Is it possible to overload an artic on the front axle on the tractor unit? If it is, can someone explain how it is done. Personally I cannot see how any weight put on the trailer would have any bearing on the steering axle.
The reason I ask is that we have had some new double deckers at work, and one of the other drivers was saying that the warehouse have to be careful how they load them so as not to put the front axle overweight. I said don’t you mean the drive axle? (Our entire fleet are 6x2), but he was adamant it was the steering axle.
I don’t mind being proved wrong if someone explains how.
I suppose if you have the 5th wheel far enough forward and the trailer is quite large there is a possibility that some weight may get transferred to the steer, but not enough to overload it.
Overloading steer axles is common for rigids, not artics. Like you said you can end up overloading the drive axle (especially on four wheelers) but not the steer from what I’ve seen.
I put 15 tonne on my front axle yesterday but it wasn’t on the headboard. The weight(I’ve been told/taught) should start in between your wheels on the unit. And if I can bang 15t there and 12t over my rear I just can’t see how a d/d could ever be over loaded on a 6x2.
I’m still learning to be fair but I was surprised after working with so many blokes who have only ever done pallets that told me this and that was over weight on the front axle.
The front axles are plated 7500kilos, and whenever I’ve gone over an axle weigher the weight is normally 7000-7100 kilos. And the fifth wheels sit just inbetween the midlift and drive axle.
I thought this was a particular problem with fridge trailers on multi-drop work, as in when some pallets have been taken off the back you lose the ‘balancing effect’ of them? Or is that the drive axle on the unit which overloads?
I’d imagine if you have a 7,100 or 7,500kg steer axle on a unit there isn’t actually all that much tolerance for overloading when you take into account the weight of the engine, cab, cooling pack, chassis rails and all the rest of it… and in many cases the driver. Certainly a rigid with a 7,100kg steer is very easily overloaded and the engines and cabs in those must weigh considerably less than a high-power, big cab unit…?
If you pushed the 5th wheel to its most forward point you might reach an overload, more likely on a 4x2 than a 3 axle tractor.
I suspect in 99% of cases the tractor GVW would have to over by a fair margin to get the steer axle overweight, don’t ever recall finding an artic steer axle over on any vehicle i’ve driven, and i’ve used a lot of axle weighers.
Did a test day (MIRA i seem to recall) many years ago, a boffin with a set of portable axle weighers had me and another chap running round the counties weighbridges compiling comparisons between the proper bridges and these portables (glorified bathroom scales), that was in '86 i think, even though the lorries were deliberately badly loaded (by request) so we had technically overloaded axles, i couldn’t get the steer overweight unless i dumped the air in the second steer.
I’d imagine that the amount of weight you’d need to put on the trailer in order to push the steer over the limit would certainly ensure that your drive (and mid if fitted) would be way overweight. In fact I’d imagine that the fine for overloading the steer would seem like a lottery win when compared to the fine for your drive axle!
Something the dcpc should of covered in depth regarding the science of how an artic works but they chose to cover a lot of crap that didn’t help any one in any shape or form. Also load securing would of been a good module if approached properly with physical exercises of how to strap or chain a variety of loads.
I know that on a twin steer with a tandem trailer loaded to 40 tonne the front steer becomes lighter when you are loaded as the exhaust would brush the petrol station canopy and miss when empty.
OllieNotts:
Something the dcpc should of covered in depth regarding the science of how an artic works but they chose to cover a lot of crap that didn’t help any one in any shape or form. Also load securing would of been a good module if approached properly with physical exercises of how to strap or chain a variety of loads.
agreed!
ifyou put the 5th wheel FORWARD as far as poss and if you loaded the trailer with a lot of weight right at the BACK then the rear of the unit might be lifted up, concentrating all the weight on the front axle
It is easy to overload a front axle, as most will only have capacity for a ton or so, empty weight on a front axle is 5+ tons as the weight of the cab, engine etc all goes to the front axle, your drive axle will register only a couple of tons empty. Now put some weight on it and proportionally most of it goes onto the drive axle/rear axle group, but 5th wheel positioning is critical to ensure that as the weight is proportioned it doesn’t put too much onto the front axle.
This should not be a problem with a 3.8+m wheelbase tractor, but on a shorter wheelbase it will have more of an effect, especially if it’s close coupled.
Think of 5th wheel positioning as a fulcrum/center of gravity thing, somewhere along the chassis will be a point that loads exactly the right weight to the rear axle/s and the front axle, if the 5th wheel is positioned behind that point, more weight will be sent to the rear, if it is in front of that point, more weight will be sent to the front
newmercman:
It is easy to overload a front axle, as most will only have capacity for a ton or so, empty weight on a front axle is 5+ tons as the weight of the cab, engine etc all goes to the front axle, your drive axle will register only a couple of tons empty. Now put some weight on it and proportionally most of it goes onto the drive axle/rear axle group, but 5th wheel positioning is critical to ensure that as the weight is proportioned it doesn’t put too much onto the front axle.
This should not be a problem with a 3.8+m wheelbase tractor, but on a shorter wheelbase it will have more of an effect, especially if it’s close coupled.
Think of 5th wheel positioning as a fulcrum/center of gravity thing, somewhere along the chassis will be a point that loads exactly the right weight to the rear axle/s and the front axle, if the 5th wheel is positioned behind that point, more weight will be sent to the rear, if it is in front of that point, more weight will be sent to the front
This is very rarely going to happen on a yank tank though, seeing as you can normally drive another truck through the gap between cab and trailer, slightly off subject, but which reminds me, watched Duel last night from 1971. Love that truck, and still looking good in 2014 in a private museum apparently.
You would be surprised, a couple of notches on the 5th wheel have a big effect on weights, about 250kgs per notch. hard work if you’re at gross as there is no leeway on axle weights then, 12,000 on the front and 34,000 each on the drives and trailer, total of 80,000 and that’s the gross weight too, you can spend half a day sliding 5th wheel and trailer axles to get it right if the load is biased towards the front or back of the trailer
I’ve got a 26 tonne cf spacecab with a 9 tonne front axle 11 tonne drive and 7 tonne tag axle. It weighs in at 10500 kg with a full tank of juice. How much weight would you say I could put in the first 4-6 spaces?
jimmi:
I’ve got a 26 tonne cf spacecab with a 9 tonne front axle 11 tonne drive and 7 tonne tag axle. It weighs in at 10500 kg with a full tank of juice. How much weight would you say I could put in the first 4-6 spaces?
Not sure but I can tell you that if you were to put a 3500kg crane behind the cab the front axle would weigh 8000kg with the lift axle down when empty ,hope this gives you a clue.
