Wheelbase vs Track

Is it too late for the VEX community, especially the software and education people, to refer to these terms the way the general tech and industry worlds do?
Some get it right not all

Both affect “handling”, and drivetrain calculations, and more.


Agreed! Thanks for starting a new thread on this.

Great Photo… we’re definitely focused on wanting to get it right.

Seems like we should re-label the Drivetrain feature to “track width”… :thinking:

I may also have our team recreate that photo with an IQ robot to add to the online documentation.

Thanks for bringing this up!


Thanks for being open to this. Just a suggestion… On that screen where the value is entered, if you located the field under the robot with some arrows it would help convey what is being looked for.

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Not a bad idea. Will definitely consider what we can do - we’re working to balance keeping the UI “clean”, but at the same time a clean UI that doesn’t actually inform the user still ends up being a bad UI…

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Modkit’s drivetrain configuration page does a pretty good job of conveying this IMO:


Having an equivalent illustration in VEXCode IQ Blocks (as well as the option to specify the track, which I could not easily find) would be nice.


By default, we hide the “track width” (which, the name will be updated for 1.0) because we are using the VEX IQ Gyro Sensor to account for the accuracy of turns. The Gyro is calibrated for 2 seconds at the beginning of every project that uses a Drivetrain device with a gyro specified.

The “track width” is only needed for gyro-less turns.

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I think we get the terminology right on all of our implementations of drivetrains:
IQ Python: def drivetrain.Drivetrain.__init__(self, left_motor, right_motor, wheel_travel_mm=200, track_mm=176)
V5 Python: def vex.Drivetrain.__init__ (self, leftMotor, rightMotor, wheelTravel=319.1764, trackWidth=292.1, distanceUnits=DistanceUnits.MM)
V5 C++: vex::drivetrain::drivetrain(motor &leftMotor, motor &rightMotor, float wheelTravel=319.1764, float trackWidth=292.1, distanceUnits unit=distanceUnits::mm)


Though looking at it, we should probably use wheel circumference and not wheel travel, as I don’t think VEX robots of any type usually have suspensions…


I like wheel travel. It provides a nice discussion point that leads to circumference and the difference between distance in the motor functions and the drivetrain functions.


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What is wheel travel? (Quota - has ads)
Like other tech and engineering, has ambiguous common-sense meaning.

Yes, I have them read the tire (standard size only), says 200mm travel…

I like “circumference”, and pi and all that, even for elementary school.

So, it’s really the “bot travel”.

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Interesting, I had no idea…

I teach circumference and corresponding math in elementary as well. Some are ready for it, some not so much. But any exposure is a benefit.


Yes we do!! https://www.vexrobotics.com/228-5654.html

Cheap and fun!

But PI = 3 with the teams since in 8 feet it’s close enough and because of https://en.wikipedia.org/wiki/Indiana_Pi_Bill

And for SF buffs the name of the arms you see as extensions are called Waldo’s after Professor C. A. Waldo, who helped kill the bill.

I love the Modkit version, steal and use that please.


Been impressed by that, especially the “Calibrate”->"“COR” tweak, and the gear ratio! (Even though I don’t have them use drivetrain settings - I like to get them to remember the motors are there and deal with blocking vs. nonblocking and prepare for other drivetypes; and also curves - can’t with “drivetrain” commands)

What’s the Calibrate > “COR” tweak?

When you set up a “Drivetrain” in Modkit, you drag out a controller from the left onto the “Robot” window view. Click on the gear shape lower right of “DRIVETRAIN” framed pic, opens “Drivetrain Settings”. Click “Calibrate” lower right, opens “Drivetrain Calibration” to set the “Center of (typo there I think) Rotation”. Depends in real world on weight distribution, which wheels are driven, traction vs. omni wheels, wheelbase and track dimensions, (dirt on wheels, maybe inertial issues, other magic…)

I actually thought most of the offset should be calculated from the entries in “Drivetrain Settings” window, or why are they there, so wondered if it is just a further fudge factor fix, but it is cool…

Nice graphics, layout, too.

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