27LikesTiming on Brushless motor
08-07-2020 | 09:16 AM
#31
Its a very good dyno, and very simple to convert to brushless. The only thing really required to go brushless is to use a brushless speed control between the test motor and the dyno. You will be required to have the speed control "on", so have the switch turned on, on the speed control. Eliminate the use of a receiver and transmitter by using a servo tester, and adjust it to full throttle.
08-07-2020 | 08:55 PM
#32
Tech Master
Joined: Jul 2018
Posts: 1,011
From: Florida
There are chassis dynos with load motors. I have one but it is a simple one. Bank of resistors to give three loads. Simple amp draw of test motor and load motor voltage generation to determine wheel speed. Have thought about equipping it with a accurate sensor system for true motor rpm via the sensor wire tap off.
I will add one of my theories that is backed by Tekin esc data. On tight indoor road courses or ovals, the motor is always in acceleration or deceleration. Hardly ever does one peak out unless your gearing is too low. To get the most from a motor, it must be worked as much as possible.
I will add one of my theories that is backed by Tekin esc data. On tight indoor road courses or ovals, the motor is always in acceleration or deceleration. Hardly ever does one peak out unless your gearing is too low. To get the most from a motor, it must be worked as much as possible.
an acceleration and load dyno are very good at calculating power. the accel dyno does some things batter than the load dyno and vice versa. One of the advantages of a load dyno is it can pinpoint the exact amount of peak work you can do continuously before the motor overheats. so if you add 80 watts of resistance to a 150 watt motor and it almost overheats after running it for an hour you know that the motor can dissipate 80watts/second of heat. this means 80 watts in acceleration/deceleration or constant power.
if you know that a corner that goes from 5000 rpm on entry to 10000 rpm on exit over a 1 second time fram the average rpm is 7500. the efficiency over that range goes from 40 to 60 so you have an average of 50% efficiency. if the average power at 7500 rpm is 150watts and the average efficiency is 50% 75 watts. you can run that corner indefinately. or you can run the next corner at 85 watts of dissipated heat and still stay under the thermal limit.
so if you set the motor to run 150% for 1 second the next second should be 50% so that you stay under 100%. you can look at it this way in seconds or minutes or laps or ...
furthermore you know 100% is 160f. if you like 130f you know that the average efficiency has to stay at something like 80%.
so then you realize that instead of setting the motor to take the corner at 5k in and 10k out that you get 15% more efficiency if its 7.5k in and 12.5k out. so instead of an average efficiency of 50% you have one of 65%. which means the motor can come off cooler or you can save that efficiency for the next corner.
it gets complicated if you try to follow it all in one go but if you take it step by step you will understand how to adjust power in the unique way that electric motors deliver it.
you will also see the point of over timing a motor in special situations to induce field weakening.
08-08-2020 | 10:33 AM
#33
yea I have the minipro chassis dyno. its flywheel is aluminum. so I have an electromagnet pulsing eddycurrents on the flywheel.
an acceleration and load dyno are very good at calculating power. the accel dyno does some things batter than the load dyno and vice versa. One of the advantages of a load dyno is it can pinpoint the exact amount of peak work you can do continuously before the motor overheats. so if you add 80 watts of resistance to a 150 watt motor and it almost overheats after running it for an hour you know that the motor can dissipate 80watts/second of heat. this means 80 watts in acceleration/deceleration or constant power.
if you know that a corner that goes from 5000 rpm on entry to 10000 rpm on exit over a 1 second time fram the average rpm is 7500. the efficiency over that range goes from 40 to 60 so you have an average of 50% efficiency. if the average power at 7500 rpm is 150watts and the average efficiency is 50% 75 watts. you can run that corner indefinately. or you can run the next corner at 85 watts of dissipated heat and still stay under the thermal limit.
so if you set the motor to run 150% for 1 second the next second should be 50% so that you stay under 100%. you can look at it this way in seconds or minutes or laps or ...
furthermore you know 100% is 160f. if you like 130f you know that the average efficiency has to stay at something like 80%.
so then you realize that instead of setting the motor to take the corner at 5k in and 10k out that you get 15% more efficiency if its 7.5k in and 12.5k out. so instead of an average efficiency of 50% you have one of 65%. which means the motor can come off cooler or you can save that efficiency for the next corner.
it gets complicated if you try to follow it all in one go but if you take it step by step you will understand how to adjust power in the unique way that electric motors deliver it.
you will also see the point of over timing a motor in special situations to induce field weakening.
an acceleration and load dyno are very good at calculating power. the accel dyno does some things batter than the load dyno and vice versa. One of the advantages of a load dyno is it can pinpoint the exact amount of peak work you can do continuously before the motor overheats. so if you add 80 watts of resistance to a 150 watt motor and it almost overheats after running it for an hour you know that the motor can dissipate 80watts/second of heat. this means 80 watts in acceleration/deceleration or constant power.
if you know that a corner that goes from 5000 rpm on entry to 10000 rpm on exit over a 1 second time fram the average rpm is 7500. the efficiency over that range goes from 40 to 60 so you have an average of 50% efficiency. if the average power at 7500 rpm is 150watts and the average efficiency is 50% 75 watts. you can run that corner indefinately. or you can run the next corner at 85 watts of dissipated heat and still stay under the thermal limit.
so if you set the motor to run 150% for 1 second the next second should be 50% so that you stay under 100%. you can look at it this way in seconds or minutes or laps or ...
furthermore you know 100% is 160f. if you like 130f you know that the average efficiency has to stay at something like 80%.
so then you realize that instead of setting the motor to take the corner at 5k in and 10k out that you get 15% more efficiency if its 7.5k in and 12.5k out. so instead of an average efficiency of 50% you have one of 65%. which means the motor can come off cooler or you can save that efficiency for the next corner.
it gets complicated if you try to follow it all in one go but if you take it step by step you will understand how to adjust power in the unique way that electric motors deliver it.
you will also see the point of over timing a motor in special situations to induce field weakening.
In my own testing, if you are reaching temps of 130f with a fan on the motor at the end of your race running with 80% efficiency, it gives you a safe operating window in case the fan stops cooling the motor for what ever reason. Testing without a fan, I have seen temps reach 155-160 with the same efficiency.
08-08-2020 | 08:38 PM
#34
Tech Master
Joined: Jul 2018
Posts: 1,011
From: Florida
There is lots of truth to this explanation..
In my own testing, if you are reaching temps of 130f with a fan on the motor at the end of your race running with 80% efficiency, it gives you a safe operating window in case the fan stops cooling the motor for what ever reason. Testing without a fan, I have seen temps reach 155-160 with the same efficiency.
In my own testing, if you are reaching temps of 130f with a fan on the motor at the end of your race running with 80% efficiency, it gives you a safe operating window in case the fan stops cooling the motor for what ever reason. Testing without a fan, I have seen temps reach 155-160 with the same efficiency.
Once the heat management and efficiency becomes the “prime directive” power almost becomes irrelevant. A result of thinking about heat per second is that once you do it you learn how to think about torque per second rather than overall power and you have the right power available when it counts as a result.
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