Some BP Rocket Questions

[shockie]

My 1st question has to do with the 5/16" spoolette/rocket tubes.

will the RED 1/4" bottle rocket tube fit inside these 5/16" tubes?

what are the wall thicknesses of both the 5/15" and the 1/4" ?

does anybody make NEPT 1/4" tubes. It seems all I can find are spiral wound and I really need convolute wound.

 

my 2nd question has to do with some custom tooling....

 

Who in today's Pyrotech world does custom tooling? If it worth approaching any of the people/companies that presently sell tooling? Or would be as expensive to just give my spec to a machine shop locally, and show them some web pages so they know what I want.

 

I'm assuming a non-sparking 304/304L......can anybody provide me any specifics?

https://www.cortemgroup.com/en/about-ex/technical-articles/use-stainless-steel-explosion-proof-equipment

 

my 3rd question concerns this article:

 

https://www.skylighter.com/blogs/how-to-make-fireworks/rocket-nozzle-mix

 

I understand the why and use of grog.......but why exactly do I want wax in a nozzle that is going to be exposed to 2000F+ temperatures. How does that help with nozzle throat erosion? or help with the mechanical bond required from the pressed clay into the paper body tube.

 

I look forward to hearing what the members here have to say.

 

TIA

Edited January 27, 2021 by shockie

[justvisiting]

Caleb at Woodysrocks.com does custom work for a few of us but he's got a bum arm right now. Worth checking with him though.

 

Wax is used pretty commonly in nozzle mixes, and doesn't melt out or cause blowouts either. I've used that nozzle comp mentioned above, and it was good. Nowadays a lot of us use Dr. Elseys Precious Cat Litter (blue bag), dusted with a bit of graphite to help with sticking to the spindle.

 

When I was able to get 1/4" ID NEPT tubes, they were expensive and pre-cut. One time I was able to get full length (11" long) tubes, but the quality was so bad they were unusable and I sent them back. A 5/16" ID rocket is a lot easier to load than the 1/4" for sure I sold the 1/4" bottle rocket tooling due to the tube issue. I would think gummed tape would make good bottle rocket tubes.

[Carbon796]

303 SS is perfectly acceptable also. With the added advantage, that it machines a little nicer.

 

Tube specs, will vary depending on where you source your tubes from. Pyro direct and Precocious, both carry 1/4" red tubes, but the specs are different.

Edited January 28, 2021 by Carbon796

[shockie]

303 SS is perfectly acceptable also. With the added advantage, that it machines a little nicer.

 

Tube specs, will vary depending on where you source your tubes from. Pyro direct and Precocious, both carry 1/4" red tubes, but the specs are different.

I wasn't aware of Precocious and they list their ID/OD so I emailed Pyrodirect for their 1/4" spces....they seem to have some red kraft 1/4" that look convolute wound, unfortunately red kraft is not going to be as strong as plain virgin brown kraft paper.

 

Caleb at Woodysrocks.com does custom work for a few of us but he's got a bum arm right now. Worth checking with him though.

 

Wax is used pretty commonly in nozzle mixes, and doesn't melt out or cause blowouts either. I've used that nozzle comp mentioned above, and it was good. Nowadays a lot of us use Dr. Elseys Precious Cat Litter (blue bag), dusted with a bit of graphite to help with sticking to the spindle.

 

When I was able to get 1/4" ID NEPT tubes, they were expensive and pre-cut. One time I was able to get full length (11" long) tubes, but the quality was so bad they were unusable and I sent them back. A 5/16" ID rocket is a lot easier to load than the 1/4" for sure I sold the 1/4" bottle rocket tooling due to the tube issue. I would think gummed tape would make good bottle rocket tubes.

the Dr. Elseys Precious Cat litter is 100% Sodium Bentonite clay.

 

Sodium Bentonite vs Calcium Bentonite: What’s the difference?

There are two forms of Bentonite Clay – Sodium Bentonite, and Calcium Bentonite.

Both are predominately made up of crystalline clay minerals (Alumino-silicate) as well as either Sodium or Calcium.

It is therefore the Sodium or Calcium component that give the 2 Bentonite Clays very different properties.

a good R&D project would be to press both types into nozzles and see which one resists erosion better.

here's what the skylighter article says the wax does:

"Some folks expect their nozzle apertures to close a bit with the clay's expansion. So, right before flight, they open the hole up to the correct diameter with a hand-twisted drill bit. Wax makes the clay much less prone to this problem."

I totally don't understand this . It seems to me if you press a dry clay nozzle at 10K psi, it's not going to swell or expand afterwards. Am I wrong on this?

are there any suppiers today that offer convolute wound NEPT in 1/4" ID?

Edited January 28, 2021 by shockie

[mabuse00]

 

but why exactly do I want wax in a nozzle that is going to be exposed to 2000F+ temperatures.

You don't.

But wax makes the mixture more convenient to process, more granule like, and less dusty.

Also, and I'm not sure about this, the nozzle might be less effected by moisture.

 

 

How does that help with nozzle throat erosion?

The question is, does it hurt?

All I can say from my experience is, once grog is in there, there is no more ore very little erosion, even with 10% wax content.

 

 

Concerning grog, try to get very fine stuff, mine is flour-like. It will be a little more gently towards your tooling, the scratches will be less deep.

 

 

 

 

I totally don't understand this . It seems to me if you press a dry clay nozzle at 10K psi, it's not going to swell or expand afterwards. Am I wrong on this?

Depends on where you live. Betonite will eat moisture and swell, that's why it's used for cat litter. As I wrote above, I'm not sure this really works against moisture but it certainly wont have a negative effect in this regard.

Edited January 28, 2021 by mabuse00

[Carbon796]

Also look at the length, PD's are longer.

[justvisiting]

I didn't answer about the function of the wax in nozzle mix because I don't know.

 

I know there are different kinds of bentonite, and different bentonites within kinds, as well. Dr. Elseys is a sodium bentonite, yes. But it's a particular bentonite. The suggestion to use it was given by Edwin Brown, the late GM of Estes Industries. An end burner nozzle is the most demanding nozzle, so if Dr. Elseys is good enough for Estes end burners, it's good enough for me. Their motors store long and well, under varying conditions.

 

I'm not dismissive of the idea of knowing the finer points about something. For me, it's charcoal and BP It's funny how nozzle methods have as wildly different adherents as BP methods Some guys say nozzle clays are all the same, everything works. The other end of the scale is the analytical end, and folks use particular mixtures for particular reasons. The way I look at it is, if rocketry nozzle materials were worthy of no special consideration, there would not be so many threads about them. Eh?

[SharkWhisperer]

In ceramics, bentonite added to pottery clay improves binding of glazes in high temp kilns. Also increases the clay's plasticity before firing. Though it absorbs water well (kitty litter, drilling applications), once hardened in pottery, bentonite on the pottery surface has absorbed some water from the glaze (or fire). This water in the bentonite causes swelling that closes surface pores and then forms a barrier to the introduction of additional water. So...a water-cured water barrier function. Unsure if something similar occurs with rocket nozzles, but it makes sense. Else I'd expect to see major nozzle erosion or failure on 40-year-old Estes BP motors that fly perfectly today, some having experienced variable environmental conditions (but no major heat/cold cycles that I know of).

 

Also, I've heard that sodium bentonite has more water-absorbing tendency than calcium bentonite, but that statement is anecdotal only and would have to search for a trustworthy source to see if that claim is indeed accurate. Perhaps somebody here knows more about this?

[shockie]

1st of all, i just want to say that I really appreciate people taking the time to answers these questions. It is very helpful. I'm just asking because I don't know, and I know a lot of you peopl ehave more experience in these areas than I do. with the advent of the internet over tha past 25 years, it's like being able to just ask people who are much more knowledgeable and have more experience about most anything and hence I have learned so much. I read that sodium bentonite swells more and absorbs more water than calcium bentonite.....the context of that statement was in reference to its use as a facial mask for women.....

 

as an aside.....has anybody every considered creating spindles be they be end core burners or cored one, with a coating of teflon like pans? or just dust it with graphite lubicant might do the same thing? but would it transfer to the BP being pressed?

 

The suggestion to use it was given by Edwin Brown, the late GM of Estes Industries. An end burner nozzle is the most demanding nozzle, so if Dr. Elseys is good enough for Estes end burners, it's good enough for me. That will also work for me.

 

any idea why Estes clay looks speckled?

 

TIA

Edited January 28, 2021 by shockie

[justvisiting]

Try as I might, I can't find the data sheet Ed sent me for the Dr. Elseys litter. As I recall, the speckled look is due to the blend of bentonites that provide the best properties (for cat litter I have other bentonite that is very fluffy in comparison. Dr. Elseys seems to be a more dense bentonite than other kinds.

 

Many of us rub our spindles with wax before pressing rockets to make extraction easier. Graphite is messy to handle. I have a Wolters 3lb strobe rocket tooling set that has an anodized aluminum spindle. I don't see the value of it, but I do see potential danger when using such a spindle for strobe rockets. The anodic film has obvious wear. Anodizing makes a very tough, wear-resistant surface, so my guess would be that something like teflon would not be very durable in this application.

 

One little point worth noting is that the grip of a clay-based nozzle on the spindle is far greater than the grip of the propellant along the length of the spindle. In other words, a nozzleless BP rocket motor is considerably easier to crack free from the spindle than a nozzled BP rocket. With very long spindles in nozzled motors, I've found it useful to grab the motor from the bottom in the nozzle area to crack it free. The 'old' way of removing a motor from the spindle was to insert a flat-ended drift in the top end of the motor, grab the end TIGHTLY with a pair of Vise-Grips, and twist the motor free. With a nozzled rocket, that process is much more difficult. If I remember, I make sure to wax that are of the spindle. Another thing I tried just for larks was to paint the nozzle area of the spindle with nail polish. The nozzle then stuck to the nail polish instead of the spindle. PITA though.

[SeaMonkey]

I wonder if covering the base of the spindle where the Nozzle is formed with a layer of something

like Wax Paper or something similar with lubricant properties would help to release it more easily?

 

Whatever paper is used would become attached to the core of the Nozzle but should burn away

with ignition of the Rocket.

Edited January 31, 2021 by SeaMonkey

[justvisiting]

SeaMonkey, yes maybe a disc of waxed paper with a hole in it. Clay always seems to transfer onto tooling, and it seems that the more polished the tooling is, the more it sticks. I have a 3lb end burner set from Steve Laduke. He hardens the steel of the spindle, or at least he did with mine. Anyway, it got rusty. The clay stopped sticking to it.

 

I find that the worst area for the sticking is the throat of the nozzle. On a 3lb nozzled core burner motor, if the throat is too long (let's say 3/8"), the spindle puller will probably mash the tube before the motor comes off the spindle. Now I think a little more on it and I wonder if a piece of Scotch tape might be applied to the throat area on the spindle, where I put nail polish before.

 

I gotta get back into making more rockets, sigh.