Vex Gripper Design

How did FVC teams make their “grippers”? Or what would be the best way to make a gripper using the parts in the VEX Starter Kit?

Obviously there is no “best” way to make a gripper. Design is an iterative, creative process. The best way to optimize a design, is to evolve it over and over, continuously improve it.

Inspiration for a design can come from anywhere. Simply look in the world around you. Also try researching previous techniques and evolving them.

To try to design a ball grabber out of Vex components, one could first research prior ball grabbers (http://www.firstrobotics.net/04Gallery/index.htm) and reverse engineering them. From here, you can try to adapt these mechanisms to Vex.

When I design object manipulators, I use the following rule of thumb.
There are 3 basic ways to “grab” an object:

  1. Hold it with friction (i.e. grab something between 2 flat hands)
  2. Cage it (i.e. cup your fingers around a ball)
  3. Scoop it (i.e. lift it up on top of a flat hand)

From here, one can further design.

One of the simplest, and most easily adaptable ball grabbers is the ‘roller-claw’; this design uses a series of rollers or conveyor belts to “suck in” the ball. In this case, the ball is compressed between the roller and some opposing surface, and the friction of the roller holds it in place.

This design can be created with Vex by simply using the rotary motors in the kit, to drive a wheel.

An example of this can be seen here (as implemented by FVC Team 34):

http://www.vexlabs.com/images/vex-robots/vex-robot-pics-34.jpg

Another method of grabbing the ball is to create two rotary claws, which swing in and cage or compress the ball. This uses a combination of the 3 methods outlined above, but is more difficult to accomplish, as it is a more complex mechanism.

An example can be seen here (as implemented by FRC team 222):

http://www.firstrobotics.net/04Gallery/images/0222-1_jpg.jpg

Creating this in Vex is slightly challenging. A simple way to do it is to simply build arms off of gears which are spinning in opposite directions. (For basic gear theory, check out [

Again, creativity is the only limiting factor.
Hopefully these examples will help spur some inspiration, but the best way to be successful is to experiment!

Good Luck,
John


John V-Neun
Mechanical Engineer
Innovation First, Inc.http://www.vexlabs.com/images/vex-robots/vex-robot-pics-11.JPGhttp://www.vexlabs.com/images/vex-robots/vex-robot-pics-21.jpg](http://science.howstuffworks.com/gear-ratio.htm). )

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