Nozzle blowout due to waxed tubes?

[justvisiting]

I guess nobody caught my glaring mistake in my last post on Page 1 of this thread. It's too late to edit it now, as I found. I wrote:

 

"Now I'm curious again. It's been said that a 1 ton arbor press is not strong enough to press 1lb rockets. But, with damp propellant, if 3500psi is sufficient pressing force, a 1 ton press would do the job. A solid 3/4" rammer face has an area of .441". To get 3500psi, I need 1543 pounds of force. That's within specs for the arbor press. I checked my torque wrench on the arbor press at its maximum setting of 250 foot pounds, and it clicked at 3500psi on my PtoF gauge. BUT, I had to hang off that thing like a monkey! If I needed to press a 1lb rocket on a 1lb arbor press at 3500psi to save my life, I could do it. Hand ramming would be way easier, but I'm not doing that either. 5/8" (8 ounce) rockets would be a piece of cake on the 1T arbor press with damp propellant."

 

Here's where I blew it; a pressure to force gauge does NOT measure psi! It measures force, in pounds. Somehow, I ignored the 1543 pounds of force, and converted 3500psi into 3500 pounds of force. That's almost double the capacity of a 1 ton arbor press. Doh! Now that I've corrected that error, I see light at the end of the tunnel. Preliminary tests have shown me that with dampened propellant, I can quite easily press 1lb rockets (and maybe even 3lb rockets) on my 1 ton arbor press. I'll look into this further and report my findings when I have data to back up my observations.

[mabuse00]

Here's where I blew it; a pressure to force gauge does NOT measure psi! It measures force, in pounds. Somehow, I ignored the 1543 pounds of force, and converted 3500psi into 3500 pounds of force. That's almost double the capacity of a 1 ton arbor press. Doh!

 

But the one ton press did 3500pounds - that sounds encouraging to me

 

I was convinced of using an arbor press when I saw Ned's video, where he pressed 2lb rockets on a 1t press, I think with waxed tubes...

 

Waxing alone maked a huge difference in the force needed, additionally the use of damp fuel - well it keeps getting better, thank to the innovations of the pyro community. Thank you guys for sharing your insight

 

Hi Dave,

 

 

For the black powder, spread out your BP on a sheet of waxed paper or an analog, use 70% Isopropyl Alcohol and using a scale, zero the spray bottle and use no more than 50g on 1000g batch. Quickly mix it by hand, cover in a small tight container and dispense from the container.

 

So isopropyl... I guess that would dry out over time even in a waxed tube. Why 70% and not 98%? Because of availability? Or because you actually wanted the 30% water?

 

I will do the delamination experiment as next step and see... I use fragula alnus, I also have commercial beech, but the latter is slow...

 

 

Back to the OP, will a waxed tube cause the nozzle to blow out? Yes, unless you create a physical indentation in the tube trapping the plug, it will eject. If you crush the pulp and create fractures, the tube will fail. Just scratch the paper a little to remove a little of the wax and load one up!

 

I already created a stopper. The tubes will have to be waxed to a certain level for every tool individually...

Edited July 26, 2020 by mabuse00

[justvisiting]

Pressing 75-15-10 with straight isopropyl alcohol gave poor compaction, not much better than pressing dry. I never tried 70% alcohol. It still remains that water is a critical component in the compaction of black powder, whether it's a puck, or a puck inside a tube. Commercial manufacturers all know this. From personal experience, I can say this:

 

Pressing a 1lb end burner with damp propellant to 4500psi on a 1 ton arbor press gives better compaction than double the force (9000psi) applied to dry propellant. By 'damp', I mean 2- 2 1/2% water added.

 

I'm doing a few experiments to see just how much performance I can squeeze out of rockets made on my arbor press. Pressing end burners with mill dust is a total PITA. Pelletizing or granulating the propellant is an extra step, but saves time at the press. Core burners are slightly less annoying to fill with mill dust because of the much longer tubes.

[kaotch]

Mabuse

There will be no nozzle breakout when using waxed tubes provided you compact the bentonite well in your 15mm tubes.If you are working with an arbor press

mix 1-2% demineralized water in your BP,work in the H2O very well, and you will get very good compaction with lesser pressure.I have done this for many years without having any problems.Justvisting is right on every aspect follow all the guidelines and you will enjoy the results . Good luck and nice to see that you are back again.

[Bourbon]

Does the 1-2% water need to be for warmer fuel as It can handle a slight loss? Or would it still be applicable down to say 60/30/10, or would that suffer to much?

 

I know this is a corny question but, has anyone tried spray wax for tubes?

[dagabu]

Pressing 75-15-10 with straight isopropyl alcohol gave poor compaction, not much better than pressing dry. Yes, pure alcohol leaves much to be desired, even 91% will disappoint. I never tried 70% alcohol. As Mabuse00 asked, the 30% water is what affects the powder as a fluid allowing for better compaction both due to plastic flow as well as purely mechanical lubrication. There are whole books written on the subject. It still remains that water is a critical component in the compaction of black powder, whether it's a puck, or a puck inside a tube. Commercial manufacturers all know this. From personal experience, I can say this:

 

Pressing a 1lb end burner with damp propellant to 4500psi on a 1 ton arbor press gives better compaction than double the force (9000psi) applied to dry propellant. By 'damp', I mean 2- 2 1/2% water added. Fluid dynamics again, it also applies to "heap" storage, a dry heap will attain walls of 45 degrees, or about as much while wet heaps will slump significantly so much so that storage become problematic. When pressing inside a tube, the radial forces spread out at about 45 degrees leaving all powders beyond 1 increment inadequately compacted. Plastic flow can be exacerbated with a fluid such as water, allowing for the angle of flow to decrease, allowing for better compaction with less pressure.

 

I'm doing a few experiments to see just how much performance I can squeeze out of rockets made on my arbor press. Pressing end burners with mill dust is a total PITA. Pelletizing or granulating the propellant is an extra step, but saves time at the press. Core burners are slightly less annoying to fill with mill dust because of the much longer tubes. ​Just dampen the mill dust for dust control. Run it through a 20 mesh screen a few times and it will "granulate" for you.

[dagabu]

Nope, the water in small quantities actually propagates the flame front along the mass allowing for a faster burn in many cases. Keep in mind that any and all BP will "normalize" to the storage conditions it is kept at. This also means that if you keep pressed rocket motors in a cool basement (example) with a RH of 70%, once this motor is brought outside, sticked and seated in a rack in the hot sun at 20% RH, you will get some change in the grain burning.

 

The water will evaporate through the tube, waxed or not. Also in a bag or in a bucket. They will normalize to the bulk RH.

 

How long does it take to evaporate 70% ISO off a pressed motor? Sounds like a good test...

 

Does the 1-2% water need to be for warmer fuel as It can handle a slight loss? Or would it still be applicable down to say 60/30/10, or would that suffer to much?

 

I know this is a corny question but, has anyone tried spray wax for tubes?

[mabuse00]

 

Does the 1-2% water need to be for warmer fuel as It can handle a slight loss?

That's what I find very interesting too. Not with nozzled coreburners of course, but endburners or nozzleless, where my fuel is barely hot enough/cannot be to hot - definitely, that's a crucial point.

Especially when using justvisiting's or kaotch's process without alcohol and the whole liquid STAYS in there...(?)

 

Measurements on my TODO list...

 

 

 

Pelletizing or granulating the propellant is an extra step, but saves time at the press. Core burners are slightly less annoying to fill with mill dust because of the much longer tubes. ​Just dampen the mill dust for dust control. Run it through a 20 mesh screen a few times and it will "granulate" for you.

 

For granulation/"ricing" you need more than 2% liquid.

 

Do I understand correctly - you first granulate and then re-wet the granules?

[dagabu]

SPOILER ALERT!

 

The liquid does NOT stay in the grain*. Even some oils evaporate so as to leave the grain lighter after evaporation stalls. Measuring this is very difficult and extremely problematic due to hygroscopy, RH, storage quality, etc, etc, etc.

 

I'm sorry but I didn't go back and look for the post but I think I put it in quotes so as not to indicate the analog of ricing, just dampening and running through a 20 mesh for dust control and flow. If you rice it, allow it to "dry" to your storage conditions then use a very fine sprayer and add no more than 2% water to the fuel then press.

 

*Normalization determines evaporation rates and "dryness", your drying rate will be determined by many, many variables.

 

 

That's what I find very interesting too. Not with nozzled coreburners of course, but endburners or nozzleless, where my fuel is barely hot enough/cannot be to hot - definitely, that's a crucial point.

Especially when using justvisiting's or kaotch's process without alcohol and the whole liquid STAYS in there...(?)

 

Measurements on my TODO list...

 

 

 

For granulation/"ricing" you need more than 2% liquid.

 

Do I understand correctly - you first granulate and then re-wet the granules?

Edited July 27, 2020 by dagabu

[justvisiting]

My liquid (water) does stay in the grain. It's been checked, re-checked, and then checked some more. Anybody reading this thread should make sure to appreciate the distinction between the Daves. We are talking about different things here. I don't use alcohol (in my rockets)

[justvisiting]

mabuse00, it seems that you are mainly concerned with end burners. There are two ways that I know of to facilitate the process. I've already described the first way in various places on this forum. The first way is the dampening of the propellant with 2-3% water. I use 2% for 75-15-10 nozzleless rockets, or end burners. I use 3% for nozzled rockets. Again, as I said- the water does not leave. I 'pre-densify' the damp propellant by pressing (let's say) 50 grams at a time in a 3 1/2" puck die to 3000 pounds of force. This makes a slab less than 1/4" thick. These slabs are then crumbled back down through a tough 10 mesh screen. This can be done by hand. The propellant will now have half the volume of the original powder. It will be free-flowing, and easy to press.

 

The second way to make end burner propellant more user-friendly as a dry powder uses more water. The 75-15-10 mill dust (or equivalent) is dampened with 8% water, screened a couple of times, and left covered to 'temper'. The powder is then pushed through a 20 mesh screen and dried. When dry, it's run back through the screen to break up any lumps. It will then be a free-flowing, dry mixture that is pleasant to use.

[Bourbon]

Why does the nozzled need an extra 1%? Does this apply to cored also?

[justvisiting]

Bourbon, I added an extra 1% water for the 60-30-10 nozzled rockets because I felt that the excess charcoal would 'steal' some of the moisture and interfere with the compaction process. The rockets performed well, so I didn't change anything.

As far as moisture weakening the rocket, I haven't seen that. One volume of water turns into almost 1700 volumes of steam when it's heated. Maybe the water helps the thrust

[Bourbon]

Like a hybrid steam rocket. Cool!

 

Did you also say this applies and works with cored motors as well? I know end burners, nozzled and nozzleless was mentioned.

[justvisiting]

I did say this applies to end burners, nozzled coreburners, and nozzleless coreburners. I have made, flown, and tested these motors in sizes up to 3lb. Others have made and flown 6lb rockets made this way. When one considers that water is such an integral part of the black powder consolidation process, the benefit to consolidation of black powder in a tube can become obvious.

 

I made and tested a 1lb nozzleless coreburner yesterday with dampened, 'pre-densified' 75-15-10. The mixture was made with supermilled ERC charcoal, and screened twice through 40 mesh. It was pressed on my 1 ton arbor press. When I tested it on my Acme, the impulse was about the same as previous tests made with milled ERC BP. In those tests, the powder was pressed dry to 9000psi. The benefit of water is huge. That motor would lift a rocket weighing 24 ounces to almost 450 feet.

[Bourbon]

Thank you so much for letting me pick your brain with my endless questions. I find your answers extremely valuable and your patience with me as a newbie very honorable. Hats off to you Sir.

 

I'll stop pestering "for now" lol.. Thanks again.

[Mumbles]

Justvisiting, have you tried and side by side tests between your pre-densified and just granulated damp propellant? I understand the concept behind what you're trying to do. I'm just curious as to what benefits you may have found along the way. This is all very interesting to me.

[justvisiting]

Mumbles, I don't think I understand your question. The 'pre-densified' powder is the granulated damp propellant. If you are asking if I compared that to using the same dampened powder but without the pre-densifying step, yes I have. I thought that the pre-densifying would make a better rocket by reducing the pre-compaction volume, and that more propellant would be used, giving more power. Not so. If there is a benefit in that regard, it's small enough to be within the margin of error. I should also mention that the pre-densified stuff wants to cause tube compression wrinkles, unless the tube is waxed. The pre-densifying is an extra step that takes more time, but my opinion is that the time spent doing it would have otherwise been spent futzing around trying to load fluffy powder into a short end burner tube.

 

Another idea I've been toying with is to make 'rocket pellets'. Basically, it would involve taking damp mill dust (or other propellant) and making pellets, using a star plate. Each pellet would be one increment, and be slightly smaller diameter than the tube ID. The pellets would be dropped into the tube, and pressed into place. I would only use that method for end burners.

 

EDIT: Thanks for the kind words Bourbon. I appreciate it.

Edited July 28, 2020 by justvisiting

[kaotch]

@Davidh,

 

Would you mind sharing Orv's Glitter formula, thanks

[mabuse00]

 

mabuse00, it seems that you are mainly concerned with end burners

No. Im interested in every type. Every type of fuel. Workhorses and rockets just for the sake of itself... But I love endburners though.

Also I've been in fact very happy with 15mm rockets in the past, enough in 90% of cases. It's more about being capable to do bigger stuff when I want to...

 

 

The first way is the dampening of the propellant with 2-3% water. I use 2% for 75-15-10 nozzleless rockets, or end burners. I use 3% for nozzled rockets. Again, as I said- the water does not leave. I 'pre-densify' the damp propellant by pressing (let's say) 50 grams at a time in a 3 1/2" puck die to 3000 pounds of force. This makes a slab less than 1/4" thick. These slabs are then crumbled back down through a tough 10 mesh screen. This can be done by hand. The propellant will now have half the volume of the original powder. It will be free-flowing, and easy to press.

Finally the information I wanted

Thank you.

+Todo list... Time to get the press into action.

 

May I ask what charcoal you use for your rockets?

Edited July 28, 2020 by mabuse00

[justvisiting]

I've used various charcoals in my rockets. I used to use nozzleless rockets to test my black powders. For rockets I intend to fly as nozzleless core burners or as end burners, I'd use something fast like ERC, staghorn sumac, or willow. For nozzled core burners, I'd use a mixture of fast charcoal and coarse slower charcoal, or even just use something like mesquite that passes 40 mesh as the whole charcoal component. I'm all over the place really.

 

To be fair, I've described the granulating process I use a few times on this forum. I don't mind repeating myself at all, but I don't want to annoy the management by sprinkling the same information all over the place (any more than I already do What I'm going to do is write up an article that details everything in tutorial form, and then post it to the internet. I've got a few more tests to do yet, before I write it.

[davidh]

@Davidh,

 

Would you mind sharing Orv's Glitter formula, thanks

Star: Glitter

Name: Thirteen Plus

Source: Orv Carlisle

 

Potassium Nitrate 50

Antimony Trisulfide, Chinese needle 10

Sulfur 9

Charcoal Airfloat 9

Sodium Oxalate 9

Aluminum, atomized 9

Dextrin 4

Boric Acid 1

Total: 101

 

It's a very slight mod. of one of Bob Winokur's "glitter" formulae. It makes a very handsome and "lacy"

gold flitter star without commercial or ball milled meal powder. Orv Carlisle's "Thirteen Plus" Potassium

Nitrate 50 Antimony Sulfide 10 Sulfur 9 Air float charcoal 9 Sodium Oxalate 9 Atomized Alum 400mesh 9

Dextrine 4 Boric Acid- addl. 1% Lightly damp with water. Cut, pump or roll. Makes great pumped

comets. Be safe! John Reilly ------------ Try that mix with 7% water and it will work nicely and make nice,

hard pumped (rammed or pressed) comets. The late great Orv Carlisle told me that he liked to make

pumped stars with that mix. He ball milled the Potassium Nitrate by itself and screened in the other

ingredients. Bob Winokur or Bill Withrow both told me (as did Orv) that milling a flitter composition all

together (matals included) can impede the performance. I have milled the charcoal and Potassium

Nitrate together and then added the other ingredients and got very nice results as well. Some folks claim

that too much water in a flitter mix reduces the effect as well. The atomized aluminums around 200

mesh work well for me. Boric acid isn't necessary. I do add a little (1%) boric acid for gold flitter with

sodium oxalate and aluminum or magnalium. A mix Orv used and I still do as well, was a slight

modification of Winokur's #13 which Orv called "13 plus". Since I've got my notebook handy, it is:

Potassium Nitrate 50% Sulfur 9 Air float charcoal 9 Antimony Sulfide 10 Sodium Oxalate 9 Atomized Al.

400 mesh 9 Dextrine 4 Add 1% addl. Boric acid and again, use only 7% water (7 gms. water to 100 gms.

composition) I mill the KNO3, C and S and then screen in the other ingredients 3 or 4 times. If you cut

these instead of pumping comets, 10% water works for me when compressed in a loaf box. It's a pretty

star. John

[kaotch]

davidh, thank you very much for all the info, was there a specific choice for the type of charcoal?

[dagabu]

My liquid (water) does stay in the grain. It's been checked, re-checked, and then checked some more. Anybody reading this thread should make sure to appreciate the distinction between the Daves. We are talking about different things here. I don't use alcohol (in my rockets)

 

I'll bet you a dollar that the water 'normalizes' out of the grain over time. BP is not impermeable so science is against your statement unless you specify a timeline.

[justvisiting]

I made an observation, I didn't advance a theory. I observed that in every case, the weight of the rockets pressed with damp propellant changed by less than 1 gram in about 3 weeks, left out in the open. In one case, I put a motor in the hot sun for a couple of hours. It lost a little weight, and then regained it later, over a day. I see no reason why my motors would suffer any performance issues on storage. I expect they would have indefinite storage capability, just as Estes motors do. Now, if I kept them in a high humidity environment or an extremely arid environment, they might pick up or lose a minor amount of moisture.

 

In any case, it would make no difference to the rockets if I won or lost a dollar. They would fly the same. They would still be of the same dimensions. The grain would still be as hard as a rock. One thing to consider also, is that black powder has a natural moisture content. So, the definition of 'normalize' means what? Does it mean that my motors will dry to a moisture content of zero? Of course not. Does an NEP tube have a moisture content of zero? No, it does not. I believe my motors are 'normalized' already