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Introduction

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VEX Robotics has a steep learning curve and can be hard for both new and experienced teams. We hope to provide a wealth of information here, giving every team the resources they need to build high-quality, competitive robots.

🛠

Building

💻

Coding

📗

Engineering Notebook

🏆

Tournaments

If you have suggestions or would like to contribute, let us know!

Building

Comprehensive Building Guide

CAD Design

"Measure twice, cut once"

CAD (Computer assisted design) is an essential part of VEX robotics. It allows teams to fully plan out the robot on the computer before constructing anything in the real world.

Advantages of CAD

Disadvantages of CAD

Plans out the robot fully ahead of time

None

Reduces the time it takes to build

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Adds an element of professionalism to the engineering notebook

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OnShape is the recommended software for CAD in VEX due to its ease of use and VEX part libraries, but other softwares work just as well.

Onshape | Product Development Platform

Here's a good set of video tutorial for CAD in OnShape:

​https://www.youtube.com/watch?v=8rkEL2l4pvM&list=PL58YBuL9CL7KdaFquOuCasoTzGwnjHFUN&index=1​

How to use CAD

As important as it is, CAD is not the end-all. It is a tool that you use to plan out where everything goes on the robot. However, no robot has ever perfectly matched it's CAD design, because there are more factors to consider in the real world. For example, it's not necessary to model screws in the CAD, since it is already clear where they need to be. On the other hand, important aspects of the robot--the drivetrain and additional mechanisms--should be present in the CAD, so that you know how to build them in the real world.

Example CAD design (Over Under). Note the extensive labelling and level of detail. We don't recommend this intake design.

Design Tips

CAD Design can be intimidating at first; here's a few tips:

* Don't be afraid to take inspiration from other robots. Watch matches online. Study reveal videos. Ask other teams questions at tournaments. If you see a design you like, imitate it--don't copy.

* Imitate means "take inspiration from without copying screw-for-screw, and make it better along the way". It's okay to imitate other designs that work well. It's not okay to copy the entire robot, down to the last hole of the C-channels (i.e. holecounting).

* Don't overthink the positioning of the brain, battery, and air tanks. These don't have to go in the CAD design, because their positioning can usually be figured out later.

* Ask for help. Get experienced robotics members to review your CAD before you build it--this prevents you from having to take apart half of the robot to fix one minor flaw later on.

* Simpler is better. A well-optimized simple design will beat a complex one nine times out of ten. Less mechanisms means less things can go wrong on the robot, so don't overdesign!

Here's some specific tips for VEX Robotics:

* Use 2-3 cross-braces on the drivetrain that go across the entire length of the robot, preferably as far apart as possible. This prevents the chassis from bending over time (not good).

* Use standoffs everywhere! Seriously, standoffs are amazing for bracing, and come in handy when you're trying to mount a mechanism to the robot or brace something.

* Study how other successful robots mount mechanisms to the robot. There are myriads of reveal videos and robot explanations on YouTube; even looking at robots from previous years can give you ideas on how to design the structure of your robot. Imitate, don't copy.

Best Practices

Ideally durable, lightweight, and robust

In Vex, there are many techniques to getting a high-quality build. The goal is to allow the robot to last multiple competitions without breaking while keeping it as light as possible.

Triangle Bracing

Triangle bracing uses standoffs at odd angles to brace higher points on the robot. This greatly improves the stability of the higher mechanisms on the robot. In the picture below, the tower in the middle of the robot will not bend over time due to the triangle bracing.

For this type of bracing, we recommend using shaft collars screwed into each other and into standoffs like so:

Note how the shaft collars are oriented

Lighter is Better

Lighter robots move faster and can usually outscore heavy robots.

To save weight, always use the thin nylock nuts. They are about 50% lighter, which adds up when hundreds of them are used across the robot.

Additionally, always use aluminum metal to build the robot. Vex also offers steel, which is 50% stronger. However, it is also 136% heavier--not worth it.

Here's the same C-channel in both aluminum (left) and steel (right) varieties. Note the massive weight difference between the two pieces!

Center of Gravity

Ideally, the center of gravity should be two things:

* Low: prevents the robot from tipping over

* Centered: makes autonomous routines more accurate

Practically, this means that the bulk of the weight on your robot should be as low as possible. Additionally, try to have some balance in the weight distribution side-to-side. For example, mount the brain/battery and the air tanks on opposite sides of the robot to balance it out.

Note how all 6 drive motors and the air tank are as low as possible

Zip ties!

Zip ties are the duct tape of Vex Robotics. They work well in a pinch for meager structural support, but they don't hold up in high-stress situations. One good application of zip ties is on bearing flats for the drivetrain. That's because the bearing flats are not under any lateral stress. Additionally, this saves weight compared to the alternative (screws and nuts).

This should not be viable, but it is

Using zip ties instead of screws and nuts to attach bearing flats saves about 0.01 pounds per bearing flat. If you use 20 bearing flats on the robot in total, you can save 0.2 pounds of weight on the robot. Every little bit of weight reduction matters.

Bearing flat attachment method

Weight

Zip ties

0.001 lbs

Screws and nuts

0.011 lbs

However, zip ties should not be used for high-stress or pivotal connections, as they are prone to break over time.

Drive Trains

Unleash your inner NASCAR

Drive trains are not technically required, but nearly every robot has one. They allow the robot to traverse the field, and serve as a foundation for the rest of the the robot.

Here's the simplest possible drivetrain you can have:

Simple tank drivetrain CAD

This tank drivetrain features at least 2 omniwheels on each side of the robot. Usually, 4 or 6 motors will power these omniwheels either directly or through gears. This drivetrain can turn in place and go forwards and backwards, but it cannot strafe side-to-side (which is usually not necessary).

Here's another example of a more complex tank drive with 6 motors, 6 wheels, and a gear system: