Mobile Gantry Lift

Overview

A mobile gantry lift, often called a boat hoist or travel lift, is a self-propelled inverted-U frame that drives over a load, cradles it in slings, lifts it clear of the ground, and carries it elsewhere. The most common use is hauling boats out of the water at a marina: the machine straddles a slipway well, lowers two wide slings beneath the hull, lifts the boat, and drives it to a storage or repair area on the hard. The same configuration moves precast concrete, steel fabrications, and other long heavy items in yards where a fixed crane would be inflexible.

The geometry is what makes it useful. The Gantry Frame surrounds the load on three sides, so the lifting forces run straight down the legs into the wheels rather than overhanging like a jib crane. There is no counterweight and no outrigger setup; the machine simply drives into position, picks up, and goes. Capacities range from compact 15 tonne marina units up to 150 tonne yard machines.

Frame structure

The Gantry Frame is a welded steel portal. Two Top Beam members span the top and carry the hoist, four Gantry Leg members drop to the wheel corners, and Cross Tie braces near the bottom keep the legs square under load. The rear is closed by a removable Rear Span Gate so the machine can be backed over a boat in the slipway, then the gate refitted to brace the frame for travel. All the lifting load passes through this structure, so it is the most heavily engineered part of the machine.

Power and traction

The Power Unit is a turbo diesel Diesel Engine driving a Hydraulic Pump Pack that contains separate pumps for traction, hoisting, and steering. There is no mechanical driveline to the wheels. Instead each of the four Wheel Corner modules contains a hydraulic Wheel Drive Motor feeding a planetary Wheel Gearbox, so torque is delivered electrohydraulically and the speed is fully variable from a crawl. Hydrostatic drive suits the job because the machine spends most of its time inching precisely into and out of position rather than travelling fast.

Steering modes

Because every Wheel Corner sits on its own Steering Slew Ring and is turned by a Steering Cylinder, the wheels can point independently. The Steering System coordinates them through a Steering Controller that reads a Wheel Angle Encoder on each corner and commands the matching Steering Valve. Conventional mode steers like a vehicle; crab mode angles all four wheels the same way to move the whole frame sideways without rotating; and carousel mode points the wheels tangentially so the machine spins about its own center. This maneuverability lets a long boat be threaded into a tight storage row.

Hoisting the load

Lifting is done by the Hoist System. Two Hoist Winch units, each with a grooved Winch Drum and a spring-applied Winch Brake, reel wide Lifting Sling straps that pass under the hull. The winches hang from Hoist Trolley units that traverse along the top beams, so the operator can adjust the sling spacing fore and aft to balance the load and clear the keel and propeller. A Sling Load Cell on each sling reports the share of weight it carries, which both prevents overload and warns the operator if the load is hanging unevenly. Sheave blocks reeve the lines for the needed mechanical advantage.

Operator station and controls

The operator works from the Operator Station, an elevated cab mounted on one leg with a clear view down both sides of the frame. Control Joystick controls command traction, hoist, and steering, and a display shows sling loads, steering mode, and machine status. The whole machine runs on a CAN network managed by the Machine Controller with distributed I/O Module nodes reading Pressure Sensor and load feedback and driving the valves. Many marina units are operated by a single person who also walks the boat in by remote pendant during the final sling positioning.

Variants and use

Marina travel lifts dominate the smaller end, sized to the local fleet of sailboats and motor yachts, with frame widths chosen to clear the widest beam. Industrial gantry lifts at the larger end handle bridge segments, wind turbine components, and precast elements, sometimes paired so two machines lift one very long load in tandem. Electric battery versions are appearing for indoor and emissions-sensitive yards, replacing the diesel power unit with a battery pack and electric pump drive while keeping the same frame, wheel corners, and hoist arrangement.