Model Boat Mayhem

Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: sabre on January 27, 2022, 10:28:37 am

Title: Pushing it along
Post by: sabre on January 27, 2022, 10:28:37 am

Dribbling over a Dumas Dauntless which is 49" in length and of wooden construction.   As I know absolutely nuffin about these new-fandangle brushless things I was wondering what you learned folks think I would need in the way of  motors to push it along with a good turn of speed.   I'm not even going to think of esc and batteries just yet.

Title: Re: Pushing it along
Post by: canabus on January 27, 2022, 11:35:10 am

Hi Sabre


The only difference between brush and brushless is brush motors have two wires and brushless motors have three wires.


If the motor turns the wrong way reverse two of the wires in both cases.


Power wise the brushless motors are far more powerful.


The Dauntless would have three bladed props.


So matching the props to the motors, the ESCs(you require one for each motor) and the batteries will require more looking into.


What props  are you planning on using, so we have a starting point ????


Canabus

Title: Re: Pushing it along
Post by: sabre on January 27, 2022, 12:36:30 pm

Dumas recommend a pair of three blade two inch props.    Polarity I understand, it's just that I know zilch about brushless and these fancy new batteries.
Life was easier when all we had to think about was the cc of the motor.

Title: Re: Pushing it along
Post by: tonyH on January 27, 2022, 03:03:50 pm

OK, think about what you'd use in the way of i/c motors and then convert the hp to watts. At least it gives you a decent starting point. :-))

Title: Re: Pushing it along
Post by: sabre on January 27, 2022, 05:35:19 pm

I've just found this old Mayhem thread which has a lot of info for me to digest later tonight. https://www.modelboatmayhem.co.uk/forum/index.php?topic=51503.0

Title: Re: Pushing it along
Post by: NickelBelter on January 27, 2022, 10:28:41 pm

You'll have to do some thinking about batteries because that will dictate your kV choice in motors.  2inch props have a max effective RPM (listed) of around 5500RPM, so somewhere between that and 7000 will be fine.  Now you have to divide that by your supply voltage to find out the RPM-per-volt spec needed for the motors, which is listed as kV. 

Title: Re: Pushing it along
Post by: canabus on January 27, 2022, 10:55:30 pm

Hi Sabre


I would recommend Banggood Surpass Hobby C3542-1250kv brushless motors.


Very good strong units and the same motor mount as a brush 35mm motor(540/550).


Shaft size 5mm.


ESC required is 2-4S Lipo 80Amps.


Lipo battery size 5000mah.


Rpm on 2S Lipo about 9000 unloaded.


Rpm on 3S Lipo about 13875 unloaded.


Rpm on 4S Lipo about 18500 unloaded.


Power rating is 850Watts on 4S Lipo.


Start with 2S Lipo's and if not as fast as you require, up it to 3S Lipo.


Only a change of Batteries required.


Canabus

Title: Re: Pushing it along
Post by: sabre on January 29, 2022, 09:46:13 am

Thanks for the replies guys but I've had second thoughts on the kit.   

Title: Re: Pushing it along
Post by: canabus on January 29, 2022, 11:53:34 am

Hi Sabre


I had the kit and it's a big boat !!!


Some thing about the 30 to 36" is a good size and one motor.


Canabus