Wallerawang - Construction, February 2013
With the deadline of our first exhibition for 2013 looming, many hours were put in to have the signalling system installed in time. A total of eleven servo motors and ten signal boards were added to move the arms on ten semaphore posts. To mount the servos to the underside of the baseboard, brackets were fabricated from 50mm x 50mm x 4mm PVC angle. The mounting brackets hold a servo, a servo saver horn screwed onto the servo, stops that limit a signal's travel, and a servo horn that links the servo motor and signal together. The use of two horns gives a finer level of adjustment for signal position and movement.
The servo saver horn is designed to protect the gears in servos used for steering radio controlled cars. In our application, we are using them to protect the delicate signals from any untoward movements an errant servo may make. Once the semaphore arm positions have been set through the setup program on the PICAXE, the stops are tightened in position at each end of the horn's throw, so the horn on the servo saver can only move between the stops. If the servo does malfunction it can still turn freely, however the signal will not move past the positions it has been set up for, and neither the signal nor the servo will be damaged. The tensioning springs that come with the servo savers are far too thick for this application, so replacement springs of lighter gauge were sourced from a local hardware, cut to length and used in their place.