You know what are great dc motors? 5 Volt Drill Motors. They are rated at 5 volts but they run just fine at 12. The torque is truly amazing compared to the power consumption. They are also very small and easy to work with. One problem, when run at 12 volts and at alot of strain they make a considerable amount of heat. Also at 5 volts they work pretty good too.

Here is a nice place that has a lot of motors and fans (one fan reaches 12000, yes twelve thousand, RPM.) I was thinking of buying a high quality mirror from there to use for lapping.

Here's the the dc motors i had laying around:(big pictures)

http://clientes.netvisao.pt/carlo001/dc1.jpg

http://clientes.netvisao.pt/carlo001/dc2.jpg

Both are fast motors, with a good amount of torq.

Think how a FAN motor is constructed, it has the copperwire coils in the centre(easy to resin coat/seal) and the magnet on the outside, it's the outside that spins.

With a 'normal' motor the coils are on the outside of the shaft/magnets that spin, usualy in a curcular steel tube/case. It might be possible to encase the lot then lathe the outside and drill the centre, but then there's the bearings as well!, also the shaft is usualy ferrous metal... It's impossible if Nico says so, I recon he's carefuly considered it already :( ...

Needs to be a FAN motor people :shrug: ...

Does it HAVE to be DC though Nico?. I trust your resin as much as I trust Eheims :dome: ...

It's DC for plug and play convenience, forget about relays. :cool:

Terramex, it seems that if you turn on that motor, some spiders are going to loose their home. :D

I've made some tests, and the water drag is incredible. Just realized that was a mistake when I said that the bare hub makes 9700 rpm underwater. The motor with the base disk makes about 10500 rpm on air, and between 2200 and 3000 in water, depending on the amount of air bubbles inside the hub. :eek:

Just discovered that a small amout of air, between the coils and the magnet, improves performance a lot. Those are two concentric cylindrical surfaces very close together, and the viscosity of water between them makes a big drag.

And gekkos.
 

Probably :D. It does move alot of air, but also makes a considerable amout of noise. Anyway, i was thinking and it's a good assumption to say it wouldnt work underwater. Coating it and maintaining the rotor in working order would probably take too much time and effort ...

PS : full assembley, i found the rest later.

First performance numbers!
 

The pump, with just a 40 mm disc as the impeller, can move some water!

I tested it with 50 cm of 1/2" hose, moves 170 L/H at 0 head, and have the incredible max head of 20 cm! :p

Well, I'm happy this is starting to work, and remember that this is just a base line; Still need to make the impeller. I'm amazed that just a single disk can do something. :)

Find yourself on old cordless drill and take the motor. Those motors are designed for torque. Work excellent for water tasks.

Re: First performance numbers!
 

so are you going to make an impeller, or use multiple disks ala tesla?

and we want pics! (congrats on getting it working to some degree!)

Re: First performance numbers!
 

That's actually pretty impressive! I didn't think it could even get to that! Congratulations, and keep up the good work!

Digicam is back!
 

This is the current state of the pump. The cap was molded against the base for a perfect fit. I dremeled out a pocket for the outlet pipe, and fixed it with epoxy putty.

Well guess this info comes a bit late, but the fact is that default expoy doesnt tolerate water! It wont take any noteable damage at first. But in a while or two joints will start to fail. Epoxy decompose in contact with water. Alltrough I guess there is special epoxy which will tolerate water as well.

perhaps you can put a thin layer of silicone very thin layer to protect the epoxy if this is the case.. --Josh

This is the end...
 

Well, this experiment finished with a partial success only.

I've been trying several impeller variations, and found a strange problem: When the pump fhas too much flow restriction, it enters a pulsating cycle where it quickly stops and start spinning. It don't happens in free flow condition, but when I try a max head test, it always happens when it reach about 35 cm.

To avoid it, I had to reduce the impeller dimensions, up to a piont where it can't generate more flow than the critical level. With the straight radial blades configuration, I ended with something similar to the impeller os that water-X shit. With the two disk option, I had to reduce the diameter to 28 mm.

At first I thought it was something with the motor electronics, where it automatically cut off the power when there's too much resistance, but the strange thing is that this happened at very different rpm levels depending on the impeller shape.

At the end, the performance at the best "stable" configuration was 300 L/H and 32 cm head.

This can still be useful to move water on a secondary loop in the system, but definitely not enough for cpu cooling.

An interesting side effect: With straight blades, this made an excellent air blower!

I don't know an easy way to measure airflow cfm, but for pressure I sunk the hose in water, and the level inside it was 30 mm lower than outside. As I remember, most fans can do only small fractions of an inch of static pressure.

Here are a couple pics of the two initial impellers I made. That was the starting point, and then I was progressively reducing the dimensions with the lathe.

Common epoxy softens very quick with water, but I’ve made things with this stuff that have been more than 6 months underwater, and are as strong as the first day, with no color alteration.

A bonus pic: The pump working at free flow.

wanna send that to me .. =) --Josh

Re: This is the end...
 

That measure is based on a 1 square inch opening, I believe, so you can recalculate, if you know your tubing diameter.

I think you'll find that it's lower than spec.

Nice work. It could act as a backup, if it was possible to bypass it easily.

hey, all you need is a more powerful motor :)

Ben, the pressure shouldn't be dependent on the cross sectional area. If you used a larger tube it would take longer for the pressure to stabilize, but it wouldn't change the maximum value that the pump would produce.

or make a couple more and run them in series :D

Lol, but seriously:
Thats not bad!
What fan did the motor come off of?
I bet it didnt come off of a 60mm delta screamer, and that draws a whole ~4.5watts!
I mean a cheap VIA Aqua 1300 consumes 20 watts.

You gotta get you a nice big 120MM fan motor to really try this out on :) a whopping 6 watts!!!!! :)

For the size of the motor I'm impressed, it does'nt hit home until you see it in nicos paw how small it is!...

What did it sound like nico?, was it audible at all?...

Of course it wouldn't. I just observed Nico state that he gets a 30mm head, but didn't specify the diameter of the tube he used, to measure that 30mm.

30 mm is well over 1 inch, and as a fan it shouldn't be able to come close to that. Given that the fan was replaced with a paddlewheel, it should perform even worse.

I was merely pointing out that where fans are spec'd to say, less than 1/4" H2O, it is a measure that is based on a specific diameter, which I believe is 1 in. ^2.

Heck, with a tube small enough, I could state that my fan has a head of 1 meter!

I like the idea of using a fan motor as a pump. It's a very efficient design. The best option would have been to choose a 120mm fan as they rotate at a low rpm and could give you enough torque to move quite some water. ;)

Ben, pressure units are force/area, so area size is irrelevant. This was really a powerfull blower; but noisy at 9K rpm.

This was a 60 x 10 mm of intemediate power. It was rated at about 4 watts, but I don't know how precise that rating was.

Looking at Eheim pumps, they have a 4 watt model, the 1005 that makes 270 l/h and 75 cm head. So sure 4 watt can do more than 30 cm, but I don't know what makes that limit. Maybe head and torque are related in some way, and the low torque of the motor makes impossible to go higher.

It made some little noise, but it was from vibration of the poorly balanced impeller. I did'nt take too much care with that as it was a quick test.It was a bit tricky to center it with precision in the lathe, cause the soft plastic of the fan deforms under pressure.

the bearing was silent at UW speeds, so a carefull balance can make it really noiseless.