Golia II Details

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Golia II
Like his predecessor, Golia II was built to attend a robotic Sumo challenge during a Legofest, where he resulted second among four competitors. See the Events - Legofest VI section of the ItLUG site if you want to find out some more details about that event and the other competitors.

Golia II's main features are:

2 speed gear switch: Golia II uses a rotation sensor to measure speed. During the search phase he uses the long gear to be as fast as possible in finding the opponent. When he detects he's been slowed down he deducts he engaged the opponent and switches to the short gear to get the maximum push.
The "short gear" is actually driven by a second set of motors that are wired to an external battery box (to overcome the current limit imposed by the RCX). The gear switch mechanically controls the electric switch (5120) that turns on those motors. So, with a single motor, the RCX change gear ratio and activates the additional motors.
This way during the push phase Golia II has 4 motors pushing: two supplied by the RCX and two by the battery box.
On his front Golia II mounts 4 counter rotating wheels that help to raise the opponent transferring weight onto Golia's wheels thus increasing friction on the field. These wheels get power from the fifth motor, it connected as well at the 5120 switch an activated during push.
The sixth and last motor is wired to the RCX and drives the gear switch.
Two light sensors placed on the front corners detect the border of the field.

Front view. The blue levers activate the gear switch and the electric switch.

Top view. If look at the right wheel (up in the foto) you can see that part of the gearing is inside the wheel itself.

In this picture the RCX and the actuator of the gear switch have been removed. It's easy here to understand the basic structure of the robot and identify the role of the motors. From left to right: the front wheels motor, the two push-phase motors, the two find-phase motors.

Bottom view. If you look carefully at the gearing, you notice that the gear switch is not actually a "switch". In fact the find-phase pair of motors is never disconnected, they're always engaged. The switch only insert two more motors that are mechanically connected with a lower ratio (1:24 against 1:3).

Close up view of the switch actuator.