Homebuilt ROVs Forum

This is my first build. All the detail is at http://micomarov.weebly.com/. I used 1100 gph Rule bilge pumps with 50mm props. Out of the water the motors turn fast enough to feel air, like a fan. I put the ROV in the water and there was very little if any thrust. It was so little I thought maybe the motors were not working. But when I pulled it out they were. The ROV is slightly buoyant. The thruster for up/down would not even made the ROV go down. I mean it looks like to me I might as well not have props on the motors. What did I do wrong? As far as I know from research these motors should be sufficient to at least move the ROV. The 50 mm props are suppose to be the best balance for these motors. So, what gives?

I am not against getting another type of motor but it would have to be 12v, direct connect (without an ESC), and pretty much fit the frame I have.

What size wires are you running to your thrusters?
Do you have your control relays topside or onboard?
Have you tested to see how much weight it takes to overcome your bouyancy?
Because that is how much thrust it will take to submerge.

You didnt tell, if you have the same problem with your forward/backward thrusters.

But a quick look, i would suggest this... Try to run it, without the "prop guard" (plate with little holes)

Have you tested in salt- or freshwater?
Maybe you habe a isolation problem.
If your first test was in saltwater try freshwater. It should work better if this is the problem.

While those type of thrusters should put out close to 2lbs of thrust your Rov might require more being that it looks quite large. My best guess assuming the thrusters are working correctly is your Rov is just to heavy for that little amount of thrust. How much does the complete Rov weight? I know those 4" fittings can all add up.

If it is just the vertical thruster that is not powerful enough.. I read you filled it with wax?. The problem with that is when the motor heats up the wax will melt and will cause a lot of drag on the rotor of the motor, this will also cause you to lose thrust.

Definitely remove that grate cover on the vertical thruster too, that thing is going to deflect a lot of your thrust too.

-Steve

24v is run from topside to a 24v to 12v 15amp converter then to the relays. The converter and relays are onboard. The ROV weights 16#. I don't know what having an isolation problem means. I assume it has something to do with the electricity.

All of the motors did not work well when first tried it in saltwater. Today I put it in a pool. Regarding buoyancy - in the sea it was slightly buoyant. In the pool it sank. I was able to observe things in the pool that I could not in the sea. First thing I noticed was if I ran two motors at the same time neither one had enough thrust. One motor at a time it did ok. Still not fast but I was able to get it across the pool. So I tested volts. With one motor there is 11.8v. With two going there is 8.2v. Is that the explanation? I really thought running 24v down to the ROV would give enough power for two motors to run at the same time. Guess not. I will cut out the grills in the covers to see if that helps with the up/down movement which is still anemic.