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With more truck manufacturers outsourcing their axle requirements, the axle producers are developing designs that are more versatile and cheaper to make. Meanwhile, trailer axle developers continue to focus on weight reduction and whole-life costs...Sharon Clancy reports.
Truck axles
aimlerChrysler is one manufacturer still producing its own axles at huge Kassel plant. tts Powersystems division has been establishec sell Discos truck and trailer axles and suspensions to other veh manufacturers. The HL drive axles, first used on Actros tractive un are modular, all with pressed steel casings and single-reduct hypoid gearing. HL axles have two rather than the conventional thi taper roller bearings—the nose bearing has been eliminated, wti creates more space for a larger differential, which is clamed to be more resistan wear. Mercedes-Benz fits Knorr-Bremse disc brakes, but other makes can accommodated.
The axles on Daf's new LF truck are manufactured by Glasgow-based Alb Automotive, now owned by American Axle Manufacturing. Albion builds 20,000 axle year, and counts Renault as well as Oaf among its customers. Its range includes cc plete non-driving steer axle assemblies with ratings of 3.6,4.8 and 6.0 tonnes, and gle-reduction drive axles of 5.25, 8.5 and 11.5 tonnes. The banjo-type drive axles hi hypoid gearing.
ArvinMeritor has made a breakthrough in developing a cast-steel axle that can customised to suit the different requirements of various chassis manufacture Casting is preferred for strength, but cast-iron axles are expensive to prodi because cast iron cannot be welded, so all the axle brackets and attachments havE be incorporated in the casting, making each axle manufacturer-specific. Steel could used, but casting it is a difficult process, so until now most steel axles have bE pressed.
However, ArvinMeritor has overcome the technical problems of casting steel, 2is developing a range of cast-steel single and tandem drive axles. The first design is MT32.610, a tandem drive-axle bogie for construction and off-road vehicles. Cam disc brakes can be specified.
US-based Dana Corporation's Heavy Axle & Brake Division has introduced a n family of drive axles for European truck applications, manufactured In Spain. TN are four, ranging from 18to 44-tonne gross weights. All drive axles use hypoid geari have unitised wheel hub bearings and can be configured to accept either drum or d brakes.
In the UK, the Dana Spicer specialist axle division at Leeds produces 75,000 ste axle beams a year for trucks and buses. The present NDS axle range uses the at material technology, resulting in the lightest beams consistent with the imposed lo Capacities range from 3.6 to 8.0 tonnes,
Rear air suspension is increasing in popularity, especially as its weight disadv; tage over mechanical springs is reduced. Volvo, for example, has made air suspens standard On most FM and FH models.
Independent front suspension ir medium-weight trucks is getting oser, it seems. At last year's tankfurt show, ZF announced it id developed an independent ont suspension for trucks for 5.1id 7.5-tonne axles, while fellow erman company Krupp Jtornotive Systems has designed a system for trucks of up to 15 tonnes gvw.
rrailer axles and suspensions
eller running gears are becoming even lighter. Changes incorporated in SAF's tradisc Plus range have saved 60kg per axle. A 19.5in disc brake axle now weighs less an 400kg per unit, says SAF, making it the lightest available. The suspension arm is irrower, allowing a smaller, lighter hanger bracket to be used. The shock absorber is also been redesigned to improve wear, and the component is now included in 1,000,000km six-year warranty.
BPW's latest nine-tonne Airlight II suspension should be available in the UK by e end of the year. It has a new trailing arm, a redesigned hanger bracket and a ambed axle connection which saves 25kg per axle. The suspension needs no a ntenance and, says BPW can be easily repaired in the event of an accident. le stiffness of the trailing arms is adjustable according to application, and the :sign includes more accurate axle tracking to minimise tyre wear and reduce ad stress on the vehicle frame. It comes with a five-year unlimitedHinge warranty.
Holland Europe's HSA90/110 axle and suspension unit is designed to riinate U-bolts and welding of the spindle, collar and suspension tachment. Axle tube walls can be thinner, saving weight and cost. The ie-piece forged beam incorporates the spindle and collar, and has ternal venting to improve airflow to the bearings and aid heat ssfpation. Holland uses parallel bearings, claiming the life for the ime axle loadings is double that of pared bearings. The inner and iter bearing packs are the .me size, promoting even lubrication and reducing the incidence of dry bearings, which can cause components to fail if they go undetected. Axle capacities are nine and 11 tonnes.
The Neweld connection eliminates both U-bolts and welding of the actual axle tube. Instead, the suspension is clamped in place using a two-piece adaptor, which is welded.
Discos has introduced a new HDB trailer axle with a thinner axle tube and a redesigned hanger bracket. The axle tube is now made with a wall thickness of 9./mm. A trailer steering axle should be unveiled later this year.
Cigant is the latest axle manufacturer to switch to long-life cassette bearings on its axles: Protec axles now have SKF cassette bearings. The new Delta profile air suspension is designed to allow for faster build times to help reduce the initial cost. The suspension bolts on to a cross member, which replaces separate hanger brackets.
Steering axles
Operators have been won over to self-track axles, mainly by proven savings in tyre wear. There is a weight penalty of about 150kg with self-tracking axles, but the recent vehicle weights uplift means their appeal might be extended, especially as they can be useful in certain applications for ensuring compliance with turning circle requirements. BPW, one of the pioneers of self-track axles in the UK, says the market for self-track axles remains steady at about 2% of all sales.
Fully steered axles, either hydraulically or mechanically driven, have been even more specialised. ArvinMeritor's RSD command-steer axle, however, is said to be both simpler and lighter than rival designs and virtually maintenance-free. Instead of a turntable it has a rotatable king pin driving a hydraulic actuator at the front of the trailer. This drives hydraulic fluid through an inter-loop system to a similar actuator on the rear steer axle. No trailer chassis strengthening is required, says ArvinMeritor, so the weight penalty is minimal. An accumulator in the hydraulic circuit prevents the sys tem overloading should the trailer hit a kerb.
New from Dutch manufacturer Tridec is a version of its TD mechanical steering axle for low-floor trailers. The redesigned TD is more compact, with a trailer fifth-wheel height ofjust 95mm.