Crawl before you walk

12 MinutesBy NZ Trucking magazineSeptember 6, 2018

For two years we have read and seen Volvo promotional material on the I-Shift gearbox fitted with new crawler gears. New Zealand Trucking magazine went to Mount Cotton to drive a fully rigged 203 tonne heavy haul unit fitted with the new bottom end cogs. 

Volvo Group Australia president Peter Voorhoeve oversaw the launch of the I-Shift with crawler gears in Australia at the Mt Cotton facility last month. On hand was Ove Wikström, heavy duty transmission and rear axle manager Volvo Trucks Gothenburg, Sweden. There was no shortage of technical firepower or product passion.

Making ourselves comfortable in the driver‘s seat of the Volvo FH16-700 Globetrotter fitted with the latest incarnation of the company ‘s critically acclaimed I-Shift gearbox we‘re staring into the teeth of an 8.8% gradient loaded to 203 tonne GCM. The instruction comes to select ‘C1‘, release the park brake, and gently apply a little pressure on the accelerator. What happens next is jaw-dropping. There is a gentle rumble from the D16G-700 and the left side of the cab awakens and gains a little altitude as the torque is steadily applied, and with that the combination is away. The ease in which this happens beggars belief. The experience leaves you grinning and shaking your head with astonishment as to just how effortless it was. We now understand completely just how much of a game changer this new feature is to the placement of Volvo‘s line-up in the industry.

Problem – solution
The issue that has plagued the entire transport industry for a millennium was a driving force for the Volvo Trucks‘ I-Shift research and development team. How to specify a strong drivetrain with ratios that work well together with the I-Shift, allowing ease of startability at maximum GCM from a standstill, while not compromising fuel economy at open road cruising speeds. Historically we have had to make a sacrifice at one end of the rev range or the other; no longer. The concept, now reality, simply introduces a new module containing the crawler gears, directly in line between the rear of the bell housing and the front of a reinforced and strengthened standard I-Shift gearbox. This crawler unit is specified at time of order in either one of two variants, the ASO-C or ASOULC. Both of these options can be fitted to the AT2612F, ATO3112F, or ATO3512F gearboxes behind either the D13 or D16 Euro 5 engines within the FH16, FH, FM or FMX models. The ASO-C version will give the operator one extra forward crawler gear below first gear, and the ASO-ULC two extra forward crawler fears below first gear.

The magic
he crux of the new crawler gear options is found in the numbers. Using the ATO3112F gearbox as an example, it becomes very easy to see exactly where the magic occurs. In standard guise first gear has a ratio of 11.73:1. Now add to this the ASO-C option and you have a completely new crawler gear below first with a ratio of 17.54; a significant step lower. Taking this another jump by specifying the ASOULC option will place two new gears below first gear, the first being an impressive 19.38:1 ratio, and the second a massive 32.04:1, allowing the capability of a near stationary crawl at 0.5 kph with Volvo‘s Engine Control feature engaged and locked at just 600 rpm. As impressive as the new gear ratios are on paper, driving them introduces you to a new dimension of heavy vehicle control. The development of the crawler gears was an exclusive in- house Volvo Trucks programme. “ This has resulted in a unique selling point for Volvo Trucks that no other heavy truck manufacturer can offer,” said Ove Wickstöm.

The added advantage once either the ASO-C or ASO-ULC modules have been specified is the ability to add the optional MSR (multi speed reverse) to the order. This will add two extra reverse gears in to the line-up.

The standard ratios for R1 R2 R3 and R4 in the ATO3112F are 13.73:1, 10.78:1, 3.16:1, and 2.48:1, respectively. Add the ASO-C module with MSR and you go from a choice of four reverse gears to a line-up of no fewer than six. This is achieved by an extra gear with a ratio of 4.72:1 being placed in the middle of the existing four reverse gears, as well as a completely new crawler gear added below R1 with a 20.53:1 ratio. Once again take the next step and specify the ASO-ULC with MSR and those two new ratios step to 8.62:1 for the new gear between the existing R2 and R3, and down to a whopping 37.49:1 ratio for the new crawler gear.

Strain on the train
Although the picture that has been painted for crawler gears depicts heavy haul applications, their application is in no way exclusive to the heavy haulage sector. D uring the test day at Mount Cotton we were also introduced to an on-highway specified example in the form of a FH16-540 curtainsider B-double loaded to a GCM of 61 tonne. As we set off from nice level ground and ventured off around the test track, our guide informed us about the attributes of the ATO3112F gearbox with ASO-C and MSR installed in this particular tractor unit. He was quick to inform us of just how the new features assist operators of all walks to ease the strain on the entire driveline, especially when at maximum loading. This could not have been more apparent than when we undertook a hill start, pulling the rig up to a complete stop on a respectable incline. Selecting ‘Auto‘, we press gear down once to select C1 (Crawler Gear 1), release the park brake and apply a little pressure on the accelerator, and again a gentle growl from the D16G and off we go with the I-Shift progressively and very smoothly working its way up through the gears. Once more we are left in awe of just how effortless the drivetrain had to work to get the 61 tonne unit rolling. Not a bead of sweat on the brow.

Photo: Ove Wikström, heavy duty transmission and rear axle manager Volvo Trucks Gothenburg, Sweden, imparted with passion the attributes of his baby.

Total control
Alongside of ease of startability, the other welcome attribute with the use of crawler gears is accurate control while manoeuvring at low speeds no matter the weight, either in forward or reverse gears. Combine this with Volvo Dynamic Steering and the real benefit of control in tight confines – whatever conditions are thrown at the situation – become immediately appreciated. By utilising the lower ratios of the crawler gears from a standstill start, the energy applied to the clutch during application is reduced to only 25% of what is normally required for a standard I-Shift, again assisting with smooth and controlled vehicle movement. Add to this the ability to customise each and every individual I-Shift with a software package that best suits the intended application, and you end up with a truck where the behavioural characteristics of the driveline can be heavily influenced. This feature also enhances appeal in terms of redeployment or resale, as programmes installed can be removed and a more appropriate package installed for the new owner if the need arose.

The road forward
Our introduction, and experience with the crawler gears at Mount Cotton, was eye-opening. The I-Shift has undergone significant development since its release in 2002, and today there‘s no question it ‘s among the pacesetters in the AMT game. The question begged is where next? Ove Wikström told attendees the much-vaunted dual clutch system is now available for the Australasian market and ready for ordering. The concept and application of the dual clutch system within passenger vehicles and light commercials has been revolutionary. In principle it separates the gearbox in two and applies a separate clutch for each side of the gearbox. This allows the ability to have the vehicle rolling with an engaged gear while having the next gear preloaded and ready to be activated with virtually zero disruption to power flow. The benefits to heavy-duty trucks are obvious; not least the ability to maintain constant high turbo pressure while making shifts. Not resting on their laurels, Volvo Trucks initiated revolutionary change, developing the SPO2812 I-Shift 12-speed gearbox with dual clutch, available up to 2800Nm (2065lb/ft) and 70 tonne GCM.

We cannot wait to try that out on the Kaimais!