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<\/p>\nThe Society of Motor Manufacturers & Traders (SMMT) in the UK has reported that silica compounds,\u00a0lighter weight and aerodynamic\u00a0designs will shape the fuel-efficient\u00a0truck tyres of the future.<\/p>\n
In an in depth report on its website, www.smmt.co.uk says that since 2012, EU tyre labels have rated the fuel economy, wet grip and noise level\u00a0of all new tyres sold, providing a handy point of comparison for customers and\u00a0spurring competition between new and established players. But in the CV world,\u00a0where fuel costs have a huge impact on the bottom line, fleet operators and other\u00a0customers are often the ones driving improvements in fuel economy from new\u00a0tyre technology.<\/p>\n
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Reducing rolling resistance to improve fuel economy has been the major trend in\u00a0truck tyre development for some years. The adoption of so-called \u2018green tyre\u2019\u00a0compounds in passenger cars, pioneered by Michelin in 1992, has led to the\u00a0increasing replacement of carbon black with silica as the principal filler in car tyre\u00a0compounds, leading to better wet grip and lower rolling resistance.<\/p>\n
Silica is used to some degree in truck tyres, too, but where car tyres can use\u00a0predominantly synthetic rubber-based silica compounds, the situation in trucks is\u00a0complicated by their reliance on the extra strength and durability that natural\u00a0rubber provides.<\/p>\n
\u201cHistorically, low rolling resistance tyre tread compounds have tended to wear out\u00a0faster and be more susceptible to tread cutting and chipping than their \u2018standard\u2019\u00a0counterparts,\u201d confirms Gary Schroeder, Director of the truck and bus tyre\u00a0business at Cooper Tyres. \u201cThus, when a tyre design achieves lower rolling\u00a0resistance, it can result in undesirable side effects if the tyres are not carefully\u00a0engineered.\u201d<\/p>\n
\u201cAnother typical difference is that low rolling resistance drive tyres tend to have\u00a0shallower tread depths. The disadvantage can be fewer overall miles to removal,\u00a0although many have been engineered to achieve a reduction in rolling resistance\u00a0without compromising other areas of performance. Compared to passenger tyre\u00a0treads, truck tyre treads are very lightly loaded with fillers of any kind, and we are\u00a0unlikely to see compounds that resemble passenger tyre compounds in the near\u00a0term.\u201d<\/p>\n
One of the leading scientists working to bridge the divide between natural rubber\u00a0and silica is Dr Anke Blume, professor of elastomer technology and engineering\u00a0at the University of Twente in the Netherlands. She begins by explaining how\u00a0natural rubber offers the extra strength needed to make durable truck tyres\u00a0capable of carrying heavy payloads.<\/p>\n
\u201cNatural rubber crystallises when it stretches, adding strength,\u201d she says. \u201cWhen\u00a0the strain is released, the crystallization immediately disappears \u2013 it\u2019s completely\u00a0reversible and happens very fast.\u201d<\/p>\n
\u201cYou can try to use very pure, synthetic polyisoprene as a replacement for natural\u00a0rubber, but you can\u2019t simply add the broad variation of proteins required to make\u00a0it behave in the same way. But while we cannot replace rubber [with] other\u00a0synthetic polymers, we also know that the silica\/silane system that is normally\u00a0used with synthetic rubber in passenger car tyre treads cannot be transferred as-is to natural rubber. We have to find new ways of making it work with silica.\u201d<\/p>\n
Blume\u2019s team is looking at ways to modify the natural rubber polymer in such a\u00a0way that it interacts better with the silica during mixing, resulting in a strong, even\u00a0mix rather than clots of one material or the other. Experiments using epoxy\u00a0rubber have shown some promise but the temperature window where effective\u00a0mixing occurs is very narrow, between 135-150\u00b0C. Another goal for future studies\u00a0will be modifying the silica to find the right coupling mechanism to suit the\u00a0structure of the natural rubber polymer.<\/p>\n
\u201cWe have to consider the chemistry behind it, modify the polymer or the silica,\u00a0and test it,\u201d adds Blume. \u201cIt\u2019s a lot of testing. There\u2019s a lot more potential there\u00a0and I think we can go much further, but it\u2019ll be years of work.\u201d<\/p>\n
\u201cIf we can reduce the rolling resistance of truck tyres then the fleet owners will\u00a0save a lot of money, but the abrasion resistance has to work well and this is\u00a0always a weak point with silica inside. If we can find a way to maintain abrasion\u00a0resistance while reducing rolling resistance by 10-20%, as it has happened in\u00a0passenger car tyre treads, then there will be a big step forward.\u201d<\/p>\n
Blume points to weight reduction as a parallel stream of research being explored\u00a0by the tyre industry to reduce rolling resistance, with Aramid or other fiber\u00a0materials being lined up to replace some of the heavy steel cords within the tyre\u00a0structure. This of course reflects a wider trend in the automotive and commercial\u00a0vehicle industries for replacing parts that were previously metal with weight-saving plastic or composite alternatives. Key factors to consider are always that\u00a0strength must be maintained and costs must be kept down.<\/p>\n
Tyre aerodynamics can also play a part in saving fuel, according to Rick Shock,\u00a0Senior Director of Aerodynamics at Exa, which has just added a rolling tire\u00a0simulation function to its PowerFLOW computational fluid dynamics software.<\/p>\n
The new Worldwide harmonised Light vehicles Test Procedure (WLTP)\u00a0regulations mean that car and van manufacturers now have to declare the impact\u00a0of individual wheel and tyre combinations on emissions performance and fuel\u00a0economy. Car and LCV makers are therefore paying increasing attention to the\u00a0aerodynamic impact of tyre designs, which can be up to half a percent of the total\u00a0vehicle drag. \u00a0WLTP doesn\u2019t apply to heavy trucks, but the customers\u2019 focus on\u00a0fuel mileage means that Exa\u2019s new tool is being applied there, too.<\/p>\n
\u201cEuropean truck manufacturers are not beholden to WLTP but to something much\u00a0stricter \u2013 their fleet operators,\u201d says Shock. \u201cIt doesn\u2019t matter to the operators\u00a0what the OEM puts on the sticker or advertises as the drag value. They just want\u00a0to know in actuality, as they\u2019re operating their vehicle, what the consumption is\u00a0going to be. Simulation gives the manufacturer the ability to know that a particular\u00a0set of tyres can meet the on-road target that their fleet operators are aiming for, to\u00a0accurately predict the on-road condition.\u201d<\/p>\n
Exa has worked with Class 8\u00a0commercial truck customers in North America to evaluate the impact that different\u00a0treads can have on the aerodynamics of a heavy vehicle, with some surprising\u00a0results.<\/p>\n
\u201cThe aerodynamics are very complex as the air goes through the tread and\u00a0around the shoulder and is then accelerated down toward the contact patch,\u201d he\u00a0explains. \u201cYou might have some tyres that are nobblier than others but that\u00a0doesn\u2019t necessarily mean you\u2019ll have more drag, it might be less! The interaction\u00a0of the airflow around the grooves, with the rest of the vehicle, is very non-intuitive.<\/p>\n
\u201cWe\u2019re finding that on the drive tyres, the impact of the rotating tread is not a\u00a0huge contributor to linear drag \u2013 how much drag the truck experiences by the\u00a0wind flowing over it,\u201d Shock continues. \u201cBut it does impact the rotational drag.\u00a0When you\u2019re rotating the tyres there\u2019s a torque component, a resistance to the air\u00a0due to the rotation, that can manifest itself as equivalent drag. You have to give\u00a0the vehicle more power to overcome that aerodynamic torque resistance.\u201d<\/p>\n
It\u2019s thought that aerodynamic studies such as these will help to shape new, low-drag tyre designs to add to fleet operators\u2019 fuel savings. In combination with other\u00a0incremental changes such as weight reduction measures, plus the promise of a\u00a0large fall in rolling resistance if the challenge of using more silica in tread\u00a0compounds can be overcome, the future\u2019s bright for fuel-efficient truck tyre\u00a0technology.<\/p>\n","protected":false},"excerpt":{"rendered":"
The Society of Motor Manufacturers & Traders (SMMT) in the UK has reported that silica compounds,\u00a0lighter weight and aerodynamic\u00a0designs will shape the fuel-efficient\u00a0truck tyres of the future. In an in depth report on its website, www.smmt.co.uk says that since 2012, EU tyre labels have rated the fuel economy, wet grip and noise level\u00a0of all new […]<\/p>\n","protected":false},"author":2,"featured_media":18785,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-18783","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"yoast_head":"\n