Couplings, Dollies, Trailers

Looking for ‘Real’ Modularity

Looking for ‘Real’ Modularity

PowerTorque Technical Columnist, Bob Woodward, reckons the industry needs to get serious about looking for ‘real’ modularity!

Late last year I followed a BA-triple (six decks of cattle) in regional NSW, it should not have been on the road, he tells us. The performance compared to an AB-triple (six decks of cattle) on the same road was chalk and cheese.

I had an associate send me a photo last week of a converted dolly that had been ‘modified’, supposedly on the recommendation of an enforcement officer, to get a combination within the category overall length.

A technical description of ‘modularity’: a very general set of principles for managing complexity. By breaking up a complex system into discrete pieces, which can then communicate with one another only through standardised interfaces within a standardised architecture, one can eliminate what would otherwise be an unmanageable spaghetti tangle of systemic interconnections.

Applied to vehicle configurations the modular approach has two objectives: coupling complying vehicle units in configuration will (should) result in sub-configurations being compliant. However, in some examples the smaller configurations are not compliant.

Type 1 and 2 road trains have been modular, as maximum trailer length increased so did the overall length of road trains, typically removing the last dog trailer from a type 2 resulted in a complying type 1 road train. If a type 1 road train is more than 36.2m or a type 2 is more than 53.4m then at least one vehicle unit is non-complying; but rule makers of the day opted for rounding-up 36.5 and 53.5m. Why hasn’t this maths logic been applied to the recent better performing configurations?

Image: Prime Creative Media

A 36.5m AB-triple may not disassemble to a legal B-double, the 36.5m reference is too short for general freight. The modular B-triple has enjoyed some recent adoption (good news) where the requirements stipulate that any two trailers assemble to a compliant B-double. Whilst there will continue to be debate as to how long a B-triple should be, and what constitutes a modular B-triple the same approach doesn’t apply to a modular AB-triple.

A modular AB-triple should begin with a complying B-double; overall length ≤ 26m; kingpin to rear ≤20.6m: Provided internal axle spacing comply the lead trailer can be longer in conjunction with appropriate shortening of the trailing trailer. ADR 63 requires that the tow coupling be not more than 300mm forward of the rearmost projection of the trailer.

Research completed by Roaduser Research in the late 90s identified that the drawbar of a converter dolly generally should not be shorter than 4.1m. Increasing length beyond 4.1m that did not significantly improve high speed dynamics but degraded swept path performance.

The simple mathematics: B-double length 26m less say 0.2m for coupling location, 25.8m; Converter dolly drawbar 4.1m, maximum semi-trailer reference 12.3m overall length 42.2m. Industry lobbied for 42.5m (converter dolly flexibility, up to 4.4m) but the bureaucratic brains trust opted for 42m, sound familiar!

To our knowledge there is not a published PBS Level 3B network outside of SA. Operators are then left with specific route assessments or a type 2 road train network. If limited to a road train network, why bother with the smaller configuration?

No One’s Accountable

A recent regional newspaper article referred to the Murray Darling Water Plan. Conclusion, the current water minister appears to have minimal understanding of the water policy and management complexities. But when there is a change of government or cabinet reshuffle the minister will move on but little will change; the bureaucrats will just be left to indoctrinate a new minister. And when we have the realisation that the water plan was poorly modelled or poorly delivered, no one will be held accountable.

Operators have long recognised the benefits in trailing dynamics of factors such as a longer converter dolly drawbar, where trailers are typically shorter, for example livestock and bulk transport, dolly drawbar length is typically the ADR maximum (excluding PBS).

Operating complying modular B-triple and AB-triple in parallel, means that the configurations can be disassembled into three B-doubles with an additional complying B-double prime mover. The principles of modular B-triples should be adopted to AB-triples and further embrace the concept that a modular AB-triple should require that the prime mover and any two trailers assemble to form a legal B-double.

But let’s not stop here: Modular ABB-quads and BAB-quads have safety performance benefits above conventional road trains and ABB-quad is potentially a better dynamic performer than a BAB-quad, but the BAB quad is more convent for assembly and disassembly and more suited to extreme operating conditions.

Initiate a new perspective on productivity by moving proven combinations from PBS to modular prescriptive, develop and publish access networks for all classes across all states and territories, and deliver outcomes and BE ACCOUNTABLE!


For more stories like ‘Looking for ‘Real’ Modularity’ – see below


Previous ArticleNext Article
Send this to a friend