Flatbed Tow Truck

Overview

A flatbed tow truck, also called a tilt-and-slide or rollback recovery truck, carries a disabled vehicle on a flat deck rather than dragging it on its own wheels. The deck tilts and slides rearward to the ground, the casualty vehicle is winched up onto it, and the deck returns to the level transport position. Loading the whole vehicle off the road surface is gentler than lift-and-tow methods, which is why flatbeds are used for low-clearance cars, all-wheel-drive vehicles, accident-damaged vehicles and any load that cannot safely roll. The truck combines a medium-duty Truck Chassis, a PTO-driven Hydraulic System system, a moving Tilt and Slide Deck and a recovery Winch System.

Truck chassis

The base is a Truck Chassis, a medium-duty commercial truck of around 7.5 to 12 tonnes gross weight. A boxed steel Ladder Frame carries the deck and the load, supported by a Steer Axle steer axle and a driven Drive Axle with a hypoid Differential. The Suspension uses Leaf Spring springs at both axles to handle the swing between an empty deck and a fully loaded vehicle riding high on the bed.

Braking is by a full Air Brake System air system rather than the hydraulic brakes of a car. An engine-driven Air Compressor charges Air Reservoir reservoirs, and a Brake Chamber at each wheel applies the Brake Drum drums. Air brakes are standard at this weight because they are fail-safe: loss of air pressure applies the brakes through spring force rather than releasing them.

Powertrain and power take-off

The Powertrain uses a Turbodiesel Engine, typically a five to seven litre inline-six turbodiesel chosen for low-speed torque and long service life. Drive reaches the rear axle through a Transmission and a Propeller Shaft. The feature that makes this a working truck rather than a plain lorry is the Power Take-Off power take-off: a gear drive that taps engine power from the gearbox to run the hydraulic pump. With the truck parked and the engine idling, the operator engages the PTO Clutch to power the deck and winch without moving the vehicle.

Deck system

The Tilt and Slide Deck is the defining mechanism. A flat Deck Platform with an anti-slip surface rides on a Slide Frame subframe through Deck Roller rollers. To load, the operator extends the Slide Cylinder to slide the whole deck rearward past the back of the truck, then extends the Tilt Cylinder to tilt the rear edge of the deck down to the ground. A Approach Ramp lip reduces the loading angle so even low-clearance cars clear the transition.

Once the casualty vehicle is on the deck, the cylinders reverse the motion: the deck tilts back to level and slides forward over the chassis. The loaded vehicle's wheels are secured to a Wheel Restraint Grid restraint with straps so nothing shifts in transit. The combined tilt and slide geometry is what lets a single deck reach the ground at a shallow angle while still sitting safely over the axles when loaded.

Hydraulic system

The Hydraulic System system powers every motion. A Hydraulic Pump gear pump, driven by the PTO, draws oil from the Hydraulic Reservoir reservoir and sends it under pressure to the Control Valve Bank valve bank. The operator moves spools in the valve bank to direct oil to the tilt cylinder, the slide cylinder or the winch motor, controlling each function independently. A Relief Valve caps the system pressure to protect the cylinders and hoses if a function reaches the end of its travel or jams. Flexible Hydraulic Hose hoses route the oil along the moving deck.

Winch system

The Winch System pulls a vehicle that cannot drive onto the deck under its own power. A Winch Motor hydraulic motor drives a Winch Gearbox reduction that turns the Winch Drum, spooling in a Winch Cable steel rope. The operator attaches the Winch Hook hook and chain to the casualty vehicle's frame or recovery point and winches it up the tilted deck. A typical winch develops 4 to 6 tonnes of line pull, enough to drag a seized or crashed vehicle that cannot roll freely.

Cab and electrical system

The Cab is a standard two-seat commercial cab on a Cab Shell structure, with the truck's driving controls plus a way to operate the deck. Much of the deck and winch operation is done from outside the cab using a Deck Control Pendant pendant, so the operator can watch the load while controlling it. The Electrical System system runs from dual 12 V Battery batteries and a high-output Alternator because roadside recovery often runs the engine for long periods to power lights and hydraulics. A roof-mounted amber Warning Light Bar warns traffic during roadside recovery, a legal requirement in most jurisdictions when working on or beside a carriageway.

Operation and use

Recovery operators value the flatbed for the range of vehicles it can carry and the low damage risk, since the casualty rides entirely on the deck. The trade-offs against a wheel-lift tow truck are size and cost: the flatbed is longer, heavier and more expensive, and it carries one vehicle at a time. A typical recovery sequence is to position the truck ahead of the casualty, deploy the deck, winch the vehicle aboard, secure it to the wheel grid, and stow the deck for transport. The truck is built for a long service life of frequent short jobs, and durability of the deck mechanism, hydraulics and winch matters more than outright speed or refinement.