Ducted fan thruster

[electronicscrazy]

Hi i found these fans on hobbyking and thought they would be a good thruster for my new rov i'm designing.
I was wondering what you all thought of them and wether they would be good as a thruster.

http://www.hobbyking.com/hobbyking/stor ... on%5F.html

[bikerbones1968]

Hi electronicscrazy, The only real issue in my opinion is the 4800KV rating .. Those units will really wind up. The KV rating is the number of revolutions per volt so on a 12 volt battery they will turn ridiculously fast i.e. 57600 RPM in this case and you will experience cavitation guaranteed at max volts. Most folks tend to use lower KV ratings so that cavitation isnt an issue. I am going to use 750KV brushless outrunners and testing has showed good results for thrust without cavitation.

[electronicscrazy]

Ok because when i tested a computer fan in a water it went really slowly so i thought that if i had more rpm's the more thrust i would have in the water with these turbines.

[bikerbones1968]

Its likely the computer fan motor just simply did not have enough torque to drive the blade when underwater. Brushless motors for RC's have an amazing amount of torque for thier size.

[electronicscrazy]

What power motor would you suggest for running a 60mm ducted fan unit: http://www.hobbyking.com/hobbyking/stor ... 5FKit.html

[bikerbones1968]

Good question. I really can't say for sure, maybe someone here has had some experience with ducted fans as props. I am using Robe 52mm 3 blade boat props. I am guessing where theses units are designed to move large amounts of air and not water you would have to keep the KV rating low. But this is just a guess as I have no experience with fans for props.