| March 25, 2009 |
In our previous Innovations Awards we’ve often found the most imaginative thinking going into small components, tools, accessories, things like pins and bushings. This year, a ConExpo-Con/Agg year, saw three manufacturers storm out of the starting gates with big, game-changing, mega-ton machines.
If there is a common theme to all three of these it is that they move more material faster and for less money. And for two of these machines, there is an additional imperative: less fuel use. That’s a cost savings, of course, but it’s also an environmental message, serious engineering for a serious issue that, despite today’s fuel prices, isn’t going to go away.
So we applaud this year’s three big thinkers and hope you find in their stories the inspiration to take up the gauntlet and charge into your own challenges. The winners:
Caterpillar’s D7E electric-drive dozer
has speed, fuel savings and infinitely variable power using a low-maintenance, long-life drivetrain with 60-percent fewer components than comparable mechanical models.
Deere’s 764 high-speed dozer
turns conventional wisdom on its head with a street-friendly rubber track drive system that makes it faster at final grading than a dozer or motor grader.
Volvo’s L220F Hybrid loader
borrows a page from the company’s already introduced diesel-electric hybrid drive truck and bus technology, creating a workhorse machine that has the potential to cut fuel consumption in half.
In addition to the obvious and previously mentioned benefits of an electric-drive dozer – reduced fuel costs, lower emissions, infinitely variable power – I like the simplicity of it. It’s axiomatic in science and engineering that the simpler of two explanations or designs is almost always the best path to take. And with 60 percent fewer drivetrain components, the D7E is a case study that engineers in all walks of life would do well to emulate.
When oil prices and environmental concerns started ratcheting up the cost of diesel fuel in 2006, many equipment manufacturers tasked their engineers to explore the possibilities of alternative power sources.
At Caterpillar, however, the solution was already under development – the D7E – a top secret, all electric-drive, track-type tractor with almost a decade of development behind it. And unlike some new product initiatives that have to struggle for attention and resources, the D7E was green flagged by the top executives at Caterpillar from the get-go.
“Everybody knew this was going to be game-changing technology,” says Amy Moore-McKee, new product manager. “Once we could prove the goals we set were achievable and show real customer value, there wasn’t any convincing to do.”
Back to the future
The D7E debuted March 2008 at ConExpo, but its origins date back to the late 1990’s, says Mike Betz, engineering manager for advanced tractors. “We were looking ahead to Tier 4 and some of the regulations that would hit us in the future,” Betz says. “And we were looking at what powertrain would fit those regulations and lowering our customers’ operating costs.”
Caterpillar custom built their first electric drivetrain and installed it into an existing elevated sprocket tractor. “The D7 is one of those models that does a lot of different things, from fine grading to heavy dozing – and it does a lot of different applications,” Moore-McKee says. “It was a perfect opportunity to prove this drivetrain and that the technology was scalable up and down the product line.”
The attributes of the electric drive system in the high-drive design proved popular with the test operators, but the next iteration in the development process was to design a completely new machine from the ground up that could take advantage of the electric drive’s strengths.
“Once we decided on the powertrain we wanted to do a clean sheet design,” Betz says. “The D7R was ripe for an update, so we debated long and hard about what would be the best undercarriage configuration for this size tractor.”
What the market was showing them was that the applications for this size tractor were changing. “Back in the 1980s you had a lot of interstate construction and heavy tractors. There are still those types of jobs, but not as many and we have a lot of general type construction applications, like oil and gas pads,” Betz says. This, plus the desire for improved visibility and a tilt cab led to the decision to put an oval track, rather than the elevated sprocket, undercarriage on the D7E.
Making it bulletproof
With these issues settled, Caterpillar went to work ruggedizing the componentry. “The track-type tractor application is one of the toughest, so we had to make sure the components would live,” Moore-McKee says. “The D7R will operate in water up to the fan blades and we wanted this to be a complete replacement for the D7R.”
Despite the simplicity of the electric drive design, a lot of development work went into the D7E. This included the motor configuration and the sizing of the motors and generators, plus the development of robust, high voltage wiring systems with ground fault detection, Betz says. “And we had to make them compact to fit inside the tractor. There’s not a lot of room so power density is an important consideration.”
“In the first benchmarking we didn’t even tell the operators what powertrain was in it,” Betz says. “And they came back and told us it had some of the best characteristics of the powershift and of a hydrostat.”
Prior to ConExpo several prototypes of the D7E were built and tested by dealer operators and then a group of customer operators, says Keith Heiar, tractor products marketing. These benchmark studies pitted the D7E against the D7R as well as competitive machines.
“What people really liked and were surprised at was how much performance you could get out of this tractor, just straight on pushing performance, maneuverability and turning capability,” he says. “We changed a few things in the cab to make it more comfortable, but we were glad to see how much support we had from the operator groups for the big picture items.”
How it works
Unlike a hybrid electric design, the D7E is a simple electric drive. The flywheel turns a generator that outputs current directly to the motors in the propulsion module and then on to the sealed and liquid cooled final drives. No batteries or electrical energy storage is needed. “We considered a number of advanced powertrains early on and settled on the electric drive because of its bottom line benefits,” Moore-McKee says.
One of the key benefits of delivering electricity rather than mechanical force to the final drives is that you have a continuously variable transmission – no gears and no clutches. “What we were driving for was a transmission that would approach the efficiency of a direct drive, but also be continuously variable,” Betz says. “So you’d have steady-state efficiency and its operating efficiency was high. We’ve also been able to enhance the steering performance, partially due to the electric powertrain and partially because we put a D8-size differential steer steering pump on it.” At ConExpo, Caterpillar cited 10- percent productivity gains and 25 percent more material moved per gallon of fuel.
The continuously variable transmission smoothes out peak loads on the engine. As a result, the electric version of the D7 downsized to a 9-liter engine that runs in a narrower rpm band: between 1,400 and 1,700 rpm, as compared to the D7R’s 10-liter engine running at 1,300 to 2,200 rpm. This not only saves fuel, but extends the life of the engine.
The all-electric drivetrain has 60 percent fewer parts than a mechanical system, and the drivetrain lifecycle is estimated to be 50 percent longer. “Many of those parts are solid-state components, so there are not as many moving parts to wear out,” Moore-McKee says. Powertrain oil service interval life increased from 1,000 hours on the D7RII to 4,000 hrs on the D7E. Also, powertrain oil filter life increased from 500 hours on the D7RII to 2,000 hours on the D7E. Additionally, Cat reduced the powertrain oil volume by 50 percent compared to the D7RII.
With all that electricity being generated, Caterpillar was able to eliminate belt-driven accessories, including the alternator, on the D7E. The generator also provides power to support a stand-alone cab air conditioner.
Cat redesigned the cab for the D7E with a visibility enhancing center post, wider site lines to the blade and a 50-percent reduction in noise. A single, massive blade-lift cylinder replaces the traditional two-cylinder configuration for a further reduction in parts and maintenance.
All electric rationale
The D7E was introduced just as diesel prices were beginning to skyrocket. And while diesel prices have fallen for now, the rationale for choosing an electric drive dozer has not diminished, says Heiar.
The no-shift, continuously variable transmission and enhanced visibility make it easier for less experienced operators to become more productive with the dozer quicker. “It’s nice for them to be able to dial-in the speed they want, especially for fine grading,” he says.
And fuel, regardless of price, is always an issue. “The D7E is going to consume less fuel over its lifetime, and our customers realize that they need to keep focusing on reducing fuel costs,” Heiar says. The fuel savings and reduced parts and maintenance costs will result in a 10-percent lower lifetime operating cost for the D7E, he says.
Heiar says environmental considerations will also continue to influence contractors’ decisions. “A lot of our customers are looking out for their customers too and want to be able to work in a sustainable way that preserves natural resources,” he says. “If they can do that by consuming less fuel and oil and producing less greenhouse gas, I think it helps them serve their customers.”
Contractors who field tested this machine went from scratching their heads and asking what the heck it was, to being amazed with its versatility. Deere not only tackled several customer challenges with the 764 HSD, it did so by thinking beyond present market solutions. By combining the speed of a grader with the flotation of a crawler dozer, Deere gave contractors a completely new tool, with a full potential that may take several years to completely develop.
Deere 764 High Speed Dozer
The idea came – as many good ones do – through customer interaction. In 2002, contractors attending John Deere customer groups talked about their increasing use of crawler dozers for final grade.
In one specific example, a contractor constructing landfill liners struggled with placing the layers of aggregate and rubber barrier material on top of compacted clay sloped to exacting specs. The material had to be spread as fast as possible within tight grade controls, taking care not to tear the rubber barrier material. This contractor found that the dozer spreading these materials was always the bottleneck in this operation, since the machine was limited to speeds of 2 to 3 mph.
Customers also told Deere about another drawback to using steel-track dozers for final grade: track grousers left an imprint, requiring repair by hand labor. Dozers were also cumbersome to move, especially when working on sites with streets and sidewalks in place. Not to mention the typical maximum ground speed on a dozer is around 6 mph, slowing down the site-to-site moving process.
While an obvious alternative would be a motor grader, flotation is an issue with graders, particularly in early spring mud conditions. Even though articulated, most graders also find it difficult to work in tight quarters. And graders have the same problem dozers do with final grade: they leave an imprint – this time with their two rear tires – that has to be smoothed over.
So contractors asked Deere: Is there another machine we should be using for final grade?
Working on a wish list
Dan Radke, a Deere engineer, began to realize the answer to this question could drive a new machine form. From the customer conversations, Deere designers had a wish list: the machine needed the flotation of a crawler, yet it would still have the ability to drive quickly down the street. It had to work in tight quarters while offering the visibility of a grader. And it couldn’t leave an imprint that required follow-up labor.
“Dozers are primarily intended to drive forward, turning around to pick up another load,” Radke says. “We saw that being able to return for your next load at 18 mph would significantly improve productivity.” In addition, the solution needed to have significantly more power, since the goal was to push the same load faster, not push a heavier load. A traction control system would limit the tendency to slip the tracks under low speed, high pull conditions.
Also required: a stable platform, which led to a four-track machine with a longer “wheelbase” than a traditional dozer. This would allow operators time to make blade corrections smoothly, reducing the need to compensate for sudden machine movements such as those dozers make when operators make rapid blade changes.
Concept to test
The machine concept process went into gear in 2003, with Deere engineers checking in with select contractors along the way.
“We typically work with customers on these projects, but usually not to this extent,” says Tom Porter, the Deere senior staff engineer who supervised the team that developed the 764 HSD – which stands for high speed dozer. The contractors providing feedback were receptive to the high speed dozer concept, but several design challenges first had to be addressed.
Some of the biggest challenges were where to put the operator’s station, what controls to use and where to place them. “The 764 is kind of a cross between a dozer and a grader, so we had to address the controls issue,” Porter says. Contractors asked for simplified controls, which led the team away from typical grader levers. They ended up with a modified loader cab with two electro-hydraulic joysticks, with the left joystick controlling steering and speed, and the right joystick operating the blade. And just in case someone prefers a more traditional method when roading the machine, the 764 comes with a steering wheel.
The cab is close to the 11-foot, six-way dozer blade and moves with it as the unit turns, giving the operator a panoramic view of the blade at all times.
Rubber tracks were a design given – but they had to oscillate to function properly on a slope. The design team put the four tracks on a separate frame, which required packaging all components within the frame rails. Mounting all hydraulic pumps off a splitter box taken from Deere’s forestry division allowed designers to move the center of gravity further forward toward the articulation joint.
The loader cab and forestry splitter box were just two of several components borrowed from existing machines. Others included controls out of Deere’s 850 dozer and the articulation joint from a K Series loader. “We used a lot of common technology,” Porter says, “and we were able to overcome some challenges by looking at current designs in other machines.” In fact, 60 percent of the machine’s parts are already in use on John Deere loaders and dozers.
In the field
Several limited release machines units were in customer hands throughout 2008, in both three-to-four-week demonstrations and long term evaluations.
“We saw contractors putting 120 hours on the machine in three to four weeks, so they were really using it,” says Scott Bayless, a Deere product consultant who went with the limited release machines on customer visits.
In testing, the 764 ended up performing a variety of grading applications, including parking lots, house pads, spreading the pile behind an excavator/artic combo, haul road maintenance and working on slopes.
A site developer who’s had a 764 test machine for nearly a year has seen the unit’s impact specifically on jobs around 30,000 cubic yards. Before, he would bring in two scrapers, a roller and two dozers to do the job. Using the 764, he can do the work with three operators instead of five, since he just needs two machines besides the 764.
Faster grading speeds
In these tests, contractors took a quick shine to the machine’s integrated grade control feature. With the 764 plumbed ready from the factory, customers will be able to plug in their choice of grade control units.
“With IGC, you can run at faster grading speeds than most of us were expecting,” Porter reports. While Porter cautions that these speeds are governed by soil conditions, demo units have achieved a 6 mph grading speed – in comparison to the slower speeds on a grader and a dozer.
In fact, Porter sees the 764 pushing grade control acceptance even more. “We’ll see more integrated blade control systems out there because of this,” he says.
Contractors are putting a star on another feature: the 764’s ability to move from area to area without the use of pads or trailers. Moving a steel-tracked crawler often can take two people to maneuver plus a couple of hours of downtime depending on the distance traveled; the operator of a 764 performs the same function in little time.
“Being able to finish grade and just move across the road or in another area of the project is one of the machine’s biggest assets,” Bayless says.
Field demo contractors have been asking if attachments to replace the front blade will be available, specifically finish blades and forks. One challenge, however, is keeping the front end tight enough for finish work. A wheel loader coupler, for example, would have too much play for this type of work after 500 hours.
Because of this, the 764 attachment thrust has been in the rear, with Deere planning to offer compaction wheels, box scrapers and pull-behind scrapers.
The question of rubber tracks
Of course, no machine can do it all. Steel-track dozers excel in heavy dozing, and LGP crawlers are better in extremely wet conditions. Graders also have more versatile blading ability.
Field test customers have questioned the durability of rubber tracks, especially those who have had experience running rubber tracks on tractors pulling scrapers. Deere has been pointing out machine differences in horsepower and function – a 200-horsepower unit doing medium-duty tasks versus a 500-horsepower machine in a heavy hauling situation. Porter says in addition to being backed by a 3,000-hour wear assurance program, the track has a combination of friction and positive drive. The machine does have, however, the same vulnerabilities on rocky soil as any rubber-track machine, although it excels in sandy conditions.
A job done faster
List price on the 764 HSD is $340,000 and full production begins this spring. Deere anticipates the orders will arrive if the productivity gains are obvious. (To see the machine in action, go to www.youtube.com and enter “764 hsd.”)
“We know it’s all about the money a contractor can make,” Porter says. “Being able to get a job done faster means money in their pocket.”
Volvo has long emphasized that environmental care is one of its core initiatives, and its hybrid development shows that the company is serious. The story here is not hybrid technology itself – seen in increasing amounts on today’s highways – but in the company’s commitment to seeking a construction equipment hybrid that makes sense. And using a common platform across a wide range of company products – thus decreasing the development cost for each product – is a logical, simple approach.
Volvo L220F Hybrid
It’s a matter of simple cross pollination. Volvo Group, which says it has been testing hybrid solutions since the 1980s, is now in its fourth generation of hybrids in the company’s trucks and buses. Construction equipment is next.
First up in what the company suggests will be a significant lineup of hybrid equipment is the L220F Hybrid, announced at last year’s ConExpo-Con/Agg. “We want to be out front when creating environmentally friendly machines, and hybrids are one of the best paths to take,” says Arvid Rinaldo, marketing manager for Volvo Construction Equipment’s hauler-loader business line. Volvo’s reasoning is thus: cheap and realistic fuel alternatives are not in sight, so the solution is creating more efficient machines.
Rinaldo says a large loader such as the 347-horsepower L220F has one of the best potentials for using hybrid technology. The machine, subject to starts and stops, short runs and varying loads, offers several opportunities to store and reuse energy. Another factor: up to 40 percent of a wheel loader’s time can be spent idling.
Same platform, different application
Volvo will use the same hybrid platform used in its on-highway products, only dialed in to the abuses of the construction environment. Since the job description of a loader is multifaceted, one continuing challenge is programming all the electrical currents flowing between the battery and generator/motor to make the most efficient use of energy in thousands of different working situations. “It’s not hard to install and electrical motor and battery,” Rinaldo says. “What’s hard is getting them to work as efficiently as possible.”
Ever-changing battery technology is also adding to design time. Volvo initially announced it would use lithium-ion batteries, but now is non-committal about what type of battery it will eventually use in the production machine. The same is true about the exact componentry that will go into the hybrid.
The HybriPower heart
But the company will talk about how the system works (see illustrations below). The heart of the parallel hybrid system – what Volvo calls HybriPower – is an ISG, or Integrated Starter Generator. Fitted between the Volvo D12 engine and the transmission, the ISG is coupled to a battery that has several times the power capacity of a normal lead acid battery. The ISG allows the diesel engine to turn off when stationary – and then almost instantly restart by rapidly spinning the engine up to optimum working speed using a burst of energy from the battery.
Using battery power at restart overcomes a diesel’s problem of low torque at low engine speeds. The hybrid automatically offers 516 foot-pounds of torque from standstill – or up to 67 horsepower of instant mechanical energy. And so instead of idling, the engine remains off. When ready to restart, an operator doesn’t have to over-rev the engine in order get sufficient torque to work. The battery is replenished automatically, with the ISG acting as a dynamo/alternator.
More than fuel savings
The result, says Volvo, is a potential fuel savings of 10 percent now and up to 50 percent as hybrid technology develops. While this figure admittedly had more oomph in early summer than it does now, there’s more to the hybrid than the savings at the bulk tank. These include reduced emissions and noise (due to less idling). Because the L220F Hybrid relies on the electric motor in low rpms, it has better cold-start capabilities. Since there are fewer demands on the engine, the engine will last longer, and the hour meter will run slower, extending the time between service intervals. The machine can idle up to one hour without the engine running. Braking is handled by the generator/motor, using less fuel and storing the braking energy into the battery. The high torque boost at low rpms will also give the operator the feeling that the machine is more responsive right from the start, Rinaldo says.
With the hybrid, Volvo knows it will need to calm customer fears of the unknown. The first machines will come with a special service contract, and the company will have a battery exchange program. Still uncertain, though, is exactly how long a battery will live on the hybrid loader – a function of ever-evolving battery technology.
Volvo says the strong positive customer reaction during the loader’s unveiling at ConExpo-Con/Agg was a surprise. “We found many customers who are willing to learn this technology and participate in test programs,” Rinaldo says, crediting the car industry with helping pave the hybrid way. “And many of our key accounts have talked about using the hybrid as part of their brand image, underlining the fact they are doing the utmost to make their companies environmental friendly.” All this, of course, comes at a cost, another thing Volvo is keeping closed lipped about. The company will say the hybrid premium can be returned to the buyer within two to four years. Because most Volvo Group divisions are using hybrid technology, additional volumes in years to come may lower the premium. Another possible help: U.S. government incentives, which already exist for hybrid trucks.
“Hybrids are not a gimmick,” Rinaldo says. “This is the first in the construction industry and there’s more to come.”