Best nozzle mix from kitty litter

[Pyroboy]

 

Estes rocket engines have bentonite nozzles, pressed from- you guessed it- cat litter. They use Dr. Elseys Precious Cat Litter. It was the former manager of Estes Corp. that suggested its use to the pyro community. Estes motors can be stored for a decade or more and function like the day they were made.

 

Well they sell their motors packed in plastic. That may be the secret beside the fact that most people doing scale modelling wont store their motors in a bunker like fireworks. But storing everything in plastic bags is not an option for fireworks. Especially bigger rockets.

 

I did some research and found that citty litter is not always made with bentonite but also with Palygorskite or Sepiolite. But I don´t know if thats any better. Both may not swell as much as bentonite. But scince both are Al- and Mg- Silicates without Na-, K- or Ca- kations I could imagine that they are much like Kaolinite and wont bind that good. But maybe its worth a shot.

[justvisiting]

The Estes motors are packed on a cardboard square with plastic on the front only. The packages are not moisture-proof. I've stored my Estes motors under varying climatic conditions with other fireworks materials, with no issues.

 

One thing people may be overlooking with bentonite is density. There is fluffy bentonite (maybe mined near the surface?) and there's bentonite that's much more dense. There's also bentonite cat litter that is half of 'normal' density, for people that can't lift heavy stuff. Dr. Elseys litter is much more dense than the well-filling bentonite that I have. It also appears to be a mixture of bentonites. Either way- it's bentonite- and it works in the most demanding of rocket nozzles. The swelling issue of bentonite seems to be an issue that may not apply in our application at all. It swells when it absorbs (much) moisture in the form of water, yes. I don't think that necessarily translates into it sucking moisture out of the air and ruining nozzles. Just an opinion, but I'd welcome any data to the contrary.

 

I would never use paraffin oil in rocket nozzles. First of all, oil can absorb into the tube and migrate. Secondly, it's volatile and evaporates over time. Paraffin wax is a better choice. Somebody suggested using paraffin oil as the phlegmatizer in whistle fuel. I did a few experiments, and that's when I found that it evaporates. I foresee potential problems with using it for that purpose also.

[SharkWhisperer]

I never found an MSDS for that stuff - am I blind?

But someplace else they claim:

That seems to apply for the variant you posted.

 

Really just bentonite? Assuming theres nothing else - then what makes this stuff work so good?

Maybe it's some special processing?

Maybe there just is no MSDS available. In the US, and according to UN GHS recommendations that many nations follow, a product does not require an MSDS if it contains no known hazardous materials. Some manufacturers provide, but are not obligated to, an MSDS for non-hazardous products at their discretion. No idea what funky rules are in the EU CLP Regulations (if that applies to you).

 

As others have mentioned, bentonites do not necessarily all have an identical mineral composition--it's a group of variable chemical constituency. And some kitty litters contain various additives.

 

Incidentally, I use 75% bentonite (cheap Walmart Special Kitty brand spun in a coffee grinder to a random mix of particle sizes)/25% Hawthorne fire clay, no paraffin, and have no complaints. Rockets don't store for long, but gerbs do. No erosion issues noted. And I live half the year in a humid subtropical environment. Have a brick of paraffin laying about, so maybe I'll try it some day; don't really see any major downside. And JV's graphite addition for easier spindle-release doesn't sound like a bad idea, but I don't use graphite for much else so don't stock it. 10,000 ways to skin a cat.

 

[justvisiting]

Here's a little exchange that might shed some light for those that are interested. There was a MSDS for Dr. Elseys, but I can no longer find it.

 

Mr. Brown (now passed) was the General Manager of Estes Industries, and a penpal of mine.

 

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You 10/5/14 Delete

Hi Ed. You asked me a while back if I had tried the Dr. Elsey's litter. I have not. I am currently using a mixture of clay, kyanite, and wax. It makes great nozzles but I don't like the wear on the tooling or the abrasiveness.

I don't have that brand available to me here, but I do have cat litter that looks the same, with the mottled look of the color. I have screened out a bunch of it to 10 mesh or so, and removed the dust. Do you think I should use it as is, or impregnate it with wax?

Is nozzle erosion likely to be greater than what I am currently using? I did find in one of my tests that a nozzle pressed in 2 increments was less eroded after firing than the same mixture pressed all in one go. What do you think of that?

Thanks,

Dave F.

edbrown 10/6/14 Delete Block

Hi Dave,

If it is close to Dr. Elsey's, you shouldn't need to add anything else. It has no noticeable erosion with black powder rockets. With rockets similar to Estes rockets I was able to press in a single increment. If you have problems with it, it definitely would be worth trying it in two increments. I have done that a few times, but not very often. Tooling wear with black powder was negligible, The black powder over time caused the tip of the core former to erode away, but that was a very slow erosion. i.e. thousands of motors.

***** mentioned he had very good luck with Wyo-Ben brand clay, and I've heard that Walmart has sometimes had a similar clay in their cheapest category. I don't know if it would be available, but "Black Hills Bentonite's" MSDS and Dr. Elsey's MSDS appeared to be identical.

I hope you have as good results with it as I have. I'm always looking for your posts to keep up with what you're doing. I really liked your latest end burning curves. Have you ever pressed end burners using commercial black powder and your own black powder using the same tooling for both and compared the thrust curves?

Best wishes,

Ed

Edited February 15, 2022 by justvisiting

[stix]

Sorry to here that Mr. Brown is longer with us.

 

I had a few conversations with him in the past. A really nice person who shared his learned information willingly.

 

My sincere condolences to his family. He was truly a nice person.

Edited February 15, 2022 by stix

[justvisiting]

Yes, he treated everybody with respect and kindness, regardless of skill level. Ed would have made a good science teacher

 

The single most important thing Ed taught me was about grain density in rocket motors. He mentioned determining the volume of the grain by measuring how much straight isopropyl alcohol it displaced. I complained that the method was no good because the alcohol absorbed into the grain. Ed gently explained that it was the grain that was no good, not the method. He's touched the lives of a few of us rocket makers. When we were discussing black powder and I had a question, Ed would send me literature that contained the answer and say "Here, read this." The answer to my question would be 'somewhere' in the many many pages

[Mumbles]

Thanks for that e-mail. Your or his note about Wyo-Ben clay lead me back to something I've been looking for for some time. They offer a product called Big Horn Bentonite. I've used this with great success. Reminds me of how you describe Dr. Elsey's. Hard, shiny nozzles with less erosion than other clays. It was a dream to work with. It almost acts like it has embedded wax. I'm sure it doesn't, and it's just the particular clay composition.

 

If I've ever made vague references to clay with a ram or something on it, this is the stuff.

[mabuse00]

 

One thing people may be overlooking with bentonite is density

Yes, indeed.

 

Maybe that can be corrected with high pressure pressing, but for anything above 1lb my arbor press does not give me that option.

 

I did some testing with my standardmix now. I got

 

2,3g/cm³ @ 4200psi (Pressed increments ~7,5-8mm in a 9mm tube)

 

2,64g/cm³ @ 8400psi (Pressed increments ~6,5-7,5mm in a 9mm tube)

 

 

What numbers do you guys achieve with that magic kitty litter, or other stuff you use?

I mean pressed, like you would press a nozzle?

 

 

 

 

[justvisiting]

mabuse00, I was talking about the density of the bentonite before pressing. Some bentonite is light and fluffy, other stuff is heavy, and maybe waxy, as Mumbles also experienced. I find that the denser a product is, the easier it is to press a more dense final product. End burners are not what I usually make, as rockets go.

 

I don't understand what you are trying to say with your examples. A 9mm tube? That sounds like a 2oz. rocket? Your rockets are that small?

 

When I press a 1lb end burner with my tooling, a Dr. Elseys nozzle weighs 12 grams, and is pressed to 9000psi. I pressed a slug of Dr. Elseys weighing 12 grams with my 1 ton arbor press just to see what kind of nozzle I would get. I applied 2000lbs. of force, using my torque wrench, and a slow pull. That's around 4500psi. I got a density of about 1.58g/cc. The tube was not bulged enough for my liking, but with a spindle I think it would bulge enough. From this little bit of data, I'd say that Dr. Elseys would probably not be great for using as a nozzle material in 1lb end burner rockets made on a press with 1 ton capacity.

 

As far as density of the nozzle goes, I think it's not a number that says much to us by itself. There are lighter materials that don't erode easily, and heavy materials that erode badly.

 

These are just things that come to my mind. I don't mean to imply any expertise on my part, but I enjoy talking about rocket issues.

[mabuse00]

 

mabuse00, I was talking about the density of the bentonite before pressing

Yes, I understood that.

 

I just find it easier to measure the compressed final density. Some stuff might compress more the others, who knows...

 

 

I find that the denser a product is, the easier it is to press a more dense final product

I agree.

 

 

I don't understand what you are trying to say with your examples. A 9mm tube?

I wanted to know what density a nozzle at typical conditions would have.

The tube diameter is irrelevant, I only gave it to give you an idea how long the pressed increments where in relation to the tubes diameter.

 

 

 

[Bourbon]

Magic kitty litter. Or, it's just bentonite clay. It's been working for years and years.

 

I sure hope you find what you're looking for.

[justvisiting]

I still don't understand the purpose of pressing the nozzle mix in a 9mm tube if that's not the size tube you use. It seems like the nozzle mix density examples provided are not achievable with larger diameter slugs, due to the limitations of your arbor press. What size rockets are you making with what size press? Why don't you press a slug of nozzle mix of the diameter of the rockets you actually make?