1/32 Moebius Flying Sub

[JWLaRue]

I'm surprised they would be inadequate if opened up, as they must easily be equal to the inlet area of the centrifugal pumps.

Good point, Andy. Seems like worth trying?

-Jeff

[bigdave]

Anything is worth trying.
I have my upper and lower gizmo thingys opened up as much as I could and the front vents but it runs much better with the front lower door off.
I used to have the front windows out to get the water in but Rick Teskey suggested it would run better with the windows in and the door out.
And he was right. It handles much better in the water.
A magnet holds the door on.
But I think I am going to try Scotts idea of the moving hatch. BD

[crazy ivan]

OK, I have one of BD's pumps too. Time for a little trig math (and feel free to prove my calculations in error).

The pump´s ports measure just over 3/8 inch ID at .380 inch, which I calculate to be a cross sectional area of about .113 sq.in. The raw openings in the bulkhead each come to roughly .270 sq.in. if you leave off the gratings. If you install the gratings but cut away the seven vertical bars from each one, you still have an opening of around .217 sq.in. per side. More than enough for these pumps, as Andy suggests. If that's not enough, open up the area between the fins under the two docking rings. That will add another .8 sq.in each. Plenty of water to quench your pumps' thirst with that alone. What say you, BD?

Oh, I see our posts have crossed paths. Are you talking about with your original pump setup, or with the new Rule pumps?

[bigdave]

Original
I have not used the new pumps.
My mini jets move much more water.
And I hear what you are saying about the opening sizes.
BUT (The big Bertha but)
You will find in the real world the one big opening will flow much better than the multiple smaller ones.
Stick 5 straws in your mouth and suck.
Then suck from one larger tube.
Less resistance my friend.BD

[PaulC]

BD,

Nice illustration -- and Jimmy Castor Bunch reference!

My plan was to open the grates on the forward intakes and between the fins of the upper and lower annular intake/docking ring thingies. Hopefully that will provide enough flow.

If not, I suppose I can resort back to the manipulator arm door. What about cracking open the stern door between the engines? Or even a hole in the lower hatch well. The hatch itself could be removable for running.

And hijacking is not an issue if we're all spitballing FS-1 builds and 70's pop music. I appreciate the different approaches.

[bigdave]

Thanks for the thumbs up on the hijack Paul.
I just love discussing theories with George. He is a wealth of knowledge.
I forgot about the back door. (No screen) lol
I have mine hinged and open when running.
Look at it this way. When running FTB (full tilt boogey).
The pumps require a total of about 10 gallons per minute of water.
And the more efficiently and less restrictively you supply that water the better they will work.
Take that Mr Crazy Ivan Sir. BD

[greg w]

Also most pumps have a large inlet than discharge openings.

[bigdave]

And there is a guy that knows his pumps. BD

[crazy ivan]

Look at it this way. When running FTB (full tilt boogey).
The pumps require a total of about 10 gallons per minute of water.
And the more efficiently and less restrictively you supply that water the better they will work.
Take that Mr Crazy Ivan Sir. BD

OK, Smokey Stover. But those fire monitors you're using for propulsion need a fire hydrant to feed them. I suspect that with the Rule pumps (inlet and outlet both 3/8" ID), not so much. At any rate, I wouldn't go punching any extra holes in the hull without first testing with just the inlets and docking rings opened up first, as Paul was originally planing to do.

I do enjoy these littlle exchanges with BD. Ultimately, we usuallly end up proving each other right.

[JWLaRue]

Okay....color me interested. Let's see if this keeps me away from U-boats for awhile.

I just placed an order for those pumps from goldmine-elec.com. Assuming that they really can move 280 gallons/hour (4.667 gal/min), then all one would need is an intake opening the same size as that on the pump. Don't see how it can be any other way given the non-compressable nature of water.

The open question in my mind is whether or not a pair of these pumps will push enough water to drive the FS1 fast enough....or does one really need to go with BD's fire hose approach?

-Jeff

[crazy ivan]

Two things about these pumps, Jeff. First is that they are uni-directional, with the flow going the same way regardless of which polarity you connect the power source. However, one way pumps much more than the other, so you'll have to experiment to see which is the positive pin. They aren't marked.

Second, when testing by holding the pump immersed in a stationary tub, I was not able to detect any thrust by hand when the input was set to 7.5 volts. But at 12 volts, the thrust felt pretty strong. When i released the pump, it scooted across the bottom of the tub, easily overcoming the stiffness of the heavy power cord. That's my scientific analysis.
Conclusion: you will probably want to set up your system to run at something closer to 12 volts.



Just an afterthought, pumps of this general design when used in the bilge of a real boat are generally only covered under warranty if used with an input strainer to keep any debris from jamming them. How they will fare out in the wild remains to be seen.

[JWLaRue]

CI, thanks for the confirmation...I was assuming that they weren't reversible based on the description on the web site (or lack thereof). A 12-volt system is what I would be using. Hopefully there will be some controllable flow besides a full-on volume.

-Jeff

[bigdave]

Two of them should propel the FS1 at a very respectable speed.
The faster the sub goes the worse it runs. It likes slow and steady better.
Pattie is going to install two of them in her Teskey boat, er plane, er sub. Lol

[Guest]

Have you tried running the FS1 with a leveller?

This one went fairly well I thought.

[PaulC]

On the subject of interior builds, Ian Lawrence has two FS-1 builds on his website that are fantastic. His second one is here: http://www.ianlawrencemodels.com/wipfs1.html (contains a link to the first).