This unit’s axle weights combined is higher that it’s Gross Weight (7500 + 7500 + 11500 = 26500 > 24000). This is because the weight can be unevenly distributed accross the unit’s axles.
The trailer’s Plate (VTG6T)
A lifting deck double decker (nearly but not empty)
This trailes axle weights and pin weight combined is equal to the pin weight (8000 + 8000 + 8000 + 15000 = 39000).
With this combination
you cannot load the trailer to it’s Gross Weight because you would exceed the unit’s Train Weight. (Unit weight of 8150 + Trailer Gross Weight of 39000 = 47150 > 44000 Train Weight).
you can exceed the pin weight and not exceed the unit’s Gross Weight (Unit Gross Weight of 24000 - Unit weight of 8150 = 15850 > 15000 Pin Weight).
you cannot exceed the pin weight if the combination weight is 44000 or less and the trailer axles combined are more than 20850 (Train Weight of 44000 - Pin Weight of 15000 - Unit weight of 8150 = 20850 for the combined trailer axles).
Excellent post Cuttlefish, clear diagrams showing what sort of imposed axle weights look like.
Thanks for taking the trouble.
In a perfect world i’d have wanted more weight imposed on the tractor unit, i like to see that drive axle weighing around the 10 ton mark when fully freighted, if i load the product i can generally get the weight distribution how i want it, but for many drivers on different work that’s not always possible…the reason for more weight forward is overall stability (dog wagging the tail) and drive axle grip.
My weights would be different to yours empty, empty with mid lift raised the tractor unit (with trailer connected) runs steer axle 6100 drive axle 4400 and all 3 trailer axles around the 1680kgs mark.
Loaded usually around 6200 steer, 4700 (small mid lift), 9900 drive, and all three trailer axles around the 7500 mark for a GVW of 43300.
It might be interesting to see if you could get a little more weight onto the drive axle by moving the fifth wheel back a couple of clicks, doesn’t always work how you think it might though, moving back can also increase the mid lift weight whilst not doing anything for the drive axle, doesn’t sound right does it but that’s sometimes how these things result in practice, mid lifts are funny things sometimes to get absolutely right…edit see Dan is thinking along the same lines.
In the example weighed the Unit GVW is only 19200 while the trailer bogie is only 250 kg under its maximum allowable 24000. At 8070 drive axle weight laden it might be possible to raise the 2nd axle and still move at highway speed . If so it would be interesting to see what the drive and steer then weigh along with any difference to the trailer bogie weights. My assumption with this loaded example is that the trailer bogie would then be overloaded if the ride height of the unit alters.
With 7500 axle weights for the first two axles I don’t see tyre ply rating being the reason for such a low plated GVW for the unit when its design weight is 25000. This might be worth querying.
Punchy Dan:
The 5 th wheel looks too far forward / drive axle weight not enough may spin a bit .
Juddian:
In a perfect world i’d have wanted more weight imposed on the tractor unit
Yes, traction control and stability control dash warnings pulling away on small inclines in the damp. Press the weight transfer button when you stop at the traffic lights.
Juddian:
if i load the product i can generally get the weight distribution how i want it, but for many drivers on different work that’s not always possible
It was a preloaded shop delivery. Not the best loaded, certainly not the worst.
cav551:
At 8070 drive axle weight laden it might be possible to raise the 2nd axle and still move at highway speed . If so it would be interesting to see what the drive and steer then weigh along with any difference to the trailer bogie weights. My assumption with this loaded example is that the trailer bogie would then be overloaded if the ride height of the unit alters.
I am almost certain it would not lift (except weight transfer). I also would think the rear trailer axle would be overloaded. I will try if I get the chance.
cav551:
In the example weighed the Unit GVW is only 19200 while the trailer bogie is only 250 kg under its maximum allowable 24000.
Juddian:
Am i looking at something different to you, far as i can see the tractors plated at 24t for UK, where’s the 19t you refer to?
Juddian:
Cav.
Am i looking at something different to you, far as i can see the tractors plated at 24t for UK, where’s the 19t you refer to?
I am looking at the actual GVW of the unit for the example loaded trailer. Addition of recorded axle weights. The load is biased towards the rear of the trailer. The weight imposed by the kingpin is only 11050.
Juddian:
Cav.
Am i looking at something different to you, far as i can see the tractors plated at 24t for UK, where’s the 19t you refer to?
I am looking at the actual GVW of the unit for the example loaded trailer. Addition of recorded axle weights. The load is biased towards the rear of the trailer. The weight imposed by the kingpin is only 11050.
I still can’t bloody see it, have to get some better readers at this rate
As for the rear trailer axle being heavier, on almost all of the tanks i pull despite the front of the tank being appreciably higher than the rear end, its almost always the front trailer axle that is heavier than the other two when loaded (little difference if any when empty, tractor unit is slightly higher with mid lift raised), always puzzled me why its the front axle heavier, presumably set up in this way at the factory.
Anecdotally going back to steel springs, when the weights went from 32 to 38t, my boss of the time like many others had a number of trailers stretched and a third axle slotted in front of the existing tandem, one particulat tipper trailer was shorter than the others with the rear overhang of the two previous axles already quite far forward, it certainly looked odd when converted with suc h a long rear overhang on a tipper trailer.
Rear axle tyres always looked under pressure when loaded, until one day i happened to use an axle weigher at a modern farm, short trailer meant even with wheat the body was nearly full all the way along, trailer rear axle at legal GVW weighed off at 12 tons , no way could you possibly load far enough forward to make it work so trailer immediately off the road and converted to fluidride, which was fine except the thing now weighed so ■■■■ much it couldn’t carry any more than it did at 32t.
cav551:
The load is biased towards the rear of the trailer.
It was a sloped front lifting deck double deck. The upper deck is only 2/3(?) of the length and at the rear so the neck has only one layer. They do load the heaviest stock on the neck but the load is not uniform.
Juddian:
Cav.
Am i looking at something different to you, far as i can see the tractors plated at 24t for UK, where’s the 19t you refer to?
I am looking at the actual GVW of the unit for the example loaded trailer. Addition of recorded axle weights. The load is biased towards the rear of the trailer. The weight imposed by the kingpin is only 11050.
I still can’t bloody see it, have to get some better readers at this rate [emoji38]
As for the rear trailer axle being heavier, on almost all of the tanks i pull despite the front of the tank being appreciably higher than the rear end, its almost always the front trailer axle that is heavier than the other two when loaded (little difference if any when empty, tractor unit is slightly higher with mid lift raised), always puzzled me why its the front axle heavier, presumably set up in this way at the factory.
Anecdotally going back to steel springs, when the weights went from 32 to 38t, my boss of the time like many others had a number of trailers stretched and a third axle slotted in front of the existing tandem, one particulat tipper trailer was shorter than the others with the rear overhang of the two previous axles already quite far forward, it certainly looked odd when converted with suc h a long rear overhang on a tipper trailer.
Rear axle tyres always looked under pressure when loaded, until one day i happened to use an axle weigher at a modern farm, short trailer meant even with wheat the body was nearly full all the way along, trailer rear axle at legal GVW weighed off at 12 tons , no way could you possibly load far enough forward to make it work so trailer immediately off the road and converted to fluidride, which was fine except the thing now weighed so ■■■■ much it couldn’t carry any more than it did at 32t.
When taking moments one should remember the formula applies “to Rigid systems”. When springs are involved things get trickier.
Assuming the OP’s trailer is an air suspension tri axle, with no electronic method of inflating the axles separately, and all the air bags/springs are equal, then moving the C of G of the load won’t make much difference to the individual axle weights. (Within limits!)
That is one of the reasons air bogies are used after all.
Moving the load will affect the bogey loading but it should be automatically be balanced between the 3 axles, and looking at the figures provided, that looks true to me.
Same principle applies to altering the 5th wheel height, again within limits.
cav551:
At 8070 drive axle weight laden it might be possible to raise the 2nd axle and still move at highway speed . If so it would be interesting to see what the drive and steer then weigh along with any difference to the trailer bogie weights. My assumption with this loaded example is that the trailer bogie would then be overloaded if the ride height of the unit alters.
I am almost certain it would not lift (except weight transfer). I also would think the rear trailer axle would be overloaded. I will try if I get the chance.
Looking at the figures again I think you are probably correct. The unit would still weigh IRO 19t so would be grossing more than the permitted 18t on two axles. Around one tonne less imposed though may probably allow the second axle to stay up.
The object of 44t on 6 axles is to reduce axle weights.
25t on the unit would be silly pin weight as opposed to around 20-22t on the unit and around 7.5-8t on each trailer axle.
20-22t on the unit still means 10.5t on the drive ( hopefully ) .
So 22 t gross on the unit, 10.5 of that on the drive, leaves 11.5 shared between the mid/tag and steer.
Leaves 7.3t on each trailer axle.
7.9t on each trailer axle obviously leaves 20.3t on the unit which obviously means even less drive axle weight.
Either way the traction flaw in the 6x2 44 tonner is obvious.
As opposed to two drive axles loaded to 8t each at 22t, or 7.15 each at 20.3t gross.
cav551:
With 7500 axle weights for the first two axles I don’t see tyre ply rating being the reason for such a low plated GVW for the unit when its design weight is 25000. This might be worth querying.
Having had another look at the regs I think this 24t GVW for the unit is because of the outer axle spread.
, no way could you possibly load far enough forward to make it work so trailer immediately off the road and converted to fluidride, which was fine except the thing now weighed so ■■■■ much it couldn’t carry any more than it did at 32t.