There is a weighbridge on the A23 that weighs a single axle at a time then adds the axle weights up to give you a gross weight. Surely this is wrong.
I took a 7.5t up there last week. On paper at the depot I weighed 7.4T, but when I weighed it on the bridge it was 500kg overweight. The front axle and rear axle weighed within the plated limits for each axle, but when it added the two axles together it showed over.
Trouble is you can’t get an accurate weight by simply adding two axles together. If I added an extra tonne to the rear axle some of that weight would be transferred to the front axle. It’s like if I weighed myself by placing one foot on the scales at a time then adding the two weights together I would weigh 20 stone! Which I don’t … yet
I also took an empty 18T on the same weighbridge today and it showed a gross weight of 12T, but when I’ve weighed it before on a full weighbridge that weighs all axles at once it weighed in at 10T … the plated rating.
So surely VOSA cant use the combined axle weights to fine you. I’m hoping that as long as axle weights are ok then there is no problem. But surely that means the gross weight reading is useless on these single axle weigh bridges.
I’m not sure I understand, if you stood on two sets of bathroom scales, one foot on each, the combined total weight would be exactly the same as if you stood on one set with both feet.
And also you can be within limits on every axle but still be over your MGW, this is to allow leeway on your axle weights.
Squiddy:
There is a weighbridge on the A23 that weighs a single axle at a time then adds the axle weights up to give you a gross weight. Surely this is wrong.
I took a 7.5t up there last week. On paper at the depot I weighed 7.4T, but when I weighed it on the bridge it was 500kg overweight. The front axle and rear axle weighed within the plated limits for each axle, but when it added the two axles together it showed over.
Trouble is you can’t get an accurate weight by simply adding two axles together. If I added an extra tonne to the rear axle some of that weight would be transferred to the front axle. It’s like if I weighed myself by placing one foot on the scales at a time then adding the two weights together I would weigh 20 stone! Which I don’t … yet
I also took an empty 18T on the same weighbridge today and it showed a gross weight of 12T, but when I’ve weighed it before on a full weighbridge that weighs all axles at once it weighed in at 10T … the plated rating.
So surely VOSA cant use the combined axle weights to fine you. I’m hoping that as long as axle weights are ok then there is no problem. But surely that means the gross weight reading is useless on these single axle weigh bridges.
Either you braked or drove too fast or you were driving a tanker, as harry said, get two sets of identical scales and weigh each foot.
The dynamic axle weigher is more accurate than a plate bridge
No, if I stood with one leg on the bathroom scales and one leg on a book (same height as the bathroom scales) then I weigh 10 stone. And I don’t weigh 20 stone!.
Same with my two axles. When I weigh the front axle some of the weight from the rear axle is transferred to the front and vica versa.
And looking at the plate on the 7.5T I was driving, if you add the max permissible weight for front and rear axle together it comes to much more that 7.5T. Cant remember the exact weight, but it was about 10-11 T or the train weight.
Squiddy:
No, if I stood with one leg on the bathroom scales and one leg on a book (same height as the bathroom scales) then I weigh 10 stone. And I don’t weigh 20 stone!.
Same with my two axles. When I weigh the front axle some of the weight from the rear axle is transferred to the front and vica versa.
And looking at the plate on the 7.5T I was driving, if you add the max permissible weight for front and rear axle together it comes to much more that 7.5T. Cant remember the exact weight, but it was about 10-11 T or the train weight.
Ok, weigh yourself with one foot on a book and the other on a scales then swap add them together and then weigh yourself with both feet on one scale, it might be slightly out as your body wont be stood in the same stance both times, a lorry will stay in the same position each time unless it has a liquid on board.
Some how I dont think the goverment would let VOSA use them weigh in motion sensors if they were not accurate
Squiddy:
No, if I stood with one leg on the bathroom scales and one leg on a book (same height as the bathroom scales) then I weigh 10 stone. And I don’t weigh 20 stone!.
Only if you are subconsciously placing more of your weight on the scales than on the book.
Squiddy:
And looking at the plate on the 7.5T I was driving, if you add the max permissible weight for front and rear axle together it comes to much more that 7.5T. Cant remember the exact weight, but it was about 10-11 T or the train weight.
Yes, that’s right. If your MGW was the same as the combined total of your plated axle weights then it would be almost impossible to load to your MGW without being overweight on one or other axle, so there is tolerance built into your axle weights to allow for front-heavy or rear-heavy loads.
Squiddy:
Trouble is you can’t get an accurate weight by simply adding two axles together. If I added an extra tonne to the rear axle some of that weight would be transferred to the front axle. It’s like if I weighed myself by placing one foot on the scales at a time then adding the two weights together I would weigh 20 stone! Which I don’t … yet
Yes, you do get an accurate weight by weighing each of two axles separately and adding them together.
The fault in your logic is that each of your feet carries your whole weight when the other is off the ground.
There can be a problem with compensating axles, such as on a six wheeler or a tri-axle trailer but this is solved by driving the vehicle over the weigh plate at a steady 2.5 mph and on a flat surface when no compensation takes place.
When dynamic weighbridges were first introduced, I worked for John Forman’s in Hull.
We did have a problem to start with when the men from the ministry weighed the vehicle too soon after it was stopped and the load was still moving inside the tank.
In that case, some of the load was indeed weighed twice but once they realised what was going on,an allowance was made and no one was ever prosecuted.
It didn’t do any harm that we all carried a record of the weight at the weighbridge in Hull either.
I’m not trying to be obtuse, but surely when weighing the front axle some of the rear axle weight is transferred to the the front axle and vica versa.
Like I said, I weighed one of our 18 tonners on a full weighbridge and it weighed in as 10T empty. The same as it says on the plate. But when I weighed it empty on a single axle weigh bridge it’s gross weight was over 10T (baffled smiley)
Adding the weight’s together for all axles is the way most VOSA sites operate using a single axle weighbridge and this is perfectly normal and the right way to do it, also all VOSA sites are calibrated on a regular basis as proof of calibration has to be provided for any prosecution.
I know the one at the top of Handcross Hill on the A23 and have been stopped there myself, there is also one on the A21 at John’s Cross just North of Hastings.
I often used the axle weighbridge in Tilbury Docks at the Finn Forest shed if I thought I was getting close to maximum weight and that would produce a printout showing each axle weight and also the total. Whenever I compared this with other weighbridges at the delivery point there was rarely any big difference.
Never trust the paperwork when working out your weight, I found that it was often wrong and usually the wrong way!!
A difference of 2t that you found between the 2 types of weighbridge has to be a calibration or operator error.
Squiddy:
Trouble is you can’t get an accurate weight by simply adding two axles together. If I added an extra tonne to the rear axle some of that weight would be transferred to the front axle. It’s like if I weighed myself by placing one foot on the scales at a time then adding the two weights together I would weigh 20 stone! Which I don’t … yet
Yes, you do get an accurate weight by weighing each of two axles separately and adding them together.
The fault in your logic is that each of your feet carries your whole weight when the other is off the ground.
There can be a problem with compensating axles, such as on a six wheeler or a tri-axle trailer but this is solved by driving the vehicle over the weigh plate at a steady 2.5 mph and on a flat surface when no compensation takes place.
When dynamic weighbridges were first introduced, I worked for John Forman’s in Hull.
We did have a problem to start with when the men from the ministry weighed the vehicle too soon after it was stopped and the load was still moving inside the tank.
In that case, some of the load was indeed weighed twice but once they realised what was going on,an allowance was made and no one was ever prosecuted.
It didn’t do any harm that we all carried a record of the weight at the weighbridge in Hull either.
Regards,
Nick
Nick, with a tanker they are obliged to let it settle for 15 minutes before weighing, as a tanker man you will know it settles quicker though if you don’t put the handbrake on!
Squiddy:
Like I said, I weighed one of our 18 tonners on a full weighbridge and it weighed in as 10T empty. The same as it says on the plate. But when I weighed it empty on a single axle weigh bridge it’s gross weight was over 10T (baffled smiley)
By how much? It shouldn’t do this, are you sure you did not have more fuel on board when you weighed it on the dynamic weighbridge, or that maybe you were not in the cab when you weighed it on the plate weighbridge?
Possibly Mr Monk… there has been a long running dispute between trunkers and transport managers over this. I thought I had it all right when I posted this, but to be honest it does look like I am wrong here.
Seems like our TM’s are encourgaging us to use overweight 7.5T just to save on fuel when an 18 or 26T is needed.
Trouble is, it is the driver who gets in trouble when the TM says ‘oh that will be ok, dont worry about it’
Squiddy:
I’m not trying to be obtuse, but surely when weighing the front axle some of the rear axle weight is transferred to the the front axle and vica versa.
Hi Squiddy,
When you weigh on a dynamic axle weigher, the weight recorded for the front axle is the weight of the front axle itself, plus all load imposed upon it. The same goes for the rear axle.
Adding the two weights together must give the gross weight of the vehicle.
If you think about it, nothing can “transfer” during this process.
