Super Soaker Central

I think this thread is in the right place, if not, please move as required.

Anyway, I was wondering whether it would be possible and practical to build a circular crank-style pump with a handle that you turn to pressurize the water gun, instead of a traditioanl pump which you move up and down. If you are confused by what I mean, look at the pump system of the "Shield Blaster 2000". However, this would be different in that water does not come out immediately as you turn the crank. The turning would just build up pressure, which would be released with a normal trigger.

It would work like a car engine in reverse. A car engine uses the up-and-down motion of the pistons to turn the crank shaft. Here, you would turn a wheel attached to a pump, and as the wheel turns, the pump would go in and out. If you are confused by this description, look at the attached sketch in Paint.

I realize that there are several drawbacks to this setup. One, it could be tricky to build. Two, the pump will not move very far unless the wheel is very big. So with less pump volume more pumps are required.

The main advantage, though, is that I think it would be easier/more comfortable to turn a crank than to move a pump in and out. I don't know about you, but it just seems like it would be a lot more convenient to me. A traditional pump is good for most soakers, but for one that requires many pumps, this might be more efficient, I don't know. So, is it feasible to have a crank-style pump which converts turning motion into pumping motion? This setup might be on a homemade or added to a stock water gun.

You won't need the pump to move very far, so don't worry about that. The pump stroke of pumps in this style usually is short when compared against normal hand pumps. What matters is the amount of energy used to pump, and because you're not switching back and forth like on a normal pump, there shouldn't be any significant difference between a short and long pump of this style aside from practical differences.

There shouldn't be too much difficulty in making this, so if you think it could be helpful, start building.

You can definitely build this type of crank-based piston pump. As noted, it''d be like a car engine piston (or train steam engine) in reverse. However, from my personal view, I found crank-based pumps not as easy to use for a water gun; pumping and shooting is more shaky when using a crank as opposed to a regular back'n'forth pump. That said, if you like the style, definitely go for it!

At first I thought you wanted a rotary pump like one of those shown here.

I agree with iSoaker about the pumps though; they just don't feel right. Regular pumps work because the vectors of the force going through each grip are coaxial - your hands push and pull directly towards or away from each other. With a crank, there's orthogonal (perpendicular) distance between, which leads to torque (a twisting force). In other words, the water gun may rotate and jump around as you pump.

That said, maybe the end result is smoother and less jarring, so go for it! If there's no good place to mount the axle of the crank, use a sheet of Plexiglas. I'm not sure of what to use for the crank - maybe a bicycle arm with no pedal?

I wouldn't use a crank. That will result in wildly varying forces as you turn the handle, which won't feel good - you want the force to be constant.

A peristaltic pump is an option, but I don't know if they can generate high pressures.

I reckon best would be a centrifugal pump. You'd likely want to use gears to increase rotation speed, so make sure they're good - I've heard Mecanno gears work well and are cheap.

Another idea is to do similar to the Water Warriors Scorpion. Have a small nozzle that can be powered from cranking directly, while holding the trigger open, and larger nozzles that need pressure stored up.

In fact, if you're going to use a rotary pumping mechanism, why not stick a motor on it?

Motor pumps would open up new possibilities. More power and faster pumping. But you'd need to heft around a semi-powerful motor and large battery. Unless it was gas...

Actually, perhaps not a centrifugal one. There are rotary positive displacement pumps, as in that link Silence posted.

Indeed, motors have potential. However, retail motorised guns have tended to be lacklustre. Probably the best was the Water Warriors Scorpion, since it has a pressure chamber, allowing to build pressure over time and then let it out all at once - just as normal pressurised guns are more powerful than piston pumpers.

I'm not sure you'd need too large a battery. You're always limited by water capacity, and realistically much more than a few tanks worth of firing before recharge isn't needed.
For internal combustion power, model aircraft engines naturally have good power-to-weight-ratio, and are easily obtained.

I'm planning a motorised gun myself, will report when I've built it.

just mod a shield blaster with a cps bladder, like it says in the guide used to convert a vaporizer to cps. for pressurized water tank, i have no idea.

I'm not sure how much pressure the shield blaster can generate. It might not be enough.