Suggestions please for a suitable Twin Axle.

[TheTravellingRooster]

TR - I think your head is in the clouds.

Why try to have twin axles on a relatively lightweight van. It seems senseless. inch:

Hi again WoodlandsCamper. Try asking these people :- Trip Buddy,they are based in Derbyshire.
I had previously seen some rather nice Twin Axle Glass Fibre bodied goods trailers and though Hmmmmmmmmmmmmm I wonder and then I spotted these at The NEC but could not remember what they were about nor where I had seen them.

With a car as light and as short a wheelbase as the BMW Z3 has the twin axle set-up will remove most of the inclination to pitch and consequently will ride in a flatter plain.

 

[ProfJohnL]

...........................With a car as light and as short a wheelbase as the BMW Z3 has the twin axle set-up will remove most of the inclination to pitch and consequently will ride in a flatter plain.

Hello TR

You are mistaken in those two criteria:.

The fist thing to say is all the interactions between a car and its tailor are a highly complex and integrated set of motions. But the primary and most significant forces and motions can be considered in a simplified way:-

Consider a car towing a SA caravan as the caravan axle crosses the deformity, the caravan will be lifted but because the caravan CoG is in front of the axle as the caravan is lifted, the inertia will naturally tend to pitch the caravan forward increasing the the nose load, all be it momentarily.

Now consider a TA trailer. The leading axle meets the deformity first, But because it is in front of the caravans CoG it will lift the caravan and try to pitch it backwards, doing so it will relieve the nose weight on the hitch, and then as the trailing axle meets the deformity, and because it is behind the CoG it will also try to lift the caravan but this time pitch it forwards and increases the nose load. This is why one of the sensations of towing a TA is so very different to a SA caravan as it has a dual punch which actually tries to increase the pitching effect, but because of the very short time difference between the opposite motions the displacement of the hitch does not appear to be that great, but the forces are involved are considerable.

The ride attitude (angle of the floor platform) of a caravan is determined by the height of the floor above the caravan axle and the height of the hitch when connected to a car. If both SA and TA chassis are basically made from the same set of bits, the floor height at the axle will be very similar. So if a SA caravan assumes a nose down attitude on a given car, the TA from the same range will also assume a nose down attitude. The degree of tilt is determined by the distance from the hitch to the axle(s).

These are Mechanical and geometric facts, and if these are your prime reasons for going down the TA route, you will be disappointed.

 

[TheTravellingRooster]

...........................With a car as light and as short a wheelbase as the BMW Z3 has the twin axle set-up will remove most of the inclination to pitch and consequently will ride in a flatter plain.

Hello TR

You are mistaken in those two criteria:.

The fist thing to say is all the interactions between a car and its tailor are a highly complex and integrated set of motions. But the primary and most significant forces and motions can be considered in a simplified way:-

Consider a car towing a SA caravan as the caravan axle crosses the deformity, the caravan will be lifted but because the caravan CoG is in front of the axle as the caravan is lifted, the inertia will naturally tend to pitch the caravan forward increasing the the nose load, all be it momentarily.

Now consider a TA trailer. The leading axle meets the deformity first, But because it is in front of the caravans CoG it will lift the caravan and try to pitch it backwards, doing so it will relieve the nose weight on the hitch, and then as the trailing axle meets the deformity, and because it is behind the CoG it will also try to lift the caravan but this time pitch it forwards and increases the nose load. This is why one of the sensations of towing a TA is so very different to a SA caravan as it has a dual punch which actually tries to increase the pitching effect, but because of the very short time difference between the opposite motions the displacement of the hitch does not appear to be that great, but the forces are involved are considerable.

The ride attitude (angle of the floor platform) of a caravan is determined by the height of the floor above the caravan axle and the height of the hitch when connected to a car. If both SA and TA chassis are basically made from the same set of bits, the floor height at the axle will be very similar. So if a SA caravan assumes a nose down attitude on a given car, the TA from the same range will also assume a nose down attitude. The degree of tilt is determined by the distance from the hitch to the axle(s).

These are Mechanical and geometric facts, and if these are your prime reasons for going down the TA route, you will be disappointed.

Hi ProfJohnL. You certainly appear to be a fountain of knowledge but is it proven fact or intelligent theorising?

I have been towing for a very very long-time - indeed since 1966. I have towed both single axle and twin axle with the same tow vehicle and I can assure you that my preference every time is for the twin axle.
When it comes to the safety aspects of one against the other albeit I have never experienced a blow-out - I would sooner experience it with four wheels on the road than only two.
The not so obvious downside of a twin axle caravan or trailer is that they can impose/exert stresses on the front axle/tyres that would not be seen/experienced with a single axle caravan/trailer.
This can/will and doubtless many times lead to a front tyre/tyres blow-out.
Ride height is critical with both because of the Towing Dynamics and the shift of weight onto the ball/rear tyres of the tow vehicle under heavy breaking. This can then induce al-sorts of strange and unpredictable behaviour between the tow vehicle and the caravan/trailer.

My own experiences of both is that the tendency to pitch is considerably less with a twin axle caravan or trailer.
Also in the event of pitching and sideways movements that will induce a snake the twin axle is by far the more predictable and the easier & quicker to bring back into line.

As always - there is for more to towing than just hooking the caravan/trailer onto the tow vehicle and moving away from a standstill.
I was fortunate in that I was taught/schooled by one of the best in Liverpool in the middle 60's. He was himself a dedicated caravanner and a very very long-time member of The Caravan Club having toured all over the continent and just about anywhere that a car and caravan could go.
As a very hands-on businessman and principle partner of the business he would travel every week between Liverpool,Birmingham and London with very large boxed trailers that had a flat deck on the top and the whole outfit was loaded with Full Size Billiards/Snooker Tables and all of the associated accessories roped and sheeted - these would go to our associated companies within the group for further distribution and or export.
Most of the time the trailers were pulled by either Humber Hawk automatic Estates,Ford Zodiac Automatic Estates ( The Flying Pig ) and later the Ford Granada Estates in 3.0ltr & 2.8ltr Automatics.
These were also what I cut my teeth on.