Speed help please


I made a very small robot that is very good at pushing mobile goals. But it is not as fast as I would like it. I tried to use gears, but my wheels fell off. Then I tried programming, but got an error that I couldn’t fix. Any tips?


Change to high speed motors? Also, what is the error?


Post pics. What’s your motor setup?


Ummm I have two motors in the very center with gears of the same size to each 4” wheel.


I’ll post pics later today


I can’t figure out what’s wrong with it but I will post pics on Thursday.


You need more motors. You’re really not going to be able to get any more speed out of the two, they’ll constantly burn out.


Ohh okay I’ll see what I can do thanks for the help


I would still like some help with the code though.


We still really can’t read minds :stuck_out_tongue:

(Post your code)


Yeah :slight_smile:


Here’s the code


you’re missing a lot of brackets, and that *10 isn’t going to make a difference in your top speed.


Then how do I make my bot faster in code?
(Sorry guys first year of vex)


Your top speed on your joysticks are 127. Take out the multiplication and test it out when you add two more motors to the drive train (minimum).


Ok thanks I’ll see what I can do :wink:


Motor top power is 127. 4 HS motors will be a good start.


You won’t. Let’s start with the basics.
A DC motor, at given voltage, has a maximum no-load speed. That happens when it can spin freely. The more load (friction, weight on arm, robot inertia that the drivetrain has to overcome to start moving), the slower the motor will turn. But there is no way to make it turn faster by code.
If you have stock 393 motors, they turn at a maximum of 100rpm on full battery. Any command over 90 would cause them to run at this full speed (if free to turn).
100rpm powering 3.25" wheels is the top speed of 17"/s. 4" wheels would go up to 21"/s

If you want to go faster, you need gears. Motor internal gears - there is a 160rpm (high speed) set and 240rpm (turbo). Turbo at 4" wheels is 50"/s. In theory - unloaded motors and no friction.

In reality, you’ll run into the other side of the gearing “coin” - the torque. To accelerate, you need torque,but the faster the gear, the less torque you have. Worse yet, if your motor provides full torque but don’t really turn at given speed, the motor PTC will trip and you’re done. In other words, you still need to provide enough torque to move your robot. The heavier the robot, the more torque you need to get it moving. For torque, you need slower gear. Or more motors. Or something in between.

So a summary: to get the robot move faster, you need bigger wheels and/or faster gear.
To get the robot keep moving, you need lighter motor and/or more motors.


Also you need to have the while loop inside of task usercontrol.


A really fast robot would be a 6 motor high speed base with 4 wheels. Distribute the motors evenly with the cortex and power expander, and then use all aluminum, or as much as you can. Also you can only set your motors to a maximum speed of 127, however if you are using 6 high speed it might be smart to set them to 100 to avoid any chance of tripping a PTC.
Here’s some code to fit your current set up:

task usercontrol ()
while (true) 
motor[leftMotor] = vexRT [Ch3];
motor[rightMotor] = vexRT [Ch2];