Drive train gear ratio

hey everyone,
I have my robot geared 5:3 for speed, even though it does have enough torque, i am thinking of changing to gear ratio in order for us move around the field with ease.
I was think of changing the gear ratio to 3:1 instead for more speed.
Right now i have 6 motors on my current h drive, any thoughts and concerns will be appreciated.

(p.s - it is made for a dumper )

Knowing the wheel size could help.
We tried an 8 motor x-drive for speed and it was terribly inaccurate during autonomous and programming skills. Also, when our dump is raised, the speed of the drive would cause the robot to tip over, although it would tip over on its own while dumping if it wasn’t against the fence.
Normal driving might work with 3:1 but the strafing ratio should be lower.

Our wheel size is 3.25 inch omni wheels, also we have a anti pegs that acts like claws so, we can push and grab stars from the coners. it is nearly impossible to tip
We don’t have any strafing wheels, as we thought that is not worth, it.

Then I think you are referring to a tank drive, not an H drive. H drive has strafing wheels, while tank drive doesn’t.
The ratio should be fine because it is just a dump-bot, although I’m not sure how accurate the autonomous will be (wheels will slip when you suddenly accelerate or decelerate).
Also, would it tip on its side if you drive it to full speed and you suddenly make a 90-degree rotation (with the dump up)?

  1. Sorry, about that learned something new there then .
  2. no it doesn’t tip while we are turning(with or without the dumper up ), as it is very stable.

what i really wanted to ask what, is is really worth changing, to a different gear ratio

If the driver has enough time to practice, then probably.

Considering you’ve stuck to dumping as opposed to hoarding, speed is of the greatest necessity. You need to score your game pieces faster than your opponent. If your driver can handle the speed, and your robot is fairly light (limited load on your drive), then it’s worth the upgrade in speed. However, if your robot is heavy, you may end up over-stressing your motors, and they’ll stall. Assess the current performance of your robot, and if these changes will actually be upgrades or downgrades based on the above criteria.

[Deleted the last post: I misread what you were saying, my bad…] Maybe just keep the 5:3, then internally gear the motor for high speed, which will then make the 5:3 be more like 8:3.

Boi forget strafe and do a 6 motor turbo, 5:3… Trust me its fun XD <— We are using that setup

We don’t have turbo motors as 1815@ said i guess changing the internal gears would help.

We have 2 drivers in our team, and surprisingly we both started vex this year, and have came 1st in qualification round nearly every time and second in finals.

My opinion is you should not externally gear your base. I think 4 High speed motors are enough. This year we only have half of a field to work with. Also this years game doesn’t require that much speed at all, its all about the skill of the drivers. A 3:1 ratio might burn out your motors every 5 seconds unless the robot weighs so less. You could also have 6 motors on your lift geared 1:5 to lift your self.

I disagree. Speed is essential every year, and this year is not an exception. Even though you only have half of the field to drive on you still have to get to the stars and then score them; especially on a dump bot, the robot has to go back and forth from collecting stars and scoring them at the fence. Driver skill is important, but assuming equal skill levels in driving, the faster robot is going to win.

Also, the closer your robot gets to optimum speed, the more it’s going to be able to do per match.

Correction : our robot has 6 motors geared to 5:3
and we have our life geared to 1:7 using 6 motors

As for speed like mwang17@ said even though we have half a field, the bot still needs to be fast enough in-order to dump the stars and cubes over the fence

Just make sure your driver can handle your chassis’s speed. If the drive is too fast for your driver, it lowers your efficiency significantly. Allow enough time for driver practice, and you should be fine.

We have some really good drivers in my team, I am pretty sure they will be able to handle the speed.

Now thinking about it, instead of taking my Chassie apart and rebuilding it again, i should just change the internal gearing for the drive from torque to speed.

Just my opinion I think that 4 motors high speed is enough. Because our robot can move really fast and it is light as well. And I think a lift geared 1:5 using 6 motors would be okay (I mean we can lift ourselves with 4 motors geared 1:5)

4 motors high speed is “enough” for sure, but 6 motors geared faster is inherently better. The scoring rate will be faster just because you can gather scoring objects and get into a scoring position faster.

@vex2.0 If you gear a high speed motor 5:3 you get around a 2.53:1 gear ratio. For reference Discobots was running 2.4:1 on 4" wheels last year, so you’ll be a bit slower than that. If you change out the internal motor gears now you’ll gain about 50% speed.

To be honest I’m not sure why you externally geared your drive 5:3 (1.666:1) rather than direct driven high speed motors (1.6:1) in the first place. It’s pretty much the same gear ratio with a lot more efficiency and much more simplicity. Remember KISS!

This is what I meant. You did not have to externally gear your base motors. TBH it just takes up more space.

At the time we were building, we didn’t think about this, but now that i think of it, you’re right, but i guess i wil just change the internal gearing