|Combination of steering cylinders and tie rods rotates all six steering bogies simultaneously to provide tight turning radius for 40-ft long transporter. |
How do you move a 24-ft diameter, 14-ft high ladle full of molten metal from one steel mill building to another? One way is with an E2000 Series transporter, designed and built by Liftking Industries Inc. in Woodbridge, Ontario near Toronto. These transporters can lift and transport 300-ton loads. This capacity is especially impressive when you realize that the transporter is just 40 ft long and has only four axle lines.
How do you balance that huge ladle and maneuver the transporter while carrying it? The drive axle — pivoted at its center — has dual 6.5-ft diameter pneumatic tires at each end. Each of the three steering axle lines consists of two bogies, each with its own axle that has 5-ft diameter pneumatic tires at each end. The bogies also pivot. The large, air-filled tires provide low ground pressure for travel on rough pavement or slag-base roads, while the ability of the bogies to self-adjust helps keep the load reasonably level.
Hydraulics also plays a role in leveling when traveling over the uneven surfaces typically found at the sites where the transporter works. The vehicle has eight 9-in. bore cylinders that elevate and lower its load. One of these is mounted over each bogie and the remaining two are positioned above the ends of the drive axle. The cylinders over each axle line are cross-connected. If one cylinder experiences an increase in pressure from the road surface, it can dump some fluid to its mate on the other side of the transporter. (The main frame of the load platform — constructed of submerged-arc-welded T1 steel — is designed for optimum flexion consistent with long fatigue life.)
|Hydraulics powers steering and brakes, plus elevation and lowering of loads up to 300 tons on diesel-powered, one-of-a-kind ladle/pallet transporter in E2000 Series that works 24 hours a day. |
The steering system combines two double-acting steering cylinders with specially designed tie-rod linkages to simultaneously rotate all the steer bogies (fixed to the load platform with 4-ft turntable bearings). As one steering cylinder extends, the other retracts. This arrangement provides the transporter with efficient steering characteristics and a very tight 31-ft turning radius — the smallest in the industry. The steering system is designed with enough power so that the transporter’s wheels can be turned while the vehicle is at a standstill under full load. A pressure-release valve protects the steer circuit to prevent damage from pressure spikes if a wheel should hit a curb, or if the operator tries to continue to steer beyond the end of the steering cylinders’ strokes.
The transporter’s two pumps are driven by the PTO at the transfer case. A piston pump provides pilot pressure to the hydraulic system’s solenoid-pilot valves as well as operating pressure to the wet-disc service and parking brakes. One section of the tandem pump supplies elevation and steering functions, with steering taking priority; the other section is allocated to cooling the hydraulic brakes. All hydraulic functions are controlled electrically from the cab via a single-piece manifold block — patented by Liftking. Hydraulic pressures are approximately 2500 psi for steering, 4000 psi for lifting, and 750 psi for braking. Because the transporter may be exposed to high temperatures, Quintolubric fire-resistant fluid supplied by Quaker Chemical Corp., Conshohocken, Pa., was selected, and stainless- steel lines are used to deliver it.
A single electrical joystick controls all the blocked-center directional valves that operate the cylinders that elevate and lower the load. Each of the eight cylinders involved is protected by a pipe-break safety valve — also patented by Liftking. Should a connecting line break, this valve shifts to block leakage from that line. The remaining line in the double-connection piping arrangement then serves to supply fluid to the cylinder.
Liftking Industries Inc. also has a U.S. location in Youngstown, Ohio.