Ok everyone - has anyone found a good repeatable method for measuring the speed of these little motors? I am not talking about running it on a treadmill (very inacurate) to get the speed of the vehicle and then backing out the motor speed through calculations. The Tamiya speed checker is similar to this, but I am still leery about the results. I have been looking at using a technique outlined on the website by Roman Black -
www.romanblack.com - showing how to measure the back EMF pulses from the motor over a given time period to indicate motor RPM. Also there is the method of measuring the current draw at various loads to calculate the motor's characteristics and then from these calculations use this motor as a generator when connected to a drive motor. This simply makes a dyno system with the test motor coupled to the generator motor. To test the speed, you would then connect the test motor to generator motor and only power the test motor and then measure the voltage created by the generator motor. This voltage is directly proportional to the speed of the generator motor shaft, which is the same speed as the test motor. The only problem is that this proportionality constant can only be found by first knowing the response of the generator motor at various RPMs. This means that you need to know an RPM to calculate an RPM. I'm sorry for such a long posting, but I am very frustrated at this point. As far as explanations are concerned, I can only explain things to a small degree - not much time - so please do some research before asking too many questions. I might be able to offer some links to motor theory and calculations. Thanks for your input.
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