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shobley
05-08-2009, 07:47 PM
I've been trying to put together a water gun for my Dalek, and so far the results have not been so great.

The best thing is a hand-pumped pressurized water sprayer ($10 from Walmart) but the amount of force required to operate the valve is HUGE.

Does anyone have any ideas for a simple water gun to operate under servo control?

Steve

darkback2
05-08-2009, 09:27 PM
for some reason I remember electric water (http://gizmodo.com/gadgets/toy-guns/the-best-watergun-is-buzzbees-water-warriors-tarantula-277066.php)guns...Pull the trigger and a motor would squirt the water out. I'm sure you can hack the switch and swap it out with something like this (http://www.trossenrobotics.com/store/p/5467-BattleSwitch-radio-controlled-10A-relay.aspx)...you'll have to waterproof everything...

Hope this helps.

DB

shobley
05-08-2009, 09:38 PM
I've tried that, and they don't really have the power I need.

The little 6v pump used in the USB servo water gun is pretty good, but impossible to keep primed and not really the thing for a 300lb robot tank...

:-)

The irony is that as an ex-conjurer I have all the parts to hand to make a very effective fireball launcher, but that might get me arrested...


Steve

Adrenalynn
05-09-2009, 03:08 AM
Try a 12v marine sump-pump, and then reduce the outlet placing it under pressure?

robologist
05-09-2009, 07:12 AM
Why not use a windshield washer pump (http://www.dealtime.com/xDN-automotive_parts_and_accessories--windshield_washer_pump)? I've got a couple I snagged to try on a robot sometime.

shobley
05-09-2009, 07:42 AM
I went to my local Pep Boys a few days ago and asked them how much their washer pumps were. No one was able to tell me.

It seems that you can bring in your car, and get one fitted, but they can't give out pricing on parts over the counter.

I looked on ebay, but I can't work out what I would need (hoses and nozzles) to make a functional gun.

Steve

robologist
05-09-2009, 08:16 AM
For finding a pump (http://www.google.com/products?client=firefox-a&rls=org.mozilla:en-US:official&channel=s&hl=en&q=windshield+pump&oe=UTF-8&um=1&ie=UTF-8&sa=N&tab=wf&ei=6n8FSpeoOejgtgfqrcCIBw&oi=property_suggestions&resnum=0&ct=property-revision&cd=1). Most appear to be under $20, and some include hoses. I've usually been disappoionted with Pep Boys, Autozone or O'Reillys can actually be helpful.

Hardware stores like Ace typically have various hoses in either opaque plastic or those nice clear plastic ones, just find one to fit the intake and output of the pump used. For a final output nozzle, the same hardware store should have some brass tube or aluminum tube in a K&S bin. Grab one that is close to the tube size just selected, and crimp the end a little to make the stream go further.

shobley
05-09-2009, 09:09 AM
I ordered a couple of the washer pump kits, I'll post an update if it works out.

Adrenalynn
05-09-2009, 02:05 PM
No love for the sump-pump, huh? They're not putting out much more than a few hundred to a few thousand times a washer pump. :)

Testing2000
05-09-2009, 02:28 PM
A marine sump or bilge pump is centfugal, (sp) not much pressure and slow response. How about a resevoir with a a solenoid controlled CO2 cartridge?

Adrenalynn
05-09-2009, 03:04 PM
High volume becomes pressure at lower volume when compressed.
P1 + ½ ρv12 + ρgh1 = P2 + ½ ρv22 + ρgh2

Testing2000
05-09-2009, 05:01 PM
All well and good for steady state. Check some startup curves Miss.

Adrenalynn
05-09-2009, 05:16 PM
I must have missed the "I need instantaneous pressure without startup time". In that case, an unobtanium pump is the only choice.

Testing2000
05-09-2009, 05:42 PM
A slow weapon is a slow weapon. Can we agree on that? Would you accept a 500ms lag on a trigger?

Adrenalynn
05-09-2009, 06:43 PM
Sure, a simpleton would have issues with the concept of pre-priming. I'd expect better from you. :tongue:

[Note to readers: Testing and I have history, so this is good natured...]

Testing2000
05-10-2009, 06:02 AM
Growelll

darkback2
05-10-2009, 06:50 PM
Ok...I've written this post about four times, and each time I seam to screw it up. so here...

You should probably go with a pneumatic system...where a pneumatic piston pushes and pulls a hydraulic piston...The hydraulic piston pulles water through a valve when the piston is pulled to the back position...and then squeezes it out through another valve/nozzle when pressed in.

You would need a pneumatic pump
some solenoid valves
some hose
some fittings
and 2 cylinders. I'm not sure if one has to be for hydraulics specifically...
and probably some other junk that I can't think of right now.

Get the cylinders from bimba (http://www.bimba.com/)
The valves from SMC
You can also get the hose there too. (http://www.smcetech.com/CC_host/pages/custom/templates/smc_v2/prodtree_node_2.cfm?cc_tvl=&cc_nvl=((CC,smc,V_M_US,Node_27132))&CFID=780829&CFTOKEN=72033599&jsessionid=ec307f72007e1ec27152)
That way you can keep the piston primed, and have instant high power sprayage.

Hope this helps.

DB

shobley
05-15-2009, 04:14 PM
OK, here's what I went with - cheap, cheerful, and low priming times...

I just need to sync up the sound effects module now...

YouTube - The new Dalek gun

I will need a bigger water tank though, this thing can burn through 16ozs in a matter of seconds.

Matt
05-15-2009, 04:23 PM
Wow, that really works well! Nicely done!

robologist
05-15-2009, 04:53 PM
Way cool, good to see it working!

shobley
05-24-2009, 02:33 PM
An updated video - I replaced the RC system with a PCM one - much quieter...

YouTube - Dalek gun and sound effects

I linked in a gate circuit to trip the Arduino, with a wave shield, (adafruit.com) that then toggles a power transistor to switch on the pump.

Steve

shobley
05-25-2009, 10:26 PM
OK here's the first official test drive footage...

YouTube - Test Drive of the Daleks

robologist
05-26-2009, 02:31 AM
Looks really cool! And moves well too, good maneuverability.

shobley
05-26-2009, 12:51 PM
Thanks, it's only running at 1/2 power at the moment - I'm still getting confident with the RC system and the terrain.

Eventually I'll have to "open her up" on the straight.

There are some nasty bumps on the sidewalk in the neighbourhood - I'm scared the head might fall off! :veryhappy:

Once I've got some good video, I'll put up a page or two on the construction.

It's funny but I've noticed that all the BBC Daleks have the characterstic wobble from side to side when they're not being run on studio floor.

Never noticed it before now.

avayan
06-23-2009, 01:38 PM
But what are you trying to do? Is it a dinky little water flow like on a squirting gun, or do you want to clean your driveway?

If it is squirting, I remember there was this toy like water pump I bought once on All Electronics. Could not find it today, though. And I searched all the major surplus places such as the Gold Mine, MPJA, MECI, etc. You would need a DC motor driver, though, as these came up with a DC motor, not an interface you could address with an RC Servo.

Another option is to buy a pressurized bottle at harbor freight. These are pretty cool! You can even pressurize them with a bike tire pump. Then press the cap and off it goes. It is like a spray can that can be indefinitely refilled. And is only 5 bucks!

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=1102

You could use an RC Servo to press the cap and release the water, or you could even use one of those grips that transform an aerosol can into a "gun" with a handle. That should make it easier to attach the servo mechanism.

The last choice would be to use a 12V compressor to generate the pressure. That would be heavy but it appears this is a large robot, so a few extra pounds may not be overkill. These are pricey though... Or you can buy the super duper cheapo at HF: http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=4077

Will be amazed if it works, though...

Adrenalynn
06-23-2009, 01:39 PM
Did you see his final result? Watch the videos?

avayan
06-23-2009, 01:42 PM
I can see that you have solved the problem already. MEGA AWESOME!!!!!

ScuD
06-24-2009, 01:09 PM
The last choice would be to use a 12V compressor to generate the pressure. That would be heavy but it appears this is a large robot, so a few extra pounds may not be overkill. These are pricey though...
Will be amazed if it works, though...

A few years ago (actually over 12yrs, damn I'm getting old) I actually used one of those 12v compressors in a somewhat different way.

I put a cap over the air intake and along with some ghetto hardware actually had it suck up and spit out water mixed with glicerine, pumping it along copper tubing that i drilled with 1mm holes to spray an old clothes iron, instant smoke machine!

The thing drew loads of power and it was definetely a suck-squeeze-blow thing rather than a constant stream, but if you were to put the water in a tank pressurized by one of these things I'm pretty sure it would work like a charm.