Moving around is a primary function of most robots. Choosing which wheel to use can be a critical decision and can determine the success of a robot’s design; each type of wheel has advantages and disadvantages. The two major factors to consider are the wheel's diameter (the distance from a point on one side of the wheel to a point directly across on the other side) and its traction.
VEX Wheels and Tires
This section provides a visual representation of which wheel goes with which hubs.
These were the original VEX IQ wheels. These tires are made from very thick rubber that makes them excellent drive wheels. Their diameter is set up so one revolution causes the robot to travel an exact distance.
160mm and 200mm Travel Wheels are the most common wheels used on VEX IQ chassis. The 200mm travel wheel pairs well with the 200mm Omni-directional Wheel to make a chassis that is consistent and easy to turn. Both of these press onto the 44mm Wheel Hub.
The 250mm Travel Wheel is good for robots that require larger ground clearance or higher speeds. This presses onto the 64mm Wheel Hub.
These newer VEX IQ Wheels work with a large variety of new tires, as well as tank treads. They are softer than drive tires, so they don’t work as well on drivetrains—which require a consistent diameter to perform accurate movements. These work best on intakes and other game object manipulation applications
7x Pitch and 5x Pitch Balloon Tires both go on the same 48.5mm Wheel Hub. These work well when lots of compression is required to pick up objects. These also work great for flywheel launchers
Tank Treads work on both 48.5mm and 32.2mm Wheel Hubs, allowing robots to transport objects over large distances.
3x and 3.5x Pitch Balloon Tires can both be put on the 32.2mm Wheel Hub. These small but squishy wheels are great for moving around objects where larger wheels won’t fit.
Low Friction Wheels
These wheels have little traction but are good for applications where low friction rolling is required. These are good for reacting against walls or game elements when you don’t want to be dragged down by un-powered traction wheels.
The 4x Pitch Diameter (160 mm Travel) Low Friction wheels are smooth and have eight attachment holes to attach other parts to the wheel. It has a center round hole which will allow the wheel to spin freely on a pin or shaft. A Shaft Collar will need to be used in most cases with the wheels.
"Rover wheels" are modeled after the metal wheels used on NASA's various rovers.
The 160mm Travel Smooth Wheel is the only VEX IQ Wheel that has the tread permanently molded onto the hub. It has the same outer diameter as the regular drive wheels.
The 100mm Travel Tire turns the 20mm Pulley into a small, low-profile wheel. It works best when traction is needed and other wheels just won’t fit.
|200mm Omni-directional Wheels|
The 200mm Omni-directional Wheels have a series of double-set rollers aligned around the wheel's circumference. This allows the wheels to roll side to side in addition to rolling forward and backward. Omni-directional wheels' rollers allow a robot to turn much easier than rubber tires. These are best used in combination with the 200mm Traction Wheel (for example, two omni-directional wheels and two traction wheels) to create a chassis that is level and will turn consistently.
Using special orientations of omni-directional wheels allows for more advanced drivetrain designs which can move forward/backward and side to side—omni-directionally! Omni-directional wheels are included in the IQ (2nd gen) Education and Competition kits, in the IQ Competition Add-on Kit, and in 2-packs.
Using the 2x2 Center Offset Round Lock Beam
Inserting the 2x2 Center Offset Round Lock Beam into a compatible wheel (Small and Large Wheel Hub, 48.5mm Hub, and the 200mm Omni-directional Wheel) as shown in the image to the left creates a wheel that will not strip out as easily and will not bend under load.
Comparison of VEX IQ Wheels
|Tire||Distance per Revolution||Footprint||Ground Clearance||Traction|
5x Pitch Diameter Balloon Tire
|2x Wide 3.5 Pitch Diameter Balloon Tire (Trapezoid Offroad Tread)||
The diameter of a wheel (Hub and Rubber Tire assembly) can affect a number of things.
- Distance per revolution is the distance a wheel will roll with one complete revolution.
Footprint is the area between the points where the robot's outermost wheels touch the ground. Typically, the larger the robot’s footprint, the more stable it is and less likely it is to tip over.
Ground clearance is the height from the ground to the lowest structure on the robot. A larger ground clearance makes it easier for the robot to travel over obstacles.
The greater the traction of a wheel, the harder the robot can push or pull, and the easier it is for the robot to travel over obstacles. However, if a wheel has a high degree of traction it is also harder for the robot to turn.