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altimeter-controlled ejection charge: how to attach igniter?

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billdz

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Hi,

I picked up a used e-bay with ejection canisters on both sides. Neither canister has a hole, see pic below. I'm just unclear how to attach the igniter. The canisters pictured with igniters in the Canepa handbook and elsewhere seem to have a hole drilled in the bottom of the canister, through which the igniter is inserted into the BP, with wadding and tape over the powder. In my case, there is no hole, so does the igniter just come over the open end of the canister, or what?

Actually, these vials with measuring lines and a cap seem like a much easier way to go: https://jacobs-online.biz/vials.htm

Thanks for any info and thoughts,
Bill

bulkhead.jpg
 

DGBrown

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I haven't used the vials, so can't comment on those. I put my charge in the holder, insert the match into the powder, then top it off with the wadding and tape. I haven't had any issues with this method on any of my DD flights.
 

cbrarick

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maybe it's just the light, or it's just a mess....
anyhow, the match comes out the top and into the ebay by the extra hole at the 7:30 position on the photo. Just put a piece of tape on the outside to hold the match in place, put the bp in, fill with dog barf and tape over the top. I'd also stick a piece of electrical tape over the hole for the ematch once you have the wires thru it. Put it on the top of the bulkhead.....not the underside.
 

MikeyDSlagle

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Yes the ematch will just into the top of the canister. Pack with dog barf and tape. Well, don't forget your black powder. You don't want a hole in the bottom of the canister to allow gases to pass directly into the altimeter bay.
 

Zeus-cat

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I like the vials. I cut off the bottom, stick an igniter through the hole and hot glue it in place. Put BP in the vial, stuff some dog barf in the top and close it up.
 

rharshberger

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I like the vials. I cut off the bottom, stick an igniter through the hole and hot glue it in place. Put BP in the vial, stuff some dog barf in the top and close it up.
+1 centrifuge vials, for cardboard rockets though I make holders for my vials so holes dont get blown through the side of the rocket.
 

billdz

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"I make holders for my vials so holes dont get blown through the side of the rocket."

What do you use for holders?
 

Steve Shannon

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"I make holders for my vials so holes dont get blown through the side of the rocket."

What do you use for holders?
In the past I've used pvc plugs. Not caps, these have a wide flange that I simply glue to the bulkhead.
In the future I think I'll use the one from Mike Fischer/Binder Design which incorporates bulkhead terminals.


Steve Shannon
 

Handeman

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maybe it's just the light, or it's just a mess....
anyhow, the match comes out the top and into the ebay by the extra hole at the 7:30 position on the photo. Just put a piece of tape on the outside to hold the match in place, put the bp in, fill with dog barf and tape over the top. I'd also stick a piece of electrical tape over the hole for the ematch once you have the wires thru it. Put it on the top of the bulkhead.....not the underside.
+1 for this method.

I like sticking the match into the holder, folding the wire over and taping. This allows you to put both your matches in place and turn the altimeter on to verify continuity before adding the BP. It also allows you some adjustment as to how deep in the canister the match head goes.

I use terminal blocks on the bulkhead. Makes it much easier since I don't have to open the av-bay every time I want to set up a flight.
 

Tim51

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I've drilled small holes in the side of the charge wells at the base (see below) and found they work well. These were initially drilled then the edges rounded with a needle file. For tamping charges, I cut the conical tip off a centrifugal vial, carving out a small hole in the process, then feed the igniter and wrap with tape. Once the BP is in the vial, tamped and closed, I then feed the igniter wire through the drilled hole and trim down the wire accordingly before attaching to the terminal block, so the vial is seated in the charge well. The first image shows a charge well on my 3.9" Av bay after firing during clean up, with the igniter wire still attached and a few charred remains of the vial (I pull out with long nose pliers). The second is a similar set up on my 2.14". On the latter I filed a square hole with a needle file. In both cases the charge wells were home made from brass tubing bonded with JB weld to the base of one of those alu screw top key fob pill holders and work well. The last image shows commercial charge wells on my 3" again drilled with a small hole.
WP_20161204_20_17_38_Pro.jpgWP_20170514_17_38_41_Pro.jpgWP_20170514_17_41_02_Pro.jpg
 

Banzai88

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Thanks, the terminal block configuration looks nice.

Interestingly, while Rich said he makes holders for his vials so holes don't get blown through the side of the rocket, some people think a holder is not a good idea, as the holder may direct all the force at the chute or recovery harness, see
https://www.rocketryforum.com/showthread.php?109894-Advice-on-Ejection-Charge-Holders
Using a vial will direct the charge somewhat, no matter what, unless you seal it so tight that the vial itself bursts. That would be less than ideal. I use CPVC caps bolted to the av bay tops, and put my charges in vials. The vials then go into the caps vial cap down. When the charge goes off, the blast is contained in the CPVC cap. It's so effective at ensuring that the flame front doesn't get to the laundry that I routinely get the vial cap back as part of clean out of the tube on recovery!
 
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