How to Select a Type of Spur Gear

The VEX EDR system has two types of spur gears, the Gear Kit and the High Strength Gear Kit. These gears can be assembled in a gear system for power transfer, to increase torque, or to increase speed.

Gears Types

Gear Kit

The spur gears in the Gear Kit are narrow with a face width of 0.250” and have a molded 0.125” drive hub. These gears are ideal for low torque applications and designs which need to be light or have limited space. However they can only be used with the 0.125” Drive Shafts, the narrow face width allows for gear teeth to be stripped in high torque conditions, only the 60T and the 84T gears have mounting holes, and the square hub needs to be drilled out for applications where the gear needs to be free spinning.

High Strength Gear Kit

The spur gears in the High Strength Gear Kit have a 0.500” face width and a molded 0.250” drive hub which will accept the 0.250” High Strength Shafts, the metal High Strength Square Gear Inserts, or the plastic Free Spinning Gear Inserts. The 12T gear is metal. These gears hold up well in high torque situations. The 36T, 60T and 84T gears all have reinforced mounting holes. However, the metal High Strength Square Gear Inserts can cause a 0.125 Drive Shaft to twist in a high torque application and increase how difficult it is to make a repair.

Gear info

Teeth/ratio Teeth/ratio Teeth/ratio Teeth/ratio
Gear Kit
276-2169
12/1 36/3 60/5 84/7
High Strength Gear Kit
276-2250
12/1 36/3 60/5 -
84T High Strength Gear Pack
276-3438
- - - 84/7

Note: Both gear kits have the same diametral pitch and pressure angle so they can be mixed and matched.

Some Tips for Assembling Gears

  • When one gear drives another gear the rotation of the two gears are reversed to each other. An odd number of gears will have the output gear spinning in the same direction as the input gear. This is very useful when designing things like drive trains. An even number of gears will have the output gear spinning in the opposite direction as the input gear. This is useful in designing things like claws and lifts.

  • Whenever possible, it is good design practice to attach the driven gear directly to the part being driven. In these cases, the gear can be free spinning to reduce the fiction on the drive shaft system.

  • A design mistake when assembling gear systems is to place a gear system in the center of a wide span of standard Shafts. When the gear system is placed under stress, a wide span can allow the Shafts to flex and the teeth of the gears will no longer be firmly engaged. Keeping supports close to the gears can keep this from happening
Incorrect Correct
Safety Hazard:

Pinch Points

Be sure to keep fingers, clothing, wires, and other objects from getting caught between the intermeshing teeth of gears.

Different types of Gears can be purchased at https://www.vexrobotics.com/gears.html.