Redundant E-charge

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Blackbird1936

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I had a catastrophic lawn dart experience with my favorite rocket several weeks ago so I decided to go to a redundant deployment on at least the apogee drogue event to insure not having another bad experience. I used an Eggtimer Quark and Apogee to achieve this. In concept it worked but I did suffer some damage the body tube... ( 38 MM cardboard, size of charges pretested).
Question is ... does the first e-charge ignite the second causing the deployment gasses to double then causing the damage... should I use half size charges when setting them up in a combination for redundancy?
 

Voyager1

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Did you program a delay of 1-2 seconds between primary and secondary events. Make sure you isolate/separate the deployment charges so that the primary doesn’t ignite the secondary. I separate mine radially and axially with a nomex blanket between.
 

Steve Shannon

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I had a catastrophic lawn dart experience with my favorite rocket several weeks ago so I decided to go to a redundant deployment on at least the apogee drogue event to insure not having another bad experience. I used an Eggtimer Quark and Apogee to achieve this. In concept it worked but I did suffer some damage the body tube... ( 38 MM cardboard, size of charges pretested).
Question is ... does the first e-charge ignite the second causing the deployment gasses to double then causing the damage... should I use half size charges when setting them up in a combination for redundancy?
Do not use half size charges! That’s worse than no redundancy.
Separate the charges so one cannot set off the other and stagger the timing as Voyager1 says.
 

Blackbird1936

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Did you program a delay of 1-2 seconds between primary and secondary events. Make sure you isolate/separate the deployment charges so that the primary doesn’t ignite the secondary. I separate mine radially and axially with a nomex blanket between.
yes, these devices allow for a 1 second delay. However, the charges were not isolated... can redundancy be accomplished in a small environment (38 mm tube)
 

Titan II

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yes, these devices allow for a 1 second delay. However, the charges were not isolated... can redundancy be accomplished in a small environment (38 mm tube)
Yes. I use glove finger tips and the wrap the bundle in a layer of duct tape. This protects the charge from abrasions and from being set off by the earlier charge. Do not half size the charges under any circumstance.
 

GlueckAuf

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In my view, there is no need for, and one big argument against, using redundant full charge, or half-charge, black powder loads. Airframe damage due to overpressure, or failure to deploy by underpressure, respectively. I've never known 4Fg BP to fail to ignite, as long as it's not contaminated or damp.

I use a single full-charge BP charge loaded inside two nested nitryl glove fingertips (for tear resistance) into which are inserted TWO separate e-matches. The squib is secured by a small, 4" zip tie to seal it, tightened below the plastic matchguards so as not to leak BP.

Each e-match lead is in turn connected to its respective DD altimeter, one primary and the other backup with a one-second delay programmed on the backup (though probably unnecessary). (Note: On my Level 3 candidate design, I use BP only for the DROGUE event. A pair of redundant JLCRs banded in series handle the MAIN event.)

1617584565509.jpeg


I believe this setup meets L3 certification rules, provides the confidence of redundancy, but eliminates the potential for an overpressured, or underpressured, deployment event.

Good skies,
GlueckAuf
 
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cwbullet

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I have done redundant charges in a 29mm tube so 38 is doable. I have to admit, it is rarely needed.
 

Blackbird1936

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In my view, there is no need for, and one big argument against, using redundant full charge, or half-charge, black powder loads. Airframe damage due to overpressure, or failure to deploy by underpressure, respectively. I've never known 4Fg BP to fail to ignite, as long as it's not contaminated or damp.

I use a single full-charge BP charge loaded inside two nested nitryl glove fingertips (for tear resistance) into which are inserted TWO separate e-matches. The squib is secured by a small, 4" zip tie to seal it, tightened below the plastic matchguards so as not to leak BP.

Each e-match lead is in turn connected to its respective DD altimeter, one primary and the other backup with a one-second delay programmed on the backup (though probably unnecessary). (Note: On my Level 3 candidate design, I use BP only for the DROGUE event. A pair of redundant JLCRs banded in series handle the MAIN event.)

View attachment 458462

I believe this setup meets L3 certification rules, provides the confidence of redundancy, but eliminates the potential for an overpressured, or underpressured, deployment event.

Good skies,
GlueckAuf
Thank all for response... I particularly like the idea of two e-matches set up on the same charge. Back to the table to re-figure and test!
 

Mach_Seven

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Thank all for response... I particularly like the idea of two e-matches set up on the same charge. Back to the table to re-figure and test!
It's funny, I was thinking the same thing. I do have motor backup, but could I run two ematches off the same altimeter? Is the power output high enough to fire both? I used to use these ematches (we called them squibs) in the display fireworks field. They can and do fail sometimes. Any issues with two squibs from the same altimeter to the same charge?
 

Voyager1

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It's funny, I was thinking the same thing. I do have motor backup, but could I run two ematches off the same altimeter? Is the power output high enough to fire both? I used to use these ematches (we called them squibs) in the display fireworks field. They can and do fail sometimes. Any issues with two squibs from the same altimeter to the same charge?
Some altimeters have an output current limit. By doubling up on the e-matches you are effectively doubling the output current on that channel. Check the maximum output current for the altimeter you’re using. If your using them on separate channels there should be no issues. That’s not true redundancy though.
 

GlueckAuf

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It's funny, I was thinking the same thing. I do have motor backup, but could I run two ematches off the same altimeter? Is the power output high enough to fire both? I used to use these ematches (we called them squibs) in the display fireworks field. They can and do fail sometimes. Any issues with two squibs from the same altimeter to the same charge?
Attached is a very thoughtful and technically-detailed official response to that very question I posed (also appended to the response) to the owner of Perfect Flite.

Bottom line: Dual parallel-wired e-matches on the same altimeter Drogue or Main circuit MAY indeed exceed the published max current draw when fired if one e-match closes upon firing and remains in that state for up to the 1 second the altimeter energizes that circuit, despite a mitigating function within the StratoLogger CF that's intended to address that risk. The owner suggested I use the recommended 9V battery instead of the 2S 240mAh (7.4 v nominal) LiPo battery I intended to use , or use a lower output 2S (7.4 v nominal) LiPo of not greater than 125mAh.

Good skies,
GlueckAuf

(Revisions--Edited for better clarity)
 

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cerving

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The Apogee does not have a provision for a nose-over delay, however the Quark does. You should set the delay on the Quark by adding a jumper to the "+1S" pins. Assuming that your charge has been tested to be adequate, it's OK to use two ematches in the same charge well; they DO take up some volume, however, especially in smaller charge wells, so ground test it thorougly with both ematches before you fly it. It's pretty easy to blow out a cardboard tube with an ejection charge, especially a "finger charge" in the thinner Estes tubes.
 

blackjack2564

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Been doing 2 matches per charge for years, even on 2 altimeter rigs [8 matches] yes it has saved my butt 2 times.

Have used following with no issues. All perfect flies....All Missleworks...Adept 22...R-das..Raven. all run in parallel. many types of e-match.
 

Voyager1

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Not necessarily. It depends on whether you connect them in parallel or series. Pros and cons to each method has been discussed quite a bit in past threads.
Very true. I should have been more specific. It was a warning for those who choose to connect in parallel.
 
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