Next-gen suspension from Tata Hendrickson

The Ultimaax and Haulmaax suspension systems Tata Hendrickson has introduced, promise superior safety, efficiency and productivity.

Story by:

Anirudh Raheja

Hendrickson introduced walking-beam tandem truck suspension in 1926. It improved traction and greatly reduced the effects of bumps and potholes. Almost 96 years after the walking-beam suspension was introduced, the company’s joint venture in India – Tata Autocomp Hendrickson Suspensions (THSL) – has launched new suspension systems that have the walking beam concept as the basis. Promising to elevate efficiency, productivity and safety of commercial vehicles, the suspension systems are called as Haulmaax and Ultimaax. The Ultimaax suspension employs the walking (equalizing) beam concept with patented progressive rate spring and has found its way into the new Tata Prima 2525.K tipper with a with a 16 cu. m. body. The truck, aimed at construction and light mining segments, on the basis of Ultimaax as its rear suspension, promises a drastic fall in maintenance needs and costs. Claimed to be robust enough to withstand arduous working conditions, Ultimaax, in empty or light-load condition, has the shear springs carry a majority of the vertical load. This results in a constant low spring rate and superior ride.

Without an abrupt change in the spring rate, the ride and stability characteristics of the suspension change to meet the application needs, and as per the variation in load. Reducing road shock and vibration, the suspension system improves the service life of the cab, chassis and body equipment. The inclusion of a flat-bottom design enables the Ultimaax to get the truck to profit from high ground clearance even under load. For tippers, which work under arduous conditions, high ground clearance is one of the key necessities. Supported by rubber bushes in the front and rear, the suspension type also eliminates the need for periodic lubrication. It enables the truck to carry a higher payload. The best part, according to J V Narasimha Rao, VP – Business Development, THSL, is the maintenance-free nature of Ultimaax.

Aimed at long-haul highway (truck) applications, the Haulmaax suspension type builds on successful trials across diverse geographies. Showcased on the Tata Prime 3718 10×2 haulage truck at Auto Expo 2018, the Haulmaax suspension type, according to Rao, will be introduced by Tata Motors on two other haulage trucks. These include the Tata Prima 3118 8×2 and Tata Prima 4923 6×4 prime mover. Marking a distinct departure from leaf spring suspension, the Haulmaax suspension type is rubber-based. It, along with the Ultimaax suspension type, is engineered to enhance productivity and comfort.

Higher productivity and comfort

In addition to enhancing the productivity and comfort, the two suspension types are claimed to reduce driver fatigue as well. Elevating reliability and durability by a good deal, the two suspension types are claimed to be lighter by 300 kg than a typical bogie suspension. With the shear springs and the progressive springs the only bits that need maintenance, Ultimaax and Haulmaax offer a distinct advantage according to Rao. The maintenance procedure for shear and progressive springs involves checking them for signs of failure. The shear springs offer a softer unladen ride. The progressive springs enhance stability under load.

Unlike a conventional leaf spring suspension in a tipper or a haulage truck, which requires maintenance every 50,000 to 70,000 kms, the Ultimaax and Haulmaax suspension types have a set norm for spring replacement. The progressive springs have to be replaced once their height falls beyond 56 mm. Usually, when a tipper is running without a load, and returning to the pit, the rough surface over which it travels, leads to aggregate damage. In the case of Ultimaax, the damage to the aggregates due to excess movement and vibration is curtailed. Even if the driver drives at the same speed, the chances of damage are minimal. He can, in fact, do more trips as the comfort level goes up. “We observed during the nine months that we tested the suspension on the field that operators made at least one extra trip every day,” informed Rao. “If the operator is earning on per kg basis, or per tonne basis, he will earn more for certain. Vehicle downtime for repairs and suspension maintenance will also go down,” he explained.

Haulmaax highway advantage

The technology deployed to produce Ultimaax and Haulmaax has been patented by Hendrickson, and includes thinner springs and a heat treatment process, which differs from the one that is used to manufacture conventional leaf springs. “The bushes used in parabolic springs isolate the body from vibrations that are induced by the road surface. I would urge operators to not add leaves. Doing this will deteriorate the performance of a conventional leaf spring suspension,” mentioned Rao. Citing that the Haulmaax validation cycle would not be as extensive as the Ultimaax’s validation cycle since the learning from Ultimaax’s validation cycle will be incorporated into the Haulmaax cycle, Rao explained, “Haulmaax employs rubber bolster springs coupled with progressive load springs. The suspension type offers better performance in laden and unladen conditions.”

Utilising elastomeric bolster springs and a progressive load spring (PLS) that work in synergy to provide outstanding ride quality when the truck is empty, Haulmaax works such that the PLS engages and functions together with the elastomeric bolster springs as they compress to provide the additional stability vocational applications need in-line with the rise in load. Like Ultimaax, the Haulmaax also deploys a distinct elastomeric spring design, which not only helps to provide an ideal balance of ‘empty’ ride quality and stability when loaded. It protects the chassis, cargo and body equipment from excessive vibration and road shock due to potholes and other road inconsistencies. In terms of weight, Haulmaax weighs up to 400 kgs lower than a vocational rear tandem suspension. The up to 400 mm of diagonal articulation of Haulmaax keeps the axle in contact with the surface below to ensure superior traction and better off-road mobility.

Next-generation suspensions

Developed by Hendrickson at its Chicago facility, the Ultimaax and Haulmaax suspension types have been adapted for the Indian market by THSL. “The Ultimaax and Haulmaax that we have introduced in India are capable of operating in Indian conditions. To ensure that they withstand the operating conditions in India was not an easy task. Operating conditions in India differ from those in US,” said Rao. To ensure that both the suspension types succeeded in India, THSL employed a rigorous adaptation process. It could be described as re-developing them, quipped Rao. He opined, “Each country has its own operating conditions. India is a mix of how CVs operate in many countries. From the initial stages, we paid attention to develop a system that would suit the Indian duty cycles.” In 2013, the company borrowed aggregates like rear axles and other integrated components from Tata Motors. These were utilised to test the Ultimaax system on a few vehicles in US. THSL also purchased an LPK 2523.K 6×4 tipper from Tata Motors and fitted it with the Ultimaax suspension to demonstrate the delivery parameters. “We effectively showcased what the suspension could do. Work on the suspension began in 2014,” Rao stated. He explained that Tata Motors carried out rigorous tests before giving a go-ahead to roll out 10 pilot CVs. These vehicles were given to Tata Motors customers, selected carefully taking into consideration the geographical spread and the nature of their operation. The pilots were rolled out in early April last year, and found their way to stone quarries, river beds, coal mines, and iron ore mines among others. “Some of the Ultimaax suspension equipped trucks have clocked more than 3000 hours before the market rollout,” Rao informed.

The future

Confident of the advantage the Ultimaax suspension offers, Tata Motors is said to have rolled out 100 CVs. These include a few units of the 2523.K tipper. Work is underway to fit the suspension type to Tata 2518. Once done, it will mark an entry into the mass market. Justifying the cautious approach of Tata Motors towards the adoption of the suspension type, Rao stated, “If we upscale at the first instance, issues could arise. For us, they would translate into capability challenges, supply chain challenges, and others. You will find it surprising that tests are being performed as we speak on the Signa 2518 and 2523. These two are high volume products.”

Emphasising on the success of its six-tonne lift axle that has found its way to the Tata LPK 3118 and 3718, Rao mentioned that they are working with Tata Motors to develop a 10-tonne lift axle suspension for 10×2 and 6×2 trucks and tankers. “We unnecessarily run all the axles on the road. We are therefore working on a 10-tonne lift axle suspension for tankers and bottle carrier segments. We are also aiming at tippers. This will benefit them as the difference between a laden and unladen vehicle is too high,” explained Rao. After the introduction of an advanced lift axle suspension for the Tata 3718, the company is also working on a new lift axle design. Slated for introduction in 2019, the new lift axle will be superior and offer more benefits. THSL, mentioned Rao, is also working with Daimler India Commercial Vehicles to equip its BharatBenz trucks with a lift axle. The models being considered are the 3123R among others. Aware of the efforts CV OEMs are taking to keep the costs down, and in a post-BSIV scenario, THSL, according to Rao, is working closely with many OEMs to help them cut weight. “The weight of a suspension is typically in the region of 450 kgs. A 10 per cent weight reduction achieved marks a significant change,” he concluded.

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