So yesterday I had my first day on W&D. Brand new next gen scania rigid with a slightly older but well kept tri-axle drawbar trailer with a Moffett on the back. Both the same size as each other and both flatbed. Driving it wasn’t too bad and even reversing wasn’t too embarrasing. The only thing that REALLY freaked me out was the trailers inherent desire to snake. Much worse when loaded (sometimes veering into lane 2) but also noticeable when empty. Is this normal? How can I stop the snaking?
dcgpx:
Basically if your snaking it’s simply your driving too fast for the trailer to follow smoothly.
At speed any small correction you normally do are magnified by the trailer.
You might think your driving slow but if your snaking then it’s too fast
It won’t help as you’ll naturally be trying to correct the snaking but could easily be adding to it by over correcting
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Great advice mate. Thanks. Tend to sit around the 50 mark, and noticed it much worse going down hill. First thing I’ve driven since passing my class 1 last month so admittedly I’m a little naive. Perpendicular learning curve for sure
Fletch26:
Great advice mate. Thanks. Tend to sit around the 50 mark, and noticed it much worse going down hill. First thing I’ve driven since passing my class 1 last month so admittedly I’m a little naive. Perpendicular learning curve for sure
At 50 then it should follow smoothly, I’d tend to say as it’s your first thing driven then your over compensating as I mentioned earlier and making it worse.
Slow down till your used to small and SMOOTH corrections and trailer happily following then as experience builds so will your average speed.
Fletch26:
So yesterday I had my first day on W&D. Brand new next gen scania rigid with a slightly older but well kept tri-axle drawbar trailer with a Moffett on the back. Both the same size as each other and both flatbed. Driving it wasn’t too bad and even reversing wasn’t too embarrasing. The only thing that REALLY freaked me out was the trailers inherent desire to snake. Much worse when loaded (sometimes veering into lane 2) but also noticeable when empty. Is this normal? How can I stop the snaking?
Thanks all
If it’s a close coupled heap then firstly it takes a sensitive hand on the wheel with the inputs,more often no inputs,needed to dampen any sway and not add to it.Plenty of experience driving a car and caravan outfit helps in that regard I found.
Then there’s the weight distribution issue.
In which case tell the guvnor that you’d prefer an A frame in which most,if not all,of the problems above magically disappear at the expense of a little bit more thought needed when reversing it.
Load on the trailer needs to be spread evenly. Too much weight on one end or the other affects the weight on the coupling which is what causes the trailer to snake, same as a badly loaded caravan. If its a new trailer, check the counter weight on the front is the correct weight. If the trailer is empty you should be able to drop it without putting the legs down and it will stay level, but you probably need to be brave to try it
Reminds me of following one of the transporter boys down a hill on the 34 north of Chievely fully loaded - not only did he manage to get a two lane snake on, it was swaying worryingly from side to side
You need a sheet of steel on the headboard to balance the trailer ,it helps to have a front lift and the axles set back rather than central to reduce the amount of weight needed on the headboard .
dcgpx:
It won’t help as you’ll naturally be trying to correct the snaking but could easily be adding to it by over correcting
Caravanner was doing this on the A1 near Stamford last Saturday. Got so bad as a result everyone behind him slammed on their brakes waiting for the inevitable. Resist the temptation to try to counter steer.
There are a myriad of reasons for this very unpleasant feature on close coupled W+D outfits, and setting them up properly by the builder is a bit of a black art.
The relative length of both parts of the combination, length of the drawbar, position of the hitch on the drawing vehicle are all significant in determining how the outfit will handle. The most important thing though, is weight distribution. I note you say it has a Moffet mounted at the rear of the trailer. This is the work of Satan. I imagine you are on multi drop work. It will help a lot if you can, wherever possible, keep the weight in/on the drawing vehicle as much as you can, even if this means shifting pallets from the trailer to the truck as necessary.
Otherwise, it will not be, as they say up here, a comfy hurl.
As some one else has said, with an A frame trailer, all these problems go away, they are, however, "challenging to reverse.
Good luck with it!!
Punchy Dan:
You need a sheet of steel on the headboard to balance the trailer ,it helps to have a front lift and the axles set back rather than central to reduce the amount of weight needed on the headboard .
Assuming the steel is just ballast that’s more subtracted from the available payload and where is he going to find this heavy piece of steel plate.In addition to the fact that it requires an actual nose heavy positive load on the coupling for stability which then also has to be subtracted from the prime mover’s rear axle payload weight.While road surface undulations can still then set up a continuous rocking front to rear weight transfer from the trailer see sawing across it’s silly axle configuration,resulting in the prime mover then still going light on the drive axle and then going light on the steer.Which creates a continuing both types of tail wagging the dog effect from the rear of the prime mover and then at the front.Or possibly even both at once in the situation which the OP described of a possibly heavy,let alone tail heavy,trailer combinded with a downgrade.
All that aggro just to avoid applying the driving skills which previous generations here took for granted and which are still taught and taken as routine in most other parts of the world where a trailer is coupled to a rigid at least.In which the choice,between the advantages of the A frame configuration,compared to the flaws in the oversized caravan design,is rightly considered a no brainer and which really should be subject to legislation regarding any outfit of more than around 11 tonnes gross IE a 7.5 tonner pulling a 3.5 t gross trailer.
I think you will find the main cause of the snaking is the lack of weight on the draw bar of the trailer. The Moffett on the back is acting like a pendulum. If you try to load the trailer so the heavier products are at the front and leave the rear as light as possible.
I used to have a Moffett on the rear so a standard 13.6M trailer and it was counterbalanced with a cast iron weight making a false headboard. I think it weighed about 2 ton.
The rear steer trailer was ok as the rear axle was further back. The root of the problem is a badly designed trailer.
Punchy Dan:
You need a sheet of steel on the headboard to balance the trailer ,it helps to have a front lift and the axles set back rather than central to reduce the amount of weight needed on the headboard .
Assuming the steel is just ballast that’s more subtracted from the available payload and where is he going to find this heavy piece of steel plate.In addition to the fact that it requires an actual nose heavy positive load on the coupling for stability which then also has to be subtracted from the prime mover’s rear axle payload weight.While road surface undulations can still then set up a continuous rocking front to rear weight transfer from the trailer see sawing across it’s silly axle configuration,resulting in the prime mover then still going light on the drive axle and then going light on the steer.Which creates a continuing both types of tail wagging the dog effect from the rear of the prime mover and then at the front.Or possibly even both at once in the situation which the OP described of a possibly heavy,let alone tail heavy,trailer combinded with a downgrade.
All that aggro just to avoid applying the driving skills which previous generations here took for granted and which are still taught and taken as routine in most other parts of the world where a trailer is coupled to a rigid at least.In which the choice,between the advantages of the A frame configuration,compared to the flaws in the oversized caravan design,is rightly considered a no brainer and which really should be subject to legislation regarding any outfit of more than around 11 tonnes gross IE a 7.5 tonner pulling a 3.5 t gross trailer.
In the real world you will find that a sheet of steel on the headboard to add weight is the done thing ,you may not know this as you probably can’t google it and it’s not on caravan forums
Persevere with it, your prime mover is brand new and the tyres won’t be bedded in (scrubbed off) until you’ve covered about 5000kms, you should see an improvement in stabilty once the prime mover rear tyres bed in.
One other thing, check the new tyres arn’t overpressure, often the drive axle twins run a little lower pressure than the maximum the dealers stick in them…your company though more likely your your preferred tyre people should know what pressures you normally run at, even if 10psi over will make the world of difference to feel.
I drove car transporters for a long time and my mate described the feeling perfectly when you got a new set of drive axle tyres on, ‘like driving a plate of spaguetti’.
One other thing, if you get a chance, especially when loaded, try and use an axle weigher, or if not possible if you have access to a flat weighbridge weigh the vehicle by shifting it forward one axle at a time and calculate the weights that way, more accurate that you might imagine, see how the imposed weights compare with the plated weights, just in case there’s an issue with axle loadings
A side photo would show better but looks like you have a lot of rear weight on that trailer especially when unloaded. You will have a specialist Moffit licence didn’t they teach you on the course ? I have in the past been asked to tow specialist trailers that were overweight I noticed one of the times and a fellow driver noticed another one. Mine was an overweight exhibition trailer that even with all the paper work, brochures, anything else I could find was still overweight the other was a trailer with a pushout ram up front that put too much weight on the tractor unit. As someone else said find a friendly weighbridge operator and also find the speed the snaking starts and stay bellow it. Remember the Drivers moto, family then driving licence , forget anything else its replaceable . Hope they are paying you well.
