A New Life for Motor Dyno’s


How many of you have an old brushed motor dyno lying around, a brushed motor tester, or something that runs a motor? If you were like me, an old timer, I have a few of these items collecting dust on shelf. What I am about to talk about is not new. There are a few of you who have figured out what I am about to tell you but there are others, like me, that didn’t put to much effort into it to make it work with brushless motors, until now.

Since I didn’t want to keep wiping the dust off some of this equipment I decided to go find a solution to the problem that brushless motors caused me. I have two brushed motor dyno’s, a Competition Electronics Turbo Dyno and a Robitronics ProMaster Motor Tester. None of these were designed for brushless motors. Now I could have sold them before brushless took off but I didn’t think that far ahead. Besides, I wouldn’t have been able to write this article or test some of my motors.


Astro Flight Servo Tester

Enter into the picture the Astro Flight Servo Tester, item number 105. This device acts like your radio by providing a signal to your receiver that tells the servo what to do for around. The best part is it isn’t all that expensive, $35.00, when you talk about how much you spent on your dyno that is collecting dust. Well that is all fine and dandy if you have a servo but I needed something to power the motor. That is where the speed control enters the scene.

With the speed control you have to choose which one you can use. For example, I wanted one that will turn on right away and not go through a boot up sequence. I am sure you could find a way to use one that goes through some sort of boot up sequence but I didn’t. Instead, I chose one that will turn on right away and that one is the Hobbywing Justock. This unit can usually be purchased for around $50.00.

Now as I start to put the pieces of the puzzle together you probably realize that without calibrating the speed control to the servo tester I have paperweights.

Servo Tester and Speed Control

Servo Tester and Speed Control

So let’s do this first. Let’s connect the speed control to the servo tester, just like you would plug in the speed control to the receiver if you were putting it into your car. Now we need find a power supply for the speed control which is your battery so go ahead and connect it to the speed control and while you are at it connect the speed control to the motor. For the servo tester, double check to make sure the dial is set in the middle. Refer to your calibration steps for your speed control to begin the calibration process. You will turn the dial on the servo tester to simulate forward and then brake/reverse. Once you have completed the process you can now run the motor using the dial on the servo tester to ensure the motor is running in the proper direction. Once this has been set leave it at wide open throttle.

Alright, with the servo tester now calibrated to the speed control and set to run wide open, we can disconnect the battery from it. Now we will take the two power leads from the dyno, usually red and black, aka positive and negative, and connect them to the power leads on the speed control, positive and negative.

The complete package.

The complete package.

This step is important because you are using the dyno as the power source to the speed control. Never, under any circumstances do you hook up your speed control to the power source of the dyno. Most likely, the power source for the dyno is 12 volts and I don’t know of to many speed controls that can handle a 12 volt input, at least the one I chose to use can’t. So be sure the leads from the power source are going to the dyno and not to the speed control.

Now setup the motor, speed control, servo tester and dyno to test the motor. I am going to assume you know how to do that so I will not go into detail here. With that said startup the dyno to begin the test. Power will be supplied to the speed control which in turn will power up the servo tester which will tell the speed control to run at full throttle which will tell the motor to run as fast as you can. The dyno will then take its readings and once completed you can view the results.

If you wish to use a speed control that goes through a boot up sequence you can. You will need to provide a power source to accomplish this in order to keep the speed control on. I found that using 4 AA sized batteries will work as the power source. You will plug in the wire that runs from your AA batteries into the connector with the two wires. I had a battery cradle from a radio I purchased which had an on/off switch. So with the battery connected to the servo tester and the servo tester connected to the speed control, when I turned the switch on the speed control would turn on. With this setup, you don’t have to worry about using the dyno to supply the power to the speed control to turn it on.

For just under $85.00 you will be able to bring new life to your dyno or anything else that ran a brushed motor using this setup. Yes there is another way to accomplish the same thing, such as using your radio and receiver, but if you want a more permanent solution I think you will find this one to be acceptable.


About Author

I have been involved in R/C since the early 90’s. I have participated in dirt oval, carpet and paved oval, on-road and off-road racing.

I have found ideas that work and ideas that seem to be good on paper but fail for one reason or another.

I have been involved in the rules decision process and tech inspection for one of the largest indoor on-road only events held in the U.S.


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