Magtrol is making it......and according to them, its the only unit they have ever produced for R/C use......though its possible someone took an older unit and converted it to work....
makes the best magnetic particle brakes and torque sensors in the WORLD.
Just make sure they do not overdesign it...and you are right , this will be the first one they design because I have had them make the brakes for my dynos, but I designed the electronics and mechanical interface...
Magtrols existing brakes do not work at the torque/rpm levels we test motors...They have torque v RPM limitations that will prevent you from using any off the shelf torque sensor they make...If they are going to make you a custom brake, be carefull that you do not get overcharged...I have gone through that route with them many times...
They are experts at what they do, but they are used to working with big motors and brakes, or smaller servo type motors...not r/c stuff. R/C motors have a very unique RPM v torque relationship...most other motors do not come even close!!!
Make sure you get a magnetic particle break in the right dynamic range that your motors will operate. They will try to over sell and overdesign... Also, their controllers are not the right stuff for r/c motors, just the brakes and sensors.
YOu will have a GREAT dyno if you use their sensors and or brakes... I recommend you get the brake from them and get a good ME-EE to design the rest of the dyno. It will save you thousands and you will have it much sooner. I have worked with Magtrol... both at their NY office and their main office out of Switzerland. They have provided me with dynamic brakes, hysteresis clutches, and torque sensors for years...and for many applications.
Regarding the torque equation describerd above...well that takes ALL The compnents in a motor into consideration, but all fixed magnet motors have a linear torque constant called Kt. Kt is directly proprtional to current as long as you stay within the operating parameters of the motor. If the magnetic field gets oversaturated by excessive current draw then the Kt constant will not work. As long as the motor operates within its parameters the Kt constant will be linear. ALWAYS!!!!!
I dont have thetime to elaborate at the moment on the motor equations and behavior, but I will do so within a few days.
The bestway to analyze a motors performance is to plot current v torque and speed v torque.
The graphs that I saw are OK, but if you want to parametrize a motors performance yo need to plot against torque, not current, thus torque should be in the X axis and all other variables in the Y axis (RPM, CURRENT, POWER, EFFICIENCY). Try ploting this way based on the data that he provided and you will see the relationship of the two motors in front of your eyes... and how they compare to each other....
Like I said, I will elaborate more on this at a later time...I am tired and I must SLEEP
I am glad some of you started a very good thread. Hopefully together we can show most racers and motor lovers how to analyze and parametrize a motor the right way.
Just remember, there are four constants that define a motor (Kt, Ke, Kv, Km) and once you know what they are and how to use them you can reverse engineer any motor and then find the best motor that will work for your specific application.