All-New Design for Cat's Ambidextrous TH220B

Sept. 28, 2010


The new Caterpillar TH220B is presently the smallest model in the company's telehandler range, and like all its B-Series counterparts, has a fundamentally different and considerably more refined design, compared to that of the displaced A-Series models. Although the TH220B we evaluated was equipped with a cab, self-centering steering, air conditioning, tilt steering column and a cloth seat, perhaps the best way to compare relative prices between the new model and the TH62, its nearest A-Series counterpart, is to use base list prices: $57,925 for the TH220B, and $68,590 for the TH62.
According to Cat's John Adams, placement of loads with the TH220B is easier than with the TH62, because the new model allows three simultaneous, proportional hydraulic movements ( raise/lower, telescope and carriage tilt).
The TH220B, right, is some 7 inches lower at the top of the canopy, compared to the TH62, but has virtually the same ground clearance.
Scott Cooper, right, and Amanda Bates measure the TH220B's outside turning circle at 23 feet 2 inches. The comparable circle for the TH62 was 25 feet 6 inches. Even though the TH220B's wheelbase is slightly longer than that of the TH62, its 50-degree wheel cut keeps it maneuverable.
The TH220B's neatly compact engine bay (top)has a new cooling package facing forward (at the right) and accommodates under-hood placement of the muffler and air-intake. The TH62's intake and exhaust components had a somewhat more vulnerable placement, and the TH62 engine compartment (bottom) also had to accommodate the batteries.
Design Summary

Chassis Layout: TH62 engine placement necessitated a transfer case to gain acceptable drive-shaft angles. TH220B design eliminates transfer case and thus simplifies overall chassis design.

Mainframe: Completely new for the TH220B, the mainframe is heavier, provides a longer wheelbase (by 3 inches) and uses no counterweight.

Boom: TH220B boom has a more robust design and uses a flexible-chain channel to contain internal hoses.

Hydraulics: Both units have load-sensing main hydraulic systems (28 gpm/3,626 psi). TH220B's standard auxiliary flow is 28 percent greater, and a continuous-flow auxiliary system is optional.

Engine: TH220B's four-cylinder Cat 3054E engine is emissions-compliant and available in two gross-horsepower ratings, 99 and 120.

Cooling Package: TH220B's cooling package (radiator, oil cooler and charge-air cooler) is at the forward end of the engine bay, where it's better protected, stays cleaner and, says Cat, 40 percent more efficient than the TH62's rear-mounted cooling package.

Transmission: TH220B's new Power-Synchro transmission is a purpose-built unit, versus the TH62's off-the-shelf powershift.

Axles: Cat-designed axles feature larger inboard front disc brakes and heavier cast housings in the rear.

Integrated Electronic Control: TH220B's engine, transmission and hydraulics are controlled via a Caterpillar-designed, integrated management system.

Coupler: TH220B's hydraulic coupler (TH62's was mechanical) has new Z-bar linkage for more power and rotation and is compatible with an extended range of Cat work tools and with TH62 attachments.

Serviceability: Extended intervals for engine- and hydraulic/transmission-oil changes, fewer filters and ground-level access to checkpoints. Accommodates the Caterpillar Electronic Technician system, which provides in-depth diagnostics via a laptop computer.

In this story:

Caterpillar, in the past year, has completely overhauled its telehandler line—not only developing a fresh, technically advanced design for the new models, but also expanding the product range to more closely match machine capabilities with customer needs. And for the fist time in the company's telehandler history, the entire range reflects all-Caterpillar engineering, bringing to the line a uniformity of design previously lacking among models inherited through acquisition. Caterpillar considers its new range—designated the "B-Series"—a significant step toward being numbered among the leaders in the telehandler market.

From five models that provided lift heights from 25 to 44 feet, and rated capacities from 6,000 to 10,000 pounds, the new B-Series range now includes eight models, providing lift heights from 20 to 56 feet and capacities from 5,500 to 11,000 pounds. And, as with most Caterpillar machines, these models incorporate a high proportion of the company's proprietary content, on the order of 70 percent, compared to as little as 20 percent in certain previous models.

Among the newest of the Cat telehandlers, released fall 2003, is the TH220B, the smallest machine in the B-Series range. The TH220B, along with its slightly larger companion model, the TH330B, reflects the most utilitarian design Cat offers. With a hefty two-section boom, Z-bar linkage at the boom face, standard auxiliary hydraulics and a new hydraulic coupler, the TH220B is designed, says Caterpillar, to combine moderate lift height (20 feet) and moderate capacity (5,500 pounds) with an uncompromising ability to handle attachments as efficiently as forks.

During a recent visit to Cat's Clayton, N.C., facility, CE editors had the opportunity to compare the TH220B's design and general performance with those of the TH62, the "A-Series" model that most closely matched the TH220B in lift height and capacity. We worked with Scott Cooper, Caterpillar's senior project engineer, telescopic handler marketing; Amada Bates, telescopic handler marketing representative; Kim Bain, marketing communications coordinator; and demo operators Jeff Morris and John Adams.

To place the two machines in perspective, we should note that the TH220B is not a direct replacement for the TH62. Although the TH62 had a nearly equal operating weight (14,700 pounds) and used a two-section boom, it provided 25 feet of lift height and 6,000 pounds of rated capacity.

"If a TH62 user needs the machine's lift height and capacity," says Cooper, "then the smaller TH220B wouldn't be a viable replacement. The logical choice would be the TH330B, with a 7,000-pound capacity and 24 feet of lift. But, on the other hand, the TH220B could be an economical choice for the TH62 user who can live with less reach and capacity. Expanding the model range gives buyers more choice."

Refined loader control

At the Clayton demo area, both the TH220B and TH62 were fitted with a 1.3-cubic-yard, general-purpose bucket. We'd never before run a telehandler with a bucket, and were quite taken by how competently these machines work as loaders. We more or less expected them to be awkward at loading trucks, but they're not. The novice operator has to concentrate hard on controls, but full buckets are relatively easy—even for rookies. Granted, we were digging from a stockpile of crushed rock, but the material was heavy enough and resistant enough to be challenging.

Going from the seat of one machine to the other in a short time points up a fundamental design difference in the two machines, namely the joystick controller. It's an electro-hydraulic type in B-Series models (you're generating electronic signals to the main valve when you move the lever), versus pilot-operated in the TH62 (you're shifting oil around to the valve's spools).

Moving the TH62's joystick fore-and-aft raised and lowered the boom, and lateral movement telescoped the boom. It was the same for the TH220B we had on site. When you depressed and held a button on the TH62's grip, however, lateral movement of the joystick then activated bucket rollback and dump. The TH220B, by contrast, uses a roller switch on the front of the grip for bucket functions. The switch is much more intuitive than the TH62's arrangement, but does require practice to feather bucket movement.

But, the design of the new model's controls gets better. If the TH220B's control pattern is switched from its "fork" mode (what we've described) to its "loader" mode, then the joystick functions just like that of a wheel loader. In this mode, the roller switch now controls the telescope function. Changing from the fork to the loader pattern takes about 10 minutes with a laptop computer plugged into the machine's data-access port. Adams suggested that a switch to toggle instantly between the two modes might be helpful in some operations.

Expert opinions

Morris and Adams each loaded a single-axle dump truck several times with both machines, then gave us their opinions about the design differences between the two models.

Morris' first observation concerned the cab, which, he said, has a completely different, more-refined feel than that of the TH62. In particular, he noted the new cab's quietness, allowing him to operate, he said, without earplugs.

According to Adams, the TH220B allows more control than the TH62 and, in his opinion, it's a much stronger loader.

"When you're approaching the truck in the 62, you can't telescope out and dump the bucket at the same time," he said. "But with the 220 you can. The new machine has proportional control of all three functions, simultaneously. That makes the 220 faster and easier to operate. The new machine also has more breakout power, and I think the hydraulic system is considerably smoother. A return-to-dig feature would be helpful, especially in operations where bucket loading is a big part of the machine's use."

Both Morris and Adams used second gear in both machines when loading, and they agreed that the TH220B had notably more torque when driving into the pile. Although both models use the same basic engine, the Cat 3054, the TH220B's is an emissions-compliant, electronically controlled version (the 3054E) that uses air-to-air charge-air cooling. The TH220B's engine can be set at either of two gross-horsepower ratings—99 and 120. Our machine had the higher setting, and it generated about 11 percent more torque than the 105-hp engine in the TH62.

Both Morris and Adams agreed, too, that the new model we were working with delivered a smoother ride and was more stable when handling a loaded bucket. The TH220B does have a longer wheelbase and axles with a wider stance, which contribute to enhanced stability. But, in fairness, the new machine also was fitted with optional 17.5-inch-wide radial tires, versus the TH62's 13-inch bias-ply types. The TH220B's standard tires, though, are 2.5 inches wider than those of the TH62.

Adams also used both machines equipped with forks to place a pallet-load of bricks in the truck. He repeated his observation about the TH62's inability to simultaneously telescope and tilt the forks while booming down, which, he said, made keeping the load level more difficult. In addition to yielding more control, the TH220B, said Adams, also feels stronger when handling forks.

Boom, coupler, linkage

Much of the breakout power and fork capacity that Adams and Morris noted about the new model results from changes Cat has made at the tip of the boom. First, the boom face (the perpendicular structure at the boom tip) is larger and heavier than that of TH62, bolstering the overall strength of the boom end.

In addition, the stronger new structure accommodates redesigned Z-bar linkage, the same type used on most wheel loaders. The new linkage, compared to that of the TH62, generates considerably more force (because of its revised geometry and a much larger tilt cylinder) and provides a greater range of rotation for increased bucket-rollback and dump angles. The hydraulic coupler on the new machine also has been redesigned to make it heavier and stronger than the mechanical coupler used on the TH62. Also, one fork carriage, again redesigned for added strength, fits all B-Series telehandlers, including the new side-shift carriage. The rotate carriage is new, as well, having reinforced corners and sides, a redesigned spherical bearing and a larger, better-protected cylinder.

Safety and convenience

Both of the operators who worked with us in Clayton were most complementary about the comfort and convenience of the TH220B's new cab, which is exactly the same on all B-Series models. A fully adjustable suspension seat is standard, but a cloth version is optional in the roomy new cab, as is an air-suspension seat, air conditioning, adjustable steering column and self-centering steering.

The latter feature allows the operator to toggle among the TH220B's three steering modes without first stopping to manually center the rear wheels. Changing steering modes can be done on the fly, and once the rear wheels move through their centered position, the machine automatically assumes its new steering command.

Another notable feature for enhanced operating safety is the transmission's shift-inhibitor system. Downshifts made when ground speed is excessive are deferred until engine over-speeding is no longer a danger, and when making shifts moving uphill, the operator is reminded to apply the brake (to prevent rolling backward) before the transmission will shift.

New model in perspective

The Cat TH62 telehandler was originally designed to be a utility performer, and it handled its job well. We can attest to its good bucket-loading characteristics, and when you combine that with its 25 feet of lift height and 6,000 pounds of lift capacity, the TH62 was a capable worker.

That said, however, the design of the new TH220B is much more refined in almost every aspect. For example, when you combine its stronger boom face, powerful Z-bar linkage, hydraulic coupler and added (high-flow) auxiliary-hydraulic circuitry, you have a machine with the potential to handle larger attachments more efficiently. Add that capability to the TH220B's redesigned controls, which allow easier use of both buckets and forks, and you're left with the impression that the new model is designed with a keener eye toward the operator than was its competent predecessor.