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Threaded Charge Wells - for use with water bottle caps

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Landru

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They are now available for sale. I have the 3g finished, Feel free to order the 3g and put 6g in the comments and I will ship when available.

These ultralight 6061-T6 aluminum canisters are threaded to be sealed with standard low profile water bottle caps. (1.05" diameter, 1/4" high, 3 thread starts)

Each weighs in at a impressive 4.4grams empty, with an additional BP capacity of 3g sufficient for most 4" and 5" rockets.

These canisters (with cap) are 1.05" Diameter, and 0.453" high

The canisters have a threaded hole on the underside for a standard #6-32 screw for attaching to your bulkhead.

Each canister comes with one cap and stainless steel screw for mounting.

There are (2) ways of routing e-matches into the canisters:

For BOTH options, remove 75% of the e-match protector so the tip of the e-match is visible, but the solder connections are covered and prevented from shorting.

1) The easy way: Cut, drill or melt a small hole in your plastic cap. Feed the wire through the cap with the e-match on the inside. Add powder to the canister, and screw on the cap. If the wire hole was tight enough, you will not need anything additional to seal the hole.

If you are prepping ahead of time, you can seal the area where the match goes through the hole with epoxy, silicone, or hot melt adhesive.

2) The slightly less easy method: drill a 7-64" hole through the bottom of the charge canister where one of the small pilot holes are. You can fish your e-match wire under the canister before it is screwed to the bulkhead. Seal with silly putty, silicone, or hot melt adhesive if the wires are not a tight fit through the hole.

This is a cleaner looking install, but takes more time and requires access to the underside of your bulkhead to remove the charge canister each flight.

Environmentally friendly note: making a tiny slice in the center of the cap makes it split in the middle and stay with the holder for removal after flight.





PXL_20210121_034830016.jpg
 
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Bowman

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Oh nice. Its always reassuring when two people reach the same solution.
I applaud re-use of what is otherwise consider trash but I cringe at the thought of littering the area (any area) with non-degradable litter.

Building on the original good idea; Why not score the flat surface of the cap so that it functions like a burst diaphragm? That would serve the purpose of retaining the charge while allowing the gas pressure to do its job and hopefully retain the HDPE cap for proper disposal.
I envision a "X" cut through the flat plastic top or most of the way, just enough to weaken it.
You could even market a stamp or die to be used with a hammer to do the cutting. Using a razor knife seems like a recipe for nasty cuts. Safety first :).

When it discharged the cap would likely remain screwed on and intact but the top would have three or four flaps from gas escaping.

Just an idea.
 

dhbarr

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Hmm, does anybody know if toothpaste caps are reasonably interchangeable?

Would be fairly straightforward to drill through the lid and seal in a kevlar tie thread to make sure I'm not littering.
 

kalsow

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Random thought... Drill a hole in the cap and cover it from the inside with electrical tape. The tape should burst before the cap pops off the threads.
 

Buckeye

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Coming Soon: Aluminum ejection charge wells with threaded ends for water bottle caps.

1.000" Diameter without the cap.

What gram sizes would you like to see? The one pictured is about 3g.


View attachment 447263
What form does the cap take when the deployment charge goes off? Does the whole thing blow off? Does the flat portion shear off? Does the entire cap fragment into a hundred bits of plastic shrapnel?
 

Landru

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The caps I have tested are mostly in one piece, with a tear around the hole for the igniter.

Figuring out a kevlar harness would be nice, or possibly scoring them may work.
 

cwbullet

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That is a nice design. You could probably print TPU caps that could kinder on cardboard tubing.
 

OverTheTop

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Building on the original good idea; Why not score the flat surface of the cap so that it functions like a burst diaphragm? That would serve the purpose of retaining the charge while allowing the gas pressure to do its job and hopefully retain the HDPE cap for proper disposal.
I envision a "X" cut through the flat plastic top or most of the way, just enough to weaken it.
Great minds think alike, or fools seldom differ? Scoring the caps with an X is exactly what I do, using a Dremel.
 

Landru

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I am going to try and cut an X for the e-match instead of drilling a hole. I think it will act as a stress concentrator to allow the cap to pouch instead of pop.

I *could* make aluminum caps with a cut out to use a cardboard burst diaphragm which would be biodegradable, though it would double the cost of the caps...
 

Landru

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They are now available for sale. I have the 3g finished, Feel free to order the 3g and put 6g in the comments and I will ship when available.

These ultralight 6061-T6 aluminum canisters are threaded to be sealed with standard low profile water bottle caps. (1.05" diameter, 1/4" high, 3 thread starts)

Each weighs in at a impressive 4.4grams empty, with an additional BP capacity of 3g sufficient for most 4" and 5" rockets.

These canisters (with cap) are 1.05" Diameter, and 0.453" high

The canisters have a threaded hole on the underside for a standard #6-32 screw for attaching to your bulkhead.

Each canister comes with one cap and stainless steel screw for mounting.

There are (2) ways of routing e-matches into the canisters:

For BOTH options, remove 75% of the e-match protector so the tip of the e-match is visible, but the solder connections are covered and prevented from shorting.

1) The easy way: Cut, drill or melt a small hole in your plastic cap. Feed the wire through the cap with the e-match on the inside. Add powder to the canister, and screw on the cap. If the wire hole was tight enough, you will not need anything additional to seal the hole.

If you are prepping ahead of time, you can seal the area where the match goes through the hole with epoxy, silicone, or hot melt adhesive.

2) The slightly less easy method: drill a 7-64" hole through the bottom of the charge canister where one of the small pilot holes are. You can fish your e-match wire under the canister before it is screwed to the bulkhead. Seal with silly putty, silicone, or hot melt adhesive if the wires are not a tight fit through the hole.

This is a cleaner looking install, but takes more time and requires access to the underside of your bulkhead to remove the charge canister each flight.

Environmentally friendly note: making a tiny slice in the center of the cap makes it split in the middle and stay with the holder for removal after flight.



PXL_20210121_034830016.jpg
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