Brushless Motors

[Mgbss]

From what I have read you can just put a Brushless motor in fresh water and it will function properly and last is this correct is it that simple? Also one site had water proof Brushless motors

So if I was to go brushless what motor (Kvs) would a person need to run a 50mm 3 blade prop or better yet how do you figure this part out? My design is to use 500 gph bilge pumps with a ESC so this is what I would try to duplicate.

By the way I am planning a small rov for video inspection using a r/c radio and 3-5 thrusters.

Thanks for the help

[Rover]

Yes, you can run them in fresh water. The bearings may eventially fail due to rust, but if you can get a season or two out of them thats great. (we haven't had one fail yet)

I use out runners, as they come in lower KV (thousands of RPM per volt). We use 750KV and 900KV turning 50mm props.

We buy all of our brushless motors and ESC from Hobby King. Great prices.

The best way to figure out your final prop size is to test through your tether, monitoring your current draw to stay with in the motors voltage rating. I am using a 2C-3C motor (2 cell = 7.2Volts and 3C = 10.8 volts) They run great on a 12 volt battery all the way down to approx 6.5 volts before the ESC cuts out.

Have you tested your thrust rating yet? Look at Steves website, he shows you how to make a motor thrust jig out of PVC pipe.

The first ROV we built used brushed motors, and they loose torque with a lower supply voltage, brushless have great torque at lower voltage.

Good luck.

Jim

[Mgbss]

Rover

Thank you for the reply and info, just what I was looking for. The above stated reasons are the reasons I was looking into these over the Bilge cartridges.

Yes I have seen Steve's thrust tester great simple idea. I will be putting it to use although your stating the motors used with the 50mm helps a bunch.

Thanks again

Joe

[Mgbss]

I was looking at the above mentioned site at the different outrunner motors and came across a 850Kv with a 4mm threaded shaft has anybody tried these? I wonder if the thread is the same as the propellers? If not I would guess you drill through the prop and sandwich it between the 2 nuts like the planes do.

Any thoughts?

[Rover]

We drill out the center of the prop, cut off the cone tip of the prop and use the airplane prop hub adapter that was included with our motors. See the attached photos.

I have used this method with two and three bladed 50mm props. The two blade in the pictures was one of the test props we were trying out, but will be using a three bladed 50mm prop as the final prop.

The main reason we went this route, was it was faster, we didn't have to machine a prop adapter, and the collet makes for a fast prop change.

Jim

[Mgbss]

Rover

Thanks again thats what I was thinking simple

[Mareike]

http://hobbyking.com/hobbyking/store/uh ... duct=19611

that's the ones I want to use with 65mm props. 6 at all 2 for each direction, Hermetic housing and magnetic disc coupling. I tried one in a shop at home and as small they are they are monsters in power. And the price for brush less is super.
My mate had one in a helicopter and the blade broke his finger..