PLANT & CIVIL ENGINEER Test Drives

The CAT 740 Articulated Dump Truck

PT McWilliams is currently working on the new Dungannon to Ballygawley dual carriageway in Tyrone. It’s a challenging project and on one site alone, the contractor has around 50 pieces of plant and equipment.
That includes 20 dumpers, among them two of five recently purchased CAT 740’s from dealers McCormick Macnaughton, so Plant & Civil Engineer’s David Stokes went along to find out what the view from the cab was...

The 40 tonne Caterpillar articulated trucks are certainly being worked to their fullest extent; that much was clear on a day plagued with frequent heavy downpours sweeping in from the west, making life underfoot not so pleasant; in fact, the terrain resembled more of a mudbath, so how were the CATs coping?

We were impressed, and so was the operator behind the wheel of the one I climbed on board, the task made easy by the well positioned steps up. “This is the first CAT I have driven,” remarked Shane Byrne, “and I must say, it’s an excellent truck. This is not the best of weather, but it can tackle everything that’s being thrown at it.”

Operator comfort can be hard to come by on a site such as the one we were on. There were steep inclines, sudden declines, rutted tracks and other obstacles to negotiate. However, as we quickly discovered, the three-point front suspension with its oscillating axle and low-pressure ride struts, combined with the centre-mounted cab, offered pretty high levels of ride comfort. And that’s vital: they say a comfortable operator is a productive operator!

“Obviously, all of my working day is spent behind the wheel, so the cab is an important aspect, and I have no complaints about the CAT cab. It’s spacious, as you can see, plenty of room for two people,” Shane pointed out.

Operator comfort is enhanced by the provision of an air suspension seat, with a cushioned upper high back, adjustable damping with three settings, ride zone indicator and adjustable lumbar settings. It is fully adjustable to provide the optimal driving position.

The full-size passenger seat, used perhaps for a trainee or a trainer, is fully padded and features a backrest and a wide, retractable seatbelt for a secure and comfortable ride. It’s positioned next to the operator seat, giving both occupants a clear view of the instrument panel, controls and the road.

There’s ample storage space, too, for all the driver’s bits and pieces, helping to create a safe, secure and uncluttered working environment.

AirCon
“The heating and air conditioning system is brilliant. On a chilly, windy day like this, the cab remains pleasantly warm and comfortable; on a better summer’s day, if it gets too hot, the system also keeps it cool, so I have no complaints on that score,” commented Shane. “If the windows are frosted up in the morning, it’s also quick at clearing them.”

And talking about visibility; a good all round view is vital, especially with so many other pieces of plant and machinery - and men - to contend with, as was the case on this particular site. The low sloping hood and placement of the cooling package behind the cab means the operator gets exactly that: excellent all-around visibility, further enhanced by the large glass area and the central operator position.

The wet arm wiper system, too, cleans more glass area and is bottom mounted to keep it out of the operator’s line of sight. The windows, incidentally, are tinted to reduce glare. And positioned high up to the right of the driver’s seat is a colour camera, giving the driver a clear and uninterrupted rear view.

“The last truck I drove, the camera was only black and white, and it was mounted in the dash, making it difficult to see.”

The working environment also benefits greatly from the presence of cab mounts that are designed to reduce noise and vibration, while the operator’s station makes extensive use of sound-absorbing and barrier materials to keep sound levels low.

Controls
Shane was also impressed with the layout of the cab. “As you can see, all the controls are close to hand – better positioned than the previous truck I was driving - and gauges can be read quickly and easily, making driving the 740 relatively simple. It means I can concentrate more on the road ahead.”

The wrap-around dash features LED illuminated rocker switches, large LCD display and a rear wash wipe rocker switch. The CAT 2S Monitoring System provides an improved method of monitoring critical machine functions and alerts the operator to an immediate or impending problem. The system includes four levels of warning.

The operating pedals are suspended, and are easy to reach with plenty of leg and foot room. They also make for easier cleaning of the cab floor by keeping the pedals out of the dirt.

Engine
We don’t want to get too technical about the 740, which is powered by a CAT C15 ACERT engine, but here we go – The core concept behind ACERT technology, for the uninitiated, is advanced combustion. ACERT engine technology carefully controls the combustion process to reduce pollutant levels while maintaining performance and efficiency.

The Caterpillar seven-speed electronically controlled transmission incorporates Individual Clutch Modulation to ensure constant shift times even when the oil is cold. The transmission arrangement provides a second reverse gear for improved performance when operating in longer rear hauling applications. First gear reverse is of a lower ratio for increased rimpull on wet or steep grades.

Controlled Throttle Shifting significantly reduces power train stress and clutch wear by controlling engine speed, torque converter lock-up and transmission clutch engagements, while the Electronic Transmission Control protects against engine overspeeding by shifting the transmission up one gear at specified rpm settings. If the transmission is in its highest gear, torque converter lockup disengages.

The Caterpillar Engine Compression Brake provides extra braking effort on downhill grades. It is an excellent match for the C15 ACERT engine, turning it into a power absorbing air compressor. It has very fast response time and produces no additional heat, so it can be used continuously.

The power train components work together well. In first gear, for example, the torque converter overcomes grade resistance by sending more torque to the wheels and preventing engine lugging. On downhill grades, the engine compression brake works like a brake by slowing the machine. The remote-mounted hydraulic fan is temperature sensitive providing variable speeds when needed, which minimizes power requirements. The result is more power to the ground and faster cycle times.

Servicing
In these days of belt tightening, it’s good to see that the 740 boasts long engine oil change and hydraulic oil change intervals; this obviously helps to lower maintenance costs and, of course, downtime, which could be potentially expensive on a busy contract.

Easily accessible, the engine and transmission dipstick and fill caps, air and fuel filters, and the fuel priming pump are all mounted on the left side of the engine under the hood. The coolant level indiCATor and fill cap are outside the cab.

The cab tilts to the side to provide easy access underneath, which simplifies servicing of the transmission, drive shafts and hydraulic pumps. Machine electrical and hydraulic interfaces are loCATed on the right side of the cab, behind a removable cab body panel for easy access.

Support
So what initially attracted PT McWilliams to the CAT 740? Commented Gerard McWilliams: “Apart from being a great dump truck, availability was a key factor. They were readily available, and we bought five, and have no regrets.

“After hours support was also a vital element, and dealers McCormick Macnaughton provide an excellent level of back-up. That’s essential as any unnecessary downtime would be very costly for us. We like to know there will be support when and where we need it.”

Our view from the cab? Well, PT McWilliams, as we mentioned, have five CAT 740s currently operating and the overall consensus appears to be well into positive territory. The 740 is a tough and reliable workhorse, taking all kinds of terrain in its stride, as we witnessed at first hand. The driver we spoke to was certainly well impressed, and so were we.