Charge Well Design

Handeman said:

That's pretty much exactly how I do it too. The 3/4" caps leave a 2g charge about 1/2 to 1/4 as deep as it it wide. I've never had an issue with the powder all burning, but I think the dog barf and tight masking tape help that the most.

Thanks...

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Yeah,,
I'm big on the tight taping it up,,
but I also like to stay with 1/2" to make the powder deeper..
I don't know if I'm right,,
and this may be a bit anal,,
but I just put the ematch a little bit into the powder,,
so the powder lights from the top down,,,
I think that ensures a complete / thorough burn....

Teddy

Oh yeah,,
I had heard a long time ago about plastic centrifuge viles throwing shrapnel around the airframe on ignition....
Is there anything too this ???
This is why I've always avoided using them in this manor,,,
but my next build will require their use....

Teddy

Ted,

I always bury my e-match at the bottom of the well, and I have never gotten anything other than a complete burn. I think that as long as the powder is packed tightly, it doesn't matter where it lights from.

webtech said:

I have used dog house wells in the past, and they work very well.

but lately I have switch over to plastic glove tips with tape, and I am going to be using duck tape to make a BP Burrito.
So I am going to quit using wells.

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Bat-mite said:

Because ... ?

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Because it tightly confines the powder and yields total combustion, the powder won't fall out, it is easy, it doesn't direct hot and/or energetic burning BP right at my 'chutes, it doesn't require extra construction, can be used on any size rocket and it works WELL.

I don't use charge wells and I don't use switches. Ask me how many recovery failures are due to my K.I.S.S. techniques.

Bat-mite said:

Ted,

I always bury my e-match at the bottom of the well, and I have never gotten anything other than a complete burn. I think that as long as the powder is packed tightly, it doesn't matter where it lights from.

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Yeah,,
I guess packing tightly is the main thing...
Try to contain it until it all has a chance to ignite....

Teddy

llickteig1 said:

Because it tightly confines the powder and yields total combustion, the powder won't fall out, it is easy, it doesn't direct hot and/or energetic burning BP right at my 'chutes, it doesn't require extra construction, can be used on any size rocket and it works WELL.

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Thanks for the information.

llickteig1 said:

I don't use charge wells and I don't use switches. Ask me how many recovery failures are due to my K.I.S.S. techniques.

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I dare not. :grin:

onebadhawk said:

Yeah,,
I had heard a long time ago about plastic centrifuge viles throwing shrapnel around the airframe on ignition....
Is there anything too this ???
This is why I've always avoided using them in this manor,,,
but my next build will require their use....
Teddy

Click to expand...

I use centrifuge vials on all my flights and have never had anything but the caps blow off. I drill a tiny hole just big enough for the J-Tek wires, add black powder, insert a foam earplug, and close the cap. I bought both the vials and plugs in mass quantities from eBay years ago and still have enough to last many more years.

I like using the "Paint by Number" paint cups. Many crafts stores carry them.
https://www.amazon.com/dp/B005FPDC3M/?tag=skimlinks_replacement-20

Dugway said:

I use centrifuge vials on all my flights and have never had anything but the caps blow off. I drill a tiny hole just big enough for the J-Tek wires, add black powder, insert a foam earplug, and close the cap. I bought both the vials and plugs in mass quantities from eBay years ago and still have enough to last many more years.

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OK,,
Very cool,,
Thanks man,,
And you don't notice your Nomex blanket getting torn up
more then on a rocket that you use charge wells in ????

No matter,, to be honest,, my next build leaves me no choice,, I'm going to try them....

Teddy

llickteig1 said:

Because it tightly confines the powder and yields total combustion, the powder won't fall out, it is easy, it doesn't direct hot and/or energetic burning BP right at my 'chutes, it doesn't require extra construction, can be used on any size rocket and it works WELL.

I don't use charge wells and I don't use switches. Ask me how many recovery failures are due to my K.I.S.S. techniques.

Click to expand...

Did you ever use the wells? If you did, did you notice if you needed more powder in the duct tape burritos then in the wells?

I used the duct tape burritos when I first started doing DD and switched to the wells. It seemed that I could use about 10% less powder when packed and tightly taped in the well vs. in a duct tape burrito.

BTW, I'm considering going back to the duct tape on smaller rockets, just for the weight advantages.

DavieRockets said:

Hi Randy,

Back in 2011 I posted some info on making charge cups out of CPVC, then sliding pre-filled centrifuge tubes into them at the field. The thing I have really come to like with this system is that all black powder measuring can be done in advance of the launch instead of fiddling with this at the field.

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+1. I can whip up a handful of centrifuge charges in one sitting in the comfort of home.

Why then do you need the charge cups to hold the centrifuge tubes? I just use the centrifuge vials, tape them to the bulkhead, and kinda point them forward as best as I can. I am sure they fall over sideways after packing the laundry. Yeah, Yeah, I have heard all the stories about blowing holes through the airframe with a centrifuge tube pointed sideways. I never experienced this (and I use a lot of wimpy 2.6" cardboard airframes), and I think the problem is an incorrectly-sized charge, not the container.

Handeman said:

It seemed that I could use about 10% less powder when packed and tightly taped in the well vs. in a duct tape burrito.

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10% on a typical 1.0-2.0 gram charge is hardly noticeable. I would need more justification than that!

I use the plastic caps that AT puts the ejection charge in. The are free with purchase of motor and I haven't melted one yet. I use this one in a 3" rocket.

sl98 said:

I use the plastic caps that AT puts the ejection charge in. The are free with purchase of motor and I haven't melted one yet. I use this one in a 3" rocket.

View attachment 280874

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Good idea!

Bat-mite said:

Because ... ?

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With the charge wells,, the force of the pop of the BP is direct directly up, which on the payload main side is directed in to the chute..
No goods there. I have blown a hole in a chute before.. it was my dad's too

plus and I am lazy and cheap, don't have to buy wells.

I can prep the charges and extra charges at home, then screw in the wires into the terminal blocks at the field .. make pre prepping ahold lot easier.

It has been working for me the last few years..

Handeman said:

Did you ever use the wells? If you did, did you notice if you needed more powder in the duct tape burritos then in the wells?

I used the duct tape burritos when I first started doing DD and switched to the wells. It seemed that I could use about 10% less powder when packed and tightly taped in the well vs. in a duct tape burrito.

BTW, I'm considering going back to the duct tape on smaller rockets, just for the weight advantages.

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I have never used charge wells so I can't comment on any possible increase in powder requirements. My preferred method is a glove finger wrapped tightly with tape or surgical tubing charges. The latter more lately because they are so easy to build ahead of time.

Buckeye said:

10% on a typical 1.0-2.0 gram charge is hardly noticeable. I would need more justification than that!

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Understood. I can't really give you any justification. The difference between the same charges in duct tape vs. a well was definitely noticeable to me in my rocket, YMMV. I was using 2.25g in a duct tape burrito for the main of a rocket and switched to wells. The ejection seemed to be much stronger when using the 2.25g in the well so I reduced it to 2g. Was the 2g in the well equal to the 2.25g in the duct tape? I don't have any definitive evidence for that. I just happened to be as satisfied with the 2g charge in the well as I had been with the 2.25g charge in the duct tape.

I use surgical tubing charges. Wells are just extra weight. Tape the tubes to the bulkhead and then pack with some dog barf and then nomex chute protector. I've used them exclusively. The BP is in contact with the e-match and won't move around.

Edward

A like the charge wells that Public Missiles Limited sells. The base may be a little bit too large, but I like the way e-matches are threaded into the bottom.

Put me down in the temporary charge well category. Centrifuge tubes, cardboard tubes, glove tips have all worked equally well for me from 29mm rockets up to and including my 4" wildman and charges up to 4g. Sometimes I tape them horizontally to bulkhead (or hot glue in place), sometimes I tape them to the kevlar shock cord, sometimes I just let them dangle by their wire if the laundry is tight enough. Never had a problem or really noticed any difference in separation strength as long as it was ground tested and sized appropriately.

Randy,
At Dog House Rocketry we do not use standard PVC so cannot speak to the long term properties. We use a much higher maximum temperature plastic, which unfortunately costs more. Each of our offered Charge Wells designs were ground tested 20-25 times at the rated capacity with any excess volume packed with recovery wadding and covered with muffler tape. Other than very dirty there was no noticeable degradation. Obviously, this does not mean that they will not fail, but that I have confidence that the product will provide good and safe service.