Strange issue with centrifuge cartridge based ejection charges

[hball55]

Just to add another data point, here is how I use centrifuge vials:

1) Drill a hole in the bottom of the vial just large enough for the wires from a J-Tec to pass through. I use a pin vise that I keep around just for this step.
2) Insert J-Tec from the top and pull wires until head is near the bottom of the vial.
3) Add black powder to the appropriate line in the vial. I do all my testing using the vial lines to measure, so it's reproduceable.
4) Insert a cylindrical foam earplug into the top of the vial and press it firmly against the powder. If there's not enough room, I'll cut the plug in half (or thirds).
5) Snap the vial closed, attach wires to electronics, and fly.

I can't remember where I got the earplug idea, but I certainly didn't come up with it myself. I bought a big bag of vials and a box of earplugs a decade ago, and I don't expect to run out of either anytime soon.

Commercially made ejection capsules, I think made by Wildman, have the foam earplugs to keep the BP together. I have a bunch of the larger ones with the foam earplug. I have a bunch of the smaller ones, with no foam, that Pratt Hobbies once sold. In all cases, the capsules have the igniter positioned in the bottom of the capsule.

 

[cwbullet]

Commercially made ejection capsules, I think made by Wildman, have the foam earplugs to keep the BP together. I have a bunch of the larger ones with the foam earplug. I have a bunch of the smaller ones, with no foam, that Pratt Hobbies once sold. In all cases, the capsules have the igniter positioned in the bottom of the capsule.

That is what I do. I buy the test tubes and drill my own holes and then add a foam earplugs. You can get 200 earplugs for $20. Test tubes are cheap also but make sure you get the soft plastic ones so they do not shatter.

 

[hball55]

That is what I do. I buy the test tubes and drill my own holes and then add a foam earplugs. You can get 200 earplugs for $20. Test tubes are cheap also but make sure you get the soft plastic ones so they do not shatter.

Do you buy them from Amazon? If so, do you have the item # handy? Also, what sizes do you buy? 5 ml? 2 ml?

 

[cwbullet]

Do you buy them from Amazon? If so, do you have the item # handy? Also, what sizes do you buy? 5 ml? 2 ml?

Yes.

I buy these earplugs.

I have used 5ml centrifuge tubes, 2ml centrifuge tubes, and 5ml test tubes.

I have a 3d printed jig to drill the bottoms.

 

[hball55]

Yes.

I buy these earplugs.

I have used 5ml centrifuge tubes, 2ml centrifuge tubes, and 5ml test tubes.

I have a 3d printed jig to drill the bottoms.

Thanks Chuck. So you prefer the screw-on cap tubes over the snap lid tubes.

 

[cwbullet]

Thanks Chuck. So you prefer the screw-on cap tubes over the snap lid tubes.

I do not use caps (especially with cardboard tubes). I blasted on through the side of LOC tubing. I will used dog barf if there is a small gap after the BP. I use the earplug if it is larger.

I have time over the Holidays. Is there interest in a centrifuge tube and earplug how to thread?

 

[hball55]

I do not use caps (especially with cardboard tubes). I blasted on through the side of LOC tubing. I will used dog barf if there is a small gap after the BP. I use the earplug if it is larger.

I have time over the Holidays. Is there interest in a centrifuge tube and earplug how to thread?

Sure, why not; I have ideas as to what I’d do, but since you have had success making and deploying them, it makes good sense to pay attention. I figured to either hot-melt glue or rtv to secure the igniter in the centrifuge tube, definitely drill the hole rather than cut the hole for the igniter. Now, somebody said that Tony Alcocer positions the igniter above the BP, not below like my commercial ones (Pratt Hobbies) are made.

Don’t give anything away yet, wait for your “how-to” thread.

 

[cwbullet]

Sure, why not; I have ideas as to what I’d do, but since you have had success making and deploying them, it makes good sense to pay attention. I figured to either hot-melt glue or rtv to secure the igniter in the centrifuge tube, definitely drill the hole rather than cut the hole for the igniter. Now, somebody said that Tony Alcocer positions the igniter above the BP, not below like my commercial ones (Pratt Hobbies) are made.

Don’t give anything away yet, wait for your “how-to” thread.

I have never put the match near the top of the powder. I make sure it is buried in the BP.

 

[dr wogz]

I do not use caps (especially with cardboard tubes). I blasted on through the side of LOC tubing. I will used dog barf if there is a small gap after the BP. I use the earplug if it is larger.

I have time over the Holidays. Is there interest in a centrifuge tube and earplug how to thread?

Chuck, I was just going to comment on teh "leave off teh cap as it can rip a hole in your body tube". While I haven't personally have it happen, a wise old man told me to do this as I attempted my L1

But I do the same thing: cone bottom vials,

• Drill a hole in the bottom & rip off the cap.
• Insert e-match & tape in place.
• Fill with BP
• Stuff in a filler on top, usually regular wadding
• Tape in it place
• Add more tape
• And a bit more tape to make it pretty..
• Write the qty of BP with a sharpie on it, when you make a bunch at a time! (Learned that from someone at URRF!)

I do like the ear plug idea (they also make a good floating plug for fly-fishing: trout & pan fish!)


Yes, Chuck, I have mentioned a few times over the years that TRF should start having a bunch of "articles" for newbies & others to read. A bunch of "how to" and "for best results" papers / articles / essays, as well as maybe a few hobby related news items (such as new Drone rules or NAR/TRA changes).. and have these articles under an 'Articles' tab on the blue menu bar [Forums What's new Media members] so it is ever present. I can think of about a dozen articles; topics that come up time & time again.. (See "RCUniverse.com" for what I mean)

 

[cwbullet]

Chuck, I was just going to comment on teh "leave off teh cap as it can rip a hole in your body tube". While I haven't personally have it happen, a wise old man told me to do this as I attempted my L1

But I do the same thing: cone bottom vials,

• Drill a hole in the bottom & rip off the cap.
• Insert e-match & tape in place.
• Fill with BP
• Stuff in a filler on top, usually regular wadding
• Tape in it place
• Add more tape
• And a bit more tape to make it pretty..
• Write the qty of BP with a sharpie on it, when you make a bunch at a time! (Learned that from someone at URRF!)

I do like the ear plug idea (they also make a good floating plug for fly-fishing: trout & pan fish!)


Yes, Chuck, I have mentioned a few times over the years that TRF should start having a bunch of "articles" for newbies & others to read. A bunch of "how to" and "for best results" papers / articles / essays, as well as maybe a few hobby related news items (such as new Drone rules or NAR/TRA changes).. and have these articles under an 'Articles' tab on the blue menu bar [Forums What's new Media members] so it is ever present. I can think of about a dozen articles; topics that come up time & time again.. (See "RCUniverse.com" for what I mean)

I do the same but I use hot glue to seal the bottom. I may use your post as a guide when I do my thread.

 

[hball55]

You know, I bought what Apogee calls the e-match mate. It has an aluminum piece that you mount to the bulkhead and has a silicone tube that mates to the aluminum piece. There’s some kevlar thread you tie off to keep the silicone piece from being lost. They say that it keeps the hot gases or burning BP from burning pinholes in your parachute. But at $21.55 ea, the costs run up. I may do a test to see if it works as stated, but probably won’t be buying more due to cost.

I wonder if the guys that cut off the fingers of nitrile gloves to make ejection charges might want to add their “how-to” to your thread Chuck.

 

[hball55]

I was wrong when I thought the ejection cannisters I bought were from Wildman, they were from Pratt Hobbies too. Here’s a pic:

 

[Banzai88]

I drill a 3/32" hole in the bottom of the vials, and use hot melt glue to seal the MJG firewire match in place. Under 1gram I'll just put the match head as low as it will go, but 1-1.5 grams (the most I'll use in a 2g vial) I place the match head about mid way up the vial so that it's in the middle of the charge.

I cap the charge with foamy ear plug pieces as well, and snap the top on while it's expanding. I use flush cutters to clip off the hinge and the finger tab. My charges go cap down into 1/2" CPVC cap charge wells, and get 2-3 wraps of masking typical brown masking tape around the charge well and vial to hold it all in place. The blast usually breaks the tape, but not always, and I get perfect deployment without augmenting the cap seal with anything other than as made.

I found that the CPVC cap acts as sort of a blast chamber, and since moving the match head to the middle of the charge for larger charges, I've not had a single issue with 'soft' deployment or pin hole burns in any recovery gear.

Most of the time I get the foamy back from the main charge, but the drogue charge foamies are lost at altitude.

1.5ml vials

2.0ml vials

Earplugs

 

[cwbullet]

I was wrong when I thought the ejection cannisters I bought were from Wildman, they were from Pratt Hobbies too. Here’s a pic:

View attachment 495446

I thought you were referring to Pratt. There was one other company that produced them and I think with was Newton's Third.

 

[hball55]

I thought you were referring to Pratt. There was one other company that produced them and I think with was Newton's Third.

Aw shucks, I want a lil’ Johnny rocket now.

 

[cwbullet]

Aw shucks, I want a lil’ Johnny rocket now.

I have a few in my shed. I just need a few more parts.

 

[hball55]

I have a few in my shed. I just need a few more parts.

Let me know if you ever get them together.

 

[cwbullet]

Let me know if you ever get them together.

I will.

 

[0011001100]

I wonder if the guys that cut off the fingers of nitrile gloves to make ejection charges might want to add their “how-to” to your thread Chuck.

I'd be willing to add that. I mostly fly fiberglass rockets so the charge blowing out in all directions isn't as much of an issue.