16 minute read
BREAKING OUT
by nzlogger
Story: Keith Raymond, Forest Growers Research
Tigercat LS855C winch-assisted feller buncher with EMS TractionLine.
WINCH-ASSIST TECHNOLOGY IS
now well-established in New Zealand – but how did it come about?
The safety and productivity benefits of mechanical tree felling on easy country are well known, but the development of winchassist has enabled these benefits to be gained in steep slope harvesting operations.
Since 2006, new machines and systems were being developed by New Zealand contractors to mechanise felling and pre-bunching on slopes, with the aim of eliminating manual chainsaw felling in cable operations. In March 2009, researchers from Future Forests Research (FFR) visited Ross Wood’s operation in Nelson with a view to studying his steep terrain bunching operation. This was initially an old Komatsu roller crusher tractor, with a pre-tensioned winch drum brake, an “active system” with the winch rope moving up and down the slope as it was wound in or out to assist the feller buncher.
At about the same time the second machine that had been developed back in 2009 was being tested by Nigel Kelly of Kelly Logging in Nelson. This was a Hitachi excavator with a Satco boom and felling head with a built-in winch to aid traction. This was a single machine system, a “passive system” as the winch rope is static as the machine moves up and down the slope, winding the cable in and out. This means less rope wear as it is not moving across the ground, and as the winch rope is tied off on stumps at the top of the hill, it does not require access to the back line or top of the slope.
In practical terms
So, how can a winch cable be used to assist the traction capability of a ground-based machine on a steep slope?
As shown in the illustration in Figure 1 above, the basic physics for retaining traction on a slope is that the Gravity Force pulling the machine downslope (Wg in red) should not exceed the Traction Force (T in blue) that the machine is able to develop on the ground surface. Otherwise, the machine will start to slide downslope.
Put simply, the greater the Traction Force the tracks can generate in the soil, the steeper a machine can operate without slipping.
FIGURE 1: THEORY OF WINCH-ASSIST HARVESTING
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This robust fast-acting grapple (or bulk materials clam shell grab) is suspended from a single rope or chain connected to a winch or crane and can be used on land or below water. The prototypes are designed for retrieval of bunched or individual logs, however could be used for recovery of harvesting slash with minor alterations. The design provides a grab that is versatile and easy to connect to a variety of large pole hauler rigging arrangements. The grab does not require interlocked winch drums, a motorised carriage or changes to the skyline. The unit is simply connected to an existing standard rigging arrangement using a shackle or similar coupling connection, making it a cost effective and versatile tool that is fast to change out to suit the purpose or conditions. The Snatch-n-Grab does not require a separate external power source and utilises a wireless remote control to operate the mechanism that opens or closes the jaws as the unit is being raised. The grab is typically connected to a single main line used to raise and lower the unit, therefore allowing for faster movement and the ability to drop into deep and/or steep gullies without bridging. It can also be utilised in a north bend, rigging arrangement to enable recovery from a greater area than that immediately below the skyline. It is suitable for recovering logs or quickly cleaning up slash. The Snatch-n-Grab has a patented mechanism that opens or closes the jaws as the unit is being raised off the ground. Two separate wireless remote controllers that switch the mechanism to ‘Open’ or ‘Close’ mode enable one controller to be used at each end of load transfer operations if there is a long or restricted line of sight. A camera may be installed into the mechanism to enable remote visual monitoring and more accurate positioning if required. Snatch-n-Grab Speci cations SPECIFICATIONS
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The benefit of winch-assist is that the Tension provided by the cable will add to the Traction Force of the tracks, and thereby greatly increase the operating range of the machine, without it reaching its traction limit.
Traction Force is a function of the soil’s Coefficient of Traction, sometimes called Tractive Efficiency, for a given machine type (either tracked or wheeled). This is illustrated in the chart on the right of Figure 1. The slope limit is indicated where the Wg purple line intersects the Traction line for a given coefficient of traction.
In this example, if the soil had a coefficient of traction of 0.4 (the blue line), a 37-tonne machine would start to slip on a 22-degree slope, without traction assistance.
By adding a winch-assist with 10-tonnes of tension provided by the cable, C (represented by the black arrows) the Traction Force is augmented by the Cable Force, which extends the operating limit of this machine to about 37 degrees, a major improvement in operating range on steep slopes.
Adapting to New Zealand terrain
But winch-assisted harvesting is not new; with this machinery commercially available in forest operations in Europe since the 1990s. A number of different companies were offering cable winch products initially on forwarders and later on harvesters, to expand ground-based harvesting onto steeper terrain.
The separate winch units were mounted to the rear of the machine as shown bottom right of Figure 2 below – and more recently for skidders (top right).
In Europe, independent self-powered winch units were also being developed (as shown bottom left of Figure 2). However, New Zealand conditions include very steep slopes and unstable soils, in combination with large tree size - which has required larger felling machines with larger winches and bigger diameter wire ropes than were commercially available in Europe. So in New Zealand the tracked excavator winchassist systems were developed (top left of Figure 2).
There is a wide range of winch-assist machinery. In Europe the most common approach was to mount the winch onto the chassis of the primary machine. Several manufacturers preferred the ‘bolton’ option to provide the opportunity to remove the unit when not required. The Ecoforst T-winch was one of the first independent self-powered remote winch John Deere 909 winch-assisted feller buncher.
units developed in 2012.
In New Zealand the first commercial winch-assisted harvester was the ClimbMAX steep slope harvester, developed by Trinder Engineering of Nelson, with funding assistance from the Steepland Harvesting Primary Growth Partnership (co-funded by MPI). The ClimbMAX had an integrated winch, mounted into the track frame of a Hitachi excavator, with a Trinder boom and felling head.
Electrical and Machinery Services (EMS) in Rotorua produced a dual winch system on an excavator base called the TractionLine.
Rosewarne & May in Whangarei also produced the Remote Operated Bulldozer or ROB winch-assist, which is a dual winch mounted on a hydrostatic drive John Deere tractor.
And DC Equipment of Richmond, Nelson produced the Falcon Winch Assist, a single drum winch on an excavator base.
In the US, Summit Attachments & Machinery, in Washington State, has produced a single drum winch on an excavator with a boom extension.
And in British Columbia, Canada, T-Mar Industries produced the Log Champ remote winch-assist, an independent self-powered winch unit, similar to the Ecoforst T-Winch.
Implementation of winch-assist
Looking at some data from the Forest Growers Research (FGR) Benchmarking
Track Excavator
Versatile and Cost Effective Compatible with Quick Attach System
4WD/6WD Wheeled Skidder
Mounted to the front Fix mounted or tiltable
TimberMAX Elevator
Powerful self-powered winch unit High-performance. Flexible Powered by CAT 300 hp Tier 4 Final
Wheeled Harvester
Mounted to the rear Fix-mounted or tiltable
ROB, or Remote Operated Bulldozer, manufactured by Rosewarne & May, Whangarei.
database, run by Dr Rien Visser at the School of Forestry, from 2013 the database started to record operations on steep slopes using winch-assist.
This early analysis in 2014, of only 13 mechanised felling operations compared to manual felling, showed operations on steeper slopes, with higher productivity and lower costs than manual felling.
A survey in 2016 found that over 90 winchassist machines had been manufactured in New Zealand.
There are now four main New Zealand companies manufacturing winch-assist machinery – DC Equipment, E.M.S., ClimbMAX Equipment, and Rosewarne and May. Together they have reportedly manufactured more than 270 winchassist machines since the first commercial machine appeared in 2012.
The Benchmarking Harvesting Cost and Productivity project has been running for 12 years now. And the data tells us that around 65% of cable harvesting operations now have access to winch-assist machines. That’s about 200 machines across the New Zealand logging industry.
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Safety and training
With regard to safety, consideration of the actual tensions in the winch rope becomes critical if the machine is not stable on the terrain without the cable. From 2014, work at University of Canterbury Forestry by Hunter Harrill looked at winch rope tensions. From these studies it was found that average tensions during felling and shovelling were usually below Safe Working Load (SWL) of the winch rope, but tensions during machine movement often exceeded SWL for very short periods and during the moving phase only.
Since 2016, the School of Forestry has been running Workshops on Winch-Assisted Harvesting, using information from FGR harvesting projects and the Benchmarking Database. Objectives are to undertake operational planning of productivity and cost, support contractors and operators in safe use of winch-assist, and to determine areas for further research and development
The Workshops look at operating techniques. In New Zealand, most operators use trees or stumps to change the rope angle to facilitate better machine utilisation. When the feller buncher gets to the top of the ridge they go around the next stump and back down the hill to avoid shifting the winch-assist machine on every pass. Some manufacturers’ guidelines specifically allow for the use of these hold stumps. However there have been issues with the winch rope pulling over trees, or cutting through the stump, causing hold stump failure.
Also, on the subject of safe use of winchassist machinery, the workshops look at areas such as the connectors between the
Summit winch-assist.
DC Equipment’s Tama Rakau.
winch rope and the felling machine: which are best, and how to inspect and maintain them.
Studies underway
Coming up to date, there have been numerous studies of winch-assist harvesting operations published over the last 10 years with several recent studies by University of Canterbury Forestry, of different applications with skidders, forwarders and harvesters. They include a skidder extraction, using a Falcon Winch Assist which took place at Speirs Logging’s operation in Gisborne.
The winch-assist gave the skidder the ability to extract away from the riparian zone, hauling loaded uphill. The skidder was operating on slopes up to 33 degrees, with an average of 25 degrees. Utilisation of the winch-assist was increased when used by the skidder (80%) compared to just the falling machine (50%).
In another study of a cut-to-length harvester/forwarder operation near Napier with Rayonier Matariki Forests in April 2021, a John Deere 1910 forwarder was operated supported by a T-Winch model 10.2 ClimbMAX Steep Slope Harvester, manufactured by Trinder Engineers, Nelson (first commercial New Zealand-made winch-assisted harvester).
Grooved Drums and Sleeves
EMS Tractionline working at McCormick Logging.
winch-assist. In another operation the harvester used a TractionLine winch-assist for cut-to-length processing at the stump. Stumps are used to hold logs in place on the slope, and designated slash tracks are set up for the forwarder using processor slash to reduce ground disturbance. Delimbing on slopes, first mooted back in 2013 in an FFR study, is now a reality with the use of winch-assist.
Future forward
Winch-assist harvesting systems have seen rapid adoption and implementation in New Zealand, Europe and North America during the last 10 years and will continue to do so in other parts of the world.
This technology is considered to be one of the major innovations in steep terrain harvesting in the early twenty-first century. There will continue to be more research undertaken looking at machine stability, safe operation, environmental impacts, and system productivity and costs, not only comparisons between winch-assist and conventional systems, but also between different winch-assist systems. The substantial body of literature will continue to grow.
The focus on mechanisation and modernisation of steep terrain harvesting systems across the industry over the last decade has shown significant improvements in both productivity and safety. A major step-change has been the development of winch-assist technology which has proven to be a robust, safe, and high-performance forest harvesting technology that has significantly increased the operating range of ground-based, mechanised harvesting on steep slopes. Implementation, and the understanding of its limitations, is continuing to grow, and FGR will continue to support this growth.
This article showcases a significant technology innovation in New Zealand harvesting operations, coming out of the first Primary Growth Partnership (PGP) in Steepland Harvesting, managed by Future Forests Research (or FFR, the predecessor of Forest Growers Research), and co-funded by Ministry for Primary Industries (MPI), and the forestry industry, and supported by research at the University of Canterbury School of Forestry.
The FGR project has been a collaboration between Forest Growers Research supported by the Forest Growers Commodity Levy and MPI through the PGP, the forestry company stakeholders, and the University of Canterbury (notably Dr Rien Visser at the School of Forestry) and New Zealand manufacturing partners. NZL
If the recent disruptions to the logging industry have reminded us of one thing, it’s that logging can be a volatile and stressful industry to be in. With the high levels of debt and risks associated with running a logging business, impacts of log price downturns to the Covid-19 pandemic have been huge. Reducing debt through leased logging equipment is one way to mitigate unnecessary financial risk, so here, we look at the benefits of leased logging equipment. It goes without saying that having reliable, quality equipment is key to hitting production and running a successful harvesting operation. But quality gear is expensive, and lots of loggers fall into the trap of purchasing less than reliable gear that ends up hurting their bottom line, with massive downtime and repair bills coming at them. Leasing logging gear is an alternative solution, that’s gaining more traction and reducing financial risk and stress for many contractors. Log Lease Director Ross Davis started out in forestry almost 40+ years ago, with a small ground-base crew. Since the early 2000’s, he’s been bringing gear into New Zealand, importing his first hauler from America.
“As our numbers of haulers grew, it was a natural transition to lease out haulers to other contractors, which was the start of Log Lease, formalised in 2010,” says Ross. Log Lease carries a range of specialist lease equipment for the logging industry, with a fleet of Haulers, Loaders & Processors. Ross’ daughter Sarah is the operations manager, while son-in-law Rob is the Fleet Manager/ Diesel Mechanic based in the Whangamata and Maramarua workshops. As a team, they have broad and varied experience, plus, they’re all on the same page about the benefits of leased logging gear, which are becoming more well-known. “Financially, a monthly lease payment is often more manageable, if contractors are asked to ‘gear up’ quickly to take on new contracts,” he says. “The model we’ve seen working well, is buying new gear to work alongside lease gear which means you have new reliable equipment across the board rather than purchasing older gear when starting out.” With leasing, costs for insurance, breakdown and maintenance are covered. We also offer flexible contracts, so when there’s a downturn for example, you’re not stuck with a machine you don’t need.”
“We treat our customer relationships like a partnership – we want to help and support these contractors to succeed. I have been a contractor and I know how hard this industry can be, so we are always wanting to support them however we can.” He encourages anyone thinking about reducing debt in their logging business or anyone starting out to check out the Log Lease website and get in touch. “Even if we don’t have something you need listed, you never know, we could have something lurking in the back. Get in touch and we’ll try to help or point you in the right direction.”
benefits of leasing
• Less debt – In a volatile industry less debt can help reduce stress levels • Maintenance – Log Lease Diesel
Mechanics or suppliers are on-call to get machines repaired / operational asap • Reliability – we stock high quality equipment that is regularly serviced and reliable • Flexible terms – you can negotiate the terms and conditions of your lease so that you only have the machine for as long as you need • Expertise and knowledge – benefit from the experience and knowledge of a team who have been in the industry for yonks and who know what’s happening at a wider industry level
