outrunner ROV thruster

Hi all,

So what I'm trying to do is make an open direct drive ROV thruster using a BLDC motor. I want to use a BLDC motor with potted coils and sealed electronics and control it using back emf and then have the motor housing open to sea water. Before everyone jumps at me for lack of reliability, this unit will be fire and forget and will only have a run time for one hour so rust and corrosion are not an issue. As long as I get an hour and a half of use out of it once it hits the water I'm golden. I need the unit to generate 110 pounds of thrust. I've done a fair amount of prop analysis using Open Prop 3.3.4 and basically need 10Nm at 2000 with the prop I optimized. 3 blades, 4 inch hub, 9 inch diameter. The power source is a monster, so I'm not to worried about efficiency. We're currently using thruster that generates 110 pounds of thrust at 2.7kwh.

Basically what I'm asking if its in the realm of possibility to use a turnigy bldc outrunner direct drive as a power source. I saw some forum posts from a while back about someone trying to use one as an outboard but couldn't find much information from them. I'm weary of buying one because hobby motors are so poorly characterized and no one makes industrial outrunners(that I know of).

Best,

Pascal

You might want to read through the esurfboard threads. The main issue has been gearing. Depending on your voltage the 130kv motor turns 6400 RPM at 48v. You will have to gear it down or it will cog. In theory it should work for you though.

What about rewiring to lower the kv. I think the 100 cc has a kv of 150 and someone lowered it to 50?

You could do that or just use a gear reducer. The successful have used a Neugart 5:1 reduction.