Puck press

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Pyro-Gear
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Puck press

Post by Pyro-Gear »

After a lot of conversations with people regarding puck presses I have decided to manufacture a few.

The press is made of a die in aluminium 40mm internal diameter and a 60mm outside diameter giving a side wall of 10mm depth of the die is 30mm.

The piston or punch is 40mm and 20mm in length my calculations tell me this will give you a compressed puck of around 10mm, of course the density of the puck will be dependent on the charcoal used and a few other things like pressure applied.

I chose this size to cover a wide range of pressing applications :IE arbour/hydraulic presses, let me know your thoughts and interest.
davidg
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Re: Puck press

Post by davidg »

Sounds of interest to me.
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Pyro-Gear
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Re: Puck press

Post by Pyro-Gear »

Thought it might! The materials are due in Monday I will machine up the components and post up a picture retail will be around £20 +shipping around £2.50
Tyvole
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Re: Puck press

Post by Tyvole »

In one of your previous posts, you mentioned using about 3 tons on a 40mm puck. To get an equivalent pressure using a 1 ton arbor press, I think the puck diameter would have to be around 22mm. Small can still be beautiful! ;-)
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Re: Puck press

Post by Pyro-Gear »

I can take a hint, I went for the 40mm option because a member has a 2.8 ton arbor and the rest are on hydraulic, I will ask Santa if he has a 20mm die I expect he will have one. :D
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Re: Puck press

Post by richardh08 »

A quick back-of-an-envelope calculation tells me that, to get to a density of around 1.7g/cc in a puck about 10mm thick, the charges and pressing forces for some different sized moulds are - in approximate, round figures - as follows.

Puck diameter (mm) 65, 40, 20
Powder charge (g) 50, 20, 5
Pressing force (tons) 5, 2, 0.5
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Tyvole
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Re: Puck press

Post by Tyvole »

Pyro-Gear wrote:I can take a hint...
'Subtlety' is my middle name! :-D
(And if you believe that, you'll believe anything.)
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Re: Puck press

Post by Pyro-Gear »

Ok as promised here is the 40mm press fair amount made so there available as we speak.
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davidg
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Re: Puck press

Post by davidg »

Finally got round to trying the press tonight. Pressed five pucks and had no issues. They are currently drying and I will let you know the resulting densities asap.
Nice tool Ken.
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Re: Puck press

Post by davidg »

Densities varied slightly from 1.68 to 1.72 g/cc.
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Re: Puck press

Post by Pyro-Gear »

That sounds pretty good, what tonnage did you put on the die Dave? Good to know the tool works well.
davidg
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Re: Puck press

Post by davidg »

Pyro-Gear wrote:That sounds pretty good, what tonnage did you put on the die Dave? Good to know the tool works well.
2 ton.
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Re: Puck press

Post by Starfire »

When pressing how damp should the powder be, Is it best with dextrin, as I've not made pucks.
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Re: Puck press

Post by Pyro-Gear »

1ml of water to 100g of powder should be fine no Dextrin is used as the sulphur will become elastic and bind the puck, my press is set for a pressure of two tons so 20mm of composition in to the press apply pressure @ two tons for a minute or so job done allow to dry density should be spot on.
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Re: Puck press

Post by Starfire »

Thanks Ken
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Re: Puck press

Post by Andibates »

to ask a stupid question why do you press powder into pucks
i have no idea what this is all about
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Lloyd
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Re: Puck press

Post by Lloyd »

Andi,
Commercial BP is produced by a process known as "pressing and corning". The Pressing part is "pressing into pucks", which are solid disks pressed to approximately 1.7g/cc density.

Corning is the process of breaking up those pucks between rollers, and subsequently of classifying the grains that result by screening.

This is the way all commercial BP is made.

When you hear of someone "pressing BP pucks", almost always their intent is to make "corned" powder.

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Re: Puck press

Post by Andibates »

thank you very much lloyd
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sambo
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Re: Puck press

Post by sambo »

I've got to admit I struggle with "corning". Pressing is fine but corning makes me nervous and I don't seem to manage to avoid a lot of either fines or large chunks. That is, I find it hard to get the grain size just right, I'm sure there is something I'm missing but I have no clue what.

Ken you're puck press looks nice and I must say outstanding value compared to the price I paid for mine a couple of years back.
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Re: Puck press

Post by richardh08 »

I use a meat tenderiser hammer a bit like this one: https://images-na.ssl-images-amazon.com ... 3HM7OL.jpg

I put the puck in a plastic bag and hit it until it starts breaking up. I then screen the pieces to the mesh size I need (usually 4-mesh). The lumps that don't pass the screen go back in the bag for further 'treatment' until it all goes through the screen.

I find that using the textured surface of the hammer reduces the amount of fines to a reasonably low percentage of the total. I have to admit that, after a few cycles, the bag is in a pretty sorry state :lol:
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Re: Puck press

Post by sambo »

Thanks Richard,

neat idea. I'll give that a go in fact as I had reserved plans to put together the corning machine featured on passfire !
Dave F
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Re: Puck press

Post by Dave F »

I've been pressing some pucks lately to help quantify the performance of black powder made by my own method. With guidance from the Passfire article, I chose to use 8% water to help consolidate. The author (Kyle Kepley) states that the use of more water- up to 10%- actually results in drier pucks. I believe him.
With 8% water, three quarters of it is squirted out during hydraulic pressing. A few drops per puck is all it adds up to. Yes, some of the potassium nitrate dissolves in the water. But not much. Making a 76-15-10 mix should address that minor issue.
If you only use 2% water, you will not consolidate the puck as readily as with 8%. The whole 2% will remain in the puck. I believe the water, being incompressible, displaces air within the mass. Not enough water means not enough air displaced, which means not as much consolidation at a given pressing force- IMHO.
I corn my test pucks to 2FA size for doing baseball tests. If I do it properly, about two thirds of my batch will be in the 2FA range. I describe this range as 'about ' 4-12 mesh.
Here's how I corn my pucks: I use the end of an aluminum meat hammer mounted on the end of a baseball bat. I take a large (10 cm) flexible plastic cap and put the puck on it. I take a piece of plastic pipe about 45 cm long and a bit smaller diameter than the ID of the cap. This pipe is lowered so the puck is inside. Then I go up and down with the bat. For each set of impacts, I shake the pieces on a 4 mesh screen, sitting on a large bowl. What remains on the screen is poured through a canning funnel, back into the pipe. Again, a few swats are applied. The process is repeated over and over until the puck is processed. Before the whole thing is crushed, I've already introduced the next puck. This way I'm not wasting so much time and impacts. If I don't do it this way, I will get more small grains than I prefer. After all the grains have passed the 4 mesh, I pour it all on the 12 mesh and shake. Voila! Everything in my 2FA range is left on the 12 mesh. Since there is 'some' risk of ignition, I place the screen assembly and unprocessed pucks a few steps away.
I've corned the powder before and after drying. The pucks are certainly harder after drying. It's probably a bit safer and more expedient to corn them damp.
Please forgive my natural tendency to write long, rambling stories when I describe things. I can't help it :)
If there is any interest, I will describe my process for making the black powder itself. I have been able to achieve commercial powder performance with single component milling, in apples to apples comparisons. I believe my process would be very popular with Europeans, because of the population densities over there.
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Re: Puck press

Post by sambo »

Dave,

don't apologise. I really enjoyed reading that and you've basically answered all my questions, thank you. Sounds like something to try out this weekend !

You're statement regarding the amount of hydration is an interesting one and you make a strong argument. I'd also wonder if surface tension helps to draw the water out of the puck, the effect being greater with slightly more hydration.

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Re: Puck press

Post by Boophoenix »

Andi, it hasn't been mentioned yet unless I missed it so I'lol add a little rid bit about Corning powder.

By Corning you remove some of the variables associated with granulating as you should be pressing to the same density with each puck. This should give you a much better comparison between powder batches. This is fairly important if you want to do some highly specific testing as DaveF has been doing with his screen mixed BPs. That's my opinion of the subject of why we might corn as hobbiests.
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Re: Puck press

Post by richardh08 »

Dave, the method you describe for corning your pucks sounds pretty darn efficient. I'd try it if I ever made enough BP to make it worth my while.

I generally use only 2 to 3% water when I press pucks, because I don't like dealing with the mess that presses out when I use more. Since I normally only make BP to evaluate its performance against previous batches, I'm pretty much stuck with using the same technique every time.

To some extent, I guess it's all down to personal preference. If you leave a puck long enough, it will dry out, regardless of its original water content. Corning the damp pucks, as long as they are hard enough, is one way to get the stuff to dry out faster.
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Re: Puck press

Post by Dave F »

Yes Boophoenix, you are right. While it is not necessary to make pucks, generally speaking, it makes for better consistency in testing. I was expressing my black powder results as thrust curves from nozzleless rockets on BP tooling. Lots of (OK, most) folks can't relate to that. I thought it was ideal. No water to skew results through drying conditions or otherwise. The number of grains was 1. I have a scientific instrument to do the testing in a more controlled way than flying baseballs. But alas, flying baseballs won out as a way to express things that everybody could relate to, and do more cheaply.

Richard08, I understand totally about the consistency. I did quite a few tests with my first puck die. Now that I have another I question the results, and would not compare them directly to powder made with the first set. I have recently worked on scaling down my process so that only 50 grams of charcoal is needed to make up a test batch. In batches of this size, mediocre charcoals are weeded out automatically :)

In my way of looking at it, the ideal amount of water used in pucking would be such that one drop is squeezed out of each puck. I guess this could change for some 'thirsty' charcoals, but we have to draw the line somewhere. So I use the same amount every time and don't worry exactly how much comes out. My pucks are as hard as rocks when freshly made. They are as hard as harder rocks after drying.
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Re: Puck press

Post by sambo »

Something I have never tried, pressing my pucks with acetone or IPA. I've frequently riced my BP / my rocket mixes with IPA. Some folks may object to the cost, but it'd be interesting to compare. Point being, they'd dry a lot quicker and the potassium nitrate wouldn't dissolve appreciably.
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Re: Puck press

Post by Dave F »

Sambo, I have wondered the same thing. So I tried it. I took 99% isopropyl alcohol and used it instead of water at the same w/w percentage (8%). Interesting! The black powder was very much against the idea. The same powder that consolidated perfectly with the water would not compress nearly as well with the iso. Not a drop came out either.

I jacked the pressure up another 30% or so and got hardly any more compression. Again, not a drop oozed out. Also, the puck did not stick to the pump or the base. As a matter of fact, the puck expanded when the pressure was relieved, so that the gap between the sleeve and the base was about 1mm. The pucks were quite obviously soft and did not clink at all. They were easily scratched.

So, at least in my mind: that settles that. The water performs a very important function, it seems. I've pressed dry powder, and I've pressed waxed powder. Both gave poor density for the force applied, with the waxed powder giving the least density, at 1.42. This surprised me.
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Re: Puck press

Post by sambo »

Hmmm, that's really interesting. Isopropyl alcohol is "quite a bit" less polar than water. There could be some merit in trying the same with acetone or dichloromethane. I also have some acetonitrile which could be better again when I get time I might give it a try just for curiosity sake. Clearly, from a practical perspective, water is the way forwards, but I like to understand why and how.

Sam.
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Re: Puck press

Post by Boophoenix »

Dechloromethane ( methylene Chloride ) is somewhat rare or costly in the US n most pyro's stashes. I'm not sure about where Dave is in Canada though. Strangely enough I keep a few gallons handy as a chlorine donor with the secondary ability to fuse plastic hemi's.
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