A New Generation in Low-Deck, Electric Drive, Multi-Axle Heavy Transporters

The Doerfer Companies’ TDS Automation Division in Waverly, IA specializes, among other things, in both light and heavy capacity automated manufacturing systems.  Heavy capacity vehicles have come to the forefront as a means for TDS’s customers who assemble very large products that can incorporate much of the same assembly line manufacturing techniques used for much smaller products.

TDS’s Wheelift Systems Group now builds a revolutionary line of multiaxle transporters in both AGV and operator driven versions. Wheelift transporters are designed for loads ranging from 60 tons to several hundred tons and provide entirely new capabilities for in-plant handling that have just never before been available to industry. With their unlimited carrying capacity, ultra-low-deck profiles, and ability to move freely over any type of floor surface, including ramps, and being self-propelled for traveling between buildings; this new multi-axle technology expands the size and types of heavy machinery customers can now build within their existing facilities.

The new generations of Wheelift transporters are actually quite amazing.  Fully self-contained engine driven transporters can have overall flat-top deck-heights of less than 18” which will allow them to enter and exit stand-supported machinery from any direction.  With up to eight inches of vertical travel, transporters can lift and carry any machinery where support stands provide 18” or more of drive-through clearance under their frames.

From a beginning as all-fluid-powered-transporters, Wheelift now concentrates on building electrically driven transporters that have LP engine driven generator systems.  While battery operated systems have been the norm across industry for conventional AGV applications, the move to engine-generated power dramatically expands the operational parameters for both in-door and outdoor operations.

Wheelift transporters are now electrically driven, all-wheel drive vehicles; wherein, a transporter may have six, ten, even twenty or more axle assemblies and every wheel will be independently driven.  The onboard SynchroSteer^® PLC based computer handles the complexity of “differential” steering, by controlling the individual motor speed and direction that provide the vehicle’s fully omni-directional travel capabilities.

Typically every axle assembly under the transporters will have wide-faced solid urethane tires on each end of laterally articulating axles.  This arrangement allows the tires to load equally on sharply varying floor surface slopes and irregularities.  Further, each axle has a vertical travel center column that provides fluid equalizing suspension across every axle in the system, as well as providing lift for self-loading. The fluid lifting center column is the key to allowing independent on-center rotation of each axle for the transporter’s all-directional travel capability.

Whether needed or not for the particular application, the omni-directional travel capability is inherent to the basic functionality of this system. The transporters can not function without it. For instance, a transporter carrying a 100-ton load may only need to drive straight or make relatively long radius turns, and have no requirement to move laterally, rotate on-center, or make very sharp radius turns; or even need to lift up and down, yet it must have the same capability to equally share the load across every tire in the system.  To avoid crushing or torsional damage to floors and equipment, that capability can only affectively be accomplished with a system that absolutely assures that every tire is seeing only its share of the load, regardless of minor or major undulations and other variations in the floor surfaces.  Those capabilities allow transporters to travel over relatively thin and weak floor systems without the damaged caused from or to conventional wheel systems.

There is no in-between. Until now, as industry products get larger, and the required loads reach into these tonnage ranges, only equalizing suspension, multi-axle rail systems or very large pneumatic tired systems could carry these loads.  For these heavier ranges of tonnage, the cost for the required increase in complexity of a Wheelift transporter is simply a reality that can not be avoided.  The practicality will come down to the frequency that the intended load has to be moved, whether its weight is too heavy for conventional equipment, and an evaluation of why conventional heavy trailers, overhead cranes, machinery moving “skates”, air bearings, or in-floor rail systems CAN NOT do the job.   If there are compelling reasons why conventional handling means will not work, then it may well be possible to cost-justify a dramatic jump in raw system cost.  If price is more important than functionality, then the Wheelift technology will not be applicable to that application.   Generally speaking, this technology only applies to loads that have to move often and the requirements are so complex that conventional means will not allow it.