Denman Island, British Columbia
The Lassievator
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Figure 1: Overall view of installation, showing
trolley in folded (stowed) position at the top of
the track, and control box mounted on wall.
This is an elevator designed for use (with human assistance) by a disabled dog who, due to a back injury, was unable to negotiate stairs. It consists of a slanted track attached to the wall beside the stairs, a folding trolley that travels up and down the track, an automotive winch, and associated power and control circuitry.
Figure 2: Closeup of the trolley in open position, with
winch and control box in the background.
The track consists of a 10-foot barn-door track mounted on a length of 2x10 wood. The winch is also attached to this plank, and the whole assembly is bolded to the wall studs.
The trolley is supported by two wheel units (matching the barn-door track) attached to a length of angle-iron that supports the rest of the trolley, and to which the winch cable is attached. The torque of the off-centre load is absorbed by an additional set of wheels on the lower part of the trolley, which roll on a flat strip of iron mounted on the 2x10 base. The floor of the trolley is hinged so it can be folded out of the way when not in use. When opened, it is supported by two lengths of chain, covered in pieces of bicycle inner tube.
Figure 3: Cross section of trolley and track
Power for the 12-volt winch is supplied by a heavy-duty battery charger. The elevator is controlled by a custom-built control unit and two remote switch boxes. There is a switch box mounted on the wall at the upper and lower end of the stair, Each switch box has buttons for UP, DOWN and STOP functions. The control unit contains two heavy-duty relays providing power to the winch in the RAISE and LOWER modes, and two low-power control relays that latch the UP and DOWN functions and provide an interlock against both modes being activated at once. Limit switches mounted on the track disengage the control relays when the trolley reaches the top or bottom of the track, and the STOP switches on the switch boxes can disengage the relays at any time. The power relays provide dynamic braking to the winch when they are disengaged.
Figure 4: Electrical schematic diagram
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Copyright © 2005 Keith Walker
Last modified: 3-Jan-2005