Hi dcb,

I don't target to reach 80 kph, rather I want the kart to go as fast/powerful as it is capable of going (so highest torque & highest speed, and engine running at say 75% of its full capability). In addition, the data available is for the situation in which the engine isn't mounted to the kart (kart isn't driving). If its connected to the kart, the speed (rpm) will be lower, and the torque (Nm) will be higher. These figures can be considerably different. If you look at

http://www.me.umn.edu/courses/me2011/arduino/technotes/dcmotors/motor-tutorial/, you'll see that the difference between the nominal torque and stall torque is 1200% .

The only thing that's useful to calculate from the "14,45 Nm @ 3618 rpm" is that it's only 5,47 kw so 1/1,8 of the full power (10 kw) -when the engine is running free-. So, for this situation, it could easily handle 1,8x more resistance, or hence a gear ratio of 1:1,8

But as said, that's just for when the engine is running freely (not in the kart), and for giving the engine no stress/resistance at all. My guess is that it could handle up to a ratio of 1:51 (see previous posts), at least in an ideal situation (flat terrain, little or no road resistance, ...). So, it's probably going to be less than that, but more than 1:5 (which is the ratio that is normal in electric karts).

The only option I see to make the kart run more efficient would be to put in a gear box, which has say 10 gears, allowing it to shift up from 1:5 to 1:51, and just try the gears out (or use some sort of instrument that can calculate the above and store the data -not sure whether such a tool exists-). And even then, if a gear is found that still wouldn't be ideal since it would only run perfect on flat terrain.

Another possibilility is to use such a calculation tool, and have a 1:5 to 1:51 gearbox, and have the system change gears depending on the calculations it makes. Again, this probably doesn't exist yet, and I doubt electric cars today hence run very efficient.

As for your speed calculation, that isn't possible with the engine speed of the free-running engine data. Here's the silly high speed it gave:

vehicle speed per minute = engine rpm * gear ratio * 3,14 * wheel diameter

@ 3500 engine rpm and no gears, vehicle speed would be 3500 * 1 * 3,14 * 24 cm

@ 3500 engine rpm and no gears, vehicle speed per minute would be 263760 cm

or hence 2,63760 km per minute or 158,25 km/h;

with a 1:5 gearing, it would be 791,25 km/h