Textrix Robotics https://www.tetrixrobotics.com/:
Standard Hole distance between holes is 1 inch for FRC and 16mm between large holes for FTC and 8mm between large hole and small holes. Standard hole size for FRC is 3/16″ and standard hole size for FTC is 1/8″.
C Channel and Square Tube are great for structural support that has multiple items attached in multiple planes. C Channel is easier to get nuts and screws to be hidden inside, where square tube usually has screw end and bolt outside.
L Brackets are great for supporting metals at different directions. When unsupported on one end of the lever, is the weakest point, so when this case increase thickness, change to steel, or increase width.
3″ to 4″ in length in both directions with 2″ height which comes in thickness of 3/16″ and 1/4″. This allows for the first inch at the corner to not need a hole.
Sizes go from tiny to 72″x144″
Sheet is create for supporting metal in the same plane. Last years FRC robot used a lot of these pieces.
Many different diameters and thicknesses. Have not had much of a use for these, but could have used on last years FTC robot.
FRC Standard Screw Sizes: 10# (3/16″) 28 Threads/Inch (3/8″ nut),
FTC Standard Screw Sizes: 6# 32 Threads/Inch (5/16″ nut)
Gearboxes, most range from 4:1 to 10:1, and some go as far as 100:1. All the ones I know are gear reduction. The greater the reduction, the greater the torque. At some point if to much torque is placed on the gearbox, it will explode.