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pump pressure? - psi?

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Postby petn7 » Fri Jun 27, 2003 1:43 pm

for those subs that need "high" pressure pumps to fill ballast tanks under pressure...how much pressure can they produce in psi?
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Postby David H » Sat Jun 28, 2003 2:29 am

G'Day,

I have a Pump tank in my boat that uses the system I think you're talking about. Pumping water into a sealed tank and pressuring the air behind?

I bought a 12v high pressure centrifucal pump from my local Dick smith (Electrical store) They are similiar to Windscreen wiper pumps but you can buy ones that are completely sealed and waterproof.

I could not tell you exactly the PSI. However what i have written above should help.

I bought mine for about $15 Aus dollars probably cheaper in the states.Hope this helps.

regards,

david H
"Baldrick ,you would'nt recognise a subtle plan if it painted itself purple and danced on top a harpsichord singing "Subtle plans are here again!!" Blackadder.
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Postby petn7 » Sat Jun 28, 2003 11:37 am

yeah, that's what i'm trying to do. how big is that pump?
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Postby David H » Tue Jul 01, 2003 3:37 am

G'day,

If you type in "Dick Smith Electronics australia" You should find a big website for all things electronic.

In the little search window for serial numbers type in P8907.
This should lead you to the exact little pump that has made model submarining such a pleasure for me.

Sorry for the run around....

Now i assume you are in the States. You can probably get an equivalent some where.

I dug up some notes on the pump. it's 12 v runs at about 20,300rpm

dimensions:
72mm x 47mm x 47mm

I fit mine into a 80mm dia acrylic tube. you really need to run it off 12v for it to really fill the tank. It is a v reliable pump and will fill the tank to about 60%. You may feel that it doesn't fill it enough but It can send my boat to the bottom on that.

I really hope that this helps, please tell me how you go.

regards,

David H :)
"Baldrick ,you would'nt recognise a subtle plan if it painted itself purple and danced on top a harpsichord singing "Subtle plans are here again!!" Blackadder.
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Postby Sub culture » Tue Jul 01, 2003 6:12 am

Hmmm. Generally 7-10psi is the norm, for a windscreen washer pump, the geared variety.

Generally, if pumping into a sealed tank, you can expect to fill between 50-70% of the tank volume.

Norbert Bruggen supplies a neat range of peristatic pumps, which are self selaing and will pump to high pressure- no problem. Feedback from other members who use this system report that they can be a bit sluggish at pumping though, and they're a bit pricey too (DIY?).

I'd look for a good quality metal geared pump (breakers yards are a good source, and you want to be looking at the older cars IMHO), the plastic ones tend to live short lives in this application.

Andy
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Postby smwarships » Tue Jul 01, 2003 8:57 pm

Hello ,
I have a question for you about pumping water into a sealed
ballast tank .
I have a water pump that I purchased from Dick Smiths
that I plan to use to fill a sealed ballast tank . How do you
keep the water in until your ready to dump the ballast ??
???
Darle
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Postby JWLaRue » Tue Jul 01, 2003 9:18 pm

>> How do you keep the water in until your ready to dump the ballast ??

One way to do it is with a solenoid valve or a check valve.

Whether you need something like this or not depends on how the pump is built. If it prevents 'backflow' then you probably do not need it. If it doesn't (i.e. it 'leaks'), then you need something like it.

-Jeff
Rohr 1.....Los!
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Postby ThorDesign » Tue Jul 01, 2003 10:29 pm

Guys,

If you want to see the exact system you are speaking of in action refer back 2 issues of the SCR to John Slater's beautiful Permit in 1/72. He explains the ballast system in detail. I am using the very same pump in my upcoming ABS ballast system. So far it works exceptionally well and draws very little current for the volume it is pumping. I order them from Dick Smith electronics in Australial over their website. If you order several it is worth the purchase.

:D
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Postby Slats » Wed Jul 02, 2003 12:48 am

Thanks Matt for the nice comments.
I would like to add the following: -extensive testing of my system described in my article in the SC Report March 2003 edt, by Jim Russell of Model Submarine Systems Australia, indicates that pressure is no more than 20 PSI. At this pressure the pump still operates but will not push any more water in to the sealed tank. At this pressure you ballast tank will be 60% full of water. There can be some variations in pressure (but 20 PSI seems to be an absolute maximum). Variations in pressure depend on the state of your battery and between impeller pumps, and this figure is based on 12 volts using the Dick Smith pump. Furthermore, a follow up article on answering FAQs I have recieved will be published in an upcoming SC Report. By the way do not attempt to run the Dick Smith pump on 6 volts - you won't even get your ballast tank 20% full!

For those people using this post who are not Subcommittee members, I would encourage you guys to consider investing a little in a Subcommittee membership - you won't be disappointed in the range of artciles on hand that add volumes in your understanding of the hobby. I could not have built my subs without reference to past efforts of others who documented techniques in the SC Report.
All the best with installing the pump system.
Cheers
John.
:D :p
John Slater

Sydney, Australia
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Postby David H » Wed Jul 02, 2003 3:25 am

G'day all,

I've seen john slaters boat and it's a beauty. I would have bought it if I had the cash. I agree , you can't really run the Dick Smith pump off less that 12v to be effective.

I Simply use a pinch valve servo set up to regulate the flow of water in and out of the Tank. At Neutral the servo arm is pushing hard against the Nitro tue line. It swings one way to release pressure on the tube, the water flows back out under pressure. You surface. The other direction hits a small microswitch and turns the pump on, v reliable. Use a metal geared servo though.

regards,

David H :)
"Baldrick ,you would'nt recognise a subtle plan if it painted itself purple and danced on top a harpsichord singing "Subtle plans are here again!!" Blackadder.
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Postby petn7 » Wed Jul 02, 2003 12:13 pm

if the sub i'm building acutally works, i'll strongly consider joining ur little club... *checks wallet*
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Postby smwarships » Wed Jul 02, 2003 5:33 pm

Hello ,
As for joining this little group . Don't wait until your sub is
working to join . I am a new member , I just joined this year
and when I joined I purchased a number of back issues .
I am glad that I joined and bought back issues . I have saved
myself a lot of extra work and wasted money by my actions.
There is a vast amount of knowledge and talent in this group
and everyone is willing to help you with your project .
I only wish that I had joined years ago . :D

Darle
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Postby petn7 » Wed Jul 02, 2003 10:51 pm

i'll tell u what. if i get all the back issues for free, i'll join right now.
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Postby smwarships » Thu Jul 03, 2003 2:11 pm

Hi petn7,
Well you won't get all the back issues for free , however if you
do let me know I would like copies of all those issues also .

Well , like I was saying , you won't get the back issues for
free , but once your a member you can get them at a
reduced price . You will save money when purchasing back
issues and you will save yourself a real headache when
building RC Subs because you will get articles about this
hobby that will save you time and money .

The investment of fees to join the group is small
in comparison to what you get in return .
Darle
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Postby petn7 » Sat Jul 05, 2003 7:47 pm

i got the two pumps; they are much smaller than i thought and provide enough pressure to pump water into a sealed ballast tank. now to figure out how to fit it all in a submarine...
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