Sharon Youth Robotics Association

Robot Design

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Load our PowerPoint presentation "Designing for FTC with the Vex Robotic Development System", in .ppt and .pdf formats.

Chassis Design:

A good starting point is the Squarebot design from the Vex manual.   You can build and test this robot to gain experience and confidence with the materials.

Websites posted for FIRST Robotic Challenge teams (FRC, the competition with 120lb+ robots) can give many mechanical design ideas, and almost every team has one.

Your chassis will usually be four sided - but the placement of the widest side influences balance and ease of turning.  Center of gravity is always an issue for robots that must reach above the chassis.  More complex chassis designs might be shaped as a U or and H.

Support and protection of the wheels can be enhanced by containing them within the chassis, but climbing is easier if the wheel extends beyond the front and/or rear of chassis side supports.

Motors can drive individual wheels, or be geared or chained together on each side.  4 independent motors can be difficult to adjust for straight travel.  Gearing tends to dictate wheel placement - chain and sprocket designs can be more flexible (much more common with the large robots, as large/strong gears are expensive).

If using a six wheel robot (three wheels per side), the center wheel can be shifted down slightly, thus allowing much easier turning with only the center and one end wheel pairs on the ground at any one time.  With good traction, torque is not lost when the multiple motors are geared together in pairs.

Consider the type of robot design issues mentioned on the Strategizing page.  For example:

  1. If you intend to be able to park or hang, it is necessary to have enough clearance to climb onto the rotating platform, perhaps ruling out the small wheels.
  2. For stability, a lifting mechanism may require a larger chassis to keep from tipping.
  3. A robot that will try to gain the doubling ball under autonomous mode may need to climb onto the platform very easily, and may need to deflect balls in its path without turning.
  4. Any chassis could be used to push balls (with a suitable "blade" attached), but a chassis optimized to score in the low goal may have an advantage over one using it as a fall-back strategy.

Lifter design:

"Elevator" designs tend to require many parts.  Tank treads and VexLabs optional slider components can combine to make a good lifter, but will probably need multiple motors to implement.

With "Arm" designs, it is good to avoid multiple pivot points, as each will have to counter the mass of the lifted softballs.  One arm pivoted from a fixed tower can give a better same result.

In general, doubling up (on chains, on motors) can result in a more reliable robot.  Set doubled chains in opposite directions for better resistance to giving way under tension.

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Sharon Team Unlimited FTC website    Last modified: 07/26/08     All Rights Reserved © 2007 by Team Unlimited