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With Euro-6 heavy truck chassis shaping up to be 150kg heavier than today’s models, there is scope for weight savings on an 8x4 tipper, where every kilo counts
Words: David Wilcox When it comes to tippers, less is more. Less tipper means more payload. The principle is straightforward but removing vehicle weight without reducing durability or reliability requires more thought.
Chris Bartlett, sales and engineering director of aluminium tipper body specialist Wilcox Commercial Vehicles, estimates that every 100kg saved could earn an extra £5,000 of proit over a vehicle’s lifetime. There is also a fuel consumption beneit when unladen. Compared with motorway running, tippers on short shuttle operations are likely to see greater fuel savings from weight reduction. Having reviewed the evidence, our best guess is that trimming 500kg from an 8x4 would improve its fuel consumption by 1% to 1.5% when running empty.
CM has scoped out the weight savings for a typical 8x4 tipper with a steel body suitable for the rigours of muckaway work. Our starting point is a vehicle with a 19,377kg capacity, neither sylph-like nor unduly portly for muckaway. We then set about identifying opportunities for trimming weight. Initial indications suggest that Euro-6 models will be up to 150kg heavier than Euro-5 equivalents thanks to the extra emissionsreduction kit, so our weight reduction exercise is timely.
Engine
Our analysis of UK truck engine choice (CM 19 July) revealed the sales-weighted average engine speciication for 8x4 trucks registered last year is a swept volume of 12 litres, developing 384hp and with peak torque of 1,917Nm. This conirms that tipper people like bighearted trucks. Smaller engines are widely shunned, despite the weight savings they offer. For example, the 9.2-litre PR engine in Daf’s FAD CF75.360 8x4 is 200kg lighter than the 12.9-litre MX in the FAD CF85.360. But the latter outsold the former by six to one last year. Most operators conclude that the smaller engine’s weight savings are not worth its deicit in torque.
The 9.4-litre engine in Volvo’s FM9 8x4 tipper was similarly unpopular, but the newer small engine option is doing better. Volvo Trucks UK product manager John Comer says 45% of Volvo 8x4 chassis ordered so far this year have the 10.8-litre D11C engine rather than the 12.8-litre D13 engine. He believes uptake of the smaller engine could be even better. “I think it’s a case of people buying what they had before,” he says. “If people tried the 11-litre engine, I think they would be pleasantly surprised. It saves 100kg and has good fuel consumption.” New small engines such as Mercedes-Benz’s 10.7-litre OM470 – 150kg lighter than the 12.8-litre OM471 – might help change opinions at Euro-6.
Gearbox
Automated gearboxes have many advantages over manual boxes: less weight is one of them. ZF’s 12-speed ASTronic is 65kg lighter than the equivalent 16-speed ZF Ecosplit manual. Volvo’s 12-speed I-Shift is also about 65kg lighter than the nine-speed manual box. Small wonder that 85% of Volvo’s 8x4 chassis speciied this year include I-Shift. Resistance to automated gearboxes for off-road work has all but dissolved.
The exception to this ‘automated boxes are lighter’ rule is Scania’s Opticruise, because it retains the manual’s synchromesh rings.
Chassis options
Many truck manufacturers offer light/mediumand heavy-duty tipper chassis frame options: the latter have more litching to resist bending when mounting bodies without a sub-frame. It pays to investigate these carefully. For example, Scania’s heavy-duty 8x4 frame adds about 300kg. Fortunately, it is rarely necessary for UK tipper work, so most Scania 8x4 chassis use the medium-duty frame, with litching conined to the rear bogie area. Comer conirms that most Volvo UK 8x4 chassis are ine with a light-duty option, and points to several areas where weight can be saved. For example, choosing disc brakes rather than drums saves about 100kg. A straight front axle gives additional ground clearance but adds 55kg. Hub reduction axles (as opposed to a singlereduction axle) improve ground clearance but usually add from 70kg to 150kg on a double-drive bogie.
Most tipper people shun the shortest cab options, wanting that extra 300mm or so of storage space behind the seats on extended cabs. This has weight implications. For example, the short cab on a Scania P series is a modest 33kg lighter than the extended version: choosing Mercedes’ short S construction cab on an Actros 8x4 rather than the longer M day cab saves 70kg.
Body
A typical steel muckaway tipper body, 6.5m long with a 15m3 capacity, weighs anything from 1,700kg to 2,500kg, so with 800kg between these two extremes, there is plenty of scope to boost payload by moving towards the lighter end of this spectrum. “The important point is that the body must remain it for purpose,” says Simon Shields, director at the UK’s largest tipper body manufacturer Thompsons.
The basic choice is between singleand doubleskinning. Double-skinning, using a 3mm-4mm-thick steel liner, is widely preferred for tough work such as carrying rubble. It may be just the sidewalls that are double-skinned or the headboard and tailgate too.
Hard, abrasion-resistant steels such as Swedish Steel’s Hardox or Ruukki’s Raex allow thinner lighter panels to be used, saving weight. Such steels are used in varying thicknesses and amounts – either just the loor or the sidewalls. High-yield steels reduce the weight of the proiles that provide the body’s structural strength and rigidity. The remaining contribution comes from design, with clever proiles adding strength without weight.
Thompsons director Scott Burton says demand for his company’s steel 8x4 tipper bodies is evenly split between the double-skinned Loadmaster and the single-skinned Loadmaster Lite. “Loadmaster is the bullet-proof solution,” he says. “Double-skinning protects the outer walls, so you don’t see the knocks from the outside.” Loadmaster weighs about 300kg more than Loadmaster Lite. On the other hand, the single-skinned Loadmaster Lite costs about £500 more: it uses a thicker (4mm) and a higher grade (Hardox) abrasionresistant steel for the sidewalls. Burton expects interest in Loadmaster Lite to overtake Loadmaster in future, particularly as operators begin to feel the extra weight of Euro-6 chassis.
Boweld director George Boden also reports demand for double-skinned and single-skinned bodies is evenly balanced. “We see a north-south split,” he says. “Operators in the South seem keener to preserve the appearance of the body, so they go for double-skinned. Many of our northern customers pay more attention to payload and want single-skinned bodies.” Boweld’s double-skinned muckaway body, the Mightylite, weighs 2,450kg. In comparison, the single-skinned Mucklite weighs 1,950kg. The company’s lightest steel body is the Taperlite, coming in at 1,700kg. As well as boasting a novel tapered body shape, Boden says Taperlite makes extensive use of hard Raex 400 steel and a sophisticated proile for the body’s top rail.
Thompsons and Boweld can subtract weight by customising their bodies. For example, Boweld’s standard sidewall height is 1,050mm but it can be reduced to save a few kgs if the customer needs less volume. Thompsons will do likewise, and for one customer has built a hybrid, with sidewalls double-skinned at the bottom and single-skinned at the top.
Tipping gear
Edbro and Hyva have taken weight out of their front-end tipping gears in the past couple of years, introducing new lightweight hoists aimed at weightconscious 32-tonne GVW tippers. In both cases, cylinder diameter has been reduced. This means less hydraulic oil is required, and a smaller oil tank. Other weight savings come from detailed attention to mounting brackets and the like. Exact weights depend on the mountings needed for individual chassis.
Edbro’s CX14 hoist is claimed to have an average weight of 477kg, almost 60kg lighter than the alternative CX15. Although the CX14 has a lower nominal lift capacity – up to 25 tonnes, compared with the CX15’s 32 tonnes – this is suficient for UK work. It is down to operators to decide whether they feel the weight savings are worth the reduction in the margin of excess capacity.
With a quoted weight of 485kg (for a Daf CF85), Hyva’s FC137 hoist is 50kg lighter than the FC149. Hyva UK MD Tony Davies makes no bones about the fact that the slender cylinder on the FC137 inevitably means its side-load strength and rigidity are less than the FC149’s. “But it is still more than enough and higher than the competition,” he claims. The FC137 costs the same as the FC149 and Davies forecasts that it will become the most popular.
Fuel and air tanks
The standard tank on an 8x4 chassis is usually about 300 litres, suficient for some 400 miles. The easiest way to save weight is to reill it with only what you need for the next day, rather than brimming it. If 200 litres sufices, 85kg has been saved. Provided the tank is brimmed at regular intervals, operators can keep tabs on consumption. Trimming the AdBlue by a third saves another 11kg. Specifying a tank in aluminium rather than steel saves about 20kg in a 300-litre tank.
Some manufacturers offer the option of air tanks made from aluminium instead of steel, saving between 15kg and 30kg.
Batteries
The typical 8x4 tipper has a pair of batteries each rated at 165Ah-175Ah. The pair weighs about 90kg but it is possible to cut 20kg by opting for 135Ah-140Ah batteries. Operators are more likely to upgrade to 200Ah0-220Ah batteries, weighing about 110kg. But battery weight can be slashed without compromising. In the past couple of years, US-made Optima Yellow Top 5.5 batteries have become popular in the UK bus industry. An Optima battery’s six cells are vertical cylinders rather than lat plates. At just 75Ah, its capacity is modest but that is no indication of real-world performance, says Gordon MacKay, regional manager at Johnson Controls Power Solutions, the UK arm of Optima’s parent company. “You need to look at the cold cranking amps [CCA] rating, not the Ah capacity,” says MacKay, “because this tells you what the battery can deliver when starting the engine on a cold morning.” He says Optima’s low Ah capacity is of little consequence because its cell construction has low internal resistance, accepting a charge far quicker than conventional batteries. So, although its ultimate capacity is lower, an Optima battery is more likely to be in a higher state of charge. An Optima’s CCA rating of 975A is comparable to that of the typical 165Ah-175Ah battery, but a pair weighs just 53kg, saving almost 40kg on standard batteries. An Optima Yellow Top 5.5 battery is likely to cost about £50 more than the usual 165Ah-175Ah battery.
Sheeting system
The lightest powered sheeting systems are the front-to-back, lip-over type with springloaded arms and electric rewind. They generally have a mesh sheet, designed to provide basic protection against material coming off the load. Such a system for an 8x4 tipper weighs 80kg-100kg.
Is it possible to save a little weight by using aluminium instead of galvanised steel for the side arms, or opting for a manual cranking mechanism rather than an electric motor to rewind the sheet?
“We offer those options on the Flip ‘N’ Load,” says Ben Harrington, director of sheet system manufacturer Dawbarn & Sons, “but you only save a few kgs, so it’s not really worth it.” According to Carl Hinds, MD of tipping gear and sheeting system supplier Harsh, the addition of the cranking and gearing mechanism means the manual version of its Flip ‘N’ Go system weighs slightly more than the 80kg electric model. And counterintuitively, the aluminium arms are also a shade heavier than the steel arms. This is because they have a much beeier section than the steel arms, designed to make them stiffer and ideal for long bodies and trailers. Hinds says Harsh’s lightest sheeting system, weighing 72kg for an 8x4 tipper, is a Pulltarp. “It works like a roller blind,” says Hinds. “You pull it out manually and retraction is spring-loaded.” Although lip-over systems are commendably light, this is one instance where it probably pays to add weight, choosing instead a more comprehensive system designed to seal the top of the body. The aerodynamic advantages of keeping air out of an empty tipper body are proven.
Tests have shown that a well-sealed sheet will improve fuel consumption by 6%-9% (compared with an unsheeted body) on an empty 8x4 tipper. Such systems are heavier because they need waterproof sheeting and domed end panels to keep the sheet off the load. Side-to-side systems with hydraulic operation are usually about 220kg, or 150kg-180kg if manually operated. Harsh’s front-to-rear electrically operated Slide ‘N’ Cover for an 8x4 weighs 102kg. Choosing the manual version saves almost 20kg.
Tarprite, based in Wickford, Essex, says its Smarttarps mesh sheets improve the aerodynamics of lip-over systems.
Smarttarps have elasticated triangular side-laps that can be pulled down to fasten to the body sides, keeping the sheet taut and resisting lapping on an empty body. They add only 4kg to the weight of a typical lip-over mesh sheet.
Wheels and tyres
The default tyre for most 8x4 chassis is 295/80 R22.5. But the optional 315/80s offer higher load capacity, an additional 10mm-13mm of ground clearance and a wider contact patch for off-road work. They also lengthen overall gearing by 3%. Their downside is weight. A typical 315/80 R22.5 weighs 6kg-9kg more than a 295/80. Rim width also needs to go up, from 8.25in to 9in, adding another couple of kgs to each wheel. The net result is that specifying 315/80s rather than 295/80s adds 100kg-130kg.
Aluminium wheels can recover all of this and more, so chassis weight ends up 60kg115kg lighter than the original speciication, despite using bigger tyres. If operators stay with the original tyres but swap steel for aluminium, savings increase to 150kg-190kg on 8.25in rims and 190kg-220kg on 9in rims. Not all aluminium wheels are created equal, so it is important to research the options.
If retro-itting aluminium wheels, expect to pay about £3,000 for a set of 12. Budget for a further £300-£500 for new (longer) wheel studs or for using sleeved wheel nuts; an aluminium wheel’s nave is twice as thick as a steel wheel’s. If the steel wheels removed are in as-new condition, their trade-in value is about £35 each.
Light wheels reduce rotating mass and hence rolling resistance, so each kg saved should give a bigger fuel consumption beneit than a kg saved elsewhere on the truck. Alcoa says testing found a 3% reduction in rolling resistance, leading to a 1% fuel saving.
On-board weighing system
A typical onboard weighing system using four strain-gauge load-cells weighs about 80kg. The load cells and the junction box are the heavy bits, so it is worth considering lighter ways of measuring weight, such as pressure transducers in the air suspension or the hoist’s hydraulics.
Alternatively, lightweight micro electromechanical systems (MEMS) sensors mounted directly on the axles or suspension determine weight by measuring delection. Such a system, available from PM Onboard or Air-Weigh, for example, weighs just 5kg-10kg. However, operators must sacriice a degree of precision. Load cells are typically accurate to within 0.5%-1.0% of their full-scale delection, whereas 2% is more typical for MEMS sensors and pressure transducers.
Lights and horns
Six spotlights on a stainless-steel light bar and a pair of air horns weigh 25kg. If perched on the leading edge of the roof, they will worsen fuel consumption by 0.5%-1%. ■
Results
All these savings add up to 983kg, increasing the truck’s payload potential and earning power by 5%. The baseline truck was not the heaviest and these cuts are realistic. We did not pinch the driver’s space by opting for a shorter cab or downgrade the body from steel to alloy. The weight saving should improve fuel economy by 2%-3% when running empty, and a better sheeting system will make an even bigger contribution. Lighter wheels and removing lights above the screen will help fuel economy when laden. This all adds up to a worthwhile result, particularly in a business where profit is notoriously thin and chassis weights are set to increase.
WHERE HAS THE WEIGHT GONE?
kg saved Engine 100 Steel body 400 Tipping gear 55 Batteries 37 On-board weighing system 70 Fuel 85 AdBlue 11 Aluminium wheels 200 Lights and air-horns 25 Total saved 983kg