Axle weight conundrum !

Discussion in 'Tech/Mech General' started by pappajohn, Jul 7, 2016.

  1. pappajohn

    pappajohn Funster Life Member

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    Not van related but a mystery nonetheless.

    My new trailer has a gross weight of 750kg
    It is a twin axle with an individual axle weight of 375kg per axle.
    This is stated on the cert of conformity yet it also states "number of axles 2 x 750kg" (Alko)

    The overall length is 3.9 meters, the load bed is 2.7 meters and the axle centres are just 750mm apart and center of the load bed.
    how the hell can you attain an axle weight of 375kg with them being so close ?
     
  2. Minxy Girl

    Minxy Girl Funster Life Member

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    ... whilst I like puzzles this is toooooo much like an old maths test! :D
     
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  3. Derbyshire wanderer

    Derbyshire wanderer Funster Life Member

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    It possibly has a compensator joining the axles that will enable them to share the load evenly. I suppose it has no brakes hence the 750kg gross weight?
     
  4. Geo

    Geo Trader - Funster

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    Why can't you?
     
  5. Steve

    Steve Funster Life Member

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    you just spread the load evenly, i put my scooter over both then geny at the front and something similar at the back it seems to work
     
  6. pappajohn

    pappajohn Funster Life Member

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    Axles are of the rubber indespension type so no interlinking of any kind.
    Simply bolted to chassis.
     
  7. pappajohn

    pappajohn Funster Life Member

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    Agreed, but in the extremely unlikely event of being weighed both axles would technically be overweight if the load was more than 375kg.....unlike a car or van the axles are too close together to be weighed individually.
     
  8. John Laidler

    John Laidler Funster

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    2 * 375 = 750, so it is correct, but it assumes when loaded to 750kg both axles share the load evenly, which they will only do if the load platform is horizontal. However, I guess there is a good safety factor built in so it should be fine.
     
  9. pappajohn

    pappajohn Funster Life Member

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    Because as the axles are close coupled the total load, or very close, will be imposed on both or either axle regardless of which is being weighed unlike a van with an axle at both ends each sharing a percentage of the load.
     
  10. pappajohn

    pappajohn Funster Life Member

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    Oh yes, there's a safety factor of 100%....2 x 750kg axles.
    If it's loaded to 750kg and one axle is raised (on scales for example) then the raised axle is carrying the full 750kg, yet the cert of conformity limits each axle to 385kg.

    It doesn't bother me in the slightest but I would like to know the formula they used to get to these individual axle limits.
     
  11. John Laidler

    John Laidler Funster

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    Are you concerned on the practicalities of measuring the axle weights because they are close together? Otherwise, in terms of axle loading it makes no difference how far apart they are providing it is symmetrical either side of the centre of the load platform, assuming the load is distributed evenly. Each axle will carry half the load.
     
  12. Steve

    Steve Funster Life Member

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    me thinks that this is one of the questions that makes my head hurt :coffee: i can see your point but i wont ponder on it too long.(y)
     
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  13. pappajohn

    pappajohn Funster Life Member

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    Yes......
    It will only carry half the load if both axles are on the ground.
    If, unlikely yes, it was weighed for each axle then the full load would be imposed on the one axle being weighed which would exceed that axles weight by 100%.
    As I said, I'm not bothered...just confused how it can work.
     
  14. John Laidler

    John Laidler Funster

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    It only works if both axles are at the same level when measured. I don't see it as a problem. Just ensure the gross weight is no more than 750kg. Let the axles share the load. :)
     
  15. pappajohn

    pappajohn Funster Life Member

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    That's my point.
    If just one axle is being weighed the second axle may even be off the ground depending how tall the roadside scales are..it cannot carry any weight if it is so 750kg will be imposed on the axle being weighed increasing its plated limit by 100%.
    In 40 years of driving and towing I've never been stopped and weighed so it doesn't bother me....Just curious.
    I'm technically breaking the law anyway as my car has an unbraked trailer limit of 450kg
     
  16. funflair

    funflair Funster Life Member

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    Tow bar has to be set to the correct height for the axles to share the load and as @DBK says to weight the scale pads must be at the same level as the road.

    Martin
     
  17. pappajohn

    pappajohn Funster Life Member

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    That's the answer I was looking for.
    Makes a lot of sense as the load is then shared between one axle on the scales (375kg) and one on the ground (375kg)
    My towbar ball is within limits, around 390mm and the trailer is level using a 2 mtr spirit level.
    Normally tow with the car unloaded.....that's what the trailers for. ;)
     
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  18. gus-lopez

    gus-lopez Funster

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    that's not your problem.

    The trailer has a max of 750kgs carrying capacity. They just divide that by 2. =375kgs per axle.
    I had a trailer with 1500kg suspension units but with a 750kg capacity .still had 375 per axle.lol
     
  19. grumps147

    grumps147 Funster

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    DVSA weighing codes of practice guidance shows the following which includes reference to compensating axles, hope it helps..

    3.2 Single plate weighbridges
    This equipment comprises a single weighing plate connected to an indicating mechanism. Vehicles are weighed whilst stationary.

    If a single plate weighbridge is to be used for separately weighing axles and bogies or to summate those results to produce the gross/train weight of the vehicle, the weighbridge must have been approved for that purpose by an Inspector of Weights and Measures. The authorised officer must be aware of any particular requirements relating to such use as determined by the Inspector of Weights and Measures.

    Prior to weighing on a single plate weighbridge, care should be taken to ensure that the weighbridge plate is not binding against the surround.

    When weighing on a single plate weighbridge, the following specific requirements must be observed:

    • all of the tyres on the axle(s) being weighed must be wholly on the plate
    • where the whole of the vehicle is not being weighed and the vehicle is fitted with compensating axles, care must be taken to weigh the compensating axles together as one unit
    • where only part of the vehicle is being weighed and:
      • the driver of a vehicle fitted with a manual gearbox must be instructed to comply with the following sequence: the parking brake applied, engine switched off, a low gear engaged and all brakes released
      • the driver of a vehicle fitted with an automatic or semi-automatic gearbox must comply with a similar, suitable and safe sequence
    If a single plate weighbridge has been used to weigh individual axles or bogies or to add up those results to produce the gross/train weight of a vehicle, the accuracy limit is +/- 50 kgs per axle or as specified for that weighbridge by a Inspector of Weights and Measures.

    3.3 Multi-plate weighbridges
    This equipment typically comprises two or more independent static weighing plates connected to a single console. Vehicles are weighed whilst stationary.

    Prior to weighing on a multi-plate, care should be taken to ensure that the weighbridge plates are not binding against the plate housings or other components of the weighing equipment.

    The following specific requirements must also be observed:

    • all of the tyres on the axle(s) being weighed must be wholly on the weighbridge
    • when weighing vehicles fitted with compensating axles, care must be taken to weigh the compensating axles together as one unit on the same plate
    • the driver of a vehicle fitted with a manual gearbox must be instructed to comply with the following sequence: the parking brake applied, engine switched off, a low gear engaged and all brakes released
    • the driver of a vehicle fitted with an automatic or semi-automatic gearbox must comply with a similar, suitable and safe sequence
    The accuracy limit for gross or train weights of a multi-plate weighbridge is +/- 50kg multiplied by the number of plates used for the weighing. Where an axle or group of axles is weighed on the same plate the accuracy limit is +/- 100kg.
     
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