Homebuilt ROVs Forum

This is what i want to try, If the motor housing(pvc pipe) is full of mineral oil,and the bilge pump case inside is open on the motor to let oil in, Will the rubber cap on the pipe act like a diaphragm and balance the pressure inside and out? Creating less pressure on shaft lip seal. Any idea how to test? beside just going for it.

I like the idea.... it might just work and it looks pretty easy to do too.

Unless you have a test chamber though you might just have to go for it. Send them down to depth and run an amp meter on the motor to see whats going on. The only thing you have to make sure is the you get all of the air out of the housing. The motor will probably draw a few more amps then normal because of the motors armature spinning in the oil but other than that it looks good.

I for one am interest to know how this works out... keep us in the loop.

-Steve

thanks for the reply Steve, spent couple hours tonight & built me a constant amp meter, 0-30 amps running off a .75milvolt shunt. Maybe dept runs next weekend, after turkey. Have a good holiday...

That .68 amps is on the bench, no prop, no oil, 200 feet cat5 4wire pos/4 wire neg. very low volt loss, will test this way because i plan on full on board power. will see what happens?

Do you think you'll have any problems running the brushed DC bilge pump motors in oil? I've heard it can cause problems, but sometimes works? I really have no idea. Interested to see your results.

Johnson pump cartridge 1000 gph. 200 ft cat5 cable,dc volt drop to 7.1v First 2 test done,Test-1 thruster with no oil just under waters surface 50mm propeller, 2.41 amps. Test-2 thruster full mineral oil,same conditions,2.48 amps. Run with oil for 1 hour,amps consistently @2.46-2.49. next try with batt volts 12.5 at pump motor. video link of this test http://youtu.be/-FFc8PBcIj0

Test again on 12/2-100 ft romex, still no problem with dc brushed motor in mineral oil. Total 3 plus hours so far, many starts and stops. video link to this test= http://youtu.be/Opnjm-UkGQg

Over time as the brushes in a normal brushed motor degrade (wear) the particles from the brushes get suspended in the oil and the oil then becomes conductive ......... which is not too good for obvious reasons. If you keep swapping out the oil as it becomes darker (if it does) or after certain periods of time this may or may not be a problem.

Why can't you use the bilge pump as is, just attach a propeller to the shaft? The bilge pumps are meant to be submerged, but I agree the question is, how deep can you go?

I am interested in building thrusters that can go up to 150 feet deep and powered using copper wire.

Thanks,

Brian

You can use them as they are, and many people do. Filling them with oil is a way that they can go deeper than stock. I know people have taken stock bilge pumps down to 150' and deeper; search through the mission footage and ROV build threads for more info.