Modular Ejection Charge Wells

[danielhv]

I know I'm not doing anything ground-breaking here... just wanted feedback on my idea for my little 4" dink.

I'm not the biggest fan of the glove tip method. I don't know why, I just always worry about getting them packed tight enough, etc. I'd rather just run charge wells on my next build... but I also don't want to mess with BP at a field. SO, I did my own variation of the charge wells from LOC and came up with this. (radius is for the 4" dink AV bay). The idea is I print several of the "charge modules" and those get prepped and packed before the launch. Go to the launch, screw the modules into the base which is epoxied to the AV bay, hook the wires up, and send it. After recovery, unscrew the old, screw in the new, rinse and repeat.

Thoughts?

 

[secretagent]

It’s a good idea IMO. I 3/4” PVC caps that I screw on so that they are easily replaceable, but this would allow for a little easier packing and changing.

 

[cwbullet]

I like them. Any chance you might share the STL files?

 

[cerving]

So what would really be cool would be if you could put contacts in them and the socket, so you could pre-fill the charges and swap them out like screwing in a light bulb. Obviously filled charges would need to be stored in an ammo box or similar container...

 

[danielhv]

I like them. Any chance you might share the STL files?

Not quite sure yet - still tinkering with them!

 

[danielhv]

So what would really be cool would be if you could put contacts in them and the socket, so you could pre-fill the charges and swap them out like screwing in a light bulb. Obviously filled charges would need to be stored in an ammo box or similar container...

That would be slick, just not sure what would produce the ignition source inside the module... getting current to it wouldn't be an issue I don't think.

 

[cwbullet]

Not quite sure yet - still tinkering with them!

I can respect that. thanks

 

[darrenf]

These are amazing. I think you would have no problem selling these if you chose to.

 

[jhill9693]

I’ve done something similar using the nozzle end of any Estes 18mm motor. The orange thick cardboard spacer used in D-to-E engine mounts makes a perfect charge well.

Chop off about 3/4” of the nozzle end of the spent motor, clean out the inside with a Dremel reamer bit, and run the ematch wire through the clay nozzle hole. Fill with BP and close off with mounting putty.

 

[anbhtblr]

The screw-in replacable wells are really neat, but:

I am a big fan of the glove-tip method - never had a failure. I make up many more than I'll need for each launch and they are easy to insert during prep.

To make it more convenient I printed (pla/pla+) the wells/holders in the picture.
The features are:
Mounting screws also provide electrical paths out of ebay.
Short ematch wires from the protruding thread/washer/nut assembly go through the slot on top of the well to the glove-tip inside.
The top on the well reduces the hot material projection into the laundry.
The side openings reduce the hot material projection into the laundry.
I slap a single layer of painter's tape around the opening to capture the glove-tip and to stablize the wires.

The picture also shows walls I've printed to prevent a direct blast onto the u-bolt and shackle.

The ebay bulkhead in the picture has flow at least 6 times and the wells/holders have held up very well. I don't anticipate replacing anytime soon.

Before I started 3D printing I would assemble simmilar wells/holders from PVC components.

 

[danielhv]

Did some testing yesterday... Each well holds a little over 2.5 grams of BP. Filled them both up and set them off. Gray is PLA, Black is PETG. Saw no difference. I don't love how much BP gets thrown forward and then ignited, but I also don't know if that's normal behavior for charge wells.



I did try to keep the ematch in the top half of the charge.

 

[danielhv]

 

[danielhv]

And the aftermath. Cups look unphased by the charge.

 

[scschulte]

VERY interesting! One question: How long can the FFFF Black Powder remain in the charge cups before using it? If they are covered with masking tape (let's say 1.5 grams of FFFF Black Powder) - can these be used after 3 months, 6 months or longer? (Not stored in a plastic bag - I'm guessing that might extend the life). Thanks anyone for comments on the life of FFFF Black Powder if stored in a charge cup (but not inside a plastic or glass jar). Steve on Sunday 12 May 2024

 

[secretagent]

VERY interesting! One question: How long can the FFFF Black Powder remain in the charge cups before using it? If they are covered with masking tape (let's say 1.5 grams of FFFF Black Powder) - can these be used after 3 months, 6 months or longer? (Not stored in a plastic bag - I'm guessing that might extend the life). Thanks anyone for comments on the life of FFFF Black Powder if stored in a charge cup (but not inside a plastic or glass jar). Steve on Sunday 12 May 2024

I’ve kept powder in shotgun shell and PVC charge wells secured with blue tape for more than four months, so I assume 3 to 6 should be no issue. YMMV.

 

[Steve Shannon]

VERY interesting! One question: How long can the FFFF Black Powder remain in the charge cups before using it? If they are covered with masking tape (let's say 1.5 grams of FFFF Black Powder) - can these be used after 3 months, 6 months or longer? (Not stored in a plastic bag - I'm guessing that might extend the life). Thanks anyone for comments on the life of FFFF Black Powder if stored in a charge cup (but not inside a plastic or glass jar). Steve on Sunday 12 May 2024

It really depends on your circumstances. I just recently had a guy fly a rocket with charges he had made up last year. Wherever he stored the rocket for the winter didn’t agree with his black powder. He had redundant charges and neither fired. The powder charges had caked into a gummy mess.
I prefer to keep my powder in my sealed powder can until I use it.

 

[scschulte]

I’ve kept powder in shotgun shell and PVC charge wells secured with blue tape for more than four months, so I assume 3 to 6 should be no issue. YMMV.

Thanks and I believe the powder would be fine - but now here's an additional condition: Let's say you prepared an AvBay with drogue and main parachute charges with igniters inserted at the pad but the weather suddenly changes and you pack-up and leave. AvBay is in an explosion-proof box, but it's not airtight. 6 months later: The 4F BP may be fine but what about the igniters? Are the igniters degraded somehow being immersed in BP for 6 months? YES these are theoretical, not actual cases -- but I did have an AvBay fully prepped in just such an explosion proof box for over a month and it worked 100% OK. Just wondering if others have had any similar real-life experiences. So to summarize: (i)Is the powder going to degrade in 6 months (maybe and I see Steve Shannon has replied with a case where it did degrade) and (ii)Will the igniter degrade being in intimate contact with about 2 grams of BP for 6 months? Appreciate any real-life experiences here as well as any comments or theories. Thanks! Steve on 12 May 2024

 

[scschulte]

It really depends on your circumstances. I just recently had a guy fly a rocket with charges he had made up last year. Wherever he stored the rocket for the winter didn’t agree with his black powder. He had redundant charges and neither fired. The powder charges had caked into a gummy mess.
I prefer to keep my powder in my sealed powder can until I use it.

Thanks for your reply Steve and trust all is well! Please see my reply to "secretagent" above -- just trying to understand this better. Sunday 12 May 2024

 

[secretagent]

Will the igniter degrade being in intimate contact with about 2 grams of BP for 6 months?

In my case it was Chris’ Rocketry Firewire Electric Matches in 2-3g of homemade FFFF black powder; multiple times of 2 months, sometimes nearly 6. As @Steve Shannon pointed out though (and per my YMMV note), I live in Arizona and keep them outside in what is often a furnace of a garage. Moisture is probably a non-issue for me in a way that would be completely untrue in other parts of the country.

 

[Steve Shannon]

Thanks for your reply Steve and trust all is well! Please see my reply to "secretagent" above -- just trying to understand this better. Sunday 12 May 2024

Hi Steve,
All is well and I wish the same for you, also. Comeback to Montana and fly with us. Bring your wife!


I doubt that under usual circumstances BP in these charge wells will degrade over time. After all, the powder in single use motors lasts years and years.
But I do share the concern about the powder being in intimate contact with the electric match head for long periods of time. Salt plus moisture plus electric components over time is a combination that might cause problems.
My friend’s powder charges that had the bad results at a recent launch were an extremely unusual occurrence and I don’t know exactly what happened there, but the fact that it did happen proves that it can happen. But again, I don’t know what odd thing happened that caused the powder to form that gooey mess. I could believe that a moist parachute packed in the same compartment could have caused it or even cat or rodent urine if it was somehow exposed. I just don’t know but it’s not something I’ve ever seen before.

To the OP: those charge canisters are very cool. Nice job.

 

[Capt. Eric]

Always keep your powder dry, so to speak, and you should be fine. Not just away from water, but humidity too.

 

[Rschub]

That slo mo where the black powder was ejected in a line of 6-10 inches before igniting was quite educational....
I think I will use charge cannons the length of the av bay for my next one, even though the modified glove tip method I am using has worked perfectly for me.