Quote:
Originally Posted by squeeforever
no offense by anymeans, but i dont think its to accurate. i had a emaxx with a xl3100 on 12 cells and its was doing appoximately 50mph and your calculator says 35?!?!?!?

No offense taken.
What spur/pinion and diff were you using? What tires were you using?
The cell voltages are assumed to be 1.2v. If you have really good cells with not much voltage drop under load, or if the load isn't really high, the cell voltage could be up to 1.3v per cell. That alone could account for up to 1012% increase in mph. Also, tires ballooning increases the ratio as well. A 5.5" tire ballooning up to 6" can make a 10% difference. MetalMan said his calculation came to within .5 MPH, so it works. There just might be other factors at play.
The point here is that there are a lot of variables, which tend to be skewed especially at higher speeds. Tire ballooning alone is a function of tire rpm, tire composition, tire temperature, truck weight, etc. If you want more accurate results, take the things I've mentioned into consideration using best guesses and enter those values. I bet the answers will be VERY close.
The script simply uses the following formulas:
Total motor RPM = kv x battery voltage
Total Reduction = spur ratio x tranny ratio x diff ratio
Axle RPM = Total Motor RPM / Total Reduction
Tire Circumference = TT x Tire Diameter
Wheel speed = axle RPM x Tire Circumference.
Convert from inches per minute to MPH, which simplifies to:
MPH = Wheel Speed / 1056
That's it. If there is something wrong here, please let me know.