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Topic: Where can I get very small dc motors and propelers? (Read 3403 times) previous topic - next topic


I am searching around but I can't seem to find micro sized dc motors or small propellers to fit on them. What I am trying to do is make a small hollow tube in which I put the smallest dc motor that I can with a propeller, then I tie a string to the hollow tube and toss it in water and drag it around to generate some electricity that powers a small led attached to the dc motor...

basically my idea is to create electricity underwater to power a small LED using dc motor but I cant find a small dc motor or a propeller that I can use. If you have some other methods of creating underwater electricity I would be open to new ideas.



you would be better off making a water wheel with a belt drive to turn the motor
to keep the motor well away from contact with the water
unless you can find a water tight motor


Thank you! I was told that dc motors can do suprisingly well underwater so I thought that it would be fine if I let the motor stay in water without water proofing..


I'm afraid this doesn't sound at all workable to me:

Salt-water will totally wreck a motor in no time.  Fresh water will be more forgiving, but once you generate a voltage the water will electrochemically corrode the thing progressively till it fails.  The iron stator laminations will rust, buckle, expand and probably cut into and short the copper windings.

The bearing lubrication (phosphor-bronze sleeve bearing probably) will leach out and the bronze will corrode and seize the shaft solid after some time.

The presence of water in the motor will cause much greater viscous frictional losses so it might not even turn.  Towing speed in water will cause very low RPM values so the motor won't produce any significant voltage or power (small motors run at higher RPM in general).

The tube will add to the losses by reducing flow-rates through the propeller compared to an unconstrained propeller (unless careful venturi design is done).

It all sounds unlikely to work and will destroy the motor.

The closest piece of technology I can think of is a diving/snorkeling scooter - run in reverse it might be feasible to get usable amounts of power, but its not a trivial undertaking.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


A better setup for determining speed would to have a free running propeller with magnets at the tips and either a reed switch or a hall effect device and count the pulses.



You can dig up more examples of these if you try a Google image search for "submarine motor".

The stock propeller is undoubtedly too small but you might be able to figure out a way to replace it with a larger propeller used for an RC boat.

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