Ejection Canisters

I am interested to hear or see pictures of how you do you ejection charges. I have used several types.


1) SafeEject by Spacetec



2) Blacksky Ejector



3) BlastCaps
https://www.blastcaprocketry.com


4) Dog House Rocketry Charge Wells
https://doghouse.blastzone.org/DogHouseRocketry/Charge_Wells.html

5) PVC pipe

6) Glove fingers

7) Centrifuge and test tubes

8) Cardboard tubes

Any body else have and ideas?

Chuck

I use two primary methods: 1) centrifuge tubes of various sizes bought in bulk from eBay and, 2) copper pipe from Home Depot, Lowes, etc. of various sizes from 3/8" to 3/4" cut to length and plugged on one end with epoxy/FG slurry.

Copper pipe:



Centrifuge tubes:

i use blastcaps from Gary T
or Ez canisters from quickburst.net

EZ Canisters by quickburst.net are an example of cardboard canisters / tubes.

I was thinking of using a spent .45ACP shell casing since I already have a bucket full (push the primer out and replace it with a screw). But then I went and bought some Pyrodex because I couldn't find BP, so I'll be using centrifuge tubes

I have done cartridges. They work well also.

Just drill a hole in the bottom for the screw.

I have used .45ACP, but I found they did not hold enough Pyrodex. I then went to .44 mag. brass, but I was pushing those limits for something like a Little Dog DD. I know I can do it with some of my .45-70 brass, but I really do not want to use the brass that way since I do reloading also, so I came up with other methods. Several are described here. I use a number of items for ejection charge canisters. I use ground testing to determine how big a charge and then determine what I can use for a canister of the size I need. If it is a small rocket I use a soda straw. I place an ignitor in one end, a rolled up ball if recovery wadding and then seal it with hot glue (using a gun I bought in the crafts department at Walmart). Then I pour my pyrodex or BP in from the other end, another ball of recovery wadding and some more hot glue. I can do this at the launch site with a cigarette lighter power converter for the hot glue gun. The next size up I use water tubes that you see on the ends of flowers from the florist. You can buy them in bulk for a penny a piece or one of the local florists sells them to me for $0.10 each. Since they are sealed on one end I pour in my powder, install an ignitor, some more balled up recovery wadding (and party streamers, made of crepe paper work great and are flame proof; 100' long roll for a dollar in the party supplies at Walmart), push it down a bit, and then duck tape. These will fit into a 1/2" copper tubing cap that can be screwed into the e-bay bulkhead. On larger rockets, I repeat the following; Get a PVC threaded cap and secure it to your electronic bay bulkhead, which also has a hole drilled in the side for the ignitor(s). I have a piece of PVC pipe of the appropriate diameter glued into a PVC threaded coupler. Into this piece of PVC with coupler I seal off one end with duct tape, add some recovery wadding and then pour in my pre-measured powder. (I put it in small baggies, one load, one bag. I then screw this onto my threaded cap, like I do when I install the ejection charge on an Aerotech motor, powder assembly up, threaded cap down, so the powder does not spill. Then I push an ignitor or ignitors in and plug it with wadding and tape. Then I am ready to go. I hope this helps.

With a cartridge, I use the head of the screw holding it the bulkplate to seal the hole. I have never used hot glue, but plan to try it with cardboard canisters.

I don't used fixed canisters. My very first DD rocket had 1/2 a spent Estes motor casing epoxied to each AvBay bulkhead to contain the charges, but then ~10 years ago someone showed me the glove finger and baggie corner plus tape method and I've never used a canister since.

My method of choice now is surgical tubing and zip ties. Charges assemble quickly, can be made up in advance, and the powder is always contained nicely. I use them for everything from 29mm through 8" airframes. Small diameter (< 2") rockets use smaller diameter tubing.

I have had great success doing ejection charges that way.

--Lance.

llickteig1 said:

I don't used fixed canisters. My very first DD rocket had 1/2 a spent Estes motor casing epoxied to each AvBay bulkhead to contain the charges, but then ~10 years ago someone showed me the glove finger and baggie corner plus tape method and I've never used a canister since.

My method of choice now is surgical tubing and zip ties. Charges assemble quickly, can be made up in advance, and the powder is always contained nicely. I use them for everything from 29mm through 8" airframes. Small diameter (< 2") rockets use smaller diameter tubing.

I have had great success doing ejection charges that way.

--Lance.

Click to expand...

This is one I have not tried, but want to try in the future.

https://www.wimpyrockets.com/page16.html

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cwbullet said:

This is one I have not tried, but want to try in the future.

Click to expand...

Once you get the hang of making surgical tubing charges, they assemble really quickly. Most of the rockets in my active fleet require 4 charges and I can make them all in just a few minutes. They handle easily and I just attach them to terminal blocks on the bulkheads and go. I have the required tools: tubing, zip ties, scissors, etc. together in a small ammo box that goes everywhere with me. Assembled charges also go back in the box for safe keeping.

--Lance.

I have seen people use plastic wrap, but that make me worry of static charge. Is that me overthinking or is it a possible problem?

I make my charges from masking tape. Roll a tube, pinch over the e-match head, add powder and pinch closed. I run the e-match leads through a hole in the bulkhead and connect directly to the altimeter. Works with real BP, not substitutes.

Tom can you post a picture?

I use a corner of a "baggies" but Gary's Blast cap is the way to go.

Bob
TRA 6797

I use the Blastcap :wink: I designed them with NO E-Match lead hole in the side as I want 100% of its force going in the direction its pointed in, All be it only a small amount of the charge escapes through it but why have any?

There is allot of debate whether the charge blows the chute out or the Nose cone pulls it out, IMO it's a little of both, There are a ton of things that can influence this like how tight a fit your chute is in your BT, With a tight chute the charge below it will push it like a plug, Lose chute and the some of the blast bypasses it and the NC pulls it out, These are the reasons why I choose a Canister over the bag tube or glove type.

As for the Centrifuge tubes I've had them blow a perfect circle right through the wall of the BT, Granted the material was phenolic but when the charge was loaded into the the rocket it managed to face itself right against the BT wall, The charge went off blowing a hole in the side and not deploying the main.

Anyway as you all know there are a whole slew of options in this category so good luck to all.

But Remember The Blastcap! All the best dressed Av-Bays are wearing them now a days.

I use blastcaps also, but I cam going to have to try tape and the rubber tubing material.

I use duct tape. Make a 4" by 8" or so piece, place the e-match in the middle with the leads going out the long end. Pour the powder on top. Fold in half the long way, then wrap up into a nice square and hold it together with another small piece of tape. I think you can get by with a 2" wide piece of tape on smaller (<2gram) charges, but I haven't done that in a while.

Edit: I find duct tape preferable to bag corners and such because it seems much less likely that a redundant charge will penetrate the tape and set off the charge as there's usually 2-3 layers surrounding the black powder the way I make them.

The surgical tubing charges have worked up to 42K.

Tony

llickteig1 said:

Once you get the hang of making surgical tubing charges, they assemble really quickly. Most of the rockets in my active fleet require 4 charges and I can make them all in just a few minutes. They handle easily and I just attach them to terminal blocks on the bulkheads and go. I have the required tools: tubing, zip ties, scissors, etc. together in a small ammo box that goes everywhere with me. Assembled charges also go back in the box for safe keeping.

--Lance.

Click to expand...

Lance,

Does this work with "black powder alternatives" like pyrodex? Obviously, I'd have to test regardless, but if anyone has done tests to see if the tubing provides enough containment I'd appreciate the feedback. Surgical tubing looks like a low-cost, easy way to get a system in place.

I am starting to plan out my dual deploy plan of attack and this thread on ejection canisters is very timely and informative. Thanks to all who contributed thus far!

I use drinking straws..No, seriously! I cut a straw into about 3" sections(Hardee's straws are best as they are FAT!), then place over my prepped xmas light with its tip broke off exposing the filament..A wrap of masking tape to secure straw to base of xmas light..Fill with appropriate amount of BP, tamp in some dog barf and then tape off the end.And another wrap of tape over the entire length..Run leads in through hole in bulk plates and attach directly to altimeter..Cheap and easy!

I use a black iron pipe nipple, about 9/16in ID, 4 in long, with a cap brazed onto one end. The nipple is screwed into a threaded bushing epoxied into a bulkhead. The rocket this canister is being used in uses rear ejection, and none of the commercial canisters I had seen seemed to provide the level of accessability I desired.

That has to be heavy?

RadManCF said:

I use a black iron pipe nipple, about 9/16in ID, 4 in long, with a cap brazed onto one end. The nipple is screwed into a threaded bushing epoxied into a bulkhead. The rocket this canister is being used in uses rear ejection, and none of the commercial canisters I had seen seemed to provide the level of accessability I desired.

Click to expand...

Pantherjon said:

I use drinking straws..No, seriously!

Click to expand...

Wow, you have given me a new cheap method. Between this and tape from Tom. I am set.

dixontj93060 said:

That has to be heavy?

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Yep, that's what I thought to.

But running the calcs, a 1/2" NPS XS nipple at 4" length will only weigh about 5.8 oz (~164 g) when it's carbon steel (iron and carbon steel have nearly the same density). Now if it is made out of aluminum, it's only about 2 oz.

Greg

I typically use the corner of the bag that the reload came in, and masking tape. Though when I need more, I'll grab any bag available -- almost always someone nearby with the bag from a reload they're not using.

I've seen Lance with his surgical tubing charges and they do work well. I've considered going that route, I just need to buy some surgical tubing, first!

-Kevin

dixontj93060 said:

That has to be heavy?

Click to expand...

Yep. Given my experience with rear ejection in LPR though, rear ejection always results in a rocket that is heavier than it would be otherwise. This canister is also great at keeping the gasses contained. I've tested it with FFg pyrodex and the stuff will ignite immediately if packed correctly.

troj said:

I typically use the corner of the bag that the reload came in, and masking tape. Though when I need more, I'll grab any bag available -- almost always someone nearby with the bag from a reload they're not using.

-Kevin

Click to expand...

That might be the ultimate in thriftyness. You have sold me into using one of the low tech options. It will be especially great in the smaller rockets I fly.

cwbullet said:

Tom can you post a picture?

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Here's a set of pics:
Roll the tube
Insert e-match and pinch over lead, side and end views
Add powder, in this case inert salt:
Pinch closed and fold over. Exposed adhesive holds tab down.
This charge would be about 3 grams if BP. This size would be used in my Deuce.