Originally Posted by cycleeric
Im converting a TC3 into a Late Model dirt oval racer and owndering what kind of run times can I expect with a 10t and 19t motor with 4200mah NiCD or a Lipo? What would be the difference between the 2 motors and batteries? Can I run it with a higher voltage battery and what would be the advantage of that?
Sorry for all the questions but Im a newbie at Electric, I've been running Nitro for a couple years.
After two or three hot laps before the Main, then a 5 minute Main, I have taken 4200 Nimihs, placed them on a bulb (30 amp) discharge string and timed them and had an average of 1 to 1 1/2 minutes charge left in them with a 10D motor. Now after running LiPo's the same way, I have recharged them and only put a max of 2400mah in them. Not very scientific, but just some ballpark information.
Difference between the motors (19T and 10T) is thousands of RPM's and how the motor makes it torque.
Most of my motor tuning has been done at 5 volts on a Dyno. Over time, I found that motor turning 33000 rpm at 5 volts; at 7.2 volts it will turn roughly 47520 rpm. With a 7.4 LiPo the same motor will turn 48840 rpm - - - initially. Again, not in controlled environs, just ballpark information.
Unlike gassers where you have a consistant power* throughout your race, whereas Electrics loose power. At the start of a race, a NiCad/NiMih will put out 7.6 plus volts in the first 15-20 seconds then the voltage will fall off in a curve, lets say, .03 volts every 15-20 seconds until a point where it will being to fall of more rapidly. This battery performance curve varies with the battery type & manufacture, gearing on the car, motor load, car set up and the driver. Again, not scientific, just ballpark information.
While I have given some numbers on motor rpm and battery performance; these are, even though not concrete and will be disputed. The discribed behaviour of these components exist to one degree to another - always.
*Then there is the problem of heat build-up, a problem that exists with both types of toys. Electrics have more heat build up throughout their components (speed controller, battery, wiring and motor) more so than gassers. Sort of like having a pinched fuel line.
Though lengthy, I can only hope this answers at your questions or at least get you in the ballpark.
There are several threads over at DirtOval.Com that will help you with your endeavors in converting your TC3. Use the forums "search" for faster results. Have fun!