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Thread: 3500kg ADR towbar

  1. #11
    Join Date
    Mar 2009
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    NSW Mid North Coast
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    221
    Quote Originally Posted by rfurzer View Post
    Yes Warwick, Aaron has the 3500kg ADR.

    Your bar is very nice too!
    Very good work and well done. I'd like to clarfify a few things,

    Its great that your engineer has certified the bar at 3500kg. But unless the vehicle has been certified ( which yours obviously will be/has been) then the tow rating will be limited by the lower of the bar and vehicle. If you were to sell the bars commercially how do you/the engineer intend to certify each vehicle its fitted to? Can a type certification be done?

    In one of your posts you stated that there was NO GCM for a perentie (which I agree with) how did you (or the engineer) esrablish this?

    With your production design have you considered locating the receiver tube within the cross bar rather than underneath (as many 3500kg rated production bars are done for other vehicles)?

    This would minimise the compromise to departure angle that you design has.

  2. #12
    Join Date
    Dec 2007
    Posts
    257
    Rathgar

    I'm not sure how a type certification would work (or if it's possible).

    As for the GCM - there is no GCM currently existing and so you (and the authorities and insurers) have two choices -

    1. Use the military recommendation for a 1200kg towed weight (would probably still need trailer brakes on civvy street) + 3200kg GVM = 4400kg as the "existing" GCM and then to engineer a mod for each vehicle (perhaps becoming easier with precedence).

    or 2. Using data for a similar vehicle as per either the NVD or Operators manual - all of which allow a towed weight of 3500kg or greater (up to 4000kg for a 110 Isuzu "cab chassis").

    I have chosen number 1 because it is rigorous and wasn't much extra effort as I was also changing the seating capacity and needed a mod plate anyway.

    And for the hair-splitters - you need to consider the tow-ball down weight when you calculate the towing vehicle load capacity so GCM is actually less than 3200 + trailer weight.

    If the receiver tube were higher then it would need to have more rear-wards overhang as (AFAIK) only the 21126 TBM gives 3500kg with a short shank that wont foul the spare. A longer overhang is detrimental in terms of towing dynamics. This design was the best compromise for my situation.

  3. #13
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    Mar 2009
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    NSW Mid North Coast
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    Quote Originally Posted by rfurzer View Post
    Rathgar

    I'm not sure how a type certification would work (or if it's possible).

    As for the GCM - there is no GCM currently existing and so you (and the authorities and insurers) have two choices -

    1. Use the military recommendation for a 1200kg towed weight (would probably still need trailer brakes on civvy street) + 3200kg GVM = 4400kg as the "existing" GCM and then to engineer a mod for each vehicle (perhaps becoming easier with precedence).

    or 2. Using data for a similar vehicle as per either the NVD or Operators manual - all of which allow a towed weight of 3500kg or greater (up to 4000kg for a 110 Isuzu "cab chassis").

    I have chosen number 1 because it is rigorous and wasn't much extra effort as I was also changing the seating capacity and needed a mod plate anyway.

    And for the hair-splitters - you need to consider the tow-ball down weight when you calculate the towing vehicle load capacity so GCM is actually less than 3200 + trailer weight.

    If the receiver tube were higher then it would need to have more rear-wards overhang as (AFAIK) only the 21126 TBM gives 3500kg with a short shank that wont foul the spare. A longer overhang is detrimental in terms of towing dynamics. This design was the best compromise for my situation.
    Fair Enough good work but i don't think you've "cracked the towing nut" for the wider population. Even if you make and sell an ADR approved 3500kg towbar the vehicle may be the limiting factor in towed load depending on your interpretation of the rules. Personally I think there are more than the 2 options that you put forward.

    And I'm not sure I agree with your comments about deducting ball weight from the GCM but then it comes down to whether your talking a GCM of 6700 or a maximum towed load of 3500kg.

  4. #14
    Join Date
    Dec 2007
    Posts
    257
    The nut is hard to crack without a civvy NVD, which isn't going to happen.

    Having an ADR towbar that is designed to suit the unique rear chassis is (IMHO) a big step in the right direction. There is no overseas sourced solution. A self-made setup or a modification of a bar from another vehicle would be illegal. The setups that only use the pintle mount without side elements might not be strong enough.

    Without a mod plate stating a max towed weight, you might have uncertainty if pulled over by a transport inspector, but I'd actually suspect that they'd be satisfied with the compliance plate on the bar, a OneTen drivers handbook and the closest NVD on their system (ie a 3.9 diesel 110).

    The time in which you might need the rigour of a mod plate (and therefore the indemnity of an engineer) is if you had a prang while towing. Perhaps ask your insurer what they require?

  5. #15
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    Mar 2009
    Location
    NSW Mid North Coast
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    Quote Originally Posted by rfurzer View Post
    The nut is hard to crack without a civvy NVD, which isn't going to happen.

    Having an ADR towbar that is designed to suit the unique rear chassis is (IMHO) a big step in the right direction. There is no overseas sourced solution. A self-made setup or a modification of a bar from another vehicle would be illegal. The setups that only use the pintle mount without side elements might not be strong enough.

    Without a mod plate stating a max towed weight, you might have uncertainty if pulled over by a transport inspector, but I'd actually suspect that they'd be satisfied with the compliance plate on the bar, a OneTen drivers handbook and the closest NVD on their system (ie a 3.9 diesel 110).

    The time in which you might need the rigour of a mod plate (and therefore the indemnity of an engineer) is if you had a prang while towing. Perhaps ask your insurer what they require?
    Well said

  6. #16
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    Mar 2009
    Location
    NSW Mid North Coast
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    I do find it amusing that there is a need to engineer a towbar when I can design, make and register a trailer (which I have dome) without the use of an engineer.

    But I guess maybe as the manufacturer I take responsibility for what I have done. But it's most certainly a "legal" trailer.

  7. #17
    Join Date
    Dec 2007
    Posts
    257
    Rulz iz rulz but. No need to make sense. We live in a land where you can't put a plug on an appliance. (I was given a scalectrix for xmas 1979 when we were in England and the plug came separate. I was 8.)

  8. #18
    Join Date
    Dec 2007
    Posts
    257

    finally fitted

    The prototype 3500kg bar. Subsequent ones will have a slightly different stiffener arrangement to allow the pintle to go back on.

    Aaron (the certifying engineer) plans to join Aulro and will be keen to hear of any interest. The price point will be higher than an off-the-shelf bar for a mass produced vehicle.
    Attached Images Attached Images

  9. #19
    Join Date
    Aug 2006
    Location
    Kingston, Tassie, OZ.
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    13,537
    Quote Originally Posted by rfurzer View Post
    The prototype 3500kg bar. Subsequent ones will have a slightly different stiffener arrangement to allow the pintle to go back on.

    Aaron (the certifying engineer) plans to join Aulro and will be keen to hear of any interest. The price point will be higher than an off-the-shelf bar for a mass produced vehicle.
    Thats great work! Where are you located in Tassie?

    Jc
    The Isuzu 110. Solid and as dependable as a rock, coming soon with auto box😊
    The Range Rover L322 4.4.TTDV8 ....probably won't bother with the remap..😈

  10. #20
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    23,246
    Just one comment - when did the requirement for an approved and placarded towbar come in? Certainly after my 1986 110 was built. And is it retrospective? Either in the sense of fitting a towbar today to a vehicle built before this date, or a towbar that was installed before that date. I think certainly not the second case, as it would have made illegal almost every towbar in existence then.

    I suggest that for many Perenties, an approved and plated towbar is not actually required. But that does nothing to help with towing anything above 1200kg!

    John
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

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