# What are the limits to the Vex motors?

To better my programming I’m doing some research. What’s the RPM on VeX Motors at full speed. How would I know it’s RPM if i were to add weight to it. For example. If the motor had X amount of pounds exerted on it, how would I know how to find the change in RPM. Any help is useful.

Sujeethan,

The speed and torque of the VEX motors have been discussed at great length here. I suggest you start by searching for “speed” and “torque”. Once you’ve read and digested what’s already been there, feel free to post specific questions if you still have any.

Eric

That isn’t the only question i had, I was also trying to find out how to mathematically find out the rpm of a motor when a certain amount of weight is exerted on it.

You would have to consider the force to make the motor reach that resulting velocity, and then work backwards by calculating the velocity from the force of the motor minus the resisting force. I could spend a few minutes to set up a specific equation, but I would just follow what I hinted at and look for some basic physics equations. I may post something later if I get time.

That would be great if you could!

Wouldn’t you also have to consider the moments of inertia of what ever weights you are adding as well as the “radius” from the center of rotation? If you are talking strictly weight from a position then thats one thing, but it would be fun to go through the calculations for I and such, get to practice integrals and fun!

I’m mostly doing this for the fun of it. I’m mostly going to use this to help me with calculating drive on the drive train. I just need to know RPM for finish my calculations.

heres a speed chart too
if that makes your life easier
https://vexforum.com/gallery/showimage.php?i=72&catid=favorites

There are updated Speed Charts here: [https://vexforum.com/wiki/index.php/Motion. The old chart does not support drive trains which use the high strength sprockets.](https://vexforum.com/wiki/index.php/Motion. The old chart does not support drive trains which use the high strength sprockets.)

Note that these charts are simple no-load ratios of rpm in to rpm out, and do not represent the user experience in a real robot drive train.

Max power is typically at half no-load RPM for this type of motor,
and you won’t be able to check the load until you build your robot, or one like it.

On some robots, my experience is that 36 gear on motor and 12 gear on 4" wheel will tear up the clutches or motor gear sets every few minutes.

Alright thanks guys, I guess I’m just going to have to build something to test on the robot after it’s built to find out it’s RPM.

O.o
what you described there is 3:1
and MOST robots run 1:1 or a bit higher
for a robot to run 3:1
it will have to be three times lighter
just something to keep in mind
the faster you want it to go, the lighter it must be