The uppermost level has more than 2,300 sq. ft. of living space, including two bedrooms, two baths, a living room, office/den, kitchen and a deck overlooking the lake. The other two levels are for parking.

At the driveway level there are 2,000 sq. ft. of space and below grade, more than 6,100 sq. ft.

Building a ramp to the underground garage would have consumed valuable real estate, so the concept called for a hydraulic lift with a platform large enough to accommodate the largest vehicle: a 55’ long recreational vehicle weighing in at more than 50,000 lbs.

Total Lift Weight Exceeds 100 Tons

The lift needed to retract completely into a 13’ deep pit, followed by the 90,000 lbs. “lid” of steel and concrete that doubles as part of the driveway when in the lowered position. Add the platform itself, and the total weight to be lifted would exceed 100 tons.

The fact the lift must fully retract into the pit and yet be flush with the driveway when raised required that the platform guides terminate some distance below grade, presenting a formidable design challenge.

A shallow water table and environmental concerns precluded a deep pit under the platform. The short length of engagement between the platform and guides would offer little help in keeping the platform level under uneven loading.

PFlow was contacted to design and manufacture a state-of-the-art lifting system. To ensure a level platform throughout travel, and to provide accurate positioning at loading and unloading points, a servo-hydraulic system was incorporated.

Hydraulic Cylinders Raise, Lower Platform

Lifting is accomplished via six 12” bore telescopic hydraulic cylinders and a 75 hp, 600-gallon hydraulic power unit delivering 160 gpm. Oil is supplied to each cylinder through an independent hydraulic circuit with servo-proportional control valves for regulating flow.

To track position, individual linear transducers are incorporated on each cylinder providing absolute position feedback to the multi-axis servo control module. Through this module, position, velocity, drive level, position error and many other values can be monitored in real time and plotted. The parameters for each axis can also be tuned independently.

With absolute position data available for each cylinder, important safety-monitoring functions were possible. The system automatically stops travel if any cylinder axis fails to follow the prescribed path within a pre-set tolerance, or if an axis goes out of synchronization with any other axis.

A programmable logic controller is used to link the servo controller to the rest of the system, receiving signals from position switches and other input devices, monitoring system status and controlling the operation of the hydraulic power system and the safety features. Fault diagnostics and audible/visual alarms indicate action required by the operator: to reset the system or call for service. If the platform drifts downward at the upper level, it will automatically re-level.

PFlow is not a stranger to unusual and challenging lifting applications. Previous designs include systems for operating 18,000 lbs. windows in a Florida mansion, lifting and transporting cruise missiles during testing, and raising 300,000 lbs. fuel cells during their manufacture. Other vehicle handling lifts include platforms traveling at 400 FPM, delivering automobiles in a fully automated parking system.