SpudFiles

Yup, we do.

jyrtshrsdtiktyd

That's cool!
He's so much better than the AMerican guy, we should get the British Guy In AUS. Maybe a Mix of both.

Ok, it's all looking even more ghetto now. The part I epoxied held beautifully but the mag kept disintegrating so I resorted to keeping everything together with cable ties. To aid feeding, I put a lead weight in the mag after the coins and it improved reliability to no end.

Here's a few videos at 110 psi:

[youtube][/youtube]


[youtube][/youtube]


[youtube][/youtube]

Cardboard is about the limit of what it will penetrate, it won't go through 1/4" ply or the bottom of a soup tin. Note also that penetration depends heavily on how the coin hits the target. Coins flying like a frisbee slice clean through the cardboard while those that impact face-on are usually deflected.

Nice. Now let's just imagine a longer barrel.....................
And maybe a sharpened coin or two .........

Oh the humanity!

The blade somehow skipped over the coin and punched through the magazine, CATASTROPHIC FAILURE!



you know you're still a kid at heart when something like this happens and you simply go "Duuuuude.... sweeeet!"

edit: That was an easy fix, the blade wasn't permanently bent or anything, now I just have to put the magazine together (again!)

Here's one of my favourite damage shots, straight through an acrylic chocolate box and embedded in the cardboard behind:

Are you going to fix it or leave it as a silent tribute to JOHN-117....erm, I mean coin-launching, too much Halo 3(well, wishing for Halo 3).
Anyway, throwing coins is always a good substitute(hold between middle and index fingers, flick wrist sharply) but this was way cooler. If you ever fix it, try using washers, or widening the barrel to shoot tungsten rings(I found one when disassembling a vcr or dvd player i don't remember they were both built into a tv). Tungsten hurts .

already repaired, see edit above

Nice gun, have you tried anything to spin the coins and make impacts more consistent?

cheers I might add a strip of rubber or sandpaper to one of the rails but for now I'm just happy I got it to feed.

The thing with this sort of launcher is that the projectile can only go as fast as the piston launching it or is it? I always wondered, if you hit a golf ball with a golf club at a certain speed, would it travel the same distance as a golf ball taped to a club then released?

hmmm...

I would imagine the coin (or golfball) would be traveling slightly slower than the piston, due to losses (heat, friction of the initial impact). Makes sense to me. Taped then released would *have* to be faster.

hmmm, thats a tricky question jack... But i believe i have an answer.

An object requires energy to move, and an object moving has kinetic energy, but a rubber band stretched has potential energy, or in more relevance, compressed air is potential energy.

The piston pushing has a certain amount of kinetic energy, governed by the formula
Kinetic energy = 1/2(m(v^2))
m = mass
v = velocity

The piston will hit the coin with a certain amount of kinetic energy propelling it forward with that amount of kinetic energy (excluding energy loss to sound, wind and friction). Since the piston is probably heavier than the coin, for the coin to have the same kinetic energy, it will have to travel faster than the piston.

With regard to the speed of the coin, the coin will travel faster than the piston, but with the same amount of kinetic energy (disregarding energy loss to sound, friction and wind)

The golf club thing is slightly more complected. My understanding is that by strapping th golf ball to the club, you will decrease the distance the ball travels because you are not transferring energy from the heavy club to the light ball, you are just swinging and releasing the ball. By looking at the kinetic energy formula above, you will see mass and speed coming into the equation. The ball will have less kinetic energy, thus less distance because the ball will travel at the same speed as the club, but the ball has less mass, this means it will have less kinetic energy. The club because its heavier will have more kinetic energy than the ball traveling at the same speed, which will be transfered to the ball when the club strikes it, apposed to the above scenario i just described.

I have to disagree with you Marco, if the coin was rubber i could agree however i'm having serious trouble understanding how the coin (being solid) would be able to travel faster than the piston, if we were talking about an air setup it would be different. With JSR's setup the striker or piston "hits" the coin, imagine a pedestrian (i know bad example) being hit by a car at 60 kph, they don't accelerate so why should the coin?

The coin is given kinetic energy, from the piston. BTW, the coin should only travel faster than the piston if the piston is heavier than the coin.

I believe my theory should be true, since kinetic energy is is directly related to mass and speed, and the piston is transferring kinetic energy to the coin, the only thing that can change for it to have equal kinetic energy is the speed (unless its going very very fast). (this is however not including energy loss due, but it should be that much energy loss).

EDIT: My theory is an application of a fundamental law of classic physics, the conservation of momentum. But applied in the sense of kinetic energy, but as you can see by the formula, my argument and theory works for both fomulae

Momentum = mass x velocity

I respect you opinion, but.. i still disagree.
I spose we will have to wait for more responses

The way a golf club achieves a fast golf ball is by way of two things, the speed of the head of club when striking the ball (high speeds are achieved by way of a large arc, which creates high surface speed of the club head, you don't have to increase an arc's radius much to produce a lot more speed, if it is still capible of being spun.)
The other way they transfer energy is by way of a "bouncy" material, hence it bounces off the end of the club, (think off a super ball vs a solid ball, say nickel of the same weight- the super ball will win every time)

Check....

Edit: momentum = mass + velocity is correct, however that law is applied to a mass that is already moving.
How does the piston apply both, i.e. mass AND velocity, it applies one (Velocity) without the other.
If you assume it to transfer both you have un-equal or impossible equation.

Novacastrian wrote:I respect you opinion, but.. i still disagree.
I spose we will have to wait for more responses

The way a golf club achieves a fast golf ball is by way of two things, the speed of the head of club when striking the ball (high speeds are achieved by way of a large arc, which creates high surface speed of the club head, you don't have to increase an arc's radius much to produce a lot more speed, if it is still capible of being spun.)
The other way they transfer energy is by way of a "bouncy" material, hence it bounces off the end of the club, (think off a super ball vs a solid ball, say nickel of the same weight- the ball will win every time)

Check....

Yeah we will have to wait and see. But i understand where you are coming from, it might sound weird if the coil travels faster than pistons motion.

I agree, but you missed one thing, heavier club means more distance, combined with, as you said, a wide arc creating most speed at the head.
Once again referring to the kinetic energy and momentum formulae.

I just got a coin, grabbed a heavy object and a plastic pen and ran a few rough tests. I moved the heavy object and hit the coin at a speed, i then hit the coin with a light pen at the same speed, the coin traveled much further when i hit it with the heavier object at roughly the same speed. it was on the floor, i repeated it multiple times and got the same result.