Working comparisons show the Bobcat T590’s overall design efficiency compared to its predecessor T190.
When designing its new M-Series models, Bobcat convened a number of focus groups and encouraged members of the groups—equipment owners and operators—to speak their minds about machine features and performance. Practical insights gained from these sessions gave the company’s engineering staff an added resource when developing M-Series models, which, says Bobcat, combine the best of the preceding K-Series with new features that add overall efficiency to the machine—even in the details.
“A surprising amount of design work went into small items,” says Jeret Hoesel, Bobcat’s training strategy manager, but previously a lead engineer on the M-Series project. “For instance, you’ll find very few 90-degree fittings in the hydraulic plumbing of an M-Series machine, because when you force oil to make right-angle bends, you waste horsepower and generate heat.”
Further gains in overall hydraulic efficiency, says Hoesel, result from such changes as elevating the M-Series reservoir above the pumps, compared with its position below the pumps in K-Series machines. Gravity provides a positive pressure at the M-Series pumps, he says, which minimizes power requirements to overcome negative pressure.
Bobcat also redesigned the main hydraulic control valve, which gives priority to the tilt circuit if an attachment stalls and goes over relief. Before, lift and tilt functions were disabled in a stall, necessitating stopping the attachment and repositioning the machine. Now, a simple adjustment of the attachment with the tilt cylinders solves the problem. The new valve also helps keep attachments properly positioned by eliminating any tendency for lift- and tilt-circuit creep during high-pressure operation.
In addition, says Hoesel, more efficient M-Series hydraulic plumbing results in a slight gain in system flow, which combines with a modest increase in main relief pressure (200 psi) to boost hydraulic horsepower for more competently handling high-pressure attachments.
“At the end of the day, these small gains in efficiency taken together—a percent here, a half percent there—probably result in an overall boost in hydraulic efficiency of 10 to 12 percent,” says Hoesel. “That means we’re giving the operator more useable power without actually adding horsepower—and without increasing operating costs for the owner.”
Gains in hydraulic efficiency, however, are just one aspect of the M-Series design, says Hoesel. The entire machine, he says, was subject to a critical design process, resulting in significant alterations to the cooling system, lift-arm configuration, weight balance, and operator’s station.
“We took what we learned from our voice of the customer meetings,” he says, “then formed small design teams that were challenged with developing systems that would work across the product line—from 800- to 500-frame-size models—by just changing the scale.”
Bobcat began this overhaul of K-Series models in 2009, applying the M-Series design, in turn, to the company’s 600-, 700-, 800- and, most recently, 500-frame-size models—the latter officially launched January 2013. M-Series models, says Hoesel, have a family appearance, share a high percentage of common parts, and, given their consistency of design, are easier to manufacture—for example, permitting many welds to be placed in exactly the same manner, model to model, except that welds might be longer on a larger machine.
Recognizing that Bobcat’s aim with its new M-Series models is to develop more efficient machines—machines that do more work than their predecessors with no increase in horsepower—Construction Equipment editors welcomed the opportunity to work with the company in evaluating what might be called in-the-dirt benefits of the new design.
Included in the recently announced 500-frame-size models is the T590 compact track loader, which replaces its K-Series counterpart, the T190. Given the popularity of this machine size and Bobcat’s success with the T190, we thought that comparing the performance of these two models working at several hydraulically demanding tasks would be of some interest and would put numbers, so to speak, to the differences in the two designs.
Construction Equipment visited Bobcat on its home turf, West Fargo, N.D., where the company had arranged with the city to use the fairgrounds for trencher and auger comparisons, and a municipal equipment yard, slated for repaving, for comparing performance with pavement-milling attachments.
We’ve provided the details for these comparisons in sidebars throughout the report, but to quickly summarize here, we found the T590, on average, to be nearly 20 percent more productive overall at these tasks, compared with its T190 predecessor. Along the way, we also took note of other advantages that the M-Series design imparts to machine performance—lift-arm design and the cooling system, for instance.
“The cooling system in 500-frame-size models is the same as that in the 600-frame-size,” says Hoesel, “which means it’s oversized for the smaller machines. Depending on ambient temperature and conditions, the T590 has about 20 percent more cooling capacity than the T190, so it can work in more severe conditions and at higher elevations. We’ve basically taken a cooling system designed for a 74-horsepower machine and installed it in a 66-horsepower machine.”
Cooling system details that have changed with the M-Series, says Hoesel, include replacing the “squirrel-cage” type fan with a more efficient axial fan, changing oil-cooler and condenser mounting from a lift-out design to a more convenient pivoting arrangement that allows easy access to the radiator, and designing new intake screens that stop finer debris, yet have contours that discourage material build-up and are easier to clean.
Among the T590’s more obvious engineering enhancements is a new lift-arm design, which includes a sizeable increase in cross-section, both width and height, as well as a new “inset” configuration that places the lower portion of the arms in a different (narrower) plane than the upper section. According to Bobcat, the new design results in a more rigid, more stable structure that contributes to the machine’s increased lifting and breakout forces. The lift-arm design, when combined with a flatter vertical-lift path, says Bobcat, also contributes to the T590’s higher rated operating capacity (ROC), 2,100 pounds versus the T190’s 1,900 pounds.
Also, the upper cross-tube, which connects the lift arms, has been raised and dramatically increases rearward visibility. In like manner, the cross-tube at the front has been lowered, again providing significant improvement in visibility to the attachment. Accompanying these changes in lift-arm design and further enhancing visibility are the M-Series’ repositioned cab (2 inches farther forward) and repositioned coupler (moved nearly 1.5 inches rearward).
“Visibility to the cutting edge is very good on M-Series machines,” says Hoesel. “We’ve not only moved the operator closer to the cutting edge, we’ve moved the cutting edge closer to the operator.”
Repositioning the coupler also contributes to the T590’s higher ROC, while maintaining the compact dimensions of the K-Series, although the length of the machine has increased nearly 3 inches on M-Series models.
“With this increase in length,” says Hoesel, “we repositioned the track carriages on the machine, versus the K-Series, to optimize the weight balance and the resulting ROC of the machine. The optimized weight balance also resulted in less horsepower required to turn the machine.”
In addition to the new “cab-forward” design of M-Series models, the cab itself is all new and is exactly the same for all M-Series frame sizes. The new cab is roomier than the K-Series cab (10 percent more interior volume), and the enclosed version of the cab is pressurized and has a redesigned one-piece door seal. Interior sound levels are down some 60 percent, compared with the K-Series, according to Bobcat, due in part to a redesigned, three-point, engine-mount system that reduces vibration.
Visibility is much enhanced for M-Series models, with a rear window 14 percent larger and the roof window 43 percent larger than the K-Series design. Also, rear corner posts of the cab index with the upper portion of the lift arms, which means that the lift arms cause no more restriction to visibility than do the cab posts.
A quite notable change for the M-Series cab is its overall larger front door and its considerably lower threshold, 4 inches lower than that of the K-Series. The result, says Bobcat, is a more natural progression, step-to-step, when entering the cab, and significantly easier cab entry and exit.
When the comparisons were completed, Mike Fitzgerald, Bobcat’s loader product specialist, and Justin Odegaard, attachments product specialist, loaded the test machines onto a trailer, along with grapple-bucket attachments, and drove 25 miles or so southeast to Sabin, Minn., where local contractor Fitzgerald Construction was tearing down an old factory. Operators Kevin Murray and Russell Peterman were using a large excavator to pull down the steel upper structure and masonry walls of the old building, then sorting the rubble with a Bobcat excavator.
We asked if they would use the T590 and T190 to move and stack the steel and concrete debris, taking note of performance and operating differences between the two. After an hour or so, we asked their opinions about how the two models compared.
The first comment from both operators concerned the improved visibility from the T590’s cab:
“Better visibility all around,” said Peterman, “especially through the rear window. When I turned around, I could see much better from the new machine.”
“The T590 felt bigger inside,” said Murray, “and it definitely makes it easier to get in and out of the cab. But I’d say the biggest difference between the two models is the new machine’s hydraulic power—it has a definite edge in the way it performs.”