drive ratios


is anyone willing to share their current gear ratios, and motor configurations for their drive systems?

our robot uses 1:1 and we seem to be overheating our drive motors far more frequently than other teams

our robot only weighs ~12lb

It’s a function of:

Amount of power available (number and size of motors)
Size of wheels
Gear ratios
Friction in drive system

If you are driving 4" wheels on direct drive with four drive motors of any size, you should not be experiencing any problems. The most common reason that this will be overheating is high friction in your drive system. If you are using chain drive, your chains may be too tight.

Tell us more, and, if possible, post a picture. We’d be glad to help.

How many engines are you using? and which type? the 393s, 269s, or the old three wire?
We have four three wire motors hooked up to wheels with a 60 tooth gear driving a 36 tooth gear with no problems. (thats a 1.67:1 ratio, right?)

Woops, I knew I’d forgotten something.
We’re using one 393 on each side of our drive (total two 393’s for driving), powering one driven wheel each, by chain.
The motors are fitted with torque/strength internal gearing.

The wheels are 4" omnis.

I’ll post a pic when I can take one in a few hours.

Yes, I’d agree that that ratio is correct.

EDIT: Whoops, didn’t post this until much later and did not see the above post. Ignore the following: Related to your specs: How many and which kind of motors are you using? A 1:1 gear ratio with a 12 pound robot should be alright with 4 “low-strength” motors, or maybe 2 “high-strength” ones.
Also what size wheels are you using? (I’m assuming 4" because of the problems you’re having but it’s still nice to know. :))

Our robot(24C)'s specs:
<8 pounds. (with 4 tubes)
4-wheel tank drive. (Back two wheels driven directly, front two wheels chain-driven from the back.)
4-motor drive, two 3-wire “low-strength”, and two 2-wire “high-strength”.
1:3 gear ratio. (geared up for speed)
2.75" “small” wheels.


With a 12 pound robot I would think your robot would be alright, so as Rick TYler said, I’d say check for an excess of friction anywhere.


our drive ratio has:
4 HS motors
“internal gearing” so the ratio is 1.6:1
we have 4 4" omni’s
its around 12lbs (didnt weight it in a few months!)
and its heavier than it looks :frowning:
we have no problems with friction because we add an extra chain and use spacers to reduce the “slack”
ill take a pic of it if you dont know what i mean

Quad-Carrier robot prototype frame uses dual 4" omniwheels in each corner of X-holonomic frame, with a direct-drive 1:1 std (100rpm) 393 motor at each corner.
I have only driven it on a 4-tile mini-field, but it stalls out shortly after adding the 4th goal as cargo. I’d already have converted it to 3:1 (torque) drive, but the swerve drive brackets don’t have the right mounting holes.

There are lots of reports in the forums of high-ratioed drives this year, and lots of reports of stalled motors for the same.
Too close to the Leading edge of performance, becomes the BLEEDING edge.

hey, today we added 2 extra motors on the drive and changed the to gearing 1:2 and it it working fine, i guess it just needed that little bit extra :slight_smile: so now we now have a faster robot and everything else still works the way it did before as we had 2 extra motors on the lift

Thanks for everyones help, but it would still be nice to find out if this is normal :slight_smile:

We are looking to run two 36 tooth gears to a 12 tooth.

Video of us test driving it here:

We will see how it reacts once we get some weight on top of it, but for now it’s running very smoothly.

True, before we created our latest “stripped-down” robot, (~7 pounds) we had problems with our drive motors stalling and timing out. Usually this was only when we got in a pushing match, except for our 2nd design robot, it had drive motor failures all the time. (1:2 geared up tank drive with four 269 motors.) With our latest design we have not seen any problems at all, because of how light it is, and we didn’t have to push our motors. (Heck we took out the power expander and it still works fine.) So just remember never assume that you will get the stall torque out of your motors! Because, if you did, then it means you are on the brink of stalling them, and they will time out. A big lesson I learned this year. :o


A lesson well learned by us as too. Which was why our robot only moved for half the match in our second competition…

As of now, our robot consists of a 1:2 gear ratio (tried 3:1, but our weight brought us down again). Our drive motor configuration consists of 6 regular motors connected by sprocket to the 4" omni wheels. We also have a side drive wheel powered 1:1 with an internal torque 393 motor.

I would say our robot is light, but definitely not 7 pounds.

Though our robot’s drive is nothing fancy (1:1 ratio), the we do have an fairly elaborate gearing that lefts our device’s arm,… it’s a 1:21 ratio…(we believe our device arm is heavier than the chasis, roughly a total weight of 14 lbs…at least).

I’m 1:1, with 3-wire motors. The first joint of my arm has a 60:12 gear ratio with a 393 motor, and the second joint has a 36:12 gear ratio with a 393 motor.

Just wanted to add another picture of our team’s drive base. This is prior to getting to back frame pieces cut down so that we fit within the 18" bounding box.

We will see how it operates this Saturday after we have our mechanism attached and post a video to see how four 393’s handle on the drive with our 3:1 gearing.

It probably depends on weight, but I’ve seen 1:3 gearing with four 393’s work well on team 12A’s robot.

I thought 12A was geared for speed?

It is, the “correct” way to give the gear ratio would be 1:3, but it’s still usually best to add in whether it’s geared up or down, as some people say 3 teeth on the driver gear to 1 tooth on the driven gear, vs 1 revolution of the driver gear gets 3 revolutions of the driven gear.


Correct - after seeing the absolute speed of their dominating robot we decided to modify our drive train. Previously we had experimented with using the 36 tooth to 12 tooth setup but didn’t get great results. However, this was when we were using the original 3-wire motors. When using the high strength 393 motors, we haven’t had any problems yet.

Some have cautioned us in regards to tripping breakers, so we are trying to keep the robot as light as possible to avoid putting a lot of load on the motors. We will probably use a power expander as well to split half of the drive on one battery and the other half of the drive on a separate battery.

Gear Ratios are done in order of driven gear:driving gear.

A robot driven for a 3x increase in speed is driven 1:3.

A robot driven for a 3x increase in torque is driven 3:1.