Vehicle loading
Discussion
esselte said:
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?
Nail - head! That's why I asked public/LA because the LA/DOT ones don't normally have ramps but public ones often do.
However - that would tend to give a higher GWt than TotalAxWt, not the other weigh
around.
Surely it is to do with the fulcru, effect, and the weight on each axle will be dependent on how much of the is over the weighbridge at the time.
If you get your ruler and push ittowards and over the edge of the desk, until a certain point it will remain on the desk. Push it too far, and it will fall off, as the overhanging weight is poor than the supported weight.
Wouldn't the same procedure follow on a weigh bridge?
Surely to be accurate the weights front and back should be measured at the same time with the vehicle level and not having been moved?
I know nothing about weighbridges by the way!
If you get your ruler and push ittowards and over the edge of the desk, until a certain point it will remain on the desk. Push it too far, and it will fall off, as the overhanging weight is poor than the supported weight.
Wouldn't the same procedure follow on a weigh bridge?
Surely to be accurate the weights front and back should be measured at the same time with the vehicle level and not having been moved?
I know nothing about weighbridges by the way!
echo said:
There are two possible offences - axle weight overload and vehicle plated weight overload hence the axle readings and the gross weight reading.
Three actually!! - and he's getting done for all three (Front axle overloaded, rear axle overloaded, gross weight overloaded)
echo said:
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?
Cheers, that what I thought. Not sure about the type of weighbridge it was but I think if we can prove that the weights taken at the time are questionable, perhaps the case could be dismissed (wishful thinking maybe)
Cheers for all the inputs guys!!
chrisgr31 said:
Surely it is to do with the fulcru, effect, and the weight on each axle will be dependent on how much of the is over the weighbridge at the time.
If you get your ruler and push ittowards and over the edge of the desk, until a certain point it will remain on the desk. Push it too far, and it will fall off, as the overhanging weight is poor than the supported weight.
Wouldn't the same procedure follow on a weigh bridge?
Surely to be accurate the weights front and back should be measured at the same time with the vehicle level and not having been moved?
I know nothing about weighbridges by the way!
Cheers, yes, the split between front and rear would vary according to the fulcrum, but the sum total of the two should remain constant.
And with regards to your ruler example, yes as the ruler is getting pushed closer to the edge of the desk, the weight over the end of the ruler will increase (as it's getting spread over an area that is getting smaller), but the weight of the ruler (as a force exerted on the desk) will always be the same.
Phew!! never thought Pistonheads and Physics would mix!!
turbo tim said:
And with regards to your ruler example, yes as the ruler is getting pushed closer to the edge of the desk, the weight over the end of the ruler will increase (as it's getting spread over an area that is getting smaller), but the weight of the ruler (as a force exerted on the desk) will always be the same.
Phew!! never thought Pistonheads and Physics would mix!!
With regard to my appallingly badly typed ruler example if you weighed the end left on the desk it would weigh less, in fact when counterbalanced over the end it would in fact be in negative weight as it is seeking to go up!
However if I was weighing both ends of my ruler at the same time the total weight should be the same...... I think!
However in your friends case both ends of the van were not measured at the same time, but were measured seperately hence the different total.
"other weigh around"
ohhhhhh, that's bad!! :groan:
Yes, that's had me stumped too. But as said Eliminator said on page one, regardless of the split the total should be same (within 10Kg's or so)
Anyway, apparently there was no on/off ramp - the weightbridge was level with the ground surrounding it.
The mystery continues.....
ohhhhhh, that's bad!! :groan:
echo said:
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?
Nail - head! That's why I asked public/LA because the LA/DOT ones don't normally have ramps but public ones often do.
However - that would tend to give a higher GWt than TotalAxWt, not the other weigh
Yes, that's had me stumped too. But as said Eliminator said on page one, regardless of the split the total should be same (within 10Kg's or so)
Anyway, apparently there was no on/off ramp - the weightbridge was level with the ground surrounding it.
The mystery continues.....
....but surely when the front wheels are resting (and being weighed) on the weighbridge, the weight/moment of the van is essentially pivoting around the rear wheels?
I take your point about the fact that both ends were't measured at the same time, hence the differing readings (still not sure of the Physics behind this tho) but surely that's the point. I would have thought for these things to be valid and stand up in court, all four wheels should be weighed simulatneously to give the real picture of the weight distribution over the four wheels/two axles??
I take your point about the fact that both ends were't measured at the same time, hence the differing readings (still not sure of the Physics behind this tho) but surely that's the point. I would have thought for these things to be valid and stand up in court, all four wheels should be weighed simulatneously to give the real picture of the weight distribution over the four wheels/two axles??
turbo tim said:
I take your point about the fact that both ends were't measured at the same time, hence the differing readings (still not sure of the Physics behind this tho) but surely that's the point. I would have thought for these things to be valid and stand up in court, all four wheels should be weighed simulatneously to give the real picture of the weight distribution over the four wheels/two axles??
Don't ask me about the physics either but I suggest carrying out some experiments with something lighter which I have just tried with my stationery holder and the postal scales. Definitely the weight chages as the fulcrum moves!
However as you say to be accurate all the measurements should be taken at the same time. I believe for racing cars they place weights under each wheel at the same time. You can then add up the weight in any combination you like.
IMHO Chrisgr31 hits the nail on the head. The axle weights will be affected as to the manner the vehicle is loaded. All on the tail end rear axle sinks down front axle lifts so shows less weight and vice versa.
Look at the Manufacturers/Ministry plate. This will show the axle weights not to be exceeded also the gross vehicle weight not to be exceeded. Add the first two together. Are they they same as the gross weight? IIRC no.
Used to be overload shown in percentage. Under 5 warning and get it sorted asp. 5 to 10 warning and no movement until sorted.Ten and over prosecution.
Weighbridge should have a certificate of accuracy by Trading Standards.
dvd
Look at the Manufacturers/Ministry plate. This will show the axle weights not to be exceeded also the gross vehicle weight not to be exceeded. Add the first two together. Are they they same as the gross weight? IIRC no.
Used to be overload shown in percentage. Under 5 warning and get it sorted asp. 5 to 10 warning and no movement until sorted.Ten and over prosecution.
Weighbridge should have a certificate of accuracy by Trading Standards.
dvd
Dwight VanDriver said:
IMHO Chrisgr31 hits the nail on the head.
I agree completely. and his stationery holder and the postal scales experiments are quality
(Chrisgr31: Just picturing those around you in your office wondering what the hell you were up to 
) And the analogy with the racing car example is spot on too, which is what I'm trying to say (not very well obviously) - if the weighing of the van had been done in this manner (i.e. all four wheels being measureed seperately, but at the same time) the Plod would have had a different result, and surely that's not fair!!
Dwight VanDriver said:
Look at the Manufacturers/Ministry plate. This will show the axle weights not to be exceeded also the gross vehicle weight not to be exceeded. Add the first two together. Are they they same as the gross weight? IIRC no.
Again DvD, you speak the truth! The sum of the plated/permissable weights for each axle don't (and shouldn't) add up to the permissable maximum Gross weight (this presumably to allow for slightly uneven loading).......
.....but the actual measured weights should!!
No??
I think there's some iffy physics being proffered here.
I would guess that the issue relates to the way the weighbridge works.
However the force is measured in the weighbride, there must be some kind of guide system. The guides prevent one end lifting if all of the load is concetrated at the other end, but still allow the surface to move freely up and down.
If the load is concentrated at one end, the guide system will exert some of the reaction forces. It is unlikely that these reaction forces are measured in the bridge.
If the total measured weight is less than the total of the axle weights, then it's likely that the operator of the weighbridge has added a "fiddle factor" to compensate for the forces lost to the guide system. Shame on him for not adding the forces up, and checking.
Another possibility is that the computer has different modes of operation, for uneven loads, and automatically, but erroneously, compensates.
I reckon that the total weight is probably accurate. I can't see why the total of the axle weights would be more than the total weight. It should be less.
>> Edited by dilbert on Tuesday 4th October 18:38
I would guess that the issue relates to the way the weighbridge works.
However the force is measured in the weighbride, there must be some kind of guide system. The guides prevent one end lifting if all of the load is concetrated at the other end, but still allow the surface to move freely up and down.
If the load is concentrated at one end, the guide system will exert some of the reaction forces. It is unlikely that these reaction forces are measured in the bridge.
If the total measured weight is less than the total of the axle weights, then it's likely that the operator of the weighbridge has added a "fiddle factor" to compensate for the forces lost to the guide system. Shame on him for not adding the forces up, and checking.
Another possibility is that the computer has different modes of operation, for uneven loads, and automatically, but erroneously, compensates.
I reckon that the total weight is probably accurate. I can't see why the total of the axle weights would be more than the total weight. It should be less.
>> Edited by dilbert on Tuesday 4th October 18:38
chrisgr31 said:
The mystery continues.....
No! No mystery. The answer is that when the heavier end was weighed more of the van was over the fulcrum point. When the lighter end weighed vice versa. The fulcrum point was not constant, and therefore the total weights don't add up.
Nope, the ruler example is completely irrelevant because the fulcrum point changes with respect to the ends of the ruler. With a vehicle, the fulcrum points are at the wheels, and the distance between them and the ends of the vehicle cannot change. As long as one pair of wheels is off the weighbridge (and, crucialy, the weighbridge and surrounding area are level) the sum of the axle weights should = the gross vehicle weight.
The only way in which I can think that the individual axle weights are heavier, is if the weighbridge has ramps leading down to it at both ends. This would transfer more weight to whichever axle was on the weighbridge. I guess it's also possible that the weighbridge is broken/out of calibration and has a scaling error, i.e. the axle weights might have been in the right ballpark, but it reads low with increasing weight making the gross weight low.
In either case, it would seem there is reasonable doubt that the measurements were made accurately.
MR2Mike said:
Nope, the ruler example is completely irrelevant because the fulcrum point changes with respect to the ends of the ruler. With a vehicle, the fulcrum points are at the wheels, and the distance between them and the ends of the vehicle cannot change. As long as one pair of wheels is off the weighbridge (and, crucialy, the weighbridge and surrounding area are level) the sum of the axle weights should = the gross vehicle weight.
The only way in which I can think that the individual axle weights are heavier, is if the weighbridge has ramps leading down to it at both ends. This would transfer more weight to whichever axle was on the weighbridge. I guess it's also possible that the weighbridge is broken/out of calibration and has a scaling error, i.e. the axle weights might have been in the right ballpark, but it reads low with increasing weight making the gross weight low.
In either case, it would seem there is reasonable doubt that the measurements were made accurately.
Home now and been carrying out more experiments!
Using kitche scales, two cassette boxes and a book! Each cassette case weighs 24 grammes and the book weighs 602 grammes giving a total weight of 652 grammes. (Sorry for the delay wife wanted to know what I was upto!
) Place one cassette box upright at the far right of scales and the other on a book at the same level. Place book on top and you have a weight reading of 340 grammes, move to the centre of the scales and you have a weight of 342 grammes, so fairly modest difference, placing fully on the scales gives 652 grammes.
Now on a vehicle the wheels are not at either end of the vehicle and may be offset by unequal distances so leaving one support at the end of the book, and moving the other in by 1 1/2 inches the weight readins are 240grammes on axle at end and 444 on the inset axle.
Experiments trying to recreate a slope were unsuccessful as the weight of the book toppled the cassette boxes over!
Not sure what all this proves though!
>> Edited by chrisgr31 on Tuesday 4th October 20:19
turbo tim said:Which Magistrates' Court is it listed before?
Got a friend who has recieved a summons to go before for overloading a van.
I try to avoid traffic law as much as possible and have only defended a few cases like this.
But a friend of mine is a Crown Prosecutor and is rather an expert on commercial traffic law.
If you let me have a copy of the summons, the relevant weights and whether your hapless mate was driving as an employee or on his own account and whether the load was commercial, or just a domestic journey, then I can have a chat with my tame prosecutor and give you some idea whether your mate is:
i: Stuffed
and
ii: What he might be looking at in terms of a penalty.
Cheers
Pat
MR2Mike said:
With a vehicle, the fulcrum points are at the wheels, and the distance between them and the ends of the vehicle cannot change. As long as one pair of wheels is off the weighbridge (and, crucialy, the weighbridge and surrounding area are level) the sum of the axle weights should = the gross vehicle weight.
The only way in which I can think that the individual axle weights are heavier, is if the weighbridge has ramps leading down to it at both ends. This would transfer more weight to whichever axle was on the weighbridge. I guess it's also possible that the weighbridge is broken/out of calibration and has a scaling error, i.e. the axle weights might have been in the right ballpark, but it reads low with increasing weight making the gross weight low.
In either case, it would seem there is reasonable doubt that the measurements were made accurately.
Thank you MR2MIKE - everything you said is what I've been thinking for the last few days!! (thought I was going crazy) And the bit about the 'ramps leading down' explaining the discrepancy makes sense too (the same theory echo touched on a few posts ago), but the weighbridge and surrounding ground in this instance was completely level.
Anyone know any good Lawyers that would like a shot a this case???
PatHeald said:
Got a friend who has recieved a summons to go before
Which Magistrates' Court is it listed before?
I try to avoid traffic law as much as possible and have only defended a few cases like this.
But a friend of mine is a Crown Prosecutor and is rather an expert on commercial traffic law.
If you let me have a copy of the summons, the relevant weights and whether your hapless mate was driving as an employee or on his own account and whether the load was commercial, or just a domestic journey, then I can have a chat with my tame prosecutor and give you some idea whether your mate is:
i: Stuffed
and
ii: What he might be looking at in terms of a penalty.
Cheers
Pat
YAATHM
(You Are About To Have Mail)
Cheers
chrisgr31 said:
MR2Mike said:
Nope, the ruler example is completely irrelevant because the fulcrum point changes with respect to the ends of the ruler. With a vehicle, the fulcrum points are at the wheels, and the distance between them and the ends of the vehicle cannot change. As long as one pair of wheels is off the weighbridge (and, crucialy, the weighbridge and surrounding area are level) the sum of the axle weights should = the gross vehicle weight.
The only way in which I can think that the individual axle weights are heavier, is if the weighbridge has ramps leading down to it at both ends. This would transfer more weight to whichever axle was on the weighbridge. I guess it's also possible that the weighbridge is broken/out of calibration and has a scaling error, i.e. the axle weights might have been in the right ballpark, but it reads low with increasing weight making the gross weight low.
In either case, it would seem there is reasonable doubt that the measurements were made accurately.
Home now and been carrying out more experiments!
Using kitche scales, two cassette boxes and a book! Each cassette case weighs 24 grammes and the book weighs 602 grammes giving a total weight of 652 grammes. (Sorry for the delay wife wanted to know what I was upto!
Place one cassette box upright at the far right of scales and the other on a book at the same level. Place book on top and you have a weight reading of 340 grammes, move to the centre of the scales and you have a weight of 342 grammes, so fairly modest difference, placing fully on the scales gives 652 grammes.
Now on a vehicle the wheels are not at either end of the vehicle and may be offset by unequal distances so leaving one support at the end of the book, and moving the other in by 1 1/2 inches the weight readins are 240grammes on axle at end and 444 on the inset axle.
Experiments trying to recreate a slope were unsuccessful as the weight of the book toppled the cassette boxes over!
Not sure what all this proves though!
>> Edited by chrisgr31 on Tuesday 4th October 20:19
I have an explanation!
I think I've figured out what's going on here. It may not be a case of "fiddle factor", as I previously stated.
There was nothing wrong with my physics, but there could have been a problem with my assumption about how the weighbridge works.
The problem is definately the rotating force of the unevenly loaded weighbridge. If the weighbridge has a stop at each end to prevent the surface from lifting, then the surface of the weighbridge can act as a lever.
Edited to add;
Seems PH destroys alpha diagrams. Ahh well.
Further edited to add;
So:
>> Edited by dilbert on Tuesday 4th October 21:29
PatHeald said:
If you let me have a copy of the summons, the relevant weights and whether your hapless mate was driving as an employee or on his own account and whether the load was commercial, or just a domestic journey, then I can have a chat with my tame prosecutor and give you some idea whether your mate is:
i: Stuffed
and
ii: What he might be looking at in terms of a penalty.
Cheers
Pat
YHM
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