Chassis

The Chassis is the base of the robot. The chassis design can affect how the robot drives, scores, and moves around the field. A chassis can have the added benefit of protecting essential and fragile parts like the motors, wiring, and V5 Brain. It can also prevent the robot from tipping over.

There are some common chassis shapes that students build in VEX robotics. Each has pros and cons, so choose your Chassis wisely. However, the most important thing to know is that the axles holding wheels or gears need support from both sides.

The drive shaft or axle sits on a pivot point like a teeter-totter when only one metal side is used. This creates a loss of structural integrity and less precision when driving because the axle is not secure. Using two pieces of metal (as shown below with the grey rectangles) keeps the axle and wheel sturdy and secure. Using the bearing flats to reduce friction when the axles turn in the metal square holes is also important.

You also need to consider how many motors and wheels you think your robot needs. The more motors, the more power. Remember to follow the constraints related to the number of motors allowed as described in the game manual.

Turning scrub is also something you will need to keep in mind. Turning scrub is the friction that resists turning. This friction is created by the wheels dragging sideways on the ground as a robot turns. Ideally, you want to reduce turning scrub using Omni Directional wheels in your design. However, there are some instances where friction may be beneficial.

The shape of the chassis also affects the turning scrub.

Common Chassis Shapes

Square/Rectangular

The square or rectangular-shaped chassis is a sturdy structure that can handle much stress from the abovementioned mechanisms. It also blocks the game pieces from entering the inside of the robot and getting stuck. Sometimes, the metal frame acts as a plow to move objects around the field.

It is essential to consider how the robot will need to interact with the game pieces. For example, the four walls may get in the way of grabbers and intake systems. Therefore, design all three robot subsystems together before building the chassis.

H-Shaped

The H-shaped chassis is another sturdy base and uses less metal than the square or rectangular shape. It also allows areas for the other subsystems of the robot to operate in the front and back of the robot.

It is essential to consider how the robot will need to interact with the game pieces. For example, the central bar may get in the way of larger grabbers and intake systems, so design all three subsystems of the robot together before building the chassis.

U-Shaped

The U-Shaped chassis loses a bit of structural integrity along the front of the robot. The central bar can be moved forward a bit, and several screws can be used to help reinforce the back to help maintain the structural integrity.

However, the benefit is ample room to operate a grabber or intake system inside the robot. Consider the game pieces, as they may get trapped inside the U-shape when driving on the field.

Holonomic Shaped Chassis

The holonomic U-shaped and H-shaped chassis are built so the wheels are at 45-degree angles. This is a difficult chassis to build and program. It also has less space to operate mechanisms and attach sensors.

However, if built correctly, the significant advantage of a holonomic drive is getting to exact X and Y coordinates on the game field. In addition, the holonomic allows for driving left or right while keeping your claw parallel to your goal. This can be especially beneficial in autonomous programming.

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