Please share some examples to understand Differential & Bevel Gear Pack use case for vexiq

Hi members,

please share some use cases for Differential & Bevel Gear Pack use cases , docs or videos to see how they help the drive train or arm movements ?

Google VEXIQ differential gear. Get the page, slide all the color choices and at the end is a great picture on how they work.

In my opinion, differential gears are unnecessary for IQ drivetrains. I mean, just use omniwheels if you want good turning, because in almost cases omniwheels will be better in efficiency, and turn speed.

The only two reasons I think you would want this kit are:

  1. The other pieces (bevel and side connecter)

  2. If you want to build an off season non competition robot. (E.g. Vex IQ Snake)


In this manual, Part 3, Project #1 is a Tricycle Drive. It uses the differential and bevel gears for steering.

The Dual Differential Drive with LEGO used to be popular. It allowed one motor to be devoted to steering, one for drive, and was especially helpful if you wanted to drive perfectly straight during autonomous before IMEs/rotation sensors were built into the motors-- no worries about the imbalance of motor speeds. The old LEGO motors (compatible with RCX) were much more compact and conducive to building this type of drive train.


Differentials are really not that handy for the normal team. However I’ve seen teams use the differential to solve problems that can stump even the best of teams.

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Yep, for example, you want to drive both sides of your four bar linkage but there isn’t outside to drive the gear train. So the differential can be on the inner part of the robot, motor below and have it drive the first set of gears in the lift.

It’s a part you should mess around with and make sure you fully understand how it works and goes together. The picture I referred to is good, the other links are good. But the key thing is build one and see how it does all of the gears work in concert

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3 Motor drive base where all three motors push your bot forward!!!

How you ask?

You have one motor on each side like normal. Then you have the third motor on the differential that runs at the sum of the left and right motors. It will assist when driving forward and backward, so you can gear up everything to go fast. When turning left or right, it won’t help because the left and right will cancel out.

Most three motor drive bases are H drives, but you could do this instead to get more forwards and backwards faster actions. (If that made any sense…)

I made a standard “car” a few years back with this kit where you had one motor powering the rear wheels like on a car, and one motor was used to do the steering in the front. It’s interesting, but not as efficient as the old tank drive. It’s a lot of work to get your bot to do less.


That is basically my point. Why not just use H-drive?

That was in reference to making your robot with a standard car layout, using a motor to steer the front wheels.

What you could do with three motors and a differential…

…is have all three push your bot forward and back. Doing so with three motors instead of two would make you 50% faster, and would give you more “forward and backward” torque than any other competitive bot out there. You would lose a degree of freedom as opposed to doing an h drive, so there is always a tradeoff.

(Typically, competitive bots have two motors that can push the bot forward. There are some 4 motor drive bases in IQ, but using all those motors for your drive is typically not very competitive.)