Model Boat Mayhem

Technical, Techniques, Hints, and Tips => Other Technical Questions... => Topic started by: roycv on November 24, 2008, 02:43:27 PM

Title: Squirting water
Post by: roycv on November 24, 2008, 02:43:27 PM
Hi all, my next model will probably involve squirting water, as in a fire pump about 12 inches above the water surface..

I have a pump unit which is a small 380 size motor driving a gear type pump  but it needs to be primed by sucking water through it.
I remember using an old type car water pump that I gave up on as it used to stick.  It had a 'rubber' impeller.
I have not checked again what might be available from the car spares shops though.

I built a successful system in a Bremen 9 about 12 years ago, now no longer with me, which used an orange coloured pump and that worked very well, but I don't remember who made it.

Does anyone have some simple systems that prime easily?
Can anyone recommend a good electric water pump?

Regards Roy

Title: Re: Squirting water
Post by: boatmadman on November 24, 2008, 03:12:27 PM
Roy,

If you mount your pump below water level, you wont need to prime it. A gear pump will also self prime up to a degree, depends on the pump specification.

One thing to watch for with a gear pump is make sure your oulet lets enough water out, as it is a positive displacement pump. This means if you restrict the discharge, the pressure will increase with the risk of rupturing tube, or blowing off connections.

In my opinion, you are better to use a centrifugal pump for this application, you can restrict the nozzle to get a good squirt without risking the pump/pipework.

Look here: http://www.cornwallmodelboats.co.uk/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2ecornwallmodelboats%2eco%2euk%2f&WD=pump&PN=water_pumps%2ehtml%23aG1952#aG1952

The second pump down is centrifugal and suitable for fire hydrants. I have used one of these successfully. The next pump down is a gear pump, I use these for ballast pumping, they are reversible, whereas centrifugal arent.

Hope this helps

Ian
Title: Re: Squirting water
Post by: Guy Bagley on November 24, 2008, 04:30:12 PM
ROY,

 the orange pumps  were available a few years ago at halfords, they were ' generic replacements' for  car windscreen washers that had failed, - about 15 though :((

i bought one about 9 yrs ago....  i dont know if they still stock them ?- maybe worth an ask next time you're passing...
Title: Re: Squirting water
Post by: BobF on November 24, 2008, 05:33:36 PM
This is purely an assumption, but if you fit the pump at the bottom of a U bend, it will always be primed.

      Won't it?
Title: Re: Squirting water
Post by: alan colson on November 24, 2008, 05:47:32 PM
A little word of warning to everyone. If you use a water pump on a model boat and are demonstrating at a displaying, I believe it is illeagle to spray another person with water from a lake or river because of weils disease. Using fresh water from say a swimming pool or on board tank is of course ok.
Title: Re: Squirting water
Post by: boatmadman on November 24, 2008, 05:49:16 PM
Initially, yes, but but it then depends on the characteristics of the pump. If it cant maintain enough vacuum to draw water to itself (called suction head) then it will lose suction. A centrifugal pump will struggle like this, and usually lose suction. Any positive displacement pump will cope with this scenario.

Ian

Title: Re: Squirting water
Post by: FullLeatherJacket on November 24, 2008, 06:20:09 PM
I can recommend, from personal experience, both the Graupner #1951 pump and Cornwall Model Boats.

FLJ
Title: Re: Squirting water
Post by: gribeauval on November 24, 2008, 07:23:41 PM
Can anybody recommend a 12v, self-priming pump that can be run for extended periods at varying speeds without shutting down/burning out ?

Mike
Title: Re: Squirting water
Post by: Stavros on November 24, 2008, 07:48:34 PM
I have had a normal car washer pump fitted to my sea queen for 4 yrs and it's still going strong,with no ill effects

make your own mind up



Stavros
Title: Re: Squirting water
Post by: bosun on November 24, 2008, 09:12:29 PM
I use a car windscreen washer pump driving one fire monitor on my Nangee and another driving two on my Dutch Courage, 7 from my local Motor Spares shop, obviously they dont run continuosly, and I have had no problems.
Bosun
Title: Re: Squirting water
Post by: FullLeatherJacket on November 24, 2008, 09:59:02 PM
Can anybody recommend a 12v, self-priming pump that can be run for extended periods at varying speeds without shutting down/burning out ?

Mike

Mike
PM me with a description of what you want to do with this thing - I might have a solution for your particular application but I don't want to hijack this thread.
FLJ
Title: Re: Squirting water
Post by: muduck on November 27, 2008, 12:12:24 PM
I plan on using this on a slow moving Tug.
http://cgi.ebay.com/RC-Ship-60A-Water-Cool-Brushless-Motor-Programmable-ESC_W0QQitemZ270305803396QQihZ017QQcategoryZ116074QQtcZphotoQQcmdZViewItem

any thoughts of how to move the water through?
Title: Re: Squirting water
Post by: Proteus on November 27, 2008, 12:44:48 PM
I plan on using this on a slow moving Tug.
http://cgi.ebay.com/RC-Ship-60A-Water-Cool-Brushless-Motor-Programmable-ESC_W0QQitemZ270305803396QQihZ017QQcategoryZ116074QQtcZphotoQQcmdZViewItem

any thoughts of how to move the water through?


Will it spray water  %% 

Proteus
Title: Re: Squirting water
Post by: Garabaldy on November 27, 2008, 12:59:42 PM
is it generally accepted that windscreen washer pumps are more powerful than the standard model pumps such as the graupner ones?

Ive always wanted to fit a big pump to a boat which moves alot of water out of the fire monitors.  Put out real fires!
Title: Re: Squirting water
Post by: roycv on November 27, 2008, 01:41:45 PM
Hi all, as it turned out the 'motor shop' I went has just closed down.  I visited another and bought a water pump, it is a centrifugal one with the water entering at the centre of the pump.

When I got home I did some tests and it squirts about the same amount of water as the gear teeth one does, it is no better at self priming and consumes 1.8 amps on 6 volts the gear version taking just 0.6 amps again on 6 volts, so I am still looking.

Intrigued by FLJ's offer!

regards Roy
Title: Re: Squirting water
Post by: portside II on November 27, 2008, 03:59:08 PM
What about the fuel pumps the aircraft guys use , i kept mine and have fitted it in my tug to pump the water from the bilge (i have a slight leak when the rear deck goes under water :embarrassed:) it is abobe the bilge and is self priming ,and will run for extended periods of time . One warning if you are to pump water directly from the pond please fit a filter in line ,available as in line fuel filters from motorists shops i did not and broke the impeller ,luckly it was repaiable and is still going strong a year later
http://www.sussex-model-centre.co.uk/shopexd.asp?id=1280
there are others.
http://www.twenga.co.uk/dir-Toys-Games,Model-making,Fuel-pump
daz