Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: Martin (Admin) on September 24, 2018, 10:15:32 am
Title: HobbyKing / Turnigy Brushless ESC
Post by: Martin (Admin) on September 24, 2018, 10:15:32 am
Didn't know Amps were directly related to boat length.... you learn something new everyday.
Title: Re: HobbyKing / Turnigy Brushless ESC
Post by: Andyn on September 24, 2018, 10:43:35 am
How didn't you know this previously?
Boat legnth divided by rudder legnth times lake depth minus boater height equals speed controller rating. %)
Title: Re: HobbyKing / Turnigy Brushless ESC
Post by: canabus on September 24, 2018, 11:05:22 am
HI Andyn Well ewe learn some thing new ever day !!! I did work as a telephone technician and this takes the cake !!! Canabus
Title: Re: HobbyKing / Turnigy Brushless ESC
Post by: Andyn on September 25, 2018, 12:48:00 am
I see what they're getting at, typically a fast boat of X size will have X motor, which requires X esc. Doesn't really translate well though...
Title: Re: HobbyKing / Turnigy Brushless ESC
Post by: malcolmfrary on September 25, 2018, 09:41:30 am
In the elder days, motors were always sold as being suitable for boats of a given length. Oddly, probably because of the limited types of boat possible and the limited types of battery available, it worked. HK are assumng that there is only one type of model boat that needs electric power. Unlike earlier times, the only type is now fast. Might be time to revive the link to the uses of the multimeter.
Title: Re: HobbyKing / Turnigy Brushless ESC
Post by: dreadnought72 on September 25, 2018, 11:15:55 am
This is the biggest '?' for me, and I suspect many others.
Assuming the propellor size is in keeping with a scale displacement model, is there a rough guide to (brushed) watts per kilo displacement to attain a scale speed?
When I've tried to calculate it, I get weird numbers. More experienced builders might just chuck in a motor(s) knowing they'll be 'enough'.
Andy
Title: Re: HobbyKing / Turnigy Brushless ESC
Post by: malcolmfrary on September 25, 2018, 06:58:27 pm
This is the biggest '?' for me, and I suspect many others.
Assuming the propellor size is in keeping with a scale displacement model, is there a rough guide to (brushed) watts per kilo displacement to attain a scale speed?
When I've tried to calculate it, I get weird numbers. More experienced builders might just chuck in a motor(s) knowing they'll be 'enough'.
Andy
When doing a scale model, it helps to know the real things horsepower. Converting to watts and dividing by the cube of the scale, then doubling the result to allow for the difference between power out (real) and power in (model) works well. Once you know the power, since you know the battery voltage, you can get the amps for the ESC.* There can't be a formula linking weight to power required because all boats doing different jobs have different requirements. The differing hull shapes in the water don't help, either.
*e.g. a 1/350 battleship, 100000 horsepower. 100000*745 = 74500000 watts. 350 cubed = 42875000. power/scale cubed = 1.74 watts. Double that, 3.6 watts. 2S Lipo, divide watts by volts, 7.4/3.6 gives 2 and a bit amps. Provided it has a reasonable prop, the battleship will look right when going along. Any extra power is a valuable "get out of jail" card.
Title: Re: HobbyKing / Turnigy Brushless ESC
Post by: Colin Bishop on September 25, 2018, 07:44:28 pm
Suitable power has always had an element of 'suck it and see'. If you have to make adustments then there are three basic options. 1. Change the battery voltage. 2. Change the propeller(s) to alter the pitch. 3. Change the motor(s) Any combination of these will usually resolve the issue. You can end up with some useful spares...