Rolling Bascule bridge

thingiverse

A 1:43 scale (0-16.5 narrow gauge) model of a rolling bascule bridge under construction and testing. The parts are all for one side ; rolling at the lefthand side, as the bridge can not be seen from behind. The rear face is the same as the front and both are epoxied to half inch aluminium angle and thence to the underframe. For a stronger bond there is a modified copy of the bridge side, for the back. The rails already have their own deck on angle longitudinals that will bond to the underframes later. The Nema17 motor mounts on the back plate of the counterweight. Extra holes added to allow access to the lower mounting screws. An updated motor mount has been added as I found there was insufficient clearance for the drive chains. The rolling quadrants have wires where they roll - to prevent slipping. (from the top of the quadrant to the bridge end of the ground and from the ground farthest back to the bottom (bridge ends) of the quadrants. The drive uses two 25 tooth, 5mm shaft gears (RC cars parts) for the motor to drive a layshaft that runs in in brass tube bearings in the PLA frame. This shaft carries two 9 tooth Meccano sprocket wheels driving chains down either side to two much larger meccano wheels on a 4mm shafts in bass tube bearings at the centres of the rolling section. These gear shafts are made up from 2mm shafting for Expo pinion gears fixed inside 3mm brass tube inside 4mm brass tube. The pinions run along Expo rack gearing to drag the centre of the bridge backwards, tilting the bridge as it rolls. The rack is mounted on a printed rectangular frame. (might need height checked to mate with pinions) Software for the Ardino and motor shield posted on github. (It also includes servo driven crossing gates that protect the bridge opening area, flashing warning lights ) Video posted on YouTube https://www.youtube.com/watch?v=HMKdC2gcMhI