Brushless Motor Dynamometer from RCbenchmark

RCbenchmark dynamometer website

Please comment and send feedback below. A few months ago, I posted here asking if you would be interested in a dynamometer. I received quite a lot of comments. My colleague and I had the idea of a dynamometer for brushless motor after working over one month full time on a custom motor tester for our drone. We thought that there should be a better solution available on the market. Since there wasn’t anything, we have been working full time on that project, and we are ready to release the result of many iterations and prototypes!


Our dynamometer can fully characterize propellers, and brushless inrunners and outrunners up to 40A and 3kg of thrust. The tool measures thrust, torque, voltage, current, RPM, and it has a precision ohmeter to measure the motor's coils resistance. The data is saved to a CSV file manually or continuously. Here are the technical specs:

 Voltage (0-35 V)

  • Current (0-40 A)

  • Thrust (±3 kg)

  • Torque (±1.5 Nm)

  • Rotations per minute (up to 190000 erpm)

  • Motor winding resistance (0.003 to 240 Ohm)

  • Accelerometer on PCB

See the datasheet (PDF) for more information.


Our software is open source (link to the gitlab repository), and we are actively developing it. We hope it will be hacked and improved! It has safety cut offs (reduce your chance of burning your motor), a calibration wizard, unit selection, CSV export, and much more.  If you are curious, have a look at sample results of tests made with our dynamometer here.


At the time of writing we have 14 units left available at a reduced priced for the beta period. Please join us in this project and send us feedback in the comments below!



Charles and Dominic

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  • @Bjoern Kellermann 3.5 years, later, we deliver the database! The GUI can now upload data automatically. The database is still in alpha, but it is useable. We will implement more visualization features and a better UI and look soon.

    Bjoern Kellermann's Page
    Bjoern Kellermann's Page on DIY Drones
  • @DG We have not tested, although the device can be attach vertically or horizontally (nothing will prevent that in the firmware). If there is nothing in the way of the propeller (objects could cause ground effect), there should not be any difference between the two orientations.

    In practice however, we install it the way you see it in the video for practical and safety reasons. If the prop breaks, it will be ejected along the disk of rotation. It is often easier to place a protection wall with the prop aligned horizontally.

  • Do you get different results when testing with the prop horizontal to the ground vs vertical?

  • @Thijs Sillen: we already use a PGA for the load cells, current, and voltage sensors. Making our unit support more power would make it more expensive as many components (connectors, hardware, electronics, shunt, etc...) would need to be bigger. Until we release a more powerful version you can always buy our device, hack our open source software and build your own hardware to support it :)

  • Use a PGA, will allow good resolution for small motors and allow higher currents :)

  • @BacklashRC: Sorry about the delay, I think I erased my previous answer...
    The 40amps  limit is the limit of the board and the sensor. This limit is a compromise of supporting high current motors, while having a good resolution for small motors.

    You can extrapolate up to a certain point, especially for propellers, but you will have only part of the information. If you are mostly interested in the efficiency at cruise or hover state, and those states are under the 40 amps limit, the device could still be useful.

  • @Bjoern We are not quite ready to talk about it yet, but we hired a college student this summer to build a wiki with a neat sorting feature and searchable motors and props. It is working, but we want to add high quality data on it before release. The wiki will also contains video tutorials on motor testing.

  • Will you also provide an online motor prop database or integrate with Than every customer can upload his measurements.

    Would be great...

    BR Bjoern

  • I am very interested in this device.  Unfortunately almost every one of the many motors that I own is spec'ed to run at more than 40 amps continuously. (One of my smaller motors is the Tiger MT-2820 which handles 42 amps of continuous current.  The Special Sauce motor from Ritewing has no real published specs.  I would to find out more about the motor but it pull over 60 amps with the recommended 10x5 prop.)

    Is the 40 amp limit intended to keep thrust within defined parameters dictated by limits of the device?  Is it possible to test higher current devices by limiting the current draw to 40 volts and then extrapolating measured data to get an idea of how the motor would perform under heavier load conditions? 

  • Great project, i had similiar sketches a while back. However the force and motor chacteristic is highly dependen of airflow, so my idea was to guide the airflow back in front of propeller to simulate real conditions.

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