Originally Posted by
gigaplex
Simply replacing with a 17.5 wouldn't change things, but a spec/control 17.5 at fixed timing and FDR (rather than open 21.5) would change things by virtue of everyone being at the same setting. I wouldn't need to worry about finding peak efficiency and monitoring temperatures.
I did some no-load current readings last night using a multimeter plugged into my ESC, and it was drawing around 3A at the original 30 degree timing, and a touch over 6A at 34 degrees timing. I couldn't get to 40 degrees timing without blowing the 10A fuse on my multimeter. I think that's why the motor was overheating, I don't think gearing would have helped much. It's a Reedy Sonic M2.
I really don't follow your logic.
Why can't everybody be at the same setting with 21.5 but they can with 17.5? And why do you think 17.5 motors don't overheat?
That doesn't necessarily explains why the motor doesn't perform.
I suggested you measure the wheel revs because that gives you a more useable information. The current measured means nothing, especially since the motor is driven in AC/impulse. Measuring wheel revs can be then compared to performance on track. If the car doesn't show on the track the speed corresponding to wheel rev, it is clear the motor can't pull the car weight hence no point in persisting with gearing/timing. You can even build a graph of wheel rev unloaded vs loaded, and you'll see the drop off point in the graph where the motor falls off its torque curve.
You might need a partner to time you on a stretch of straight ( you can use a datalogger but you get again in the same problem as with the motor dyno - money, practicality, etc).
I have done the same thing for my cars and short of buying a motor dyno (expensive, clumsy, convoluted to use), I find this is the best way to tune timing and gearing. More reliable too, because it is actually tuned under real track conditions rather than on a bench with a dyno that may or may not give any relevant data.