Batt-man-Here are some points of interest from your reply. The drill press method in the tutorial should be able to determine RPM per Volts or Kv as it is the same method that you just mentioned. We can use this to calculate Kt with formulas you provide. Thus with a few other simple measures, Motor Resistance, No load RPM, we should be able to calculate power. The only trouble is that the calculated power is not believable in two cases that I know of. This reminds me sorely of the Tekin dyno which is a good tool to measure no load current draw and RPM, but pretty useless to measure actual power as it does not agree with anybody elses dyno's that have more straightforward approaches to measuring power. The other case is this Aveox that I saw run right in front of me. Impressive numbers but ordinary on the track. I might give this drill press dyno a try on my 11 turn tripple. 240 Watts at 7.0 V and 45 amps.
Sadly I just threw away my antique Sanwa motor checker that Jorge Tabush gave me. It measured no load RPM and amp draw. I have plenty of drill presses. Could of had me a dyno.
General Motor Tuning Observations
Here are some general rules to intrepret either the Power vs Amp draw graph or the Power vs Rear wheel torque graph which is very similar.
As you increase the spring tension the RPMs go up the torque goes down, the power peak shifts toward the right on these two graphs. This makes the motor more suitable for heavy trucks, tight courses, road courses.
As you decrease the spring tension the RPM's go down,the torque goes up and this shifts the power peak left to lower amp ranges on these two graphs. This makes the motor more suitable to light cars like pan cars or high speed tracks like ovals or open Road Courses.
Note that this effect on RPM and Torque is the opposite of what you would expect.
If you have two motors that have the same power peak(on either the power vs torque or power vs amp draw graphs) and thus the same general shape then obviously the one that has the higher graph is the better motor. This is not true, if you just look at the motor torque without the effect of the geartrains torque multiplication.
If you have two motors that have the different power peaks, like Yankees two motors, but have the same can, a good approach might be to try to tune them using springs until they have the same or similar power peaks. Then you might be able to tell what the better motor is. When the power peaks are way different like these two motors it is hard to judge the better motor, becase it depends a lot on what type of car and course that it is used in.
Good dyno work
Let each motor cool the same time after soldering on leads or let it cool 5 minutes.
don't do repeat test more often than 15 minutes air cooled, or 5- 10 minutes fan cooled and expect to get the same result or a meaningfull result.
Do your test at close to the same room temperature.
Test motors in good condition, cut the comm, seat the brushes, measure spring tension, otherwise your results will be meaningless.
Just my observations.
Last edited by John Stranahan; 12-07-2005 at 07:42 AM.