The latest camping and caravan magazine mentions the dreaded word 'snake' again. Is the snake alive and well? did it ever go away?
Many years ago amongst the advice given was, if you experienced snaking when towing, you could try gently increasing speed to level out the outfit then slow down. With the advent of stabilisers manufacturers have extended the length of caravans, particularly the overhang length. (bigger box = bigger price) Have you experienced the snake or pitching movements? A member of this site say's he will never sell his caravan he will buy a bigger car is that the answer to worrying wiggles?
The advise was to increase speed so as to 'stretch' the outfit, this is still the the best method BUT near impossible with todays heavier vans to increase speed fast enough. (Alko's new anti snake device brakes the caravan in the event of a snake, this has the identical effect of the car accelerating very rapidly).
Result advise now is to slow down gently but never brake, not ideal but less likely to get you in a bigger mess.
I don't agree stabilisers have allowed vans to grow, but it is the overhang behind the wheels in relation to that in front that has a great deal to do with stability. The larger the distance from tow hook to wheel centre as a percentage of the whole length, the greater the stability.
Longer 'A' frames apart from increasing this distance also lowers the required nose weight, again very important to stability. most UK vans with shorter 'A' frames require ideally 7% of gross weight on the towball and this with the bigger heavier vans is difficult to obtain. Continental vans with long 'A' frames require only 5% for the same stability and much more obtainable on an average car.
Shock Absorbers also aid stability considerably so good to see these are now fitted as standard on many more UK vans
Quote: Originally posted by arc systems on 30/5/2008
The advise was to increase speed so as to 'stretch' the outfit, this is still the the best method BUT near impossible with todays heavier vans to increase speed fast enough. (Alko's new anti snake device brakes the caravan in the event of a snake, this has the identical effect of the car accelerating very rapidly).
Result advise now is to slow down gently but never brake, not ideal but less likely to get you in a bigger mess.
I don't agree stabilisers have allowed vans to grow, but it is the overhang behind the wheels in relation to that in front that has a great deal to do with stability. The larger the distance from tow hook to wheel centre as a percentage of the whole length, the greater the stability.
Longer 'A' frames apart from increasing this distance also lowers the required nose weight, again very important to stability. most UK vans with shorter 'A' frames require ideally 7% of gross weight on the towball and this with the bigger heavier vans is difficult to obtain. Continental vans with long 'A' frames require only 5% for the same stability and much more obtainable on an average car.
Shock Absorbers also aid stability considerably so good to see these are now fitted as standard on many more UK vans
Post last edited on 30/05/2008 16:52:28
There is no way whatsoever that increaing the speed to get out of a snake is the right thing to do, it should never ever be tried. All that it will do is increase the violence of the snake and make it even more difficult to control. The Alko ATC works simply because it attempts to stop the caravan and in so doing straightens the outfit, but if the outfit is still travelling too fast to allow it to be stable as soon as the ATC releases the brakes the caravan will restart its Side to side motion. This will continue until the vehicle and caravan are back in a stable configuration again and this will only happen once the outfit has slowed down.
Quote: The Alko ATC works simply because it attempts to stop the caravan and in so doing straightens the outfit, but if the outfit is still travelling too fast to allow it to be stable as soon as the ATC releases the brakes the caravan will restart its Side to side motion. This will continue until the vehicle and caravan are back in a stable configuration again and this will only happen once the outfit has slowed down.
This is not really true: after the ATC releases instability will only return if the destabilising force is still present. In most cases the passing lorry or bridge column that initiated the dynamic instability is long passed.
I know I'm an old fasioned retired Chartered Engineer but the best answer to reducing the chance of snaking is to return to twin axels on any van with a shipping length over about 18 / 20ft. The more rubber in contact with the road the more stable the outfit (if its properly loaded). I cannot (will not) buy a new single axel van and therefore continue to maintain my aging twin axel Bessacarr 500 GL as no manufacturer seems to build such two berth vans these days except for the largest models.
I have towed single axel vans and experienced snaking (thought the Scott stabiliser does help reduce it) but since towing a twin axel I have not experienced the problem and I hope it remains that way.
All my snaking has started going down hill to fast on motorways (go above sixty at your own peril) Best thing to do is ease off, slow down and hold tight. Once you take speed off it's sorted. The idea of going faster in theory is good (pull van straight) but in practice last thing you want is to go faster unless you really want to cut the grass on the hard shoulder and the central reservation!
I have only been towing caravan for 4 yrs now and have never feel a snake yet although my outfit is near to 100%, the reason after reading various thread and taking advices is simple.
1.make sure your caravan is loaded properly.
2. Ensure the nose weight is correct for the car .
3. While driving planning and awareness is a must, know what is coming behind you, keep within the speed limit you are comfortable with.
4. If you feel your outfit is affected by wind, coach, white van or any other reason ease up and slow down
------------- Simply Yung.(early retiree and loving it)
09 Mondeo 2.0 TDCI,07 Senator Virginia
April 1 ~ 5 York CP
5 ~ 11Loose hill C C
11 ~ 19 Gaer Hyfrid C C
Like Ekaligreese I am convinced that the safe limit on the length of single axle caravans was passed a long time ago. I feel that the leverage effect of a large overhang can cause instability. Arc systems mentions longer A frames, this will help, offsetting the longer rear overhang. Motorcaravan and lorry manufacturers have a maximum rear overhang design limit based on a percentage of the wheelbase. Despite careful driving and loading the need to swerve suddenly to avoid an obstacle can happen. With a large 4x4 up front I would guess your chances of dramas are minimal.
Having tamed my wayward S/A 550 Bessacarr, I can say it's not just the T/A variety that are stable? This transformation in stability was mostly down to fitting shock absorbers and probably aided by adjusting the tyre pressures to suit the actual weight of the van rather than leaving them at the vans maximum weight pressure.
Tested it again today on a 95 mile trip, absolutely stable even on fairly poor roads at all speeds, nothing bothered it and a massive difference to how it was.
PS, hope no one thought I was saying to accelerate? I though I was saying it's no longer possible to achieve enough acceleration and therefore the only way left now is to slow down?
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Topic: Is the snake alive and well?
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