Vehicle loading

[turbo tim]

Got a friend who has recieved a summons to go before :judge: for overloading a van. I've had a look at the sheet that listed all the weights at the time of the alleged offence (Front axle, Rear axle, Gross weight) and what doesn't seem to make sense to me is that the 'weight on the Front axle' + 'weight on the rear axle' doesn't equal the Gross weight
:confused:

Casting my mind back to my Uni days when we learnt about Static Equilibrium - one of the basic principles of this states that the weight of any object will be shared across it's supports (i.e. when stationary, a persons weight will be shared across their two feet, and the sum total of the weight on the left foot and the weight on the right foot should equal the persons weight). I was under the impression that the same should apply to motor vehicles i.e. the weight on the front axle plus the weight on the rear axle should be equal to the total weight of the vehicle.

Can anyone shed some light on this?

[2 Smokin Barrels]

It is usual for the gross axle weights to sum up to more than the GVW. This is to allow for differing load distribution etc.

[2 Smokin Barrels]

..it also builds some tolerance in the vehicle.

The principle of load distribution can be tricky, it depends on overhangs etc. Imagine a truck with say four feet of load space behind the back axle. A load on here makes the load on the front axle less.

[2 Smokin Barrels]

..so this gives more potential to break the law! e.g. overall load within law, but one axle overloaded.

..most common offence though is to overload a vehicle, particularly vans where in general the cubic space is sufficiently large to make overloading easy

[2 Smokin Barrels]

..but if you're lucky somebody might come along who knows what they're talking about!

[rich 36]

>> Edited by rich 36 on Monday 3rd October 22:04

[turbo tim]

2 Smokin Barrels said:

..most common offence though is to overload a vehicle, particularly vans where in general the cubic space is sufficiently large to make overloading easy

Yup, sounds about right!!!

2 Smokin Barrels said:

Imagine a truck with say four feet of load space behind the back axle. A load on here makes the load on the front axle less.

Sure, that makes sense.............but even in this instance, surely the sum total of the weights of both axles equals the weight of the vehicle (or am I being stupid?) It is getting late.....

[2 Smokin Barrels]

Nope. Don't forget the weights quoted are the permissable weight on each axle, but not necessarily at the same time!

[2 Smokin Barrels]

rich 36 said:

>> Edited by rich 36 on Monday 3rd October 22:04

As soon as I saw your name Rich I knew what was coming!

[2 Smokin Barrels]

...anyway, trust me, it is usual for the combined axle weights of commercial vehicles to add up to more than the rated GVW.

[rich 36]

Tyre looks a bit flat on that flatbed,
were you still sat in it at the time?

[2 Smokin Barrels]

rich 36 said:

Tyre looks a bit flat on that flatbed, were you still sat in it at the time?

..no, but girlfriend was in boot..only place to keep her quiet!

[turbo tim]

2 Smokin Barrels said:

Nope. Don't forget the weights quoted are the permissable weight on each axle, but not necessarily at the same time!

Again, this makes sense......but......

(Sorry, don’t think I’ve described the situ that well - thanks for bearing with me)

Yes, understand that the plated weights of each axle may not necesarrily add up to the plated gross vehicle weight (to allow for varying weight distribution), but surely the actual weights should add up?

2 Smokin Barrels said:

If you're lucky Towman will come along & talk sense!

Towman, are you out there??

[echo]

turbo tim said:

Got a friend who has recieved a summons to go before for overloading a van. I've had a look at the sheet that listed all the weights at the time of the alleged offence (Front axle, Rear axle, Gross weight) and what doesn't seem to make sense to me is that the 'weight on the Front axle' + 'weight on the rear axle' doesn't equal the Gross weight Casting my mind back to my Uni days when we learnt about Static Equilibrium - one of the basic principles of this states that the weight of any object will be shared across it's supports (i.e. when stationary, a persons weight will be shared across their two feet, and the sum total of the weight on the left foot and the weight on the right foot should equal the persons weight). I was under the impression that the same should apply to motor vehicles i.e. the weight on the front axle plus the weight on the rear axle should be equal to the total weight of the vehicle. Can anyone shed some light on this?

How did they weigh the vehicle? You are of course correct that the total weight of the axles should be the same as the vehicle weight but could the load have moved between axle weighings - or did he/she get out?

Need to know how they were weighed and what the figures were

[turbo tim]

echo said:

turbo tim said: Got a friend who has recieved a summons to go before for overloading a van. I've had a look at the sheet that listed all the weights at the time of the alleged offence (Front axle, Rear axle, Gross weight) and what doesn't seem to make sense to me is that the 'weight on the Front axle' + 'weight on the rear axle' doesn't equal the Gross weight Casting my mind back to my Uni days when we learnt about Static Equilibrium - one of the basic principles of this states that the weight of any object will be shared across it's supports (i.e. when stationary, a persons weight will be shared across their two feet, and the sum total of the weight on the left foot and the weight on the right foot should equal the persons weight). I was under the impression that the same should apply to motor vehicles i.e. the weight on the front axle plus the weight on the rear axle should be equal to the total weight of the vehicle. Can anyone shed some light on this? How did they weigh the vehicle? You are of course correct that the total weight of the axles should be the same as the vehicle weight but could the load have moved between axle weighings - or did he/she get out? Need to know how they were weighed and what the figures were

Cheers echo - I'll find out and post it up......

[turbo tim]

Right, apparently the events went as follows (figures estimated as he didn’t have the figures to hand, but I’ve been assured they’re about right)

Van parked with all wheels on weigh bridge – 2300kg
Van then reversed so that just front wheels left on weigh bridge – 1200kg
Van then driven forwards so that just rear wheels on weigh bridge – 1400kg

No cargo moved, and driver stayed in place between weighings.

(1) Is this the correct procedure, and
(2) do these results seem valid? (I would have expected front + rear to equal total)

[echo]

turbo tim said:

Right, apparently the events went as follows (figures estimated as he didn’t have the figures to hand, but I’ve been assured they’re about right) Van parked with all wheels on weigh bridge – 2300kg Van then reversed so that just front wheels left on weigh bridge – 1200kg Van then driven forwards so that just rear wheels on weigh bridge – 1400kg No cargo moved, and driver stayed in place between weighings. (1) Is this the correct procedure, and (2) do these results seem valid? (I would have expected front + rear to equal total)

There are two possible offences - axle weight overload and vehicle plated weight overload hence the axle readings and the gross weight reading.

It does sound a little odd to have 300Kg 'missing' as the bridge should be accurate to a few 10's of Kg.
It would suggest to me that the weighbridge is not accurate at that weight.

Was it a public weighbridge or a local authority or DOT one? Which one was it?

[esselte]

Was there an on/off ramp to the weigh bridge?Would it make a difference if the van wasn't level when the axle weights were being done singly?

[Eliminator]

Tim

Your understanding of physics seems to me to be correct. Using the method that you have outlined, if the rear axle weight is 10 and the front axel weight is 8 then the total weight of the vehicle is 18 - neither more nor less. If the sum does not add to the total weight of the vehicle then one (at least) of the measurements is incorrect. If it is not possible to tell which, does this get you "out of jail free"?