Building with VEX

Every robot is designed with a purpose in mind – What will the robot do? Determining this is sometimes the most difficult step. Tasks can range from very easy to very difficult, and some may require quite complex robots. Some robots will be capable of completing multiple tasks.

After determining what the robot will do, the next step is to decide how the robot will accomplish the task. It is tempting to start building immediately, but often a little bit of planning and design will result in a much better robot. Creativity and innovation will be important during this part of the design process.

STRUCTURE SUBSYSTEM

In the VEX Robotics Design System, the majority of the components in the Structure Subsystem are made from bent sheet metal.

These pieces (either aluminum or steel) come in a variety of shapes and sizes and are suited to different functions on a robot. Different types of parts are designed for different applications.

The VEX structural pieces all contain square holes (0.182 in. square) on a standardized ½ in. grid. This standardized hole spacing allows for VEX parts to be connected in almost any configuration. The smaller diamond holes are there to help users cut pieces using tin snips or fine-toothed hacksaws without leaving sharp corners.

Hardware is an important part of the Structure Subsystem. Metal components can be directly attached together using the 8-32 screws and nuts which are standard in the VEX kit. The 8-32 screws fit through the standard VEX square holes. These screws come in a variety of lengths and can be used to attach multiple thicknesses of metal together or to mount other components onto the VEX structural pieces. Allen wrenches and other tools are used to tighten or loosen the hardware.

When using screws to attach parts, there are two types of nuts which can be used.

Nylock nuts have a plastic insert in them which will prevent them from unscrewing. These are harder to install, as you need to use an open-ended wrench to tighten them up. These nuts will not come off due to vibration or movement.
(This is what you will use!) KEPS nuts have a ring of “teeth” on one side of them. These teeth will grip the piece they are being installed on. This means you do not NEED to use an open-ended wrench to tighten them (but it is still recommended). These nuts are installed with the teeth facing the structure. These nuts can loosen up over time if not properly tightened; however, they will work great in most applications.

MOTION SUBSYSTEM

The most fundamental concept of the Motion Subsystem is the use of a square shaft/axle. Most of the VEX motion components use a square hole in their hub which fits tightly on the square VEX shafts/axles. This square hole – square shaft system transmits torque without using cumbersome collars or clamps to grip a round shaft.

These VEX Delrin bearings come in two types, the most common of which is a Bearing Flat.

The Bearing Flat mounts directly on a piece of VEX structure and supports a shaft which runs perpendicular and directly through the structure.

Another type of bearing used in the VEX Motion Subsystem is a Bearing Block; these are similar to the “pillowblocks” used in industry. The Bearing Block mounts on a piece of structure and supports a shaft which is offset above, below, or to the side of the structure.

To keep an axle/ shaft in place you can use one of these 2 options:

Rubber Shaft Collars are a thin rubber cylinder with a ⅛” square insert running through the center of the cylinder. These collars are designed so the shaft is inserted through the square and the collar captures the shaft by the friction applied.
Shaft Collars are metal cylinders with a round hole running through the center, sized so an ⅛” shaft can slide through the hole. On the side of the collar is a perpendicular #8-32 threaded hole with a set screw in it. These collars are designed to have the set screw tightened against the shaft. The set screws require a 5/64” Hex Key to tighten the screw. The #8-32 threaded hole in the collar allows for the set screw to be removed.

The VEX Motion Subsystem contains a variety of components designed to help make robots mobile. This includes a variety of wheel sizes, tank treads, and other options. Robots using these in different configurations will have greatly varying performance characteristics.

Tips and Tricks

2 Support Points

A drive shaft should be supported at 2 points. Support examples include bearing flats, motors, or bearing blocks.

Keps Nuts Direction

The washers on the keps nuts should be in contact with metal. Overtightening keps nuts causes them to bind less because the lock washer loses its cup profile.

Use Different Directions for Screws

Attach components together with multiple screws from different directions to keep

structural members aligned correctly and for maximum strength.

Bearing Flats

Whenever an axle is used in a build there should always be a BEARING FLAT that goes with it. Bearing flats reduce friction on the axle and support it structurally.

Building with VEX Assignment + Contract

The assignment below will be provided by your teacher to complete using this website page.

2. Building with VEX Contract

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