've never had a problem with them. Super cheap to replace...as long as you have a 3D printer.

 

[FredA]

This! I've always had it explained to me that that little ball of plasma on the tip of the e-match when it ignites "could" short to the metal container and cause damage to the flight computer.

Huh?
Are you connecting those conductive charge wells to something?
The plasma ball is already a short across the pyro output.
Your concern for "other" shorts is questionable unless there is an alternative metal path back to the altimeter - maybe if you are building an all metal EBay.

The primary concern with metal charge wells is that the edge might damage the insulation on the wires or the solder points on the head itself touch the sides and creates a short on that channel, not shorts between channels.

A good flight computer will not be harmed by a shorted channel.
But clearly a shorted channel is not going to deploy.

 

[Banzai88]

Huh?
Are you connecting those conductive charge wells to something?
The plasma ball is already a short across the pyro output.
Your concern for "other" shorts is questionable unless there is an alternative metal path back to the altimeter - maybe if you are building an all metal EBay.

The primary concern with metal charge wells is that the edge might damage the insulation on the wires or the solder points on the head itself touch the sides and creates a short on that channel, not shorts between channels.

A good flight computer will not be harmed by a shorted channel.
But clearly a shorted channel is not going to deploy.

Let's be clear, it's NOT my concern at all. It's only what I was told/read, to some extent on here at TRF. I believe that it's one of those apocryphal stories rooted in myth and legend and is, with a bare minimum of critical thinking as it relates to potential failure modes, avoidable.

 

[cautery]

Would seem to me that of the extensive list of things that are "likely" to go wrong on a launch.... THIS ain't even on the list.
Seems to me that you would all but have to TRY to cause an electrical issue.

 

[FredA]

Yep - tons of FUD around electrical things.

 

[cwbullet]

Let's be clear, it's NOT my concern at all. It's only what I was told/read, to some extent on here at TRF. I believe that it's one of those apocryphal stories rooted in myth and legend and is, with a bare minimum of critical thinking as it relates to potential failure modes, avoidable.

Concur. There are lots of mythical causes of failure. Most of the time a flight fails, the cause is much more simple than the concern of a shorted match by a metal canister.