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Abstract Ammo Design 2021! (Read 11130 times)
Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #180 - Aug 24th, 2021 at 4:11pm
 
you're right, the fins would need to be angled.
It's pretty simple to do.
Just make some fins attached to a shaft and shove the shaft up the wet clay glandes bracket whistle
If you make sure a little of the fins is also in the clay, it should hold it pretty tight when it dries.
Or the glande will split - one or the other Smiley

Right so whle the torus dries, I've gone back to the aerofoils.

I've got a basic hollow cylinder with thick base tapering to a thin top.

I've also added angled slits that should orient on the angle of rotation.
I've then tilted those so that the slits actively funnel air into the interior of the cylinder.

I have no idea if this is a good idea or not. But it makes the 'tail' lighter and we've already established I like pushing air through holes - so why not Smiley
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #181 - Aug 24th, 2021 at 4:16pm
 
And i can't think of any other way to make these that wouldn't take a long time.

size wise - the diameter is 30mm and the height is 50mm. This should be a nice fit in my sling pouch.
And with it being rigid, hopefully it will throw a lot better than the card ones did.

Plus if i can get it back from dream fairly quickly, it should be reuseable !

Won't be testing these till thursday as I want to do it on the rec field. Nice big flat short grass football pitch Smiley
And wednesday is the village boys football team training night.

So I'll make a few of these and a few without slits and see if any of them fly at all and if the slits make any difference or not.

Might even get some video, we'll see.

Plus if i have seevral of each, dream can't steal them all !
The little bugger will try Smiley
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #182 - Aug 24th, 2021 at 5:15pm
 
So first rigid 'aerofoil plus' sling missile.
Yeah it's rough, this thing was printed at saffy's top speed.
100% functional, just not pretty Smiley

Weighs about 17gm and feels pretty substantial.
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vetryan15
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Re: Abstract Ammo Design 2021!
Reply #183 - Aug 24th, 2021 at 7:36pm
 
Ca,

If u need a tester of your printed molds. I would be more then happy to test em out, and make videos again....
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #184 - Aug 25th, 2021 at 3:40pm
 
Yep - I'll try and get the parcels out next week. With various goodies Smiley

Meanwhile I've got a bunch of aerofoils to test.
Going to see if I've got a more appropriate sling to throw them with.
Either a split pouch or a flat leather pouch would probably be more suited.

These two look pretty good. Though the Tibetan type one is pretty long, the aerofoils might not be heavy enough. We'll see Smiley
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Re: Abstract Ammo Design 2021!
Reply #185 - Aug 26th, 2021 at 1:45am
 
These look mad!
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #186 - Aug 26th, 2021 at 6:58am
 
Be interesting to see if
1) they will sling.
2) throwing with a stick is better than sling
3) if the slits make any difference

So anyway, back to the torus that's been drying out.

for some reason minimal shrinkage.
The outer diamater is still 12mm.
The widest part of the interior gap has gone from 21mm to just 20mm.
While the gap from the edge of the interior to the central hub has not changed at all.
started out at 11mm and after 2 days is still 11mm.

So i can just make a blade insert the same size as the hole in the wet clay. And it should just shrink to grip, but nowhere near enough to break the torus.
Must be something specific to the shape - glandes tend to shrin a lot more.


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« Last Edit: Aug 26th, 2021 at 10:39am by Curious Aardvark »  

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IronGoober
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Re: Abstract Ammo Design 2021!
Reply #187 - Aug 26th, 2021 at 11:43am
 
Eagerly awaiting results....
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #188 - Aug 27th, 2021 at 8:18am
 
I'll take the torussessessess (Tori ?) For a walk tonight, didn't have time yesterday.

Haven't decided on a fan design yet, I'll have a play this afternoon.

The Torissies (lol) don't throw well by hand - just too heavy.

Might make a simple flat pouch sling for them as well.
We'll see Smiley
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Re: Abstract Ammo Design 2021!
Reply #189 - Aug 27th, 2021 at 12:47pm
 
Remember the thread talking about the magnus effect?

The idea is a bullet both biconical and with groves like a water mill wheel.
When appropriately thrown the wind drag in the groves pointed in the direction of the throw will cause the bullet to turn (besides the spin it gains from the throw itself).

This would ideally make the bullet fly longer or upwards with the extra lift.
You can already do this with a regular bullet but with this it should gain extra spin.
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #190 - Aug 27th, 2021 at 4:04pm
 
Magnus effect - well yes I did notice that Smiley

Now I did take a couple videos. But honestly, with the phone in one hand and the sling in the other, it does not make for great video.

So before I take pics of the wreckage and try and salvage a half reasonable bit of footage I'll go through my observations.

Throwing with a stick, whittled smooth.
No difference between slotted and solid.
I tended to throw high, with more practice I'd get it straighter.
Didn't travel terribly straight.

But with a sling, very noticeable difference.

They both went further, probably 30-40 metres.
Fig 8 with a good vertical release, went well as did a  multi rotation windup and sidearm throw.

Unfortunately with the phone in one hand fig 8 is tricky.

And then there was the other problem whistle
Phoebe and dream Smiley

Yeah, while neither brought them back to me, they did enjoy chasing them and giving them a good crunch.
So I reckon a got an average of 1.5 throws per aerofoil.

And the results are:

The solid ones flew quite well, not terribly straight - I was either throwing into the wind or across the wind - but they flew correctly oriented, just not terribly straight.

The grooved/slotted ones flew a lot straighter and tended to climb quite steeply as well.
When I got one the wrong way round, they just dived into the ground. So the grooves were definitely both giving lift and also keeping them straighter.

So if I cut down on the number of slots, they should go further and straighter.

I'd have liked to do a lot more throws, but after about 15 minutes all I had left was bits Smiley

So I really need to go down with the tripod and also make the aerofoils out of the flexible tpu, which should be a lot more dog proof Smiley

But as far as this short test goes.
Yeah, they throw quite well. Once I get the number of grooves right so they go more forward than up, should get some reasonable distance.
Tempted to up the diameter to 35 or 40, which will not only give more overall weight but more wing area.

I've got the length about right. I tried a couple that had been bitten in  half, and they were rubbish.

So maybe go up to 40mm diameter and 60 or 70mm length, and make them from 'chewable' polyurethane. And reduce number of slots.

But yep, fun new ammo type.

When I've got the design nailed down, I'll attach the stls.

Without such enthusiastic helpng friends, the crunchy pla ones would probably last for years Smiley

Oh yeah I ended up just using the shepherd's sling in the end. Just worked really well. I think it's one of Pete's, but wouldn't swear to it.

Attached pic of bits I could find, looks like I missed a couple.
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« Last Edit: Aug 27th, 2021 at 5:05pm by Curious Aardvark »  

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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #191 - Aug 27th, 2021 at 6:59pm
 
https://youtu.be/J7jI6eyEa_M

Honestly, that's as good as it got.
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Re: Abstract Ammo Design 2021!
Reply #192 - Aug 29th, 2021 at 7:15am
 
I love the idea of threading them on a straight stick.  Cheesy Thats some good thinking outside the box there. I actually am wondering if theres a way to make that a viable hard hitting weapon because it seems like it would be so easy to aim.

I couldnt see much from the flight but thats to be expected since you are holding the phone. I saw the two most important parts though: phoebe and dream. What kind of silly pups play fetch with a mans experimental aerofoil ammo?
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #193 - Aug 29th, 2021 at 12:00pm
 
Fetch ?
Nobody was playing fetch.
'Crunch' was the game de jour Smiley
Chase it, catch it, crunch it, spit it out and wait for the next one lol
They were having a grand old time Smiley

Dream will occasionally bring a tennis ball back, well he always brings it back, he just doesn;t always give it to me.
Phoebe will usually bring a tennis ball about 75% of the way back, and then expect you to go get it.

The stick was also doubly useful for picking the aerofoils up as well.

Yeah the video really needs to be on a tripod.
And better edited whistle

I'm curently printing a 35mmx60mm long with a reduced number of slits.
In dayglo yellow flexible polyurethane.
Dog proof ?
maybe lol

The smaller one had 16 slots, this one has 12 - so with the increased surface area and weight ( around 24gms) of the aerofoil, it should cut the lift down to something that will hopefully fly straighter.
The thick leading edge will keep it pretty rigid, so should throw okay.

Throwing from a stick is good fun - but as you don't have the stabilising spin, they kind of zig zag when hit by any wind.

But it's good fun.

The card ones also throw well with a stick Smiley   

video clip of the new one being made.
That's slowed down a bit, flexible filaments print slow, but not quite that slow Smiley
But she does run almost totally silent. The only things that make any noise are the 5 cooling fans.
(1 for the controller board, one for the power supply and three on the printhead itself)

They'll take approx 4x longer to print than the crunchy ones did.
About 2 hours each aerofoil.
So once I've done a test print, I'll leave it running  overnight with another 4 or 5.
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Curious Aardvark
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Re: Abstract Ammo Design 2021!
Reply #194 - Aug 29th, 2021 at 12:29pm
 
copy and paste this script into openscad ( www.openscad.org )
Quote:
// Curious Aardvarks aerofoil sling missiles

$fn=75;

// Change numbers below to change aerofoil

cd=35; // cylinder INTERNAL diameter - full diameter is this plus 2x the base wall thickness

ch=60; // cylinder height
bt=4; // base wall thickness
ns=4; // number of slits per layer
nls=3; // number of layers of slits
at=30; // angle of tilt
st=3; // slit thickness
sh=10; // slit height
sha=8; // slit height adjuster - adjusts gap between rows of slits
shm=100; //slit height mover - higher numbers = smaller adjustment - moves all slits up or down

// the bit that actually generates the aerofoil.

module cylindrical(){

// create the basic cylinder
difference(){
cylinder(d=cd+2*bt,h=ch);
translate([0,0,-0.5])cylinder(d1=cd,d2=cd+2*bt-2,h=ch+1);

// add slits
translate([0,0,ch/shm])for (z = [1:nls]){
for (i = [1:ns])rotate([0,0,45*z]) rotate([-20,0,((360/ns)*i)])translate([cd/2,0,(sh+sha)*z]) rotate([-at,0,0]) cube([cd,st,sh],true);
} // END HEIGHT REPITITION
} // end diff
} // end mod

cylindrical();


Once you've adjusted the parameters - press 'f5' for a quick preview and 'f6' for a full render (it can take a little time depending on your single core processor speed).

If you come up with a design/ size you want me to try, no need to upload the exported stl file, just screenshot your settings and I'll make it and see how it flies. Video not guarenteed whistle
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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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