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McPappy Racing DIY Brushless Dyno Today's brushless racing introduced new variables (mechanical timing, speedo timing, RPM ranges, rotor diameters) on top of the rollout variable. The new McPappy Racing DIY Brushless Dyno helps you to make sense of some of that. This dyno platform will allow you to test your motors against a brushless slave motor that provides consistent resistance from test to test. It was designed to accommodate multiple test configurations: direct coupler in between both motors, direct coupler with flywheel in between both motors, offset the motors using 2 pinions, offset the motors using 2 pinions + flywheel. The flywheel provides inertia resistance and the brushless slave provides constant resistance. Together they reproduce similar track resistance. The key component to this dyno platform is a huge peice of 1/4" 6061 aluminum which acts as a giant heat sink. Two large fans and all of that aluminum mass will bring the temperture of the motors and resistors back down to room temperature very quickly. This allows you to run many tests very quickly. To find your most powerful motor and speedo combination is actually quite simple. Your overall goal is to spin the flywheel and slave motor as fast as you can with the least amount of amp draw. The McPappy Racing DIY Brushless Dyno can help you do just that. You will be able to find your strongest motors and most efficient combination of mechanical timing, speedo timing, RPM ranges, and rotor diameters. Multiple Configurations The first test configuration is a straight coupler between your test motor and the slave motor. Notice that we provide flex tubing. Compared to a solid metal coupler, in our testing, we found the flex tubing removes vibrations and produced better consistency. Click the pictures for higher resolution.
The second test configuration is a direct coupler with a flywheel between both motors. This is an excellent combination of resistance to reproduce a similar track feel. The flywheel will test the bottom end of the motor under accelaration, and the brushless slave will provide resistance similar to drag produced by aerodynamics and tires at speed.
The third test configuration allows for the motors to be offset allowing you to use pinions. This opens up new possiblities for testing different gear ratios and assisting you with finding better rollouts. You'll be able to answer questions like, "Is higher timing + lower rollout better than lower timing + higher rollout?"
The fourth test configuration allows for a flywheel and pinions. Both types of resistance are present and you can test gear ratios as well.
Motor Mount Adjustability The dyno base allows the motors to slide to the desired location depending on your test configuration. The slots are machined to hold the locknut so that you can tighten or loosen the screws all from the top side with a single hex driver. Soft rubber feet are included which reduces vibration. The motor mounts can be used in the craddle method with carbon fiber brace, battery tape, and standoffs. Simply tighten down two screws to hold the motor. (The carbon fiber brace, battery tape, and standoffs can be seen in the pictures above.) Or you can turn the mount upside down and use motor screws for an even stronger hold.
Kit Contents and Requirements The kit comes with everything you see in the following picture.
Horsepower (Watts) vs. Kv Ratings Kv ratings stands for how many RPM's (K) per volt (v) without load. Be careful here, because you can make a motor look great if you are only looking at Kv. For example, small diameter rotors, weaker rotors, and high timing, will look outstanding for Kv ratings until you put a load on it. There are brushless motor checkers available, but keep in mind they are free spinning the rotor with no load. That's only half of the information you need. Horsepower on the other hand, looks at the combination of RPM AND Torque. Adding a load to the test motor is necessary to determine it's true power. HP (Watts) = RPM x Torque
Completed Setup Options For an inexpensive solution, you can purchase the McPappy Racing Brushless Dyno and the Novak Sentry and simply use your current electronics in your car. (In the picture below, the motor was simply removed from the pod, and even left soldered up.) Another option is to use a dedicated speed controller, servo tester, and power supply (100 Amps or more is desirable). A power supply adds the convenience of not having to wait to charge a battery and provides the same exact power on every test. Many power supplies have voltage adjustment. Personally, I race single cell, so I bought a Mean Well 5V 120A (HRP-600-5)_power supply. This particular power supply allowed me to adjust the voltage down to 4.220V. Bonus!
Dyno Benefits Of course, the final testing will always be the track, but when all things are equal, a dyno can offer some benefits.
The overall goal is simple: spin the flywheel and slave motor as fast as you can with the least amount of amp draw. That will be your fastest and most efficient setup which will keep the motor cooler, leave more juice in the battery, and fall off less at the end of the race.
Possible Future Chassis Dyno Attachment If there is enough demand for it, the dyno has been made ready for an optional chassis dyno attachment. The chassis dyno will allow for the following load methods:
Let us know if you have any questions!
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