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The cat comes back
Page 43
Page 44
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Cartwright's Cheetah Aero System is the only aerodynamic solution on the market for both cab and trailer. We put it to the test to see how much fuel and money can be saved.
Words: Kevin Swallow, Brian Weatherley / Images: Tom Lee When it comes down to tractor/trailer combinations, aerodynamic solutions invariably concentrate on just one area. It's clear tractor and trailer manufacturers work hard to ensure their respective products are either the best they can be when it comes to cost efficiency or fuel economy and productivity. But combining these factors could well produce greater results when it comes to aerodynamics.
After all, it's within every transport manager's remit to reduce the company fuel budget.
Most fleet tractors come with some sort of air management kit attached, unless an operator really is trying to cut costs or increase payload, and most mass-market box and curtainside trailers have side skirts as an option.
However, when these two are installed together, they don't always sing from the same hymn sheet. But Altrincham-based trailer-maker Cartwright has other ideas. It has had its Cheetah Aero System in place for a while, but now it is incorporating the tractor with retro-fitted air deflectors from AB Airflow [see panel].
At this year's CV Show, a revamped Cheetah Aero System appeared, which, according to Cartwright, boasts a 16% fuel saving and a "13-tonne reduction in annual carbon emissions [based on 200,000kms per annum]".
Windtunnel tests with a specially designed cab roof fairing and cab extensions, plus trailer skirts and rear roof scoop, showed a -42% total reduction in drag coefficient-. the trailer manufacturer revealed.
So what exactly is the Cheetah Aero System? On the cab, there is a patented cab extension, or cab collars, from AB Airflow, which have a lip fitted that pushes air out and away from the head of the trailer. CM previously looked at this concept with tankers [CM, 15 May 2003].
On the trailer, there are a number of devices to help air pass through the chassis and over the roof. A rounded ledge on the top of the trailer's bulkhead and an aerodynamic rear roof scoop that channels air reduces turbulence.
Model shop
Drag down the side of the trailer is reduced by using large radius skirts and a tapered rear skirt quarter-panel. Apart from landing legs and axles, the channel along the chassis is clear, which helps airflow underneath the trailer.
It's a concept that was developed over 18 years. Steven Cartwright, director, explains: "Since 1990, Cartwright has been involved with aerodynamic development, working on the original Department of Energy study on developing an aerodynamic system for articulated trailers.
"And since then, we have gained vast experience from conducting roadgoing trials and track tests, along with windtunnel tests using scale models.
"Today's net result is the Cheetah system for both cab and trailer. The cab features three-dimensional top airfoil and side ears designed to optimise airflow around the cab and on to the trailer.
"The trailer has an open chassis design to allow for better drag resistance, along with slightly tapered sides and the aerodynamic front top 'blimp', side skirts and rear roof scoop.
"The Cheetah system has proven fuel savings of between 16% to 18% over and above a tractor unit with an air kit coupled to a standard trailer without aerodynamics," he reveals. •