Aquarium Tubing BP charge

[Fdog]

I've been using the surgical tubing BP charges authored by Tony (tfish). I like them because they are easy to make in advance, easy to install in the field, and have offered consistent performance.

However.

Surgical tubing isn't cheap. If you buy it online in 100' lots you can get it down to about $0.60 per foot. At Lowes' it is about $17 for 10 feet. Ouch. Plus, the tiny little zipties are a time consumer, even with a special ziptie tool.

Sooo...I've been using hot glue instead of zipties...wow. Cuts the assembly time in half.

And then it hit me: aquarium (tygon) tubing in the same size, 1/4" ID x 3/8" OD is only $0.16 per foot!

So I built one and fired it. The report is WAY sharper and louder than the surgical tubing, so I'd surmise the Tygon-tubing charge has a sharper and higher pressure wave as the tubing first contains the explosion, then splits.

I haven't tried this for a ground test yet, I guess I'm scared of the impact the pressure might have. Anyone else tried this? I'm not necessarily looking for theories and speculation, I can speculate, too. Just those with experience.

Next up is a series of ground tests starting with a charge about 1/4 of the size that is known to work with surgical tubing. I'll see what gives (if anything).


On other notes, this sure seems like a great way to use Pyrodex, it contains the heck out of the powder. And my upcoming projects are anticipated to be somewhere around 20,000', where I was becoming worried about "ballooning" of the surgical tubing, and thus incomplete combustion, and this would certainly fix that - I pumped some Tygon up to ~30 psi and it didn't expand at all.


All the best, James

 

[troj]

Yeah, aquarium tubing is a lot stronger than surgical tubing, so it doesn't surprise me that when it lets go, it's with more of a bang, due to a higher pressure at that point.

Seems like a great way to contain Pyrodex!

-Kevin

 

[CCotner]

Watching this thread closely. Keep us updated!

 

[jderimig]

Seems very similar to a fire cracker. What about using a drinking straw?

 

[jsargevt]

What about using a drinking straw?

The big green ones from Starbucks are perfect for containing your charges. A little hot glue and they work quite well.

I am curious to know if this helps make pyrodex work in a "more" reliable fashion. Obtaining BP can be a big hassle and then there is the grey area around the legality of purchasing BP for rocket ejection charges.

 

[cerving]

I use Triple Seven, In-n-Out straws cut to size, Quest Q2G2's, and I just tape the heck out of them with masking tape until they're reasonably hard. They've worked fine in every rocket I've tried them in from 1.35" to 3" diameter. I wonder if containing the powder too tightly may be as bad as containing it too loosely; too much pressure released too quickly and you might blow up your body tube instead of simply pressurizing it. I'll defer that to someone else to test...

The big green ones from Starbucks are perfect for containing your charges. A little hot glue and they work quite well.

I am curious to know if this helps make pyrodex work in a "more" reliable fashion. Obtaining BP can be a big hassle and then there is the grey area around the legality of purchasing BP for rocket ejection charges.

 

[awseiger]

I wish I could find the picture. Last time I tried doing something like this, I lost a fist-sized chunk of paper airframe. Mind you, I was using Pyrodex.

Proceed with caution!!! Try it in a hunk of airframe you don't care about too much first.

 

[CarVac]

I wish I could find the picture. Last time I tried doing something like this, I lost a fist-sized chunk of paper airframe. Mind you, I was using Pyrodex.

Proceed with caution!!! Try it in a hunk of airframe you don't care about too much first.

Sounds like something good, then, for using at extreme altitudes.

And in Bare Necessities, it'll be surrounded by aluminum, so it's probably not going to punch a hole in the airframe...

 

[awseiger]

Sounds like something good, then, for using at extreme altitudes.

And in Bare Necessities, it'll be surrounded by aluminum, so it's probably not going to punch a hole in the airframe...

To be fair, I used 1/2 Inch CPVC capped with hot glue, filled with 0.25 grams of pyrodex RS. It was incredibly loud....

CPVC is near the same kind of pressure loading abilities as the aquarium tubing, as far as I could tell. Possibly even better, as it can balloon.

It would be perfect for high altitude deployment. I have no reason to think it would not work, it's essentially a firecracker...

 

[billspad]

CPVC is near the same kind of pressure loading abilities as the aquarium tubing, as far as I could tell. Possibly even better, as it can balloon.

1/2" CPVC pipe has a burst pressure of close to 2000 psi and a working pressure of around 200 psi. I think you'll find aquarium tubing is significantly less than that unless you're talking about the New England Aquarium.

 

[AlphaHybrids]

So - your main complaint with the surgical tubing is the price? Try a COOP or other Ranch Feed Store. I get 1/2 x 1/16" wall for about a quarter a foot, and 1/2 x 1/8 wall for .40 cents.

But, even if you had to pay $1.70 a foot at Lowes, and you used 3" each time, that is 42.5 cents each, or 85 cents a flight for dual deployment. Not even the cost of an e-match. Add in four zip ties for a dime each and your cost skyrockets to 1.25 for recovery. E-matches are generally a dollar each, so you are looking at $3.25. $3.25 and you don't have to have a hot glue gun and electricity, and you can easily make them in the field if you need to adjust them.

Seems like a lot of trouble to save a few pennies compared to the cost of the entire rocket.

Edward

 

[CCotner]

I'm interested in energetic methods for high altitude. Our charges will go off in a ground-pressure environment, so sealing isn't critical, but redundancy is nice, and if we have the charges sealed in tygon or CPVC tubing, and that inside the sealed deployment bay, well, then... =)

 

[Kehoes23]

If you really want to save money, us the tube that protects the igniter for the reload, cut the tube in 1" sections, hot glue or use electrical tape to secure the Quest igniter then add BP then some wadding and masking tape on top.
A 1" pice will hold about .75 grams of BP.

 

[grouch]

I wish I could find the picture. Last time I tried doing something like this, I lost a fist-sized chunk of paper airframe. Mind you, I was using Pyrodex.

Proceed with caution!!! Try it in a hunk of airframe you don't care about too much first.

I want to go this direction with my Nuke but I am afraid that I might blow the tube as well. I am thinking about gluing a section of BlueTube coupler where the charge will be hanging out. That should keep from popping a body tube for sure.

 

[awseiger]

I want to go this direction with my Nuke but I am afraid that I might blow the tube as well. I am thinking about gluing a section of BlueTube coupler where the charge will be hanging out. That should keep from popping a body tube for sure.

You could also contain the charge loosely in a blast cap or something metallic. Kind of like a charge well. That way the "blast" only goes up, not outward to the side of the body tube.

 

[Handeman]

You could also contain the charge loosely in a blast cap or something metallic. Kind of like a charge well. That way the "blast" only goes up, not outward to the side of the body tube.

That is what I recommend. A PVC or copper pipe cap will work fine attached to the end of the av-bay. If you really want the charge away from the bay, and you are using BP, why bother with the tube? Just lay the match on a 4" piece of duct tape with the head in the middle and the wire along the lengthwise center. Fold the tape slightly around the wire and pour the powder over the match head. Finish folding the tape to seal the powder and match head in and put it anywhere you want it. It won't blow a tube out unless you really over do the charge amount.

 

[GregGleason]

This is an interesting thing.

As I have tried to visualize what is occurring, it reminds that the BP used for DD is primarily used as a rapid, gas generator, to pressurize to airframe to separate components. If the pressurization occurs too quickly, the internal pressure is localized and can rupture the airframe at that point.

Greg

 

[CarVac]

That is what I recommend. A PVC or copper pipe cap will work fine attached to the end of the av-bay. If you really want the charge away from the bay, and you are using BP, why bother with the tube? Just lay the match on a 4" piece of duct tape with the head in the middle and the wire along the lengthwise center. Fold the tape slightly around the wire and pour the powder over the match head. Finish folding the tape to seal the powder and match head in and put it anywhere you want it. It won't blow a tube out unless you really over do the charge amount.

The tube is for containment at high altitude, not for just getting it away from the av-bay.

 

[Handeman]

The tube is for containment at high altitude, not for just getting it away from the av-bay.

You have to forgive me, my East Coast is showing again. With our low waivers around here, most < 15K, we don't really have to worry about that.

 

[Area66]

I try the aquarium tube 1/4" at the end of a motor installed in an Arreaux to see if the Aerotech mess system work, I use 0.5 ml of Pyrotex P ( equivalent to .5 g of BP ) and I have a nice ejection on a static ground test

here a pic of the fired one, only the masking tape wad tear, and with Pyrotex , it was very tight

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