Frequently Asked Questions

Thrust stands

Can I test larger systems?

Please contact us if you need to test more than 40 kgf of thrust.

Why is the thrust of the tool negative?

We recommend to test your motors and propellers in pusher configuration. Nevertheless, the load cells are bi-directionnal. If you want to test in puller configuration and you want a positive thust in your data, activate the checkbox Reverse Thrust Sign in the Utilities Tab.

Why is the the vibration safety cutoff is activated during a test?

The vibrations safety limit cutoff is a safety measure. You can increase the limit, but we recommend to balance your propeller and motor before doing so. Balancing your propellers has many advantages, including higher reliability and increase lifetime of all mechanical components on your drone, and better attitude estimation by your flight controller.

How to interpret the accelerometer reading?

The accelerometer reading is only intended to be used as a comparison tool between different power trains installed on the Series 1580. The chip used in an MMA8452Q. Onboard, the chip applies a high pass filter to remove the constant gravity. A low pass filter is also applied to smooth the readings. The magnitude of the vibration is then calculated using the square root of (AccX²+AccY²+AccZ²). You can also obtain the individual acceleration reading in X, Y, and Z in the exported CSV file.

The readings onboard the firmware are faster than the communication (about 50hz). The board averages the values read between the communication packets sent to the computer.

My optical RPM probe is not reading the motor speed.

First, please follow the installation guidelines provided in the software. To access the installation guideline, please click the ? sign beside the Optical RPM sensor in the Setup tab. In the Manual control tab, servo 1 should be unchecked.

Second, check that the system is reading the correct state when placed in front of the black section of your motor and in front of the reflective section. To do so, please follow those steps:

  1. Go the the setup tab
  2. Under GUI settings, check "Activate Debug mode"
  3. New information will appear on the left of the software. Look for Pin State Servo 1. It should display 1 in front of the black surface and 0 in front of the reflective surface.
  4. Turn the motor slowly to check that there is no false readings over a complete rotation.
  5. You can deactivate the debug mode after step 4 to increase sample rate during the tests.

Third, check the polarity of the RPM probe connection. The black wire should be aligned with the "-" row of pins on the PCB.

My motor is spinning too fast for the electrical RPM probe.

In relatively rare cases, for high KV motors (>3500PRM/V) , high number of poles motors, the electrical RPM probe's maximum RPM limit is too low for a motor. For those cases, we recommend you use our optical RPM probe, which has a limit of 100k RPM.

Can I connect multiple devices at the same time?

No, this is not supported at the moment.

Can I test racing car motors?

Our dynamometer is designed to characterize and measure the properties of all brushless motors within its measurement range. You can calculate the expected torque and speed using the Kv of your motor (please visit our youtube channel for help). You will need to generate a load on your motor with a propeller, a break, or another brushless motors.

How do you measure torque?

A lot of people get confused about how we measure torque, because they do not see any mechanical connection to the shaft. The diagram below shows how the torque on the shaft, which is the same as the torque on the motor mount, is measured:

There are two load cells in the device, measuring FI and Fr. The distance between the load cells is "distance". Using basic mechanical engineering formulas, we obtain this equation:

Prop Torque = Motor Torque = Motor Mount Torque = distance x (FI-Fr)/2

This setup was tested extensively, and it is very good at rejecting unwanted disturbances (parasitic torque). It is also simple to calibrate using the included calibration hardware.

Will the measurements be accurate for airplane propellers?

Propeller efficiency will not be exact for airplane propellers, as they are designed for an incoming airflow. If you need that information, it is possible to use reference tables, or wind tunnel tests. For example, this paper has experimental and theoretical models. For static tests however, the results will be quite similar to what you would obtain with a quadcopter hovering.

Once you choose a propeller, you know the torque and speed required. That is where the dynamometer is useful for motor selection, as it is possible to completely decouple the propeller test and motor test. If you know that you need 5000 RPM and 0.4 Nm of torque for an airplane at cruise speed, you can perform a static test on the ground at 5000 RPM and 0.4 Nm, and obtain your motor efficiency and current.

Do you have a wireless option?

No, not at this time. If you need to have your computer further away from the device, for example for use in a wind tunnel, you can use a USB extension cable. We have tested this 15 foot cable with our product, allowing the computer to be as far as 18 feet from the device. Alternatively, you can use any remote desktop software, such as TeamViewer, to control the tool from any computer.

Otus Tracker and Quadcopter

How many trackers can be connected at the same time?

Currently, the limit is 13 trackers connected to a single computer.

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