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  1. #31
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    Quote Originally Posted by hotgemini View Post
    I'm intimately familiar with this topic. Contrary to the OP in this thread, this isn't actually a new towball rating, rather it is pointing out what has always been contained in the standards but widely ignored.

    The heavier the towing vehicle, the greater the forces it is able to impart into the coupling.

    The ATM ratings on couplings were created to simplify rating selection on light vehicles for a non-technical audience and used assumptions for the mass of the towing vehicle to calculate the permissible trailer mass for a given 'D-value' of the coupling design. When you use these couplings on a heavier drawing vehicle, these assumptions cease to be valid and the coupling is outside of its original design specification.
    I cannot speak for mainland states, but it certainly was a new rating system for Tasmania. Prior to the adoption of VSB6 for new truck registrations in Tasmania, the rating of the ball or coupling was all that was observed. To this day, Boronia Towbars market a universal towbar kit designed to be fitted to larger vehicles that is dual rated, 3500Kg for 50mm ball and 4500Kg for 70mm. The supplied rating sticker makes no reference to the vehicle GVM by the way, leaving the correct rating to be applied by the certifying AVI. I can also recall the factory towbar kit for the Fuso Rosabus came with a 3500Kg rating sticker as do the factory towbars for Isuzu NPR and NQR trucks. When VSB6 was introduced in Tasmania, towbar ratings were not mentioned in the regs, however that was added at a latter stage.
    What is your experience with this topic?

  2. #32
    Join Date
    Dec 2011
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    Brisbane, Queensland
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    Let me attempt to clarify, you're confusing what the local practice was versus what was actually contained in the law.

    To understand, we need to follow a bit of a legislative breadcrumb trail. In each state there are laws which require vehicles to remain compliant with applicable Australian Design Rules whilst in service.

    In jurisdictions other than WA and NT, for heavy vehicles this has been achieved by the Heavy Vehicle National Law since February of 2014, however state legislation exists for light vehicles and applied the same requirement to heavy vehicles prior to the introduction of the HVNL.

    The applicable clause is Section 60:


    60 Compliance with heavy vehicle standards

    (1) A person must not use, or permit to be used, on a road a heavy vehicle that contravenes a heavy vehicle standard applying to the vehicle."

    So, that then takes us to the Australian Design Rules, which essentially exist as regulations to the Motor Vehicle Standards Act, which for some political reasons is in the final stages of being replaced with the almost identical Road Vehicle Standards Act. In particular, we need to look at ADR 62/02, although from memory the relevant clauses haven't changed since the first edition.

    https://www.legislation.gov.au/Details/F2010C00153

    In clauses 9 and 10, it is made a requirement for 50mm ball couplings to comply with relevant sections of AS 4177

    9. 50 mm ‘BALL COUPLINGS’ 9.1. 50 mm ‘Ball Couplings’ intended for towing trailers with an ‘ATM’ of up to 3.5 tonnes must comply with the requirements ofAS 4177.2 – 2004 50mm Towballs.

    9.1.1. The marking requirements at clause 12.4 may be used instead of those in AS 4177.2 – 2004.


    This is significant because contrary to common assumptions, the existence of an Australian Standard doesn't make it a requirement to comply with that standard. That only occurs if that standard is made mandatory by some piece of legislation.

    Right at the start of AS 4177.2 you'll find the critical statement.

    "this Standard limits the use of the towball to vehicles with a towing vehicle mass up to 5 t."

    So there has been no change in the law around 50mm ball type coupling tow ratings in Australia since June 2004. The NHVR did recently point out that the law as it stood was widely misunderstood and misapplied, but the law itself didn't change.

    As I mentioned, the reasons behind it are pretty simple. Historically it was decided by the standards committee to simplify coupling selection for light vehicles, so that they were given a simple fixed rating value rather than needing to calculate the required 'D-value' for a particular combination. However in undertaking this simplication they had to choose a mass range for which it would be applied. So they chose 5t and used it to calculate D-value. By rights this means that a 3500kg ball coupling on a 1t drawing vehicle is actually over-specificed (note: I'm not suggesting towing 4t with a corolla, just making the engineering observation).

    So contrary to your belief, no, the law did not change in Tasmania, rather a misapplication of the law was resolved.

  3. #33
    Join Date
    Sep 2010
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    Lebrina
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    Quote Originally Posted by hotgemini View Post
    Let me attempt to clarify, you're confusing what the local practice was versus what was actually contained in the law.

    To understand, we need to follow a bit of a legislative breadcrumb trail. In each state there are laws which require vehicles to remain compliant with applicable Australian Design Rules whilst in service.

    In jurisdictions other than WA and NT, for heavy vehicles this has been achieved by the Heavy Vehicle National Law since February of 2014, however state legislation exists for light vehicles and applied the same requirement to heavy vehicles prior to the introduction of the HVNL.

    The applicable clause is Section 60:


    60 Compliance with heavy vehicle standards

    (1) A person must not use, or permit to be used, on a road a heavy vehicle that contravenes a heavy vehicle standard applying to the vehicle."

    So, that then takes us to the Australian Design Rules, which essentially exist as regulations to the Motor Vehicle Standards Act, which for some political reasons is in the final stages of being replaced with the almost identical Road Vehicle Standards Act. In particular, we need to look at ADR 62/02, although from memory the relevant clauses haven't changed since the first edition.

    https://www.legislation.gov.au/Details/F2010C00153

    In clauses 9 and 10, it is made a requirement for 50mm ball couplings to comply with relevant sections of AS 4177

    9. 50 mm ‘BALL COUPLINGS’ 9.1. 50 mm ‘Ball Couplings’ intended for towing trailers with an ‘ATM’ of up to 3.5 tonnes must comply with the requirements ofAS 4177.2 – 2004 50mm Towballs.

    9.1.1. The marking requirements at clause 12.4 may be used instead of those in AS 4177.2 – 2004.


    This is significant because contrary to common assumptions, the existence of an Australian Standard doesn't make it a requirement to comply with that standard. That only occurs if that standard is made mandatory by some piece of legislation.

    Right at the start of AS 4177.2 you'll find the critical statement.

    "this Standard limits the use of the towball to vehicles with a towing vehicle mass up to 5 t."

    So there has been no change in the law around 50mm ball type coupling tow ratings in Australia since June 2004. The NHVR did recently point out that the law as it stood was widely misunderstood and misapplied, but the law itself didn't change.

    As I mentioned, the reasons behind it are pretty simple. Historically it was decided by the standards committee to simplify coupling selection for light vehicles, so that they were given a simple fixed rating value rather than needing to calculate the required 'D-value' for a particular combination. However in undertaking this simplication they had to choose a mass range for which it would be applied. So they chose 5t and used it to calculate D-value. By rights this means that a 3500kg ball coupling on a 1t drawing vehicle is actually over-specificed (note: I'm not suggesting towing 4t with a corolla, just making the engineering observation).

    So contrary to your belief, no, the law did not change in Tasmania, rather a misapplication of the law was resolved.
    Put it this way, pre adoption of VSB 6 in Tasmania, I could register a new heavy vehicle with no blue modification plate being fitted. Not so since the adoption of VSB 6. Once VSB 6 was adopted in Tasmania, the ratings for 50mm towing gear were unchanged from what had always been the norm, until the Heavy Vehicle Regulator issued a bulletin to licenced AVI's informing them of the changed ratings for 50mm towing gear. If you check the date on the link in the first post of this thread, you will see that it is 2017 09, this is the same time period that AVI's received the bulletin.
    I was foreman in a vehicle body building workshop when VSB 6 was introduced in Tasmania and we were in the first intake of AVI's trained to work under the new regime. We followed the supplied information to the letter. It is possible I guess that VSB 6 was not implemented correctly or accurately in Tasmania, but I certainly know what went on from the adoption of VSB 6 until the issuing of said bulletin. I can however see that AS4177.2 is dated 2004, which suggests that it was a long standing requirement overlooked when VSB 6 was adopted in this state and in the years prior. Interestingly, the engineer that we used for work outside the scope of our certification never mentioned anything about 50mm couplings either, (he currently is certified to work in both Victoria and Tasmania which should remove the chance that only Tasmania was asleep in class).
    I am still yet to see a failed 50mm coupling or ball, although that of course does not imply compliance.
    It leaves vehicles that were legally registered in Tasmania prior to our adoption of VSB 6 in an interesting position as they met the requirements of Transport Tasmania, but not AS 4177.2. I guess that will give the NHVR something to amuse themselves with if they are having a slow day or need to build up their Christmas fund.

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