Stabilisers

[Steve L]

Like all modern vans, my Abbey 540 has a hitch stabiliser. While this is very good at damping sideways twitches of the van, it does little to support any up and down nodding.

I'm contemplating fitting the older leaf spring stabiliser (snake master) as well as the hitch stabiliser to predominately assist the nodding.

Has anyone done this?

Does it work?

Cheers.

Steve L.

 

[JTQ]

If they use an AL-KO chassis I think I know the answer.

Whilst I cant find a Al-KO reference to doing this I recall I have read something from them stating effectively it's an absolute no no.

The chassis "A" frame is not able to take the dual bending forces induced by having two restraining devices.

The only people who can definitively answer your question and approve doing what you plan are the chassis maker.

 

[Lutz]

Not only the chassis manufacturers (AlKo, or whoever) but also the car manufacturers do not approve of using two frictional stabilisers in tandem because this increases the forces imparted into the caravan chassis and car underbody, respectively. This could have an adverse affect on durability.

Only electronic stabilisers, such as AlKo's ATC, BPW's IDC, LEAS, etc. may be used without reservation in conjunction with a frictional system, as these do not transfer any loads through the towball. On the other hand, electronic stabilisers cannot do anything to improve a pitching condition.

An outfit suffering from excessive pitching would suggest that either the shock absorbers on the car or caravan are worn or there are too many heavy items in the overhead lockers.

 

[Mikey1]

Which hitch do you have?

If its an Alko the latest version 3004 has pitching stabilising as well as snaking,i believe the earlier version hasnt.

The Winterhoff has both regardless of which model.

 

[Dave_374330759]

If you've got problems with pitching it sounds as though there is too much stuff in the front and the back of the van has been loaded to compensate causing the van to see-saw. Move some of the weight closer to the axle (centre of gravity). What are you towing the van with and what is your nose weight?. keep the nose weight near the limit of either the car or the van but don't shove loads of stuff at the back of the van to counteract the gas, battery and other stuff in the front locker.

 

[forestgump]

the alko should help with the sea saw motion as well as side to side the loading may be problem of the movment not just caravan the car needs to be loaded right as well if the boot is to light that can add to problem.

 

[colin-yorkshire1]

hi steve.

wait a minute

ok now just putting on the flak jacket??

yes I do and yes it does work perfectly with no signs of any problems despite comments to the adverse effects after 4 years the tow bar is still on the car.

all the teccies condemed it at the time but seeing as how the A frame had the holes for the bracket pre-drilled it was good enough for me. hey what the hell do I know I've only been doing this caravanning thing 35years.

one tip though steve dont have the blade set very tight it will still give the same up and down dampening but won't squeal as much round corners.

I know you are a experienced caravanner so I will not insult your inteligence suggesting you are loading the van wrong.

sometimes even when everything is done right "it does not work to satifaction" I had the same problem as you the alko was not good enough to stop the pitching but the blade cured that instantly.

colin

 

[Lutz]

If you haven't had a problem with two frictional stabilisers working in tandem, you're lucky, but frankly I wouldn't risk it - certainly not if the car is still under warranty.

The thing is, damage to the car's underbody is not readliy recognisable without looking underneath so one may have developed a crack in the sheet metal without knowing it.

 

[Steve L]

Hit the deck "in comming at 6-45"!!!!!!!!!!!!!!!

Hi Colin.

You can take the flack jacket off m8.

That sounds a reasonable point there Colin. By backing off the friction plate, all you're left with is the leaf spring tension which does the nodding damping.

You're right, like you I have getting on for 30 years of towing experience, so I would of thought loading a van should of been childs play. The rear shocks on the car were replaced with heavy duty ones two years ago.

This 18ft single axle fixed bed van we now have just seems a bit of a ****** to get balanced. Empty it had 95Kgs on the hitch. I can load it to 75Kgs which is top end for the car. I also have been carefull not to use the fixed bed storage for heavy items. Must of been spoilt by the 20ft twin axle we were last towing I guess.

I'll try the suggestion and see what we get.

Cheers Steve L.

 

[ProfJohnL]

The idea that adding a leaf spring will damp the pitching will have a limited effect. What it will do is pre-load the system and move the mean height of the pitching effect.

If pitching is excessive, then the normal shock absorbers on the car should be checked as they will have the greatest effect on damping the motion. Shocks on the caravan will only have a marginal effect because they only resolve the vertical movement of the whole caravan; pitching uses the caravan road wheels predominantly as a fulcrum.

Dave is correct when he suggests ensuring that the heavy items away from the extremes of both car and caravan.

The Alko ball friction will not make much of a contribution either, because the pads are side loaded onto the ball, and as such the will resist horizontal yawing motion by gripping the sides of the tow ball. This will have little or no significant effect on the vertical component of a pitch.

 

[colin-yorkshire1]

hi all.

thanks steve but I will keep the jacket on for just one more post, john L wrote" The idea that adding a leaf spring will damp the pitching will have a limited effect. What it will do is pre-load the system and move the mean height of the pitching effect". this is probably true perhaps it is by moving the mean hight that makes it work I dont know it just does.

while the "in theory" point of veiw is valid it must be understood that it is not the whole picture and should not be taken as gospel or set in stone it is in practice and trial and error that solves the most problems as experienced caravanners know allready.

take van deign in theroy loading the van to capacity and within the makers guidlines every one on the road should be stable an perfectly balanced with nothing needed to improve matters just hang it on and go.

so why do we need a stabiliser at all? why do we need to to load the van low down between the axels, why is the nose weight not neutral on a empty van, why are all the heavy items built into a van ie. cooker fridge, toilet with 10ltrs of water flush, fitted right at the back as far away from the axels as possible with gas bottles and some times the battery right at the front. why are ALL vans not fitted with shock absorbers stiff side walled tyres and movers as standard and included in the plated MIRO and MTPLM weight, the answer is?. well I have no idea what I do know is that it left to us the end user to make whatever adjustments are required to make the unit as stable and as comfortable to tow as possible by trail and error and if that means adding a blade into the set up so be it.

colin

 

[ProfJohnL]

hi all.

thanks steve but I will keep the jacket on for just one more post, john L wrote" The idea that adding a leaf spring will damp the pitching will have a limited effect. What it will do is pre-load the system and move the mean height of the pitching effect". this is probably true perhaps it is by moving the mean hight that makes it work I dont know it just does.

while the "in theory" point of veiw is valid it must be understood that it is not the whole picture and should not be taken as gospel or set in stone it is in practice and trial and error that solves the most problems as experienced caravanners know allready.

take van deign in theroy loading the van to capacity and within the makers guidlines every one on the road should be stable an perfectly balanced with nothing needed to improve matters just hang it on and go.

so why do we need a stabiliser at all? why do we need to to load the van low down between the axels, why is the nose weight not neutral on a empty van, why are all the heavy items built into a van ie. cooker fridge, toilet with 10ltrs of water flush, fitted right at the back as far away from the axels as possible with gas bottles and some times the battery right at the front. why are ALL vans not fitted with shock absorbers stiff side walled tyres and movers as standard and included in the plated MIRO and MTPLM weight, the answer is?. well I have no idea what I do know is that it left to us the end user to make whatever adjustments are required to make the unit as stable and as comfortable to tow as possible by trail and error and if that means adding a blade into the set up so be it.

colin

Ah Colin

I did not say no effect only limited. Its better to address the moments of inertia and the cars suspension.

 

[Steve L]

Before starting the thread, I had already checked the car suspension and tried various loading stratagies with no improvement.

I had been use to towing a twin axle where there was very little affect on the same car. Also having towed various other trailers I could narrow down the problem to the caravan.

I have also checked the front struts on the car just incase they are soft and adding to instability.

So hence the question to see if anyone had tried adding a snake master to get the leaf spring benefit.

As an engineer myself, I fail to see that the small added radial resistance to turning or the additional latteral resistance to vertical movement of the hitch and A frame would offer such added force that structural degradation might occurr. Furthermore, should that be the case, the manufacturers of caravan chassis, tow bar manufacturer and in my case Renault would have to be questioned for building items with such a narrow margin of stress durability.

You see, my snake master is quite soft in it's damping. Latteraly the force required to move the leaf spring to max deflection before the caravan bottoms out on the raised jockey wheel is approx 40Kgs. Radially the force required to turn the spring with the damper engaged is approx 50Kgs, unlocked only 10 Kgs is required.

Also to be honest, the turning motion of negotiating junctions is a slow progressive movement so minimal "shock loading" would be present.

So given that there are already existing holes in the A frame that suit the leaf bracket, I reckon Colin's idea of a practical test with "suck it and see" is an option worth a try. After all we are left to our own devices to load the car and van etc.

Cheers.

Steve L.

 

[Lutz]

Steve, you say, "I fail to see that the small added radial resistance to turning or the additional latteral resistance to vertical movement of the hitch and A frame would offer such added force that structural degradation might occurr(sic)".

If the blade type stabiliser is as effective as the hitch type, then the forces that the two together transmit through the towbar will double. This can hardly be described as a "small added resistance".

 

[Steve L]

So what Lutz!

You forgot to copy paste the data that I have already posted in the same article regarding how much force the snakemaster I have developes.

As I can not measure how much turning resistance the Al-co hitch stabiliser offers as I can not physically pick the van up and move it sideways. So unless you are superman, it would be incorrect to assume that the resistance force would double.

It would be possible to adjust the snakemaster friction pads so that near zero side turn resistance is present and the only assistance would then be in the leaf spring.

Ofcoarse if necessary I could build a test rig incorporating an Al-co tow ball and measure accurately if we are going to split hairs over a few Kgs (less than 10).

I'm still going with the Colin practical test method when the time to move presents opportunity.

Steve L.

 

[Lutz]

AlKo (and other hitch type) stabilisers fulfil the requirements of ISO 11555 which specifies the following:

350Nm of torque resistance against articulation

300Nm of torque resistance against pitching

300Nm of torque resistance against roll

In addition to the direct vertical and horizontal loads encountered when towing, car manufacturers apply these same values when performing durability tests of their vehicles, primarily to determine the noseweight limit.

There is no comparable standard for blade type stabilisers, but one would assume that, to be safe, the manufacturers of such stabilisers use the same criteria in the design of their products.