Which is the fastest gearbox For VersaPlanetary Gearbox (VexPro) 5:1, 10:1, Or 100:1.

Mentoring time…

Yes, I will give you the answer. But you should really understand the theory, which I will lay out first. I’ll be short, I promise.

Motors have speed and torque outputs–generally, high speed and high torque aren’t going to happen at the same time (at least not in the motors we’re using). Gearboxes reduce speed and increase torque, or vice versa. A X:1 ratio will normally reduce speed; 1:X will increase it (but you’ll need some torque to do so). As an example, spin the KOP gearbox from its output shaft and an input–there will be a difference.

Gearboxes will tend to divide speed and multiply torque by whatever their ratio is. A 5:1 gearbox will cut the available speed by a factor of 5, while increasing the torque by the same amount (CIM free speed goes to 1000 RPM from 5000 RPM). 10:1 cuts by a factor of 10 (for a CIM, that means your free speed will be somewhere around 500 RPM). And I think you get the picture for the 100:1–a CIM will end up around 50 RPM, which is mighty slow but mighty strong.

So, which gearbox will go the fastest would be the 5:1.

Side note: Motors actually output power–torque x speed, as I recall–which is why you have a hard time getting high speed and high torque at the same time.