[Red vs Blue] [Challenges] [Technology]

Challenge 3 - Team wolf vs. Team Tiger

"A race, at night, outdoors, on a twisting racetrack."

Before I begin, I’d like to point out that this is Team Wolf’s first foray into building a functioning, remote-controlled Lego vehicle. Furthermore he would be using pieces he’s never seen before (both teams would be using Red Team’s supply of parts, with a spare battery box donated by Blue Team).

Rules

The initial build regulations would be thus:

  • All wheels must have rubber tyres. No plastic tracks, skids, etc as the race would be outdoors, on hard concrete.

  • Only one XL motor would be available (because we’re sharing) and up to two M motors. A single IR sensor and controller would be available for each team.

  • The race will be held outdoors, weather permitting, on a winding concrete circuit in my parent’s back garden. It looks like a racecourse and I’ve been looking for an excuse to use it as one for ages.

  • Time trials will be held around a portion of the course, as well as a test of straight-line speed.

  • No modifications will be permitted between races, although repairs are allowed if something breaks or falls off.

  • If a car comes off the track, the driver may run and put it back.

    The Racers.

    Team Tiger began with an idea, got half-way and changed to something else.

    Tiger’s original idea was to make a three-wheeled vehicle, with a single back wheel for drive. For steering, the body would hinge at the middle, a single arm controlling the movement.

    The drive section was built first: an XL motor driving a series of gears down to the wheel. Chains and other transmission systems have let us down in the past so we stuck to basic gearing. A single 3:1 ratio at the axle provides a bit more speed.

    The torque of the XL motor is not to be taken lightly, and we’ve already managed to grind an 8-tooth gear when going from forward to reverse. We’ll have to be careful to let the thing stop on its own before changing direction.

    With the battery box and drive in place, the rear section was already quite long, which would have become very unstable if the body were to bend. The plan was hastily amended to a rack and pinion system, driven by a medium motor (3:1 reduction using a slip-gear). The effective steering speed worked out just right, giving decent steering at speed.

    Team Wolf began construction with no idea what was possible, and no final product in mind. The construction of their vehicle was as much a learning process as a means to an end, which makes the final result all the more impressive.

    The vehicle began as a plate, to which parts would be attached. The drive motor connects through a right-angle to a solid axle which drives two rear wheels. A medium motor is used for drive, favouring a high top speed rather than initial acceleration.

    The front wheel is mounted on a turntable, controlled by an XL motor running through a worm-screw reduction box. The result is functional, and provides a very small turning circle, but the front wheel pivots slowly. It should be fast enough for the gentle curves of the racetrack, and certainly won’t affect the straight-line drag race.

    Before the race, Team Wolf replaced their XL steering motor with a size M, which moved the wheel faster (the extra torque of the big motor was deemed overkill for a simple turntable).

    Both racers were approximately the same size:

    Results

    Stage one was a straight drag race. After a test run we lined up on a slightly bumpy patio, counted to three, and went for it. Both vehicles hopped about quite a bit on the rough ground, and team tiger’s gentle steering was better able to maintain direction.

    Winner: Team Tiger.

    Stage two was a timed run around the circuit. Team Wolf went first, completing the lap without incident in one minute 18 seconds. Team Tiger got a good start but lost control near the end of the lap and veered onto the grass. The small rear wheel got stuck, and the XL motor’s direct drive shredded a 24-tooth gear. Team Tiger’s vehicle therefore did not complete the lap.

    Winner: Team Wolf.

    Stage three was a race, both cars competing to finish a single lap. Team Tiger’s vehicle raced ahead at the outset and maintained a healthy lead all the way around. As the Tiger car crossed the line, Team Wolf still had a third of the track to go.

    Winner: Team Tiger.

    Stage four was an obstacle course, set up hastily while stage three was taking place. The course consisted of three obstacles: a bridge to drive under, a tunnel to drive through and a circular block to drive around. The course formed a figure-eight, and the cars would have to navigate the central tunnel again on the way back to the beginning.

    We didn’t time this course formally, and even switched vehicles for a bit of fun. Wolf’s vehicle was able to use its smaller turning circle to good advantage, but the larger frame had some trouble navigating the small bridge.

    Winner: Everybody.

    The final result, two wins for Team Tiger’s light, fast racer, one win for Team Wolf’s solid, dependable workhorse.