Relationship of RC Brushless Motor Power Output
Ғылым және технология
Relationship of RC Brushless Motor Power Output
Why do larger motors produce more power?
In a larger motor you can fit more copper wire and also more or larger magnets. In addition larger motors are able to remove a lot of waste heat. Increasing surface area will help shed waste heat that is produced.
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When brushless motors increase in size, naturally the kv of the motor decreases. As such this allows a motor to accept a higher voltage input thus creating more power. Other specification of the motor such as the Io and the Rm are more relative to the operating current of the motor. These values can be very similar to one another when comparing a larger vs smaller motor.
Here is the relationship between brushless motor weight and power output. Simply multiple a motors weight in grams by the appropriate number and you have a power output approximation.
Inrunners Less than 150 grams Weight X 3 = Power || Greater than 150grams Weight x 4 = Power
Outrunner Less than 150grams Weight x 2.5 = Power || Greater than 150 grams weight x 3.
A brushless car that is in the scale size class of 1/16 may use a 28 mm motor where a 1/10th scale may use a 36mm motor with a length of around 50mm. A 1/8 scales car would use a motor that is 36mm in diameter but a length of over70mm.
For a typical trainer style plane, 75-100 watts of power per pound of airplane would fly the plane very well. 150 watts of power would give significant performance.
A plane weighing 10 pounds would need 750-1000 watts to fly well. Working from the numbers above produces a motor that would weigh approximately 250grams for an inrunner or 333grams for an outrunner.
Пікірлер: 41
I love your videos! They make it so much easier to learn this stuff then reading books
@RCexplained
4 жыл бұрын
Hey Ryan, thanks for the comment! I'm glad they make it easier to learn!
Tp motor all day lol , great video as always
@RCexplained
4 жыл бұрын
Thank You!
Can u do a video on us speed run guys , high kv , or lower kv , gearing on both setups , mah , everything , more speed thax happy holidays
@RCexplained
4 жыл бұрын
Yes, what specifically were you hoping that I talk about in the video?
@bigkev7179
4 жыл бұрын
Best gears for 4370 kv motor redcat nascar
@Spacecadet0730
4 жыл бұрын
@@RCexplained I think for speedrun guys going over which motor to choose would be a good place to start (high KV low volt conservative gearing, vs low KV high volt with aggressive gearing etc). I know picking a battery is the first thing you usually want to do and work back from there
Hey I wanted to make an rc boat with a jet drive for fishing I don't need it to go faster than 30 miles an hour and I want a long run time any suggestions for motors? The boat would be 25 to 30 inches and would be hauling bait and line up to 300 meters.Thanks man and great video!
@RCexplained
4 жыл бұрын
Hi Mark, What does long run times mean for you? A long run time to me is 6 minutes. You could use a 36mm x 64mm or 36mm x 74mm motor around 1500kv on 4s to achieve the speed. As for run time you would need to bump the mAh up for the pack to hit the run time you are looking for.
@markstreight1809
4 жыл бұрын
@@RCexplained Hey thanks for the reply so you can better understand I was looking to power a vessel something like this kzread.info/dash/bejne/dKNp0LagnbO-kdo.html I was wondering what size motors and battery could approach the run time claimed in this video. I can go twin engines if I have to too. Thanks man!
@RCexplained
4 жыл бұрын
The motor above will get you close to the speed you are looking for. Run time will be tough. You will not be able to travel at top speed for that long. At the same speed as shown in the video you can achieve similar run times. I updated the kv of the motor in the previous comment.
hi can you do a video about gearing
@RCexplained
4 жыл бұрын
Thanks for the comment. I can and have one already in queue. What specifically were you looking for me to talk about?
Great work. Can you do a motor size comparison for better efficientcy for the same load. Eg 1/8 buggy 2000kv 4068 size to a 1300kv 4092. I think the 4092 bigger motor might be more efficient. I know a lower kv will use less amps too on the bigger motors, just use gearing it up to equal the smaller 4068 higher kv motor? What do you think
@RCexplained
4 жыл бұрын
What LiPo would be used on each motor?
@gregstafford2155
4 жыл бұрын
@@RCexplained 1/8 scale racing is 4s lipo. Most of the time I use 5000mah capacity
@RCexplained
4 жыл бұрын
Hi Greg. This is not an easy question to answer, I like it. I would expect in your example the race is for endurance and not maximum power output. To make a proper comparison, each motor would have to be physically tested in the application. I would expect (an assumption) and its very likely the smaller motor would have a lower Rm and Io value. Since you are not taking advantage of the lower kv value through higher voltages, it's very possible that the smaller motor would be more efficient in its power delivery. If each motor is geared to travel at the same top speed, both motors will have to output identical wattage to hit those same speeds. This equates to approximately the same input currents to the motors. The larger motor with a higher Rm value will produce more waste heat from copper losses. It will also produce more waste heat from iron losses. If the larger motor can dissipate this waste heat, it will be able to operate at this power output. However, because of the losses, more power will have to be input for equal output power. Every motor is different and the only way to make a proper comparison is actual tests. In addition, looking for these improvements in efficiency through tests will be quite difficult as the difference could be quite minimal. A very well planned and executed experiment would have to be used.
@gregstafford2155
4 жыл бұрын
@@RCexplained i have tested a 4074 1550kv motor at 4s compared to 4074 2200kv motor and results is the 1550kv motor runs cooler and runs longer on the same battery at the same speed from gearing . So im thinking a big 4092 lower kv motor will allow me to race long 30min races with the nitro buggies
@RCexplained
4 жыл бұрын
@@gregstafford2155 When you tested the 1550 vs 2200kv motors, was the output at the wheels geared to the same speed?
Hello Nice video For me the boat it means fishing/relax/nature..... unfortunately I ordered a boat ( flytec 2011-5 ) and one of the engine is not working I'm looking around to make an upgrade an the engine and also the battery. Is possible to make some suggestions ? Thank you Happy holidays
@RCexplained
4 жыл бұрын
What are your goals?
@bobbondarul7448
4 жыл бұрын
@@RCexplained To have some more speed and battery life Nothing else Thank you for your answer
@RCexplained
4 жыл бұрын
I'm not familiar with that particular RC boat. However, if you are able to understand the size of the motor it's using, you could get an equivalent brushless motor. Do you know the size of the motor in the boat? Diameter and length in millimeters. I'm assuming it's brushed, 2 wires from the speed control are routed to the motor.
@bobbondarul7448
4 жыл бұрын
@@RCexplained The size is 13.00* 7.00*4.00 End is 1100kv Yes , with 2 wire.
@RCexplained
4 жыл бұрын
The dimensions you have provided are in millimeters?
Are we saying waste heat increases linearly with size and surface area increases exponentially with size?
@RCexplained
3 жыл бұрын
Waste heat is related to the efficiency of the motor and how much power is being asked of it to deliver. Surface area can be calculated for any given motor size.
I want to make a jet surfboard with 2 impeller i have two motor options 5692 980KV and 4092 1250KV which one will make me go faster on the water i weight 49Kg my system is 5kg
@RCexplained
3 жыл бұрын
What impeller and cell count will you use?
@NabiL_Lam
3 жыл бұрын
RCexplained impeller is from a guy called Mark from Youngesters jets channel, it's 53mm and the voltage is 6s
Highly doubt inrunner are powerful than Outrunner
@RCexplained
4 жыл бұрын
Hi Rama, Inrunners and outrunner are both quite powerful.
@ramadavince6611
4 жыл бұрын
@@RCexplained Outrunner r more powerful coz of the long lever from center. Which inrunner has short lever from centre.
I just clicked on the video to give it a dislike. There is no difference between the two motors on the clickbait cover. Good day.