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.

FLL Recap

I just finished ref’ing the qualifiers for our FIRST LEGO League robotics season – 6 events in 3 weeks. I must say when this year’s theme was first introduced (Hydrodynamics), I was very excited about the project aspect, but no so much the game. As an engineer, I thought the water theme lent itself particularly well to some interesting research ideas. But as a referee, I was a little fearful that the robot missions were a somewhat complicated for most kids, especially those on rookie teams (and in my neck of the woods, we had a lot of rookie teams).

In the past, there has always been one mission that basically involved sending the robot straight out of base to push some type of lever or handle. As referees, we hate to see teams walk away from the competition with no points, especially after 3 heats. These missions were always a way to allow teams to at least get on the board. However, this year, the two missions that came closest to meeting this simple criterion (the Filter and the Flow) were both tweaked in ways that made them difficult to complete successfully.

The Filter mission required the robot to push a handle until the lock latch dropped into place, but there were two factors complicating this mission. First, the handle on the mission model was positioned perpendicular to base so that the robot needed to make a 90° turn in its approach. Second, there was an obstruction next to the handle that prevented the handle from going all the way in (literally most times the handle was only a millimeter away from letting the lock latch drop). I’m sure that’s why this was one of the higher-point missions, but it still might have been nice to remove the obstruction and lower the points. (I know, “nice” is not usually a term equated with “competition,” but as an engineer I like to see young kids walk away feeling a sense of accomplishment with at least one mission.)

The Flow mission was the challenge that straddled the two competition tables. In the past, this mission has always been in the center of the playing field making it almost impossible for all but the tallest referees to reset. Thank goodness the designers moved this to the northwest corner of the table right across from base. However, rather than simply push the handle, the robot was required to turn one of two levers to release the water cylinder to the other player’s field – not an easy maneuver to make, especially for a rookie team.

The other missions attempted most often were the Pump Addition, the Fountain, the Pipe Removal, and the Tripod – all relatively close to base and involving fairly simple maneuvers. Several teams scored points on the Rain mission, but truthfully, the rain cylinders dropped more times by the robot accidentally bumping into the model rather than actually sliding its handle. So this year’s game turned out to be easier than I’d originally thought... or maybe kids are just getting cleverer in their robot designs.