Originally posted by ottoman
Mike D... Wow... finally someone who looks at brush hood alignment the same way I do. I was beginning to think I was all alone.
I also tried trimming the leading edge of my monster brushes(.015). My results were differnt than those posted. I used my CE dyno on two motors. One was a good motor (dyno numbers) and one was below average, but both fresh. Both lost some RPM (500 to 1000) both showed a good watt gain (2 to4 watts) at 18,20,22, and 24 amp draw. Both lost a watt at 28 amps. both had higher efficency with the cut brushes. The most RPM drop was at 28 amps.
ottoman - I see that you use amp loads on your turbo dyno. I used to do the same with mine, but recently found that torque loads are much more useful when building motors. Amp loads on the CE dyno became popular years ago because people geared their motors for amp draw because the batteries had so little run time (i.e. 1700, 2000, 2400). Nowadays we have runtime to spare with 3300, so gearing and motor selection in stock is more based on motor performance instead of just amp draw. Try the following setting and let me know what you think.
Set the dyno to Torque loads... I use 3, 4.5, 6, 7, 8, 9. Input voltage is more preference then anything... I'll use 6.7 volts when testing motor setups for sedan, but use 5.0 for 12th scale and on race days so I don't trash the motor before it sees the track. If you are going to do a lot of dyno work at once, just use 5.0 - the results wil be more consistant.
Evaluating the dyno results now is much easier with these settings. The dyno numbers actually show what the motor is doing on the track. The 3 and 4.5 torque loads represent the load on the motor going down the straight. The 6 and 7 torque loads represent the load on the motor in sweepers and short straights. The 8 and 9 torque loads represent the load on the motor as it exits the turn. When the dyno is set to torque loads, you can completely ignore the power and efficiency numbers. The power is just a number calculated from RPM and torque. Since the torque is constant for all the motors tested, higher RPM will mean higher power. Higher RPM on the 8 and 9 loads means the motor is spinning faster as it exits the turn. Higher RPM on the 3 and 4.5 loads means the motor is spinning faster down the straight. The efficiency is also just a number calculated from power and amp draw. I find amp draw is much easier to understand then efficiency in figuring out what the motor is actually doing on the track. These dyno settings have predicted which motor will be faster every time I've run my car on the track. These setting will really show which is the better motor. Let me know how it works for you or if you have any questions.