Mechanical vs Motorized Attachments

As an FLL referee, one of the biggest mistakes I see teams make is with their attachments. Many teams use motors on their attachments, but if a motor can't complete its rotation the robot just stops. I can't tell you the number of times I've seen a team forget to lift the beam attached to the motor and when the robot goes to pick something up, the beam hits the ground and just stays there.

There's a motto we aspire to in engineering design - the most elegant design is the simplest. With a little ingenuity, most missions can be accomplished with a mechanical, non-motorized attachment. For example, in the Hydrodynamics Fountain mission you can build an attachment with the 5x7 beam frame - it's the perfect size to hold the Big Water. If you attach it to your robot with non-friction connector pegs, it will swivel back and forth like a teeter totter. Putting a couple 2x4 beams on the back of the frame will add enough weight to tip the Big Water back against the robot and keep it from falling out prematurely. As the robot approaches the fountain, the 2 axles in the front of the attachment will hit the edge of the fountain causing the Big Water to tip forward. Voila! An easy 20 points without motors.

Another example is the Flow mission. The rules were very strict this year in saying that the Big Water could only be released by turning the valves, but you don't need a motor to make this turn. You can use a couple 4x6 angular beams, one facing up and one facing down, to turn one of the valves in a counterclockwise direction. Actually one beam will work if you hit the edge of the valve in just the right spot, but the second beam gives you a little cushion on placement.

Reliability is another issue with attachments. Every year, at least one of the FLL missions requires a robot to pick up an object attached to a ring. This year it was the broken pipe. I've seen any number of different designs for this mission, some motorized, some not. Most of the time, when teams use a motor, it's to raise the attachment up so the ring doesn't fall off. Instead, you can build a simple locking latch that will open in one direction when you are retrieving the ring, but will lock into place when you are pulling it out of its holder allowing you to safely transport the object back to base without losing it.

Attachments can also be huge time wasters. Most teams use little black connector pegs to hook their attachments to their robots, but when you get stressed, those connector pegs often refuse to go into beam holes. A much better method of connecting attachments is to simply slide the beam holes on your attachment over a couple axles and 3x2 cross blocks. No matter how nervous you are, your attachments will slide on and off smoothly.