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Non Newtonian practice ammo (Read 614 times)
Kordwar
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Non Newtonian practice ammo
Jan 24th, 2022 at 12:47pm
 
I wanted to try and make some of the "rustyballs" that Jaegoor makes but the discussion mentioned that the sand in them doesn't really compress on impact and I wondered if a non Newtonian fluid would do that. Regular ones, like oobleck, are a liquid until force is applied in which they become a solid. So while falling down that rabbit hole I looked into Bingham plastics, which are non Newtonian fluids on the opposite end on the spectrum. Mayonnaise, ketchup, and† peanut butter are pretty good examples, where they will hold a shape at rest but then become like a liquid when force is applied. You might be able to see where I am going with this...

I filled a balloon with 80ish grams of ketchup....

Then I put more balloons around it after cutting the necks off like the regular tutorial.

...

Wrapped in 6 balloons
...

Hopefully I can give them a try soon! Hopefully it doesn't explode!
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Kick
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Re: Non Newtonian practice ammo
Reply #1 - Jan 24th, 2022 at 1:13pm
 
Now this is interesting Cheesy Please, if you can, film this because:
1. It will be interesting to see how it reacts to being slung and how it deforms on impact.
2. If it does explode it's going to look awesome and I'll want to watch it multiple times for sure Cheesy
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joe_meadmaker
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Re: Non Newtonian practice ammo
Reply #2 - Jan 24th, 2022 at 1:34pm
 
Kordwar wrote on Jan 24th, 2022 at 12:47pm:
the sand in them doesn't really compress on impact

This hasn't been my experience with them.† I remember bringing up a similar question.† When I first made some rusty balls, they were so firm that I couldn't really manipulate the shape with my hands (it's pretty unbelievable how out of context that statement could be taken).† But I was told they just need to be broken in a bit.† Sure enough, the first time smashing them against a board target easily cause a flat side.† And it was no problem to make them round again.


And +1 to everything Kick said.
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Kordwar
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Re: Non Newtonian practice ammo
Reply #3 - Jan 24th, 2022 at 1:38pm
 
Kick wrote on Jan 24th, 2022 at 1:13pm:
Now this is interesting Cheesy Please, if you can, film this because:
1. It will be interesting to see how it reacts to being slung and how it deforms on impact.
2. If it does explode it's going to look awesome and I'll want to watch it multiple times for sure Cheesy


Exactly! As long as I write things down it's science and not just screwing around, at least according to Adam Savage.

I'm hoping they deform and take the brunt of the impact, or at least spread it out in a way that robs it of as much kinetic energy as it can.

I'm slightly worried the guy who rang me up at the dollar tree thinks I have a really mean prank planned.
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Kordwar
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Re: Non Newtonian practice ammo
Reply #4 - Jan 24th, 2022 at 2:20pm
 
joe_meadmaker wrote on Jan 24th, 2022 at 1:34pm:
Kordwar wrote on Jan 24th, 2022 at 12:47pm:
the sand in them doesn't really compress on impact

This hasn't been my experience with them.† I remember bringing up a similar question.† When I first made some rusty balls, they were so firm that I couldn't really manipulate the shape with my hands (it's pretty unbelievable how out of context that statement could be taken).† But I was told they just need to be broken in a bit.† Sure enough, the first time smashing them against a board target easily cause a flat side.† And it was no problem to make them round again.


And +1 to everything Kick said.


Interesting! Definitely going to have to try the proper ones, just gotta get some sand from the hardware store.
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Jaegoor
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Re: Non Newtonian practice ammo
Reply #5 - Jan 24th, 2022 at 2:25pm
 
I use two different fillings.  Sand.  this must be very fine.  you can hit the balls into different shapes.  so you can also train very unfavorable forms.  I haven't been using the second filling for very long.  but previous tests are very good.  I use a clay with a high proportion of chamotte.  these balls are significantly smaller for the same weight.  when hit, they deform.  but they come back into the ball shape almost by themselves.  they do not deform as much as with sand.  but they are a bit softer.  I use these balls almost exclusively at the moment.  We recommend.
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IronGoober
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Re: Non Newtonian practice ammo
Reply #6 - Jan 24th, 2022 at 4:56pm
 
I bet you could suspend some denser particles in the fluid and keep the density up. The problem would be them all concentrating to one side from impact and making the density non-uniform so they wobble in flight on subsequent throws.

I didn't realize that ketchup was shear-thinning. Neat!

I wonder how it will handle the shear created when the projectile leaves the pouch. The spinning of the outer shell will create a shear on the fluid inside, so it might not hold it's shape well in flight.†

Camera phone set to 120/240 fps please. Smiley
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Kordwar
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Re: Non Newtonian practice ammo
Reply #7 - Jan 24th, 2022 at 6:44pm
 
IronGoober wrote on Jan 24th, 2022 at 4:56pm:
Camera phone set to 120/240 fps please. Smiley


I will see what I can do! I don't know if any of the cameras I own can do it but we'll see
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Curious Aardvark
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Re: Non Newtonian practice ammo
Reply #8 - Jan 25th, 2022 at 8:33am
 
So the idea is ketchup, what gets harder or sloppier ?

I can't really see the benefit to it getting sloppier as it's pretty sloppy to start with.

And yeah the rusty balls work well.
You need quite a lot of balloons and they need to be tight for it to maintain shape when throwing.

But until the balloons rot from natural uv exposure, they last for a really long time.

Of course if you leave then on a shelf for a couple of years untouched, they will fall apart and scatter sand everywhere when you find them again and pick them up - allegedly whistle

And you can always replace the outer two balloons when wear or rot starts to show.

The really fine sand they sell for kids sandpits is the stuff you want.
Easy to find and pretty cheap.

I would also like to point out that Jaegoor has 'farmers' hands.
Basically hardened machine tools - on the ends of his arms.
Got a grip like a pneumatic pincer.
So just because he can shape them by hand - doesn't mean you'll be able to lol
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Kordwar
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Re: Non Newtonian practice ammo
Reply #9 - Jan 25th, 2022 at 1:25pm
 
It's mainly just a thought I had, sheer curiosity. The idea is that it maintains shape until impact and then becomes  basically a liquid. Will it work? Probably not! But it cost $2.50 to try it out for the sake of science. I do think a Bingham plastic that holds its shape better like grease or peanut butter would work better but either would be a little bit of pain to shove into a balloon.  Also with peanut allergies as they are that might practically be a chemical weapon, lol
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Jaegoor
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Re: Non Newtonian practice ammo
Reply #10 - Jan 25th, 2022 at 6:00pm
 
Have fun. Believe me. Clay works great.
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Kordwar
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Re: Non Newtonian practice ammo
Reply #11 - Jan 25th, 2022 at 8:04pm
 
Jaegoor wrote on Jan 25th, 2022 at 6:00pm:
Have fun. Believe me. Clay works great.


I plan on making some with proper materials soon. Is clay with Chamotte something I would find at a ceramics supply place or am I overthinking it?
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« Last Edit: Jan 25th, 2022 at 10:08pm by Kordwar »  
 
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Curious Aardvark
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Re: Non Newtonian practice ammo
Reply #12 - Jan 26th, 2022 at 9:10am
 
fullers earth is a really fine clay.
OR
use ground up cat litter - which is essentially the same thing Smiley
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Kordwar
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Re: Non Newtonian practice ammo
Reply #13 - Jan 26th, 2022 at 1:15pm
 
Curious Aardvark wrote on Jan 26th, 2022 at 9:10am:
fullers earth is a really fine clay.
OR
use ground up cat litter - which is essentially the same thing Smiley


The company I work for always has damaged bags of clay cat litter, that could work nicely
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Curious Aardvark
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Re: Non Newtonian practice ammo
Reply #14 - Jan 27th, 2022 at 5:06pm
 
Just so long as it's damaged and not recycled Smiley
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Do All things with Honour and Generosity: Regret Nothing, Envy None, Apologise Seldom and Bow your head to No One †- works for me Smiley
 
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