Drivetrain

VEX V5 Technical Support
#1

Hey Everyone!

I was wondering if you guys know any good gear ratios to use on the drive train. Here’s what I’m using to be specific.

Drivetrain:

  • Freely rotating front wheels
  • 4 motor drive train
  • All of them are high-speed motors
  • Needs to be fast :lenny:

Also, It would help if you could share pictures of your drive train.

  • Akira
#2

What type of drive is it? 4 or 6 wheels? What size? 4", 3.25", etc. Sticky, omni, mecanum, etc. What is your weight? Are you using aluminum? It is hard to give advice without specifics.

#3

All Aluminum Base and Lift. The internally stacking double reverse four bar has temporarily been removed.

We are using Omni-Wheels, H-Drive, 4 Wheels, and 3.25’

#4

I thought H drive referred to the ones that had a normal tank drive but an extra wheel perpendicular to the others in the middle for strafing. Meaning either it has 5 wheels, or it’s a very weird looking drive system, or it’s not an H drive

#5

Stanley wrote this in a thread a while ago:

#6

@Easton You’re right. Typo on my part. We’re using tank drive.

#7

@Akira @ Easton

Actually, technically Akira’s just deleted post was correct. If you set up a tank drive with a fifth wheel perpendicular to that and use all omniwheels, the drive system is holonomic. It’s not an x-drive, and it’s not using mecanum wheels, but it is holonomic.

Meanwhile, this use of H-drive on this forum to describe that set-up is very non-standard. If you want to know what a real H-drive is instead of the misappropriated term, try here: https://en.wikipedia.org/wiki/H-drive to start.

#8

@Akira You have a few unknowns that you left out, so I’m going to assume a bit. If you have a regular DR4B internal stacker that’s all aluminum, then your robot will be ~12-14 lbs. Using past experience, I can tell you that just a 1:1 HS on 3.25" wheels using 4 motors will work (In fact, that’s the setup a lot of teams use). However, if you don’t trust my 100% expert knowledge, then I will leave the ideal gear ratio formula right here:

(14.76) x # of motors(In this case it would be 4)]
Divided by
(Wheel radius) x (weight of robot and game objects it carries, at max)
Equals Ideal Drive Gear Ratio

Now, to the other part of your drive. I would advise against having your front wheels free-spinning. In sticky situations, that could lead to some tippy outcomes. I’m assuming that you want it free-spinning because the motor gets in the way of the mobile goal intake. I would recommend using sprockets and chain to make all your wheels powered by all the drive motors. That allows you to power the whole drive from the back and just chain the front. Glad to help :slight_smile:

#9