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IMAGES DAVID WYLIE ENGINEERING
David Wylie revisits a truck-mounted JCB excavator log loader run by Peter McKerral & Co Ltd to find out how the bespoke machine has performed over the last six years
Peter McKerral & Co Ltd is a long-established haulage company based in Campbeltown on the west coast of Scotland, operating a large fleet of articulated heavy goods vehicles hauling livestock, animal feeds, fish and timber products. A substantial proportion of the fleet are involved in transporting timber in the Argyll area to ports such as Ardrishaig, Sandbank and Campbeltown.
Due to the vast quantities of commercial timber the company handles, McKerral has long-favoured the use of a dedicated timber loader to load its 44-tonne trucks quickly and efficiently. That said, for self-loading applications, a small number of its timber trailers are also equipped with a standard vehicle-mounted crane.
With timber extraction business continuing to expand (Scottish forests are forecast to produce 10.5 million cubic metres of the UK’s 16.5 million cubic metres of softwood per annum forecast over the next 20 years), McKerral continues to require a highly productive machine to cope with demand. The firm’s previous timber loader, which provided eight years of good service, was a 2006 MAN 6x6 TGA chassis and Epsilon 250L 13.5m reach crane.
SPECIFIC REQUIREMENTS
manager. He has very specific requirements for his timber loader. Working from their home base in Campbeltown and covering an extensive area around Argyll, the machine must be self-propelled, offer superb off-road capability and be able to load a steady stream of 44-tonne vehicles as quickly and as safely as possible. As the timber is often being loaded straight from the trucks onto waiting boats heading for both domestic and international markets, quick cycle times are important too.
With no such equipment available from any original equipment manufacturer, Donnie decided to build his own machine by mounting a big excavator onto an
Above: Xxx xx xxx xx xx xx xx x xx xxxxxxx xxx xx xx xx xx x xx xxxxxxx xxx xx xx xx xx x xx xxxxxx xxxxx. Business partner Donnie McKerral is the man who had a clear vision for this highly specialised machine.
all-wheel drive truck chassis to achieve his desired roading and loading performance. The search started with a high performance off-road vehicle. A military-grade MercedesBenz Arocs 8-wheel drive monster chassiscab was chosen from Glasgow-based Mercedes-Benz dealer, Western Commercials.
Whilst that deal was coming together, Donnie was also having parallel discussions with leading excavator manufacturers to find a machine that would fit the bill. Again, this was no straightforward exercise, as he only wanted to buy the upper structure and boom of a standard excavator. Donnie found Scot JCB, also based in Glasgow, to be very helpful and JCB was confident its base machine could handle a massive industrial crane boom and dipper. As the material handling model comes with a high-lift cab, an order for a UK-built, 22-tonne class JS220 was placed.
Donnie then turned to his long-term supplier of timber bodied trailers, Fergus Mitchell to pull the project together. Fergus is the owner of Forest & Field Engineering, based in Blairgowrie. It is the Scottish dealer for Hiab’s range of Loglift Jonsered equipment, which covers forwarder/ harvester and lorry loader cranes, as well as static industrial cranes. For Donnie’s project, the largest static, industrial spec Jonsered J2990-160 crane was selected with
Above: Arocs chassis at PM Forest & Field poised and ready to receive the JS220.
Left inset: Hand control like that used for mobile cranes operates the stabilisers.
TECH SPECS
Mercedes-Benz Arocs
● ClassicSpace S-cab low-
highlight (14 cab options)
● 6-cylinder EU4 engine,
450hp 8x8 all-wheel drive
● 16-speed manual gearbox
with low ratio, 32 gears in total
● Michelin XZYs (front drive
axles), X Works (rear)
JCB JS220
● 22-tonne class excavator ● Material-handling high-lift
cab model
● 4.8-litre, 179hp JCB EcoMAX
Stage 3B engine
Jonsered J2990-160 crane
● Boom length at 8.25m,
dipper at 5.3m, plus hydraulic extension of 2.55m
Left: 4.8-litre JCB EcoMAX engine with 179hp is averaging roughly 5 to 6mpg, which isn’t bad given the vehicle’s sheer weight.
an original boom length at 8.25m, dipper at 5.3m, plus hydraulic extension in the dipper arm of 2.55m. The Jonsered crane boom was then cut and grafted on to the JCB excavator boom.
Using a mix of computer aided design software, particularly around the stabiliser legs, and 2D scale drawings to visualise the articulation of the dipper arm and boom in both its stowed and working envelope, Fergus also designed a sub-chassis for the excavator slew turret mounting using 300mm high steel box-sections, and welded the JCB slew turret into position. No less than 350 high tensile bolts secured the subframe to the chassis. The JCB JS220 upper structure was then lifted onto the newly constructed turret and subframe of the Arocs.
MANUFACTURER SUPPORT
During the design process, Scot JCB recommended moving the top mountings of the excavator boom lift rams to a lower position, as the company had used this configuration on a demolition machine with great success. A new section was built below the neck of the boom, which allows the operator to achieve the maximum lift height for loading operations and enables the operator to park the log grapple close to the machine for transporting purposes.
Once the Jonsered boom was fitted, Scot JCB’s team of engineers supported the project by reconfiguring the standard ISO hydraulic control patterns to suit Donnie’s needs. Hydraulic power for the four stabiliser legs and eight hydraulic rams (four to extend and four to lift) is provided by the redundant undercarriage travel motor circuit. The stabilisers are operated via the hammer line foot pedal (to activate the flow) and a hand-held remote control unit, which is commonly found in mobile crane applications for the same purpose.
Fergus and his experienced team completed the project in just six months. Once operational, Scot JCB also provided on-site support to tweak the pressure settings to obtain the desired hydraulic speed, grab performance and power to meet Donnie’s requirements. The final painting of McKerral’s colourful blue and red livery was carried out by Courtney & McMillan Ltd, based at Broxburn and the JCB yellow of the JS220 make a very smart looking combination.
“From the initial discussion through to the on-site support, Scot JCB and the factory have been very supportive of what we were trying to achieve, and they did not shy away from getting heavily involved with such a bespoke order and aftersales support,” Donnie said. “Fergus and his team have done another cracking job of designing and building this machine to a very high standard.”
ON THE JOB
For my visit in 2015, I met up with Donnie just off the A819 in the Ardteatle Forest near Loch Awe and drove on forest tracks for three miles to reach the loading area. Donnie offered his thoughts on the machine’s ability. “I’m really pleased with its performance. It has great on- and off-road capability and has sufficient power from the six-cylinder 450hp engine. Fuel consumption is about 5 or 6mpg, which isn’t too bad given its heavy weight and time spent off highway.”
The Arocs has a 16-speed manual gearbox linked to a shift-by-wire system to provide more effective power-assisted gear changes. Low ratio is selected at the push of a button (making 32 gears in total) and combined with permanent, military-grade 8-wheel drive. This machine is not about to get stuck off-road anytime soon.
On reaching the loading area, Donnie applied the truck’s handbrake and switched off the engine before moving to the JS220’s cab via steps fitted on the nearside of the truck. From here on, power comes from the 4.8-litre, 179hp JCB EcoMAX Stage3B engine. But before loading commenced, all four jacks were firmly planted onto the ground and then Donnie activated the high-lift cab, raising the base about 4.5m above terra firma. At this height, the operator’s eyeline is well over 5m, meaning a great view onto the timber stockpile and the 13.6m long decks of the waiting semi-trailers.
The JCB cab is made to a high standard and packed with creature comforts such as climate control, a stereo and an air suspension seat. The view out of the large two-piece R/H window is excellent and a high-level rear-view camera helps Donnie guide his drivers back to the rear bumpstops. The machine was ordered with proportional controls on the joysticks which are used to control the rotation and
Above: The slew ring turret is welded to the subframe and over 350 bolts attach the subframe to the truck’s chassis.
HARD TO BEAT
log-grab functions. This JCB has a level 2 FOPS screen and roof guards, which have been modified by removing a portion of guard from the front screen area to provide an unrestricted view to the work area. Donnie believes that having an extra-long boom and dipper in the way means there is little risk of logs coming anywhere near the cab, although he also thought it wise not to remove it completely. The remaining guard also protects the cab from cosmetic damage, such as branches encountered along narrow roads and forest tracks.
In order to load to the maximum permissible weight of 44 tonnes and not overload the HGV trucks, there is a load cell on the dipper arm connected to the in-cab HTP 2500 load indicator (specially developed for use on timber cranes), so Donnie can place exactly 27.5 tonnes of timber onto the trailer bed. The JS220 is capable of loading 6.2m-long logs weighing nearly 2 tonnes with its large 0.8-squaremetre Loglift Jonsered grapple. When loading back-to-back on narrow forest roads, Donnie can load the front deck of the
13.6m-long semi-trailers with ease. With the stabilisers set at 5m apart and 4.25m wide, and the machine weighing 37 tonnes, this loading tool is very stable in operation. The 27.5-tonne load was accurately placed in just 8 minutes. Contrast that time with the 25 minutes it takes an operator using a standard vehicle-mounted crane powered by the truck’s power take-off unit to load the company’s trailer. Donnie reckons that during a long shift, man and machine are capable of loading 1,500 tonnes of logs, which is an increase of 500 tonnes over the previous loading tool and a good match for the boats with the same carrying capacity. Big rubber blocks had been fitted to the front of the Arocs to assist drivers that get stuck on slippery forest roads, particularly in arduous winter weather. The Arocs with its 8-wheel drive system, running on Michelin’s deep treaded X Works tyres on the rear and XZYs on the front drive axles, has been able to get trucks moving again with just a quick push. Speaking to Donnie again recently, he explained that due to the amount of traveling to and from jobsites, the big Mercedes-Benz Arocs now has 7,500 hours on the clock and the JCB JS220 has racked up the same number of hours in the forest, with both providing good and reliable service over the last six years. Donnie reported the only major part that has been changed on the JCB is the slew ring. Clearly, this component is worked harder in the longreach timber loader role than in a conventional excavator application. Scot JCB continues to provide great back up should Donnie need it, but he is also delighted to report the JS220 very rarely misses a beat. Donnie was clear that when this hybrid combination is due replacement, he and his brother Colin will be looking at a very similar set up, as they feel there is still no off-theshelf solution to match the shear loading performance of a powerful converted hydraulic excavator mounted on an 8-wheel “AFTER SIX YEARS OF GOOD,
THIS HYBRID TIMBER LOADER” drive HGV chassis. After six years of good, reliable and fast loading, Donnie remains delighted with the all-round performance of this hybrid timber loader. Considering there has been no structural issues with the crane modifications, subframes or stabilisers, what he and his suppliers have achieved is a remarkable feat of engineering.
