The other day I was fooling around with the Home Edition of my EV3 software when I noticed the button for "More Robots." What do you know... here was a whole slew of new robot programs and designs that I could try out for free. I clicked on the RAC3 Truck - a front-wheel drive vehicle that uses 2 large motors to power the rear wheels and a medium motor to steer the front wheels. The truck uses the proximity sensor for object avoidance in autonomous mode. You can also remotely operate the truck by sending steering commands with the IR beacon.
The "guts" of the truck is a fairly simple design built from basic LEGO elements, but the body has been significantly embellished with fenders, panels, crossblocks, and eyes - non-functioning elements that appeal to kids and contribute to the truck's futuristic, souped-up look.
From an educational standpoint, two things really impressed me with this model. The first is the gearing system used to steer the front wheels. The drive train is composed of two 4-tooth angular wheels and two bevel gears attached to the medium motor. This yields an extremely strong, yet very precise turning system.
Normally, when you build a vehicle with multiple gears, you always take a chance that the gears will not mesh properly when you first try to drive it. The RAC3 program, however, has a clever little My Block (called "Reset") which eliminates the possibility of this happening. The block starts by turning the medium motor at 30% power for 1.5 seconds. I'll admit, when I first started the program and heard that "click," I thought, "oh no, the gears are locking up." But then the motor turns back 120° and resets. Voila! The wheels are always starting pointing perfectly forward. Very clever.
The other thing I like about this model is the simple program used for remote control operation. It is a perfect tutorial for programming the IR beacon, as well as demonstrating how to program multiple cases in a Switch block. If you're looking for a good STEM activity to use in your classroom, the RAC3 Truck can't be beat.
