July 2007, TruckingInfo.com - Test Drives
Engineers don't buy a lot of trucks. That's why Freightliner relied heavily on customer input in building Cascadia. It's the truck the users told the engineers they wanted. Left to their own devices, the clever folks over at Corp III – Freightliner's design and engineering complex – can come up with some pretty interesting little science projects. But if the customers don't want 'em or don't like 'em, they're not going to sell.
To its credit, Freightliner took the customers' wish lists seriously. They started with few assumptions, save for the proven P3 chassis (if it ain't broke, don't fix it), and left few stones unturned in developing this machine. The company invested more than $400 million in engineering and product validation, and over a million man-hours of development and testing. If our 400-mile test ride is any indication, Freightliner has invested wisely.
Back in 1988 when Freightliner rolled out the FLD line, computer-aided design, computational fluid dynamics, accelerated testing and laser vibrometers were just twinkles in engineers' eyes. While the FLD was the state of the art at the time, it can't hold a candle to this one. Advances in engineering and materials science have given the bright people at Corp III a lot to work with, and their efforts have produced quite the truck – in fact, it seems a little oxymoronic to call the thing a truck.
Driver comfort and low life-cycle costs topped the list of objectives.
For example, a tremendous amount of research was done to reduce cab noise levels, and the results are impressive. Cruising at 1,300 rpm at 62 mph, my meter read 66 dB(A). My Ford Taurus – not a notoriously quiet car – cruises at 58 dB. For the record, I recorded Cascadia at 67 dB in a hard pull (1,300 rpm) and at 70 dB with the engine brake running at 2,000 rpm and the fan on.
If it's not the quietest truck on the road, Cascadia shares first place with another recently launched Class 8, the International ProStar. Steve Sturgess and I tested ProStar a week before I drove the Cascadia, and because we used different sound meters, we can't offer conclusive proof, except to say the numbers were nearly identical. Compare my numbers with Steve's measurements in his review of the ProStar on page 82.
The key to the incredible improvement in cab noise levels, according to Matt Markstaller, manager of product validation, is reducing or eliminating the offensive noise, and leaving the correct level of the right noise.
For example, human speech is fairly high-frequency sound, so when the driver environment is cluttered with a lot of other high-frequency sounds, speech becomes difficult. On the other hand, low-frequency sounds and vibrations from air suspensions, tire and engine noise or frame beaming can actually improve the ambient sound in the cab. It's an exercise in tuning the cab so it sounds good.
The science is to the point now where, with the use of spectrum analyzers and past experience, certain crankshaft vibrations common to all in-line six-cylinder engines at a particular rpm can be identified and filtered out so engineers can ignore that in searching for other noise sources.
Markstaller recalls a previous noise elimination challenge that eventually pointed to a washer on the fuel tank mounting clips. It rattled, sending vibrations into the frame, producing a squeak inside the cab. You won't hear that noise in Cascadia, but you will notice the fuel tank mounting bracket is just a little different than on previous models.
Larger and more obvious design changes aimed at noise mitigation include improved engine mounts, a hydraulic clutch linkage, and a superb insulation package. Sculpting lines on the cab sides – and particularly on the back of the cab – reduce low-frequency vibration of the body panels. They can, under some circumstances, act like big speakers, producing a unique low-frequency rumble. That's virtually eliminated in the Cascadia.
The money spent on sound attenuation was significant, and in my opinion, money well spent.
Also tall on the list of customer requests was a larger cab. Cascadia delivers here too. While researching the design criteria, Freightliner discovered that drivers are, on average, about 17 percent heavier than they were when the FLD hit the street. In 1988, the average driver weighed 190 pounds. In 2001, the average weight was 215 pounds. Today, an average driver tips the scales at 230 pounds.
As a result, Cascadia's cab is 20 percent bigger, allowing for a larger door opening and larger seats – with more room between them.
While other OEs have been leaning toward sexier, automotive styling, Freightliner has instead been focusing on what customers want – going decidedly against the grain, in some instances.
The two-piece roped-in windshield, for example, is less expensive to replace and requires less than 30 minutes of labor, as opposed to the single-sheet bonded windshield that is more expensive and requires many hours for the adhesive to set. Chris Hofmann, director of product strategy, told HDT that while the bonded windshield may offer a slight aerodynamic advantage, customers made it very clear they weren't prepared to lose a day's work to drying glue.
The Cascadia's dash panels have gone back to easier-to-use exposed fasteners. Customers say hidden fasteners don't thwart drivers who want into the dash, and they slow down techs. The dash panels often came out the worse for a battle with the screwdriver. In the end, practicality trumped style.
Says Hofmann, "We know what we like, and the customers know what they like. Who are we to say no? Engineers and stylists don't buy a lot of trucks."
The list of engineered improvements is a long one, but among the notables:
- The dash is fully multiplexed, so all the gauges and control switches are literally plug-and-play – they pop out and snap in, and all wiring is color- and number-coded.
- The battery box has been moved from between the frame rails at the back of the cab to the driver's side door-step position. Shorter cables mean less voltage drop, even though the frame-rail position produces less battery-wrecking vibration.
- The cab extenders are much shorter, though equally effective aerodynamically, as the traditionally larger ones. They're less prone to damage, and have breakaway mounts in case a driver still manages to knock one against a trailer.
- The HVAC system boasts improved air flow and greater control, with six cab ducts and an eight-position fan switch. The rear heater core and fan motor is tucked under the cabinet behind the driver, not under the bunk, leaving more room for storage.
From a driver comfort point of view, perhaps the greatest improvement in Cascadia is the dramatic reduction in fan-on time and fan noise. A 1,625-square-inch radiator provides enough cooling capacity that Freightliner was able to lower the dependence on fan-induced air flow to provide cooling. The result is spectacular.
"Our EPA '07 design achieves the desired cooling without the fan," Hofmann told us. "Our bigger engine-mounted radiator. combined with under hood air flow design developed in our wind tunnel, ensures all the air going under hood is used most efficiently for cooling and nothing else."