Centrifuge tubes & Surgical tube

[T-Rex]

I was looking on the web at the different centrifuge tubes available. There seems to be a multitude of sizes (and material). I assume that we would use a softer material such as polyethylene, am confused on size. What size do y'all use for your deployment charges? I would not want to purchase 500 of the wrong (ie useless) tubes.

For those that use surgical tube, where do you get your tubing? What is a good price? I am just guessing here, but you use the 1/4" ID tubing?

Thanx in advance.
Terry

[DM1975]

I just buy the standard sized ones from Aerocon but it also depends on the rocket size. That will be good for most though. I don't think material matters as much with black powder as it ignites slow enough that it just blows the cap off. No need for heavy containment.

[cwbullet]

I use tape in thin walled rockets to avoid damaging the walls. It is probably not needed.

[DM1975]

I use tape in thin walled rockets to avoid damaging the walls. It is probably not needed.

I blew a hole in the side of a 4" glassed phenolic tube once with a cardboard tube/pyrodex charge once in a ground test. Now days all of my charges have the weak spot pointed up through the tube and 4f black powder is used instead of pyrodex. I have used this in a couple different modified dual deployment Estes rockets withou a blowout yet.

[AlphaHybrids]

I use surgical tube because it is field size-able. I use 1/2" OD x 1/16" wall and 3/4" OD x 1/16 wall depending on the charge size. Generally I keep the charges under 3" total length, including double zip ties on the ends. I think I bought 10 feet of each for under $10 at a local military surplus store. Ace Hardware also carries it.

Edward

[awseiger]

I use the Centrifuge tubes... They're graduated in ml, which happens to be pretty close to a 1 to 1 relationship for grams using ffffg. No need to measure!

Of course, you have to make these up before, which can be a pain.

[cwbullet]

I use the Centrifuge tubes... They're graduated in ml, which happens to be pretty close to a 1 to 1 relationship for grams using ffffg. No need to measure!

Of course, you have to make these up before, which can be a pain.

True, but remember to subtract the match.

[T-Rex]

I use surgical tube because it is field size-able. I use 1/2" OD x 1/16" wall and 3/4" OD x 1/16 wall depending on the charge size. Generally I keep the charges under 3" total length, including double zip ties on the ends. I think I bought 10 feet of each for under $10 at a local military surplus store. Ace Hardware also carries it.

Edward

Thanx Edward! I'll slip down to the local Ace and see what they have.

I use the Centrifuge tubes... They're graduated in ml, which happens to be pretty close to a 1 to 1 relationship for grams using ffffg. No need to measure!

Of course, you have to make these up before, which can be a pain.

Thanx Alex! That's the answer I was looking for. I have 4f Pyrodex and 3f BP to work with. Looks like I'll be ordering a hand full of 2ml tubes and see how it works for me. I just didn't know if I should get big ones or little ones.

[cwbullet]

They also have them at McMaster Car. http://www.mcmaster.com/#latex-tubing/=ip0q29

[AlphaHybrids]

Instead of concentrating on getting 4.2 grams or 2.3 grams of black powder for ejection charges I decided I'd use an arbitrary unit of volume for my charges. I have these small red caps from www.caplugs.com. I chose something from this series (http://www.caplugs.com/productdetail...mno=RCL+SERIES). I measured it once and it was something like .8ish grams blackpowder. But, I don't use that, instead I use number of caps. You never need a scale, and never half to worry about trying to measure a cap. When you ground test you just start low and then work your way up. After 8 years I have a pretty good estimation of how many caps it will take. It takes me at most 3 ground tests now. And for a backup charge I usually just add another couple caps. I've found this to be a much more reliable method for myself, and a few of my fellow rocketeers have used the same method with other volume measures.

But, whichever way you go, always be consistent and ground test.

Edward

[cwbullet]

I have these small red caps from www.caplugs.com. I chose something from this series (http://www.caplugs.com/productdetail...mno=RCL+SERIES). I measured it once and it was something like .8ish grams blackpowder. But, I don't use that, instead I use number of caps. You never need a scale, and never half to worry about trying to measure a cap.

Those would also work. Great find.

[T-Rex]

you are still measuring, just using volume instead of mass. I can see where that would work as well. I just need to come up with a container to make my charges with.

[bobkrech]

Thanx Edward! I'll slip down to the local Ace and see what they have.



Thanx Alex! That's the answer I was looking for. I have 4f Pyrodex and 3f BP to work with. Looks like I'll be ordering a hand full of 2ml tubes and see how it works for me. I just didn't know if I should get big ones or little ones.

Two items to remember when you use Pyrodex(R) in place of BP.
1. Completly fill the void above the Pyrodex(R) charge with wadding so the charge maintains contact with the e-match.
2. Wrap a couple of layers of electric tape arount the tube to slow down the opening of the tube.

Pyrodex(R) burns much slower than BP and has a higher ignition threshold. If it is not confined, the complete charge will not burn and you will get less gas generation than you expect.

Bob

[T-Rex]

Thanx Bob. I originally purchased the Pyrodex because I couldn't get BP locally. While on my trip this summer I stopped in a Bass Pro Shop and was able to get 3F BP. I'm thinking the BP will go in my rockets. The Pyrodex will be used up with a lot of 'ground testing' (i.e. annoying the neighbors).
Terry

[AlphaHybrids]

A very wise flier once told me "fly what you test". I'd suggest you do your ground testing with what you are going to fly.

Edward

[T-Rex]

I will be ground testing with what I fly. But I will also be doing some further 'testing' with the pyrodex, just to make it go away and annoy my neighbors, who are at this very moment annoying me with their back yard firing range.......