Hydraulics expert Carl Dyke shares insight on forest harvesting machines and what it takes to cut-to-length.
“I grew up in logging. As a little kid, my father and grandfather would take me out to the woods to go timber cruising, which meant walking around and looking at the stands of trees,” said Carl Dyke, hydraulics expert and founder of CD Industrial Group. “Back then, it was much cruder. You’d drop the tree to the forest floor, hook up a skidder, drag the whole tree out of the woods onto a clearing, cut the branches off, and then take that whole log and put it on a truck to the sawmill.”
One concern with this whole-tree harvesting approach is that logs are nonuniform, creating a challenge for sawmills. Though more sawmills use optimizing systems to get the most value from each log, quality still begins in the woodlot.
“Very popular in the Nordic and Scandinavian countries is a technique called cut-to-length (CTL). It is also now popular in North America,” said Dyke. “If you pay attention to the types of logging trucks on the road, you probably notice that instead of trucks carrying full-length logs that go from very fat at the base to very skinny at the tip and stick way out past the back of the vehicle, 60 to 70 ft, now we see those logging trucks on the roadway between the woodlot and the sawmill with bunks — which are those racks of steel forks that hold the logs contained on the truck. All of a sudden, we see that those logs look a lot more uniform and precisely sized. The bunches of logs on the trucks have similar diameters at both the base and tip end. They don’t taper from massive to nothing. So, cut-to-length is optimizing in the forest … so that the timber is fairly uniform before it arrives at the sawmill. That’s a huge advantage.”
Sophisticated hydraulics make cut-to-length possible
Harvesters and forwarders are the two mobile machines primarily used in CTL logging. Harvesters fell, delimb, and cut trees to specific lengths in a single operation. In addition to the chassis, powertrain, tracks or wheels, cab, and controls, they consist of a hydraulic boom that extends the machine’s reach and a harvester head that does the hard work. The harvester head has several components to process each log: a grapple grabs and holds the tree; a chainsaw fells and cuts the tree; feed rollers move the tree through the head; knives remove branches; and a measuring system measures the length and diameter of the tree to cut it accurately.
Forwarders transport the cut logs out of the forest to the roadside for sorting before heading to the sawmill. These machines have a hydraulic boom to lift logs into their bunks and a grapple to grab and hold onto the logs during loading. While traditional sawmills use a merchandising deck to cut and sort logs for further processing, with CTL, that’s all done at the woodlot.
“What happens now, in many cases, is the operators of the harvesting equipment in the forest have enough data on their screens in the cab and instructions from their client who wants to buy the raw material that they’re already processing very carefully,” said Dyke. “Those advanced cutting heads with hydraulics and electronic sensors on board can cut the tree down, turn it sideways, and immediately start to size it up as it rolls through the feed rollers. Sensors already notice the rate of taper on the log, letting the operator know what diameters are present as they quickly roll it back and forth through the cutting head, and the branches come off and fall to the ground.”
The operators also look for highly unusable portions of the log and cut them out right then and there. For example, if the sawmill rejects timber with a 7-in. diameter at the tapered tip, operators monitor the screen and cut when the log reaches that 7-in. mark. Then, the system may instruct them to roll ahead 20 ft and cut again.
“The sophistication in these advanced timber processing heads, the bundle of cables from the sensors that go back to the operator cab, and the hoses that supply an electro-hydraulic proportional valve for the head — that’s high-end hydraulics equipment right there. And the performance has to be quite high,” said Dyke.
As demand for CTL quality and efficiency increases worldwide, manufacturers continuously advance equipment and hydraulic components to meet requirements. For instance, Komatsu recently redesigned its C124 harvester head’s valve block to improve durability, decrease energy losses, and save fuel. The company also refined the front and rear knives’ pressure control for better precision and gave operators control over pressure settings from inside the cab via software. Advanced length measuring is now standard on the C124 with a stronger cylinder and a modified mechanical stop to reduce wear. The tilt functions hydraulics, saw unit, feed system, and hose routing and protection have also been upgraded for better safety, performance, and longevity.
The company also introduced the new 205F forwarder with more lifting torque, larger load capacity, and telescopic widening bunks. All these upgrades, along with its digital solutions, aim to improve productivity while reducing emissions and achieving carbon neutrality goals by 2050.
As another example, Ponsse recently released new forwarders, Elk and Wisend, with improved load-carrying capacity, cabin comfort and visibility, and machine agility.
The company also introduced the new H7 harvester head with improved geometry, power-to-weight ratio, and the Ponsse Active Speed function, which allows operators to adjust the harvester head speed based on the tree species and stem diameter.
The H7 harvester head includes an HH360 rotator developed with Black Bruin’s radial piston technology. The rotator lets the harvester head freely rotate 360° without limitations, which helps expedite wood processing, reduces hose failures, and improves operations.
The company’s High-Precision Positioning solution is also available in Finland, Sweden, and Germany for harvesters equipped with the Active Crane control system. High-Precision Positioning shows the harvester head’s precise location on a map so operators can identify areas to harvest and avoid. The system saves the location of every stump in the production file, and the forwarder operator can see the harvester trail. Such solutions improve the productivity and safety of operations.
Along with safety, manufacturers prioritize operator comfort in forestry’s challenging environments and uneven terrain. Inside the cab, CAN bus joysticks and other sophisticated controls allow operators to control various machine functions precisely. Manufacturers design such controls ergonomically to reduce fatigue, ensuring reliability and performance in the field. For instance, Sure Grip Controls’ LU Handle is specifically designed for forestry machines and includes a keypad for operators to select a tree species, diameter, and cut length. The handle is made with high-impact plastic polymers with switches capable of 10 million operations. It’s compatible with various forestry equipment types and brands. The handle supports up to eight faceplate switches, two triggers, four sliders, four rockers, and two micro joysticks, with options for additional keypads and expansion pods.
Cut-to-length machines enable sustainable forestry
Along with advanced hydraulics and control solutions, the CTL approach is quickly becoming the industry standard for more sustainable harvesting. According to Ponsse’s “The Perfect Cut” report, CTL operations increased from 46% in 2017 to 57% in 2021 in North America, South America, Europe, and Russia. The method requires fewer machine types than whole-tree or tree-length methods but deploys several teams for reliability and continuous operation despite disruptions. Additionally, the method requires fewer operators, decreases fuel consumption, and reduces waste since every cut is precise and optimized.
The CTL method also enables continuous cover forestry, in which forests are strategically thinned, not cleared, and new growth occurs naturally with little intentional planting. This encourages biodiversity and promotes nutrient-rich soil to support healthy trees.
“You leave quite a bit of fiber on the forest floor,” said Dyke. “It can become a part of the humus layer, which is important for looking after the long-term soil of a forest. And then you only take the best part of that log that could be merchandisable timber and cart that off to the sawmill … If we’re talking about a plywood product, the process is similar — cut to length, get as much uniformity as possible, and then leave behind parts of the tree that aren’t needed and let that become part of the composting and back to the forest soil.”
CTL harvesters and forwarders can also navigate a forest with less damaging effects than equipment used in whole-tree or tree-length methods. Komatsu, Ponsse, Waratah, and other forestry equipment manufacturers all talk about improved weight distribution from a stability perspective, but it also helps reduce soil erosion.
In addition to the benefits of forests, the rise in CTL popularity has prompted more efficient machine designs that reduce energy consumption and emissions. For example, Kalle Einola, R&D manager of technology, product safety, and IPR at Ponsse, presented a paper on hydraulic-hybrid CTL harvesters at the 2023 Scandinavian International Conference on Fluid Power (SICFP). He and his team studied a hydraulic hybrid system installed on a Ponsse Ergo CTL harvester and tested it near Tampere, Finland. Though further research and design modifications are needed, the system optimized the harvester’s powertrain and delivered assistive power to the harvester head.
Thinking of future forests
“That cut-to-length approach has become more the rule than the exception. I notice it in the regions I travel when I see the logging trucks moving along the highway,” said Dyke, who is based in Canada.
In 2020, the Food and Agriculture Organization of the United Nations estimated that Canada had 347 million hectares and 9% of the world’s forestland. Ponsse’s report stated that only 5% of Canada’s forest harvesting operations used the CTL method in 1990, but that number shot up to 65% in 2021.
As more loggers and foresters consider productivity and cost-effectiveness alongside sustainability and environmental consequences, the CTL method should continue gaining popularity with more energy-efficient machines.
CD Industrial Group
cdiginc.com
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