Stepper motors for thrusters?

[olegodo]

Hi,
Most people use either modified bilge pumps or some kind of brushless motors for their thrusters these days.
Generally, this means relatively high rpm and small props. This works, but I am thinking maybe it would be better to have some bigger props running at a lower rpm.
So what do people think of using some sort of stepper, enclosed and oil filled and pressure compensated in some sort of housing and a 150mm +- prop either on a sealed shaft of with mag coupling. Magnetic coupling will be a challenge though because of the relatively high torque transfer from the stepper to the "big" prop. I think something along the lines of a Nema 17 size stepper. They are very cheap and widely available. Max rpm of these are 3000rpm
I believe this will provide much higher torque and much reduced power requirement.

What do you think? Have anyone tried something like this already?
Hope to get some input on this and would like to try it.

[rossrov]

Gidday Olegodo.

I would not think that efficiency of steppers suitable for common battery powered ROV use. Good idea though, and I would like to try out for ancilliary equipment (yes, been done before commercially - just Google) .
However, HobbyKing are selling brushless high-pole-count (lower RPM) motors for camera stabilization. Also more turns of wire so higher inductance so less current. I wonder of these would work for low-RPM thrusters spinning a big prop?

Cheers,

Ross

[KR2_Diving]

Gidday Olegodo.
HobbyKing are selling brushless high-pole-count (lower RPM) motors for camera stabilization.

Hey Ross,
Dont suppose you have a link to the motor you were talking about at hobbyKing?

Thanks,
Ryan
"KR2_Diving"

[rossrov]

Maybe worth investigating http://hobbyking.com.au/hobbyking/store ... otors.html

cheers mate

[a_shorething]

Hi Ole,

I also found these at the Polulu site:

http://www.pololu.com/catalog/category/51

Geared metal motors that are higher torque and lower RPM.

[KR2_Diving]

Ross,
Thanks for the link! Very interesting! I will be keeping an eye on those!