Volvo have put together a design where the truck maker is specifying a truck to save fuel. The team developing this evaluation truck have refused to compromise on any aspect of the design if it would save fuel. The result is a strange looking, but very slippery B-double set-up, which goes as far down the fuel saving route as anything on the road before it.
Diesel News took the truck for a spin, running at 62.5 tonnes GCM from Sydney to Brisbane, to see how it drives and assess how much fuel it can save. Even with minimal coaching and plenty of mistakes the results proved to be surprising.
The chassis on this model is set at a medium height for a Volvo, at 800 mm. This reduces turbulence underneath the prime mover, specially between 75 and 85 km/h, according to research.
The truck actually uses the 16-litre Volvo engine, which comes with an overdrive gearbox, useful for improving fuel consumption. This also gave the engineers an opportunity to play with ratios and optimise fuel use. The engine has been derated to 540hp, but it still has 2650Nm available in terms of torque. The rear axle ratio needed to be tall, therefore there needs to be enough torque to retain drivability in the driveline.
The transmission chosen is the I-shift with one crawling gear to aid startability. The final drive ratio is 1:3.09. This gives the driver 1270 rpm at 100 km/h. This point is judged to be the sweet spot in the rev range on this engine, and it is low enough to get some real fuel savings.
The aerodynamic modelling on the cabin is designed to get the air passing quickly down the side of the vehicle. The worst place that air can go is underneath the vehicle, where it creates a lot of turbulence. The prime mover has a bumper spoiler on the front, from the Volvo parts catalogue.
There was also a lot of work done in closing up the seams and gaps on the cabin. The sun visor was removed. The space around the steps was closed in to a large extent with custom-made extensions to the doors. The designers also closed in the space around the wheel arches with a system sold on the European track market. The tank fairings used are modified parts which are sold in Europe.
There is also an aero kit to close in the space between the cabin and the trailer. This was custom-made in Brisbane and extends around a metre back from the rear of the cabin.
MaxiTrans got involved with Volvo in order to help modify the trailers to improve their aerodynamic performance. The long skirts down the side of the trailer help keep the air flowing fast along the side of the trailer, so it does not get caught underneath with equipment like tyre carriers. They also streamline the air past the wheels, further reducing turbulence.
Low rolling resistance tyres have been shown to make an impact and, as a result, they have been used here, extensively. In fact, the tyres used in this case are super singles throughout. Even though there is a potential mass allowance penalty for using super singles their fuel saving capabilities were judged to outweigh this issue. The trailer and steering axle tyres are all 385s, while the drive axles are fitted with 445s and are all Michelin X1 tyres, used in large numbers in the US market.
The tyre choice involved a long series of tests, running different types and configurations of tyres to ascertain the optimum. The full super single set proved to be the most efficient. Just in testing low rolling resistance tyres, the team found differences of up to four cent in fuel consumption, on the test truck.
Another way to reduce fuel consumption is to reduce the weight of the truck. Smaller Adblue and fuel tanks were fitted. The inner frame rail was omitted from the truck. Some lighter components under the bonnet were chosen from the specifications catalogue, there is a high efficiency alternator fitted to reduce parasitic losses of power.
The results of the process are going to be ongoing projects for Volvo. The aero kit will continue to be developed and be included in the Volvo range on offer, down the track. The same is true of the derated 16-litre engine.
The ability to fit super single tyres is something which may become more common in the future. Michelin are actively lobbying for some amendments to the rules to enable operators who would like to fit them to be able to do so.
The truck is also fitted with Adaptive Cruise Control as part of the safety package. This can help with fuel efficiency if the truck is dealing with a lot of traffic which is speeding up and then slowing all of the time.
Once the whole combination was built, it went through a testing program for a month. A number of drivers with different experience levels were cycled through the truck to enable the team to assess and isolate the truck and trailer’s performance.
To ensure the measurement of fuel was exactly right. The fuel tanks were removed and weighed before the test run. They were weighed again when the truck came back to base at the end of the 500 km run via Ballina NSW and Plainland in Queensland’s Lockyer Valley.