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Discussion in 'OT (OFF Topic) Forums' started by flying haggis, Feb 2, 2017.
Why you should always put the heavy stuff up front
Yep, having a trailer fishtail like that is not a fun experience
Me and a kid that worked for me moved 20 cars 65 miles on a trailer one at a time. One of them was W126 560SEL that caused the trailer to behave in that way. It was loaded correctly but it turned out some guy (so called friend) took it upon himself to remove the guide rod mounts so that he could sell it to a buddy of his without asking. As we strapped the car at the wheels, the body began to shift from one side to another so badly that we could see cars behind us on every swing. Luckily everyone on the 5 lane highway pulled back and allowed us to regain control of the truck and pull off.
I'm pretty sure that he thought that I would not miss the part as the car was a parts car. But needless to say, my 'buddy' was never allowed back.
I do yes but as my tractor unit is 20tonne i think i'm covered
Actually , it is best , where possible , to put heavy items low down and over the axle , with only a slight bias toward the front .
Excessive nose weight isn't good either .
Got any pictures of this 20t tractor unit? I have artic's in all the time that only weigh 15t with trailer
The geometry is different in any case. A car and trailer has a pivot point behind the rear axle of the towing vehicle. This is what allows a trailer to control the direction of the tow car so dramatically.
The pivot on an articulated HGV is between the axles of the tractor unit. Because of this, the trailer exerts a sideways force instead of a twisting one. Additionally, the tractor carries much of the trailer weight, with the trailer axle a long way back.
Car and trailer - inherently unstable. And if the trailer is a caravan - carnage!
Here you go, 29.2t empty with its trailer
What's the equipment behind the cab?
It's a Hiab that can lift up the world.
HIAB xs 622 hi-pro. Will lift 3.35t to 14.7metres or 10.7t at 2metres
This is before it went on the road
Nice we occasionally use a guy with a similar spec HIAB but on a Scania 8 wheel unit i will have to get his on the weighbridge now to see what his weigh's just out of curiosity
People think that towing a trailer is literally about hooking it up to the car, yet the dynamics of a trailer should require a separate test in addition to the driving test.
I design and build mobile lighting towers and generators, and on every new design we have to record the gross weight and the nose weight at the towing hitch or eye. The weight is all important because if it is too heavy or too light, it affects the handling of the towing vehicle.
My stepfather followed a car towing a caravan that had started a slight snake. He kept back from the caravan and used his car to block others from overtaking until the caravan eventually took the car out with a massive snake. There was absolutely nothing the driver could do to stop the snake, even though he was driving a Range Rover. The weight of the tow car will have no impact on what the caravan wants to do.
If people only realised that they should weigh the caravan at the towing point and that if it is too light that they will have serious issues, then maybe a lot of the caravan accidents would be avoided.
Our service manager also likes caravanning, and he carries a weight scale to make sure his nose weight is right. Knowledge is a powerful tool.
you do now, B+E requires a separate test
very nice tractor unit too
They don't have electric brakes trailers in the UK? Larger trailers usually have them here with smaller trailers using surge brakes.
Towcar weight does play a big part in stability, but so do things like wheelbase (4x4s are normally relatively short), rear overhang, suspension, tyre pressures, etc. And on the trailer/caravan - weight, noseweight, vertical CG, weight distribution, side area, tyre pressures, hitch type, etc.
It is a lot more complex than most people think. I suspect tyre problems are behind most serious accidents though - many people don't even know what the pressure should be, let alone check it regularly. And the tyre tread never really wears so delamination/sidewall cracking/etc. (from age, or being left standing in one position) is a big problem.
What bumps mine up is the rear counterweight as seen in 2nd pic, this is so i can lift over 4 ton over the front. We now have new trucks with front mounted stabilisers that have nearly 70% capacity over the front.
We have overrun brakes on larger trailers ( over about 750Kg from memory ) here in the U.K. - these can be either mechanical or hydraulic in operation .
UK towing electrics have no provision for electric braking ; I've only heard of it in relation to the USA , with some imported caravans ( Airstream ) having them and needing to be converted .
Best towing I ever did was my best mates caravan all around the place when we were about 18. I only had a Leyland Sherpa van circa 1975 but I got the local neighbouring blacksmith to stick a towbar on the ends of what constituted chassis rails and it was awesome.
Happened to be just the right height, it worked so well at any speed. The wheel on the caravan started to come off on the M5, it stayed totally stable for so long. For this I was grateful!
Since then I've strongly believed in having it all as level as poss. I see vehicles sunk at the back or raised up, and worry a bit.
My reference was to a caravan snake as it happens. Obviously the heavier the vehicle, the more stable the combination, but if a caravan and contents weighing in at 1500KG or more decides to do a wobbly, and the nose is light, then the weight of the vehicle will then have little impact. Even if the towing vehicle was unmoveable, the caravan would still try to rip itself apart.
As you so rightly say, there is more to towing than just getting the nose weight right. Tyre pressure and condition also play a big part, as does distribution of weight left to right, as well as back to front. Aerodynamics can also be an issue, with caravans acting as sails.
To be honest, towing a caravan is probably one of the most unstable ways of towing, excepting those vehicles fitted with a fifth wheel. The fifth wheel tends to sit over the pivot point of the towing vehicle, whereas the pivot point on a ball hitch or towing eye usually sits forward that point, meaning the caravan will swing wider than a trailer hitched to a fifth wheel.
As for introducing a towing element to the driving license, this isn't retroactive in that people who passed their driving test before a certain date can tow a caravan with no previous experience.
If you think about it, the test for driving a car, which can potentially kill, is far simpler than many other tests for less dangerous pasttimes, such as driving fork lift trucks or earth movers. Also, once you have passed your driving test, there is no legal requirement for regular retests, whereas other pasttimes do require regular tests or checkups or even medicals to validate your fitness to carry on.