Is this possible?

[Snake847]

Here is a idea I had about a electronic Paintballgun.
the balls are propelled by spinning wheels.The wheels are powered by the electric motor which is powered by the batteries. Every wheel that propels the balls is set at different RPM. the slowest one is at the beggening of the feedneck and the fastest one is at the beggening o the barrel.After the last wheel there is a sensor which senses the FPS od the ball which adjusts the pressure in the commpressors which send air aout 1 inch infront of the compressor to get the desired FPS. all this is contoled by the electronics in the gripframe(the gears, the pressure in the compressor. And there is numerus power supply to feed this proccess

[confedman75]

eeeeww, sounds heavy. I dont want a 6 pound gun. I like the idea though. Your alo going to have to fnid a way to use the paintballs as a sort of o-ring, or else the air will go both ways no matter which way the hsoe is facing, once the ball hits the barrel all the air is going to go backwards.

[Snake847]

Now that i think about it more there would be a need for air outlet holes right before the air inlet and right after.
Also the weight thing. When you think about it the gun would weight as much as your mag with a big steel nitro tank. Also IF thise would work the batteries would need to be quick charged after everygame. It takes about10 minutes to recharge RC batteries so it wouldn't be that bad.

[Redkey]

assuming you want to shoot a ball at 300 fps or 3600 inches/second.

that means that the outer edge of the last drive wheel, where the it makes contact with the ball, must also be travelling at 3600 inches per second.

if you have a drive wheel 1 inch in diameter the circumfrence of the wheel is 2 * pi * R = 3.14159 inches. So, to get 3600 in/sec at the outer edge that wheel has to be spinning at about 1146 revs per second. More commonly referred to as 68,755 rpm. I'm not too familiar with the motors and gearing available for RC stuff but this seems kind of fast.

The blast of air used to accelerate a ball is applied to roughly half the surface area of the ball. Using wheels to accelerate the ball will apply that force to a much smaller section of the ball creating some very high shear forces on the skin of the ball.

Just something to think about should you choose to pursue this idea.

[paintbattler]

yes, it does sound heavy but it doesnt have to be box-like..it could be milled on the corners and stuff and be about the same weight as a warped mag

[Snake847]

The small surface area thing isin't totaly true. Because what I would plan on using would be miniature revy impalers mage up of rubber that would bend to the ball and give it a rubberband like effect. also there would be wind crated by them like in a fan which would speed the ball up to about 240 fps, and that is how much I want it at so that the air from the compressor would add about 40-60fps. Also a 9-turn RC car motor can go up to 30,000 rpm or more if tuned right.
To add onto that I would put a larger gear on the motor so that it would spin the small gear on the wheel faster.

[Wat]

There's this surge of interest to make all things electric powered but they always over look the single biggest limiting factor about electricity. There's no way to easily store it in a portable device. The amount of energy stored in a 4500psi tank far outweighs the amount of energy stored in a similar size/weight battery. Pound per pound, electrical energy has the worst storage capacity. You look at all those electric cars, a gallon of gasoline stores more energy than 50lbs of batteries. Thats why hybrid cars are my bet to be the next winner. It takes advantage of the energy storage of gasoline with the efficiency of electric and can use existing gas stations.

But i digress. So back to the point, there is no way you could carry the batteries required to store enough energy for 1000 shots.

[Snake847]

Yes you can. One of those batteries lasts about 10 minutes. And those are the 2500's but ever since they came out with the 4000's they will last about 20minutes of continius run wilth the weight of the car on the motor.

[bjjb99]

Let's examine this concept from an energy balance perspective:

A 3 gram paintball moving at 240 fps carries around 8 Joules of energy. You must provide at least this much energy to the ball to propel it at that speed.

Converting electrical energy into kinetic energy of a projectile is highly inefficient. I'm probably going to be accused of being pessimistic, but I will assume that the efficiency of miniature revvy-like impellers acting like rubber bands to propel a ball is around 1 percent. Now you need 800 Joules of electrical energy to get the 8 Joules of kinetic energy imparted to the ball.

Energy divided by voltage equals current times time. We will ignore battery inefficiencies during rapid discharge.

E/V = I * T

So at 800 Joules and (I'm assuming) 12 volts, each shot requires approximately 18.6 milliamp-hours of battery "juice". A couple of years ago I looked into mass of 12 volt batteries versus storage capacity, and my results at the time indicated that you need around 0.325 kilograms of battery per amp-hour of storage. This was for gel-electrolyte lead batteries; your mileage may vary using NiMH or NiCD sources.

0.0186 amp-hours/shotshot * 0.325 kg/amp-hour = 0.00605 kg/shot

So for each shot you need around 6 grams of batteries. If you want 500 shots, you'll have to carry 3 kilograms (6.6 pounds) of batteries. That's one heavy gun, and it only gets you slightly more shots than a much lighter 47ci/3K HPA tank.

BJJB

[Wat]

You can't say RC motor runs X hours at Y RPM and thus it would be fine for a paintball. because the load on the motor is completely different. As someone pointed out, the final wheel has to spin upwards of 30,000rpm. To make sure that this rotor doesn't slow down as soon as it touches the load of a paintball you'd have to make it a good 10x heavier then the weight of the ball. Thats some serious effort you need there.

Sure an RC car weighs more but what is its acceleration? It goes from 0-10mph in a second? Now a paintball has to go 0-200mph in milisconds. And thats one of the problems, power. It is a much harder for a electro/mechanical device to impart the energy to a ball as it is compressed gas.

Nevermind the fact that for your design to have no lag time before a shot, you'd have to run the motors nearly continously. The amount of friction the systems of gears would generate would be significant.

[Redkey]

"someone" actually said 68,755 rpm.

If this did work could you imagine the rate of fire? It will probably never work in a portable device... but, on a bench with lots of power...

A 6" diameter wheels spinning at 12,000 rpm should put the outer edge of the wheel spinning at 314 feet per second. Two of these wheels are put next to each other like a baseball pitching machine.

A paintball sized groove cut (half depth) into the outer edge of the wheels would help to distribute the frictional loading on the ball surface area. The distance between the two wheels would have to be precisely controlled make sure enough pressure was put on the balls to propel them... but, not enough to crush them.

You might have to accelerate the ball in stages to keep the it from shreading. Also, the rpm of the wheels would have to be exactly the same else nasty spin would be inparted on the ball.

I'm sure that someone has tried something like this before.

[J_Hoyt]

Velocity control would be really bad on something like this. A slightly smaller ball would go a lot slower as it wouldn't be pressing on the wheels as hard....I think...

[MINIMAG4LIFE]

Maybe this is a little off the wall, but remember the pitching machines they had when you played little league? Could you possibly use two 10 degree modified rc motors and gearing to propell a paintball 300 fps? If they can do it with baseballs and footballs, why not with paintballs?

[Natural Newbie]

It would probly break paint like crazy to propell it like a pitching machine does.

[Catch22]

Ok think about this. IF YOU SOME WAY got superlight batteries and 68,000 rpm R/C motors in a gun to get the paintball going, would the seven ascending speed motors create gyroscopical forces. Yeah, I don't want to be mean but try to imagine pulling against those 68,000 )and lower) RPM gyroscopes for an entire game. Now if you could get the gun to levitate with gyroscopes THAT would be cool. I don't know about levitating paintball guns though....

[Wabbit]

How feasible would a small gas turbine be to power the wheel? I was thinking mabey a 2 trigger design, one to crank the wheel, one too dump paint on top of it. That way you wouldnt have the battry problems, could refill a tank instead of recharging, and still retain insane rates of fire. Just an idea.

[Der Cockermeister]

its not going to work, notice how all the people using scientific means to figure these forces out know this. the only people that seem to think it will work are neglecting the laws of physics and provide no scientific data whatsoever to support their hypothesis.

until somebody builds one that functions, i maintain the statement that it will not work