Kenworth T909 with AIR CTI: Review

Name: Kenworth T909 with AIR CTI: Review
Brand: Kenworth

The old loggers down in Southern Tasmania have a saying that goes, “If you haven’t got AIR-CTI fitted to your drive tyres then you have ‘Buckley’s chance’ of getting out of the bush…” We sent Howard Shanks on a run into the steep Florentine Valley to check out the AIR-CTI in action.

AIR CTI – How it works

Chet Cline from AIR-CTI told us that, a fully laden log truck, tandem drive, on the highway needs 92psi only in its drive tyres. “This is actually the required hot tyre pressure,” Chet explained. “This would relate to an 80psi cold pressure, which is exactly what Michelin, and most other tyre manufacturers recommend, for 16.5 tonne on eight 11R22.5 tyres that you will see on the Muskett log truck.

"On gravel roads this loaded truck should run 60psi," he said. "In really poor traction areas, he can drop to 30psi for maximum traction, inflating back to 60 once the road improves.

"An empty prime mover with Elphinstone Easy Load trailers towed behind only requires 40psi on the highway. The eight tyres will be supporting maybe six or seven tonne only. On the empty run back to the log landing, the driver would drop his tyre pressure to 30psi on the gravel.

"To get a reasonable idea of optimum tyre pressures on the highways, look at the flat spot on the steer tyres where they meet the road,” Chet explained.

"That flat spot should be six or seven inches long, 150 to 190mm long. Then look at the drive tyres. What length is the flat spot where the tyre meets the road? Is it similar, or is it totally round? It should be similar for highway work. This provides the best traction, ride, tyre life, and safety.

"If anyone argues, just point back to the front tyres," Chet smiled.

"Sure we get so many comments from people who say you can’t run pressures that low. But do the maths for yourself, an empty semi-trailer on 12 wheels may only be supporting four tonne or less per tyre. Conversely an empty tandem drive prime mover will have four tonne on eight tyres. Think about the family Falcon car carrying two passengers for a minute, it will weigh two tonnes on four tyres. It’s the same load, but you don’t run 100psi in your falcon tyres…"

The heart of the AIR-CTI is the dash-mounted controller, which allows for quick and easy switching between pre-set pressures, in Muskett’s Logging operation these are 30psi, 60psi and 90psi. The pre-set pressures can be adjusted on the fly with a simple press of a button. Meantime, inbuilt safety measures are also installed in to ensure the driver is always aware of any issue.

How it works is simple when broken into a few sections.

Air Supply

The air supply, from the truck’s air system, is connected to an inflate and self-draining filter assembler. This assembly is generally located out of the way behind the cabin and regulates the supply of air to the Isolator assembly, which in turn regulates the tyre’s air pressure.

Deflate System

The unique automatic isolator valve block is combined with two stainless solenoid deflate-valves for safety and quick deflation. The isolator allows for instant isolation of any wheel set from the other wheels, it also prevents any uneven inflation or deflation, ensuring even tyre wear.

Durable Components

Super tough heat moulded, ‘Snizentite’ drop pipes fit close to the tires, supplying the rotator wheel assemblies and insuring that connection to the wheel is protected.

The unique AIR-CTI manufactured lightweight, zero rust Delrin rotating glands (rotators) have carbon seals and tungsten carbide seats that deliver excellent bearing protection with triple sealing rotator mounts which are easily installed using the original axle studs for reliability and fit-up ease. They also include self-sealing quick-connect fittings to make tyre changes easy with top grade tyre hoses that are 'cut to length' for easy fit up.

The Journey begins

The Derwent River glistened in the mid-morning sun, as Muskett’s Kenworth T909 wound its way up the southern outlet out of Hobart. It was a brilliant day in Tasmania, even the chilling winds had subsided. The smooth run on the bitumen would take us as far as Huonville, roughly 40 kilometres away, from here we’d head right where the narrow bitumen quickly gives way to a well-used gravel road that winds its way up into the mountains.

Peter’s lived in the area all his life and been logging for most of it. This is his second Kenworth and with a little over 12 months bush work under its belt, Peter admits he’s more than happy with the T909’s performance, ride and reliability.

The heart of this Kenworth T909 is a Cummins ‘Signature’ rated at 600 horsepower coupled to an Eaton RTLO22918B 18-speed transmission that drives Meritor RT46-160 with full DCDL rear axles riding on a Kenworth Air-Glide 460 rear suspension.

"The B-Double trailer set is a locally made Elphinstone Easy Loader, that comes standard with easy weigh scales and automatic strap tenioners," Peter explained. "It takes roughly 90 seconds to unload the back trailer at the log landing and stretch it out."

Inside the cabin, the ride was smooth and quiet with only the gentle hum of the Cummins out under the hood audible, which made for pleasant conversation.

Peter’s local knowledge is one of pride that encompasses his community, his job and its sustainability. He told us that, logging in the Huon area commenced as early as the 1800s along with whaling, where the workers would set up temporary camps.

Now that we were well up into the mountains, deep corrugations in the road below were really putting the Airliner suspension to work. Apart from the odd rattle from the trailers on the back there was nothing inside the cab to indicate the road had deteriorated.

The Air-Glide 460 was certainly getting a workout. The Air-Glide 460 suspensions use a unique, compact parallelogram geometry that maintains constant axle alignment, driveline angle and tyre contact as the road surface changes – even during extreme cross-articulation – like this run today.

"It is really well put together truck," Peter volunteered. "I’ve been really impressed with its overall performance and so far I haven’t had any problems with any of it including the engine, which I cannot fault either."

The ride inside the Kenworth T909 was exceptional. Peter added the handling of this truck is the best he’s ever had. Observing his steady hand on the wheel from the rider’s seat and the seemingly effortless ease Peter guided the T909 around the winding track its road manners were equally as impressive.

Around another corner and the countryside changed once more, tall trees lined either side of the road. "They’re what they call swamp gums," Peter said. "They are one of the softer hardwoods and are mostly used for producing veneer panelling."

"You can see here in this clearing where they have logged this small coupe and are ready to replant it," Peter explained, pointing out the windscreen a few corners further on. "The next coupe is left for several years, which leaves habitat for the animals and from a scenic point means the mountain side isn’t barren. A little further down the track on you’ll see where timber was harvested five or so years ago and then around a bit further there is patch that was harvested ten years ago. As you can see it only takes a few years growth and it is very hard to tell where the harvesting has taken place.

"These gums that are planted here are fast growing eucalypt tree that the forestry have developed specifically for the industry. It is not a scene of destruction but a renewable resource we have here," Peter emphasised.

"This is the third time this area has been logged," Peter pointed out. "There has been a real evolution in the way timber is harvested and forests managed over the last four to five decades. You can walk around some parts of the coupe and see this evolution from the old tall stumps where the fellers would cut the shoe holes for their planks to the shorter stumps cut with the chainsaw."

A call of the UHF radio broke the conversation. It was the bush crew checking his arrival time. "I’ll start heading down to the landing," came the reply after Peter informed of his position. "Just coming in around spur three". Sure enough around a few more corners dust rose from the ridge as the excavator made its way down to the large stacks of logs neatly sorted on the side of the bank.

Peter eased off the throttle and nosed the Kenworth into a small clearing, waited for the dust to clear, then selected reverse and backed alongside the log stacks. There were a couple of chains on the Elphoinstone Easy Loader to be undone then it slowly rolled off, Peter selected low, eased out the clutch and stretched out the trailers.

There was time for a quick chat with the excavator driver then the machine’s large arm with its mechanical beak began clasping logs and gently placing them between the poles of the trailer. Like most log trucks down this way, Peter’s truck is fitted with Elphinstone onboard scales, and the truck can be loaded accurately to the maximum weight.

It’s interesting to see how accurate they load the logs, as the load is near completion, Peter monitors his hand-held readout and signals the excavator driver how much weight is over each axle group. The excavator driver can then move the log either forward or backward to achieve the correct axle grouping. The loading time is approximately half an hour from when the truck arrives till it is chained up ready to leave.

A whoosh of air exhausting from the spring parking brakes signalled it was time to leave then as the big bore Cummins under the hood bit hard and the tyres gnawed through the dust searching for traction in the soft powdery dirt track, the Kenworth T909 and 40 tonne of logs slowly moved out of the landing.

A few kilometres from the landing there is a steep climb, so steep in fact, that two concrete strips have been laid to help the trucks maintain traction on the climb. However, Peter freely admits that without the AIT-CTI they would not be able to get out. "Only trucks fitted with the AIR-CTI cart out of here," Peter says.

It would be another four hours before Peter would reach the mill, a journey that would take him right the heart of Hobart and up the middle of the state, but that’s another story.

For more info about AIR-CTI click here or to view a short video click here.

Truck Specs:

Model: Kenworth T909

Engine: Cummins ISXe5

Horsepower: 600hp

Torque: 2050 lb/ft torque @ 1150-1300rpm

Gearbox: Eaton Fuller RTLO22918B

Front Axle: Meritor MFS73 7.3T

Front Suspension: 7.2 tonne multi leaf

Rear Axles: Meritor RT46-160GP Tandem drive, diff locks to both axles

Rear Axle Ratio: 4.30

Rear Suspension: Air-Glide 460, 20.9T