Bad Ematch?

[Steven88]

Today I discovered an issue with my flight yesterday at Airfest. Everything seemed fine with the flight so I thought it was a success. I had dual deploy and today discovered the drogue ematch did not ignite the powder in the charge well. I did not have the ematch buried in powder but it was on top and easily should have ignited the powder. Thankfully the flight was on a J motor and I had engine back up and the drogue was released. I am wondering if there’s a chance the ematch was bad? Only the tip of the pyrogen or whatever it is burned a little and the rest is unburned. I will attach a picture of the two ematches used for this flight. The ematch on the main worked fine. This is my first failure with dual deploy so far.

 

[Steve Shannon]

Today I discovered an issue with my flight yesterday at Airfest. Everything seemed fine with the flight so I thought it was a success. I had dual deploy and today discovered the drogue ematch did not ignite the powder in the charge well. I did not have the ematch buried in powder but it was on top and easily should have ignited the powder. Thankfully the flight was on a J motor and I had engine back up and the drogue was released. I am wondering if there’s a chance the ematch was bad? Only the tip of the pyrogen or whatever it is burned a little and the rest is unburned. I will attach a picture of the two ematches used for this flight. The ematch on the main worked fine. This is my first failure with dual deploy so far.

Was the powder or ematch free to move? Unlike an igniter, an ematch doesn’t throw a ton of sparks. If the powder wasn’t contacting the ematch it could easily fail to ignite.
I insert the head of the ematch into the powder and then place wadding on top to hold everything in place and keep it all together.

 

[cerving]

Compare it to a new one. It sure doesn't look like there's much pyrogen on those... you may want to think about a light dip with something like QuickBurst QuickDip or ProCast (the latter is great for making motor starters, too).

 

[manixFan]

Did you check the resistance both before and after the flight? How does it compare to the other ematch?


Tony

 

[Rocketclar]

I second above comments.
Several years ago I got an entire box of initiators from MJG where I had 100% failure rate. The continuity would test OK, but they wouldn't fire. (I have written about that before. Turns out MJG had gotten a bad batch of a chemical. When I contacted them with lot number they did send me a new box and I haven't had any problems since with several boxes.
I do check the continuity of each initiator before beginning to prep and I check the look of the pyrogen. (I've had a couple that had cracked off.)
After threading the initiator thru the well and adding the measured amount of BP, I fill the void with wadding and tape over. This has worked well for me. I almost always fly with redundant charges with 2 altimeters so I use at least 4 initiators and charges per flight. The backups always have a little more BP. I keep a spreadsheet of my ground testing results along with actual amounts used so this helps with preps the next time.

 

[Hobie1dog]

I'm now going to test the 25 I bought on Ebay recently.

 

[Steven88]

I fly redundant altimeters on my Loc Big Nuke and I’m thinking about next time using to ematches per charge well for the smaller rocket referred to in this thread . It only has one altimeter. Would there be anything wrong with doing that?

 

[Steven88]

I pressed the ematch into the bottom of the well with my thumb as I poured in the powder around it then I packed above with cellulose insulation and put masking tape on top. When I took it apart, it looked like the ematch had come up to the top of the powder, but was still secured with insulation and masking tape and do not see how it could not have possibly lit the powder. Needless to say, I am a little more gun shy now, as I have always had success with my charges. Also I used the same amount of powder, as in my last flight, which was succesful

 

[Steven88]

Did you check the resistance both before and after the flight? How does it compare to the other ematch?


Tony

No I haven’t done that. Like make sure there continuity with a wire tester?

 

[manixFan]

No I haven’t done that. Like make sure there continuity with a wire tester?

The number one test for e matches is checking the resistance before using in an ejection charge. Every match should be tested before use. The resistance will vary based on make, but typically is between 1.4 – 1.6 ohms for the ones I use. (A decent manual ranging multimeter works best.) Any matches that fall outside the expected range are tossed or used for testing.

Every match, every time, even if it’s been tested before.


Tony

PS: I have alligator clips on the ends of my test leads that I use to test both matches and ignitors. Seems to go a lot faster than regular leads

 

[Titan II]

I fly redundant altimeters on my Loc Big Nuke and I’m thinking about next time using to ematches per charge well for the smaller rocket referred to in this thread . It only has one altimeter. Would there be anything wrong with doing that?

Not at all. I use two matches per charge in all rockets, regardless of how many altimeters are used.

 

[Rocketclar]

I also learned not to bend the initiator head over as that can break a wire. So I just pull the tested (via multimeter) initiator down through the charge well. I should add that after I test the initiator, I twist the leads together to minimize static discharge causing a problem. That's my thing....I know there has been some discussion about that on TRF, but it's my habit to do that. Then I add the measured (on a jewelers balance) BP and I use pieces of good old Estes wadding to fill voids using masking tape to secure. Also, after I get the ebay with charges in place, I take it outside and wearing safety goggles, fire up the altimeters to see if they detect continuity and beep out the correct signals.

 

[manixFan]

I fly redundant altimeters on my Loc Big Nuke and I’m thinking about next time using to ematches per charge well for the smaller rocket referred to in this thread . It only has one altimeter. Would there be anything wrong with doing that?

Not only is there nothing wrong with that, it's a good idea. You might also consider wiring up 4 independent charges – the main ones with the typical BP charge, and the backups with a 'safety margin' of 25% extra BP. I'll program the backups to fire either 1 second or 200' lower than the main charges. I've been able to do that on even my 38mm MD rockets, although it is a tight fit. It is more time consuming, but it's cheap insurance otherwise.


Tony

 

[Handeman]

I also learned not to bend the initiator head over as that can break a wire. So I just pull the tested (via multimeter) initiator down through the charge well. I should add that after I test the initiator, I twist the leads together to minimize static discharge causing a problem. That's my thing....I know there has been some discussion about that on TRF, but it's my habit to do that. Then I add the measured (on a jewelers balance) BP and I use pieces of good old Estes wadding to fill voids using masking tape to secure. Also, after I get the ebay with charges in place, I take it outside and wearing safety goggles, fire up the altimeters to see if they detect continuity and beep out the correct signals.

I do my the opposite. I measure the resistance of all matches. Connect all matches to altimeters and power them up to verify the connections and that the altimeters see the matches on the pyro channels. Then I power everything down and add the BP to the wells. I put the matches on the top of the BP so the flame front of the burning power burns down into the cup instead of starting at the bottom and possible throwing unburnt powder out of the well. Dog barf and yellow masking tape to seal everything.

 

[Banzai88]

Orange ematches. Yuck. I've well documented several lots that have failed initial resistance checks of around 3%, with a flight failure (after passing a bench resistance check AND a resistance check in the flight altimeter) between 7 and 11% failure rate on top of that. Nope, never again. False economy!

I know that others have had world class success with them, but that's not been the experience of my nor anyone at all the several clubs that I launch with.

At this point, I fly only MJGs and save the orange ones for ground test only. Since then, hundreds of MJGs flown and not one single failure on the bench or in flight.

 

[Handeman]

Today I discovered an issue with my flight yesterday at Airfest. Everything seemed fine with the flight so I thought it was a success. I had dual deploy and today discovered the drogue ematch did not ignite the powder in the charge well. I did not have the ematch buried in powder but it was on top and easily should have ignited the powder. Thankfully the flight was on a J motor and I had engine back up and the drogue was released. I am wondering if there’s a chance the ematch was bad? Only the tip of the pyrogen or whatever it is burned a little and the rest is unburned. I will attach a picture of the two ematches used for this flight. The ematch on the main worked fine. This is my first failure with dual deploy so far.

I had a similar incident about 15 years ago. Both ematches measured about 1 ohm before flight. Neither match lit the powder. They were both commercial matches, but different brands. Fortunately the scratch rocket had too small of stability margin and it fell flat the whole way down and survived.
Turns out both matches looked the same as when they were installed, but both were open, the bridge wires had burned through but didn't ignite the pyrogen.

 

[Hobie1dog]

I just checked all of mine.

 

[Steven88]

This e-match that failed to light my black powder does not ohm out now after the flight. I cannot tell that the bridge wire is burned either, so I am wondering if it was a bad e-match. I will again attach a photo.

 

[Steven88]

A new E match out of my bundle ohms out at 1.2

 

[Banzai88]

This e-match that failed to light my black powder does not ohm out now after the flight. I cannot tell that the bridge wire is burned either, so I am wondering if it was a bad e-match. I will again attach a photo.

Typical of what I experienced with several different lots of the orange ematches.

 

[Handeman]

I ohm out the orange ematches before installing. I've never had one that read 1 - 1.5 ohms fail to work correctly. Now that I think about it, I've never had one that didn't read between 1 and 1.5 ohms when checked.

I had a couple US manufactured matches that did that, read fine when installed and open after the flight and didn't burn the pyrogen. Yours looks like the pyrogen is gone so I don't know how it could have fired, burned the pyrogen and not ignited the BP, unless there was dog barf or something else between the BP and the match.

 

[Steven88]

Banzai88 is right. The orange matches are junk. Tried another one in my garage and it didn’t light the powder in my charge well either. Same powder in well that didn’t ignite at Airfest. Tried another (packed the exact same way) and it ignited powder with a very loud bang and blew the head off the e-match. Will only be using these for testing from now on. Always had success with them before

 

[rharshberger]

Use lacquer thinner and carefully dissolve the ematch pyrogen, see ifcthe wire is burnt or broken. Obviously there was a failure, now its time to see what it actually was.