Ejection Charge ??

Can I use 4f BP Substitute?



So many rockets, so little time, and money.

Yes but BP as more repeatable results, with Pyrodex as example you have to make sure the container is more tight

Will Pyrodex work with "finger tips"?


So many rockets, so little time, and money.

I haven't tried it, but my guess is "No".

Pyrodex requires containment, and latex glove fingertips will likely not provide the requisite confinement to get the desired gas generation.

However, if you used a container that was tightly packed then you should have the desired result.

As always, ground test to confirm the desired performance.

Greg

I've never used Pyrodex in a glove tip, but I have used it in copper cap cups. It works fine but you need to use quite a bit more than you would BP, and it needs to be tight.

I wonder if it's safe and if someone have try to mix Pyrodex with BP, I may give it a try on static test.. in my case I have to travel 1:30 hours to get BP, the same store can ship me Pyrodex by courier.

Area66 said:

I wonder if it's safe and if someone have try to mix Pyrodex with BP, I may give it a try on static test.. in my case I have to travel 1:30 hours to get BP, the same store can ship me Pyrodex by courier.

Click to expand...

Basic safety rule: Never mix any two powders regardless of type, brand, or source.


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I have had success with Pyrodex in centrifuge vials, contained with a strip of duct tape. It needs to be contained to give it a chance to fully combust.

I have used Red Dot, which is another smokeless powder like Pyrodex and much easier to get than BP.
As noted above, containment is key. When you ground test, be sure to use the exact same procedure each time. I use a PVC tube, stuff any extra space with foam and wrap over the ends with exactly 4 overlapping layers vinyl elect tape. If I used 3 it might be a very different effect. - much less expansion from incomplete burning - I've tried it multiple ways and consistency is important to get the right result.
Red Dot has three times the expansion by weight, so for 3 grams BP I would use 1 gram RedDot. The powder density is different so it's not 3:1 by volume . I calibrated my scoops to the weight.

Is there an advantage to pyrodex? Less residue?

No. The only advantage might be availability. Some find it challenging to obtain BP.

What about Tony A's surgical tubing technique? I think that would provide adequate compression.



Braden

I don't know Tony A or his technique, please share.


So many rockets, so little time, and money.

UPscaler said:

What about Tony A's surgical tubing technique? I think that would provide adequate compression.



Braden

Click to expand...

I have tested this, surgical tubing does not provide enough compression for Triple Se7en (FFFG). I've tested replacing the surgical tubing with vinyl "aquarium tubing", which does provide enough compression and will result in 100% combustion of the Triple Seven; it has excellent resistance to expansion, and will not balloon, even under a vacuum (excellent for high altitude flights); it is easy to work with and inexpensive.


A deployment charge, using the "Tfish technique", made from PVC tubing


The down side is the resulting pressure wave from the charge is quite sharp and is more akin to a detonation than a deflagration. I would only reccomend this technique for fiberglass airframes.


All the best, James

Ok next question.

I have a a can of FFFg BP or I can buy this (see picture below)



Which would you recommend? And at what substation rate or ratio?




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Area66 said:

I wonder if it's safe and if someone have try to mix Pyrodex with BP, I may give it a try on static test.. in my case I have to travel 1:30 hours to get BP, the same store can ship me Pyrodex by courier.

Click to expand...

The last time I looked at the MSDS for Pyrodex, IIRC it contained either potassium chlorate and/or potassium perchlorate. Either of those will react with the sulfur in BP. Mixing BP and Pyrodex would create an unstable and, IMHO, an unsafe composition.

Greg

Don't mix powders.

Hell, from reloading, I won't even mix batches of powder.


Later!

--Coop

I have no interest or desire to mix powders.

My questions is which powder to choose for ejection charges?

My choices are:

Real BP FFFg. ( 3 F)

Or

Substitute FFFFg (4 F)


And depending on which one I use how much should I use since the calculators appear to be based on Real BP 4 F.


Thanks.


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I haven't done a test, but my guess is that, from a pure performance standpoint, the FFF BP will perform consistently better.

The gas generation will be a bit slower than FFFF BP, but with ground testing you can get the proper amount dialed in.

That's the path I would take. YMMV.

Greg

The 3f BP would be my choice as well, over a BP substitute.


Later!

--Coop

Coop said:

The 3f BP would be my choice as well, over a BP substitute.


Later!

--Coop

Click to expand...

I agree with this. Substitute will work but you need to wrap it well. I add 25 % to pyrodex and 10% to 3F.

GregGleason said:

The last time I looked at the MSDS for Pyrodex, IIRC it contained either potassium chlorate and/or potassium perchlorate. Either of those will react with the sulfur in BP. Mixing BP and Pyrodex would create an unstable and, IMHO, an unsafe composition.

Greg

Click to expand...

hummmmmmm Pyrodex also contain Sulfur and I diasgree , potassium perchlorate can be used safely with sulfur, but potassium chlorate not, and Pyrodex contain no chlorate

Anyone willing to post a few detail pictures of how to make a finger tip charge. I have seen the finished product but not positive on how to make them. Think 3f and be specific about how to improve it for 3f.

Thank you for any help!


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Post 280-282

https://www.rocketryforum.com/showt...x-quot-build-starts-now!!&p=456930#post456930

The only disadvantage I've found with FFFg BP over FFFFg BP is that the nomex burritos seem to get more burn holes faster. I attribute it to the larger grains burning longer and coming in contact with the burrito.

When using BP, I have use a piece of duct tape as a container. Tear off a 4" piece. Lay the match on the tape with the head in the center and the wire down the long centerline of tape. Crease the tape slightly, pour the BP over the match head and fold the tape over to contain everything.

Like any ejection charge, ground test first.

I have a bunch of used latex gloves that I cut the fingers off and some super small zip ties, so far it seems to be the easiest way to go. You can also write on the latex with a sharpie how many grams it is so you can keep it all strait.


TA

thobin said:

I have a bunch of used latex gloves that I cut the fingers off and some super small zip ties, so far it seems to be the easiest way to go. You can also write on the latex with a sharpie how many grams it is so you can keep it all strait.


TA

Click to expand...

I might have to try that, but duct tape is very easy and much cheaper then zip ties.

I have used tape too, it seems to pull out and spill more than the zip ties do. Maybe I just suck at the tape thing. You can get a pack of 100 four inch ties from Harbor Freight for couple of bucks.


TA