German caravan A-frames.

[cooky1]

I have been looking at some German made caravans - Geist, LMC etc. and most of them seem to have long A- frames. The brochures say that it is for increased stability when towing. Can anyone explain this?

Some of the vans also have shock absorbers. Does this also increase stability?

The vans do seem a bit on the heavy side but their build quality was excellent.

Any feedback would be welcome.

 

[Guest]

The majority of European vans have an A frame 50 mm longer than those supplied in the UK. It is curious as both A frames are usually made by ALKO, but the Europeans seem to think that the longer frame does give increased stability at higher speeds (as evidently tested by the German authorities). I cannot confirm this as I don't tow that fast, but do confirm that my van, with a longer frame, tows extremely well. It also has the advantage that you can fit an A frame bike rack if weight will allow, and if you tow with a large 4x4 there is less chance of crunching things if you take very sharp turns.

The downside, if there is one, is that the shorter A frame allows more body length for a given shipping length, and many UK manufacturers will state their vans tow just as well.

You mention weight, and of course this has nothing to do with A frame length. That is more a case of what the manufacturer wishes to put on the chassis, and is dependent on axle loading.

At the end of the day you take your choice.

 

[cooky1]

The 2005 Geist used the v-tech chassis with the Whinterhoff stabiliser but the 2006 vans have changed to the AL-KO chassis. I wonder why.

The underside of the vans have been undersealed which I have not seen in British caravans.

 

[hymerman1]

Hi Graeme

I have had a Hymer now for over six years, been over most of Western Europe and have found the Hymer to be a very stable platform. I had the misfortune to have the car breakdown on me, the caravan was towed back home behind a car transporter and the driver commended the way in which the Hymer behaved.

It has shoch absorbers.

 

[stuart_5107319]

In Germany, new caravans must be fitted with shocks to allow legal towing at 100KPH (62MPH)

My Eriba was factory fitted with ALKO shocks, it tows fantastic.

 

[rob_jax]

Hi Graeme,

Bath University - School of mechanical engineering - have completed a number of research projects on subjects like "caravan stability" some of which were sponsored by Bailey - and they basically confirmed the existing results from ADAC in Germany.

Increasing the distance between the tow coupling and the wheels (long A-frame) improves stability. Interestingly a long A-frame does not require a high nose-weight to achieve stability.

Designing the caravan so that heavy items - like the kitchen - are placed over the wheels improves stability.

Fitting shock absorbers improves stability.

Fitting a stabiliser tow coupling improves stability.

Our previous Eriba was fitted with the AL_KO rubber suspension, and it towed perfectly - all Eriba caravans have a long A-frame, low centre of mass and heavy items over the axle.

Then we bought a 2005 Eriba Triton (3-berth) which is fitted with the AL-KO octagonal shock absorbers and it's just so much better.

Our Triton has a MTPLM of 1200 kg, a typical nose-weight of 35 kg to 40 kg, and has stability that most can only dream about.

Robert

 

[Lutz]

It is only logical that a longer A-frame requires a lower noseweight to achieve stability. The purpose of providing a noseweight is to counteract the force acting on the front of the caravan due to air drag. As the centre of the frontal area is some distance above the axle, this results in a couple about the axle which would tend to lift the front end. Noseweight is present to offset this. As the frontal area of most caravans is round about the same, the force trying to lift the front end is well nigh constant at any given speed. Therefore, the longer the distance from the axle to the towball, the lower the noseweight that is necessary.

 

[WatsonJohnG]

The A frame looks longer because of the body design to some extent.

Bailey seem toh have the body well over the A frame but it would be interesting to measure the actual distance from tow hitch to axle.

Many continental caravans have this "look" and the A frame is then used for bike racks.

 

[Guest]

Seem to be getting bogged down in tecnnology here. Can anyone state this is good or bad?

 

[MikeP]

Sorry to stay at a tangent Scotch Lad.

Lutz - if I am travelling at (say) 60mph on the flat with no crosswind to confuse matters, are you saying that my dynamic noseweight would be very low? But I guess that under moderate braking it would be significantly higher.

It doesn't really matter to me - I'm just interested.

 

[RayS]

I've changed from Coachman 520 with relatively short A frame and no shock absorbers to burstner with longer A frame and shock absorbers. Although I never had any problems with the Coachman I have to say the Burstner tows better, particularly over poor roads but this is probably due more to shock absorbers than A frame. Lutz and Rob have given all the techie stuff already - and very clearly if i may say so.

In unscientific terms, the further from tow ball to van axle the more stable it is likely to be (Not will be, likely to be).

The downside is reversing round a corner or an obstacle. If the towball to axle length is longer the reverse turning circle is usually bigger. Reversing in a straight line is easier - if you want proof, try reversing a very short trailer at the tip !

 

[RayS]

I've changed from Coachman 520 with relatively short A frame and no shock absorbers to burstner with longer A frame and shock absorbers. Although I never had any problems with the Coachman I have to say the Burstner tows better, particularly over poor roads but this is probably due more to shock absorbers than A frame. Lutz and Rob have given all the techie stuff already - and very clearly if i may say so.

In unscientific terms, the further from tow ball to van axle the more stable it is likely to be (Not will be, likely to be).

The downside is reversing round a corner or an obstacle. If the towball to axle length is longer the reverse turning circle is usually bigger. Reversing in a straight line is easier - if you want proof, try reversing a very short trailer at the tip !

Sorry, meant to add: The longer A frame also goes some way to explaining why the Europeans seem to be less hung up about nose weight ratio than we are. If you look at some of the publicity for European vans you will see towcars with the vans that certainly don't make the 85% suggested figure, and we see many many outfits in Spain which must be over the 100% figure, particularly given the kitchen sink etc. some of them seem to bring down for long winter stays.

 

[WatsonJohnG]

Bailey used to advertise the Pageant had a longer A frame for better stability.

I could never understand why their cheaper range at the time didn't have a longer drawbar if they thought that it gave better towing

They now seem to have the body nearer to the coupling but is the A frame (ie from axle to coupling) any different to their previously vaunted longer A frame.

It would be interesing to take a tape measure and find out how a Senator compares with some German vans