Brushed / Brushless Motors

[theinlinaung]

Somebody have asked this but I am still confused about the use of Brushed and Brushless motors.
1. I've mostly seen brushless motors used in quad-copters and in air. So I have an opinion that brushless motors and propellers are optimized for use in air and not efficient in water.
2. Due to high rpm of brushless motors I doubt they work well in water without disturbances.
3. I am not sure which has more torque but I've seen big propellers used in brushless motors and small ones in brushed motors.
4. I can use PWM for speed control in brushed motors but I have to buy ESCs for brushless motors.
5. I've seen brushed motors widely used in home and student made ROVs but brushless motors in commercial ones.
6. I haven't found documents about the efficiency of them.
7. I am not clear about the facts influencing the use of them in ROVs.
This is confusing for me. Please help.

[olegodo]

I am no expert, but here are my thoughts

Somebody have asked this but I am still confused about the use of Brushed and Brushless motors.
1. I've mostly seen brushless motors used in quad-copters and in air. So I have an opinion that brushless motors and propellers are optimized for use in air and not efficient in water.
When it comes to operating in air or in water, it all depends on the propeller/motor characteristics. A brushed or brushless motor at the same rpm will have the same effect in the water. Yes, the brushless motor's most of us are using is designed for RC planes/quad copters/cars but also RC boats
2. Due to high rpm of brushless motors I doubt they work well in water without disturbances.
The "KV" rating on the brushless motors tells you what RPM the motor spins at per volt you give it. Note that this number is without any load on the motor. Anything below 900KV works good as a thruster motor when a suitable propeller is used. You can see some propeller/motor combo tests here in the forums
3. I am not sure which has more torque but I've seen big propellers used in brushless motors and small ones in brushed motors.
Brushless outrunners has more torque then inrunners and brushed motors at comparable size.
4. I can use PWM for speed control in brushed motors but I have to buy ESCs for brushless motors.
This is true. however you still need some sort of H-bridge circuit to control the brushed motors as the microcontroller you are using to send PWM signals can not supply the motor with nearly enough current.
5. I've seen brushed motors widely used in home and student made ROVs but brushless motors in commercial ones.
I think this mainly comes down to costs. A brushed thruster will be cheaper to make and replace if something goes wrong.
6. I haven't found documents about the efficiency of them.
Brushless motors are more efficient, but the difference I don't know. Also, since there are no brushes, they should last longer
7. I am not clear about the facts influencing the use of them in ROVs.
One of the biggest advantages to using brushless motors in thrusters is that they actually can be run directly in water without taking any electrical damage. However, rust and corrosion is still an issue. The bearings generally ceases up quite fast. Note that the OpenROV uses unmodified motors running directly in water. With good cleaning/rinsing after each use and treatment with some anti corrosion product will enable it to last for quite some time.
The best use is to either build an oil filled thruster with a shaft seal or magnetic coupling. Or seal the motor with epoxy so that it gets 100% waterproof (what I will be doing with my thrusters). These two methods will work at virtually any depth and ensure a long life and can only be done (I think) to brushless motors.

This is confusing for me. Please help.

[theinlinaung]

Hi Olegodo,
Can you tell me how you waterproofed the Brushless motors? I am uncomfortable with using electronics in water. And could you please tell me the minimum cost of Brushless motor and ESC?
Thank you for your time.

[theinlinaung]

I am no expert, but here are my thoughts

Hi again
I have been searching for good brushless motors and ESC combinations and found out that ESC are more (twice) expensive than the motors This is my first experience with brushless motors and don't know much about them. I am planning to use 2213N 800Kv motor. Are there any cheap ESC compatible with this motor?

[olegodo]

I am no expert, but here are my thoughts

Hi again
I have been searching for good brushless motors and ESC combinations and found out that ESC are more (twice) expensive than the motors This is my first experience with brushless motors and don't know much about them. I am planning to use 2213N 800Kv motor. Are there any cheap ESC compatible with this motor?

I have no experience with these, but I think they will be plenty good enough:

http://www.hobbyking.com/hobbyking/stor ... r_ESC.html

I know some users here on the forums use this one:
http://www.hobbyking.com/hobbyking/stor ... verse.html

This is the cheapest alternative I could find from Hobbyking, but rated for 10A might be cutting it close.
http://www.hobbyking.com/hobbyking/stor ... verse.html

[kenl]

I have tried both the 30a hobbbyking and the 25a turnigy ESCs listed, no problems with the hobbyking esc but the turnigy escs seem to need constant reprogramming.

I think the 10a would be cutting it very close, possible if the shrink wrap was removed and a real heat sink was put on where the small plate is now it may work ok?

[theinlinaung]

I am no expert, but here are my thoughts

Hi again
I have been searching for good brushless motors and ESC combinations and found out that ESC are more (twice) expensive than the motors This is my first experience with brushless motors and don't know much about them. I am planning to use 2213N 800Kv motor. Are there any cheap ESC compatible with this motor?

I have no experience with these, but I think they will be plenty good enough:

http://www.hobbyking.com/hobbyking/stor ... r_ESC.html

I know some users here on the forums use this one:
http://www.hobbyking.com/hobbyking/stor ... verse.html

This is the cheapest alternative I could find from Hobbyking, but rated for 10A might be cutting it close.
http://www.hobbyking.com/hobbyking/stor ... verse.html

Thank you very much. I think I have to learn more about brushless motor and ESC.

[theinlinaung]

I am no expert, but here are my thoughts

Hi again
I have been searching for good brushless motors and ESC combinations and found out that ESC are more (twice) expensive than the motors This is my first experience with brushless motors and don't know much about them. I am planning to use 2213N 800Kv motor. Are there any cheap ESC compatible with this motor?

I have no experience with these, but I think they will be plenty good enough:

http://www.hobbyking.com/hobbyking/stor ... r_ESC.html

I know some users here on the forums use this one:
http://www.hobbyking.com/hobbyking/stor ... verse.html

This is the cheapest alternative I could find from Hobbyking, but rated for 10A might be cutting it close.
http://www.hobbyking.com/hobbyking/stor ... verse.html

Can I use this one? http://www.hobbyking.com/mobile/viewpro ... entcat=712
What are the differences between 30A one?

[fryslan76]

The one you refered to has no reverse. So steering will become very difficult.

[theinlinaung]

The one you refered to has no reverse. So steering will become very difficult.

didn't see that one. I'll just stick with 30A one. Thank you for answering.