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Design Rules

Rolling Robots Rules to Build Cool Robots

There are no instructions for building competition robots, rather we follow a set of rules. Using Design Rule Checking is an engineering practice to assure that all designs that we produce will have a high chance of being successful. It is well known and defined in the semiconductor chip industry but also applied to other design projects typically when using a common manufacturing process. Ou common manufacturing process is the use of the VEX Robotics product line. Through years of experience we have learned best practices when using the VEX Robotics product line and developed rules of building that will assure that your robots function as expected. Follow these rules while building and your robot wont fall apart on the field.

Design Rules also give us a clear way to communicate problems or errors in the design. When reviewing a design we can simply quote a design rule that we all know instead of having to make a detailed description of what is wrong. With this language of design we can all assist one another in the building process. Learn the language of the Design Rules to become fluent in the Rolling Robots Design Process.

2 Points make a line, 3 points make a plane

This is basic geometry applied to robot building

2pt make a line

Always use at least 2 points of fastening when joining parts. This usually means 2 screws through the parts. this rule can also be satisfied by using the hex nut retainers with posts. In that case the posts provide the additional points for stability.

3pt plane

If you want to hold 2 parts parallel to each other we must define 2 planes. Connecting with cross rails at 3 points will do this.


Another way to do hold a plane is to use standoffs. Sometimes it is not possible to get the exact length of standoff but you can extend with spacers to make it perfect.

No metal moving on metal

Use plastic bearings and spacers. Wherever we have a metal part that needs to move it should be supported by a plastic part. Usually the plastic part should be made from a bearing material like Nylon or Delrin. These materials are strong and low friction. The bearings are Delrin, the spacers are nylon.


Shown here is an axle and a bearing. The turning metal axle is supported by the bearing that is made of a special plastic that has low friction. Also the bearing has a round hole that supports the axle more snuggly. Also shown in this design is 2 points of support for the axle. Any axle should be supported by bearings in at least 2 points.

Use locking fasteners

Star Nuts, Nyloks, Lock Tite

nuts and screws

Here is a sample of locking fasteners

  1. Star or Keps Nut, the teeth go towards the metal surface
  2. Nylock, a piece of nylon provides friction against unscrewing, stays on even when loose
  3. Standoffs have no locking, so you may have to use Locktite
  4. This screw is too long, don't do this

Use the correct length screws

Excessive length of the screws wastes time and annoys the pig.


The screws we use are 8-32 star drive. The Screws come in increments of 1/8 of an inch.

Triangles define angles

The triangle is your friend

No sharp edges

wether you use a file or go caveman style, eliminating the sharp edges keeps everybody safe. Also it is an inspection requirement.