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!

 

Cheers,


Charles and Dominic

Views: 2055

Comment by Jason Franciosa on August 26, 2015 at 1:50pm

Very nice! Definetly a market for this!

Any plans to come out with a larger one to handle more thrust? maybe the 10-15 kg of thrust range?

Comment by Charles Blouin on August 26, 2015 at 1:53pm

@Jason Thanks! It is definitely possible if there is enough interest. For now, you'd need to use your own load cells and an external current sensor.

Comment by Mark on August 26, 2015 at 4:31pm

Great, thanks for posting.  How did you go with the vibration causing the load cell to oscillate unacceptably when using it as part of the structure to support the motor?

Thanks 

Mark

Comment by David on August 26, 2015 at 6:34pm

Very cool product idea!

Comment by Charles Blouin on August 26, 2015 at 6:36pm

@Mark: We have not experienced that problem even with larger props yet. We are however using relatively balanced props, and the vertical load cell is rated to 5KG (7.5KG before damage). We limit the thrust to 3KG in software, which is quite reasonable for 40 amps motors. The device would not be suitable for gasoline engine or unbalanced loads without modifications. As for the readings, there is a small low pass filter on the board.

Comment by Kim Skatun on August 27, 2015 at 5:13am

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.

Comment by BacklashRC on August 27, 2015 at 10:01am

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? 

Comment by Bjoern Kellermann on August 27, 2015 at 12:08pm

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

Would be great...

BR Bjoern

Comment by Charles Blouin on August 27, 2015 at 12:29pm

@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.

Comment by Charles Blouin on August 28, 2015 at 6:50am

@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.

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