ALKO ATC did good

[JTQ]

For a given mass and body length, the longer "A" frame facilitates the SA being further from the hitch, and in turn with that comes a tolerance of using a reduced noseweight.
This enables car's with lower noseweight capacity to tow a van of that mass.
That of course opens up a greater potential choice of tow vehicle; a bigger potential sales market, and as we see on the Continent some more modest cars towing vans than typically seen in the UK.

Looked at from a slightly different take, this also allows lighter tow cars to tow these mass caravans, still with good levels of the inherent stability element related to noseweight.

 

[Lutz]

For a given mass and body length, the longer "A" frame facilitates the SA being further from the hitch, and in turn with that comes a tolerance of using a reduced noseweight.
This enables car's with lower noseweight capacity to tow a van of that mass.
That of course opens up a greater potential choice of tow vehicle; a bigger potential sales market, and as we see on the Continent some more modest cars towing vans than typically seen in the UK.

Looked at from a slightly different take, this also allows lighter tow cars to tow these mass caravans, still with good levels of the inherent stability element related to noseweight.

Your theory would be valid if the weight of the caravan superstructure were uniformly distributed over the chassis, but it’s not. It varies with the layout. We all know of caravans of similar size but with greatly varying ex-works noseweight, regardless of A-frame length. On top of that it depends on how the payload is distributed. I have no problems in setting the noseweight of my caravan to any value between about 20kg and 100kg.
Besides, it’s the towload limit that determines what the car can tow, not the noseweight. The noseweight limit will always be at least 4% of that. Although a greater noseweight capacity than 4% may be preferable, that value should suffice as a manageable amount. There should be no desperate need for any more.

 

[JTQ]

Your theory would be valid if the weight of the caravan superstructure were uniformly distributed, but it’s not. It varies with the layout

With any given mass the noseweight still relates to where the van's centre of gravity lays, not the weight distribution, that only influences the former.
And of course we can modify the noseweight by loading, because doing that moves the C of G, and or changes the mass.

You can't necessarily choose a tow car just because its tow limit is adequate, as you may have a van that is not stable with the cars permitted noseweight. Whist the vehicle could have a noseweight from 4% of its towing capability the van you have might not be stable within legal road speeds with just using 4%.

 

[Lutz]

With any given mass the noseweight still relates to where the van's centre of gravity lays, not the weight distribution, that only influences the former.
And of course we can modify the noseweight by loading, because doing that moves the C of G, and or changes the mass.

You can't necessarily choose a tow car just because its tow limit is adequate, as you may have a van that is not stable with the cars permitted noseweight. Whist the vehicle could have a noseweight from 4% of its towing capability the van you have might not be stable within legal road speeds with just using 4%.

Within reasonable limits, the ex-works noseweight is relatively unimportant because one always has the opportunity to set the noseweight as needed.
Your argument about having sufficient noseweight to ensure a stable outfit doesn’t tie up with your statement regarding a long A-frame resulting in a lower inherent noseweight.
Besides, if 4% doesn’t give you an acceptably stable outfit then something is wrong somewhere and it’s not the caravan.

 

[JTQ]

Within reasonable limits, the ex-works noseweight is relatively unimportant because one always has the opportunity to set the noseweight as needed.
Your argument about having sufficient noseweight to ensure a stable outfit doesn’t tie up with your statement regarding a long A-frame resulting in a lower inherent noseweight.
Besides, if 4% doesn’t give you an acceptably stable outfit then something is wrong somewhere and it’s not the caravan.

The ex works noseweight is itself unimportant, unless one is dumb enough to tow with one that happens to be incorrect for towing, unless ballasted to be correctly loaded.

With otherwise identical van's one with the longer "A" frame if that yields a longer hitch to wheel axle distance will have proportionally a lower hitch weight whilst exhibiting the same stability characteristic; no contradiction.

I totally disagree that a caravan that has a 4% noseweight always ensures a stable outfit; here very much the distribution of the masses built in or user added, their individual contributions to the units rotational inertia, are exceedingly important. A van even by its basic design. itself or the practical loading options it offers, can have poor stability margins.

 

[Lutz]

The ex works noseweight is itself unimportant, unless one is dumb enough to tow with one that happens to be incorrect for towing, unless ballasted to be correctly loaded.

With otherwise identical van's one with the longer "A" frame if that yields a longer hitch to wheel axle distance will have proportionally a lower hitch weight whilst exhibiting the same stability characteristic; no contradiction.

I totally disagree that a caravan that has a 4% noseweight always ensures a stable outfit; here very much the distribution of the masses built in or user added, their individual contributions to the units rotational inertia, are exceedingly important. A van even by its basic design. itself or the practical loading options it offers, can have poor stability margins.

Whether the caravan with a longer A-frame has a lower inherent noseweight depends on its layout.
Distributing the payload in such a way that the polar moment of inertia of the caravan is high (heavy items at the front and/or the rear) has a much greater effect than the length of the A-frame.
If caravans were basically unsafe if the noseweight is only 4% then it would be the duty of the manufacturer to point this out to the customer. Otherwise one would have to declare the caravan unfit for the purpose. After all, the manufacturer has full liability for the product.