Noseweight advice

True, noseweight is only one factor of many and there are lots more that you haven't mentioned such as tyre pressures, fitment of shock absorbers on the caravan, load distribution in both the caravan and the car, etc., but towball height is not one of them.

I'm with you on that one EasyT. I have emailed the clubs so called matching service twice about my vehicles weight being totally wrong and never had a reply, even when i spoke to them at the NEC show. towcar/info is the most accurate of them all.

tow ball height has an effect on the tendency of an outfit to be susceptible to pitching. particularly with a low nose weight .  

If the noseweight is set correctly with the coupling at the actual height when hooked up, thus compensating for any variances in towball height, it doesn't make any difference how high or low the towball is. Why should it?

The higher the tow ball height the nearer the van becomes to its point of equilibrium. Dynamic nose weight when moving is different to static vertical weight . Road conditions wind pressures loading speed passing lorries lateral body movement about the chassis tyre pressures outfit suspension et al. As an empiric example quite some years ago I had a detachable tow bar fitted which was at the top end of the height  spec but the outfit was level

the outfit stability was not good when this was queried a different tow bar was fitted which resulted in a slight nose down attitude result much improved stability the only difference between the two tow bars was a different detachable tow ball the only reason for changing the complete tow bar was to ensure conformity and to prevent any possible warranty issues.  

The higher the tow ball height the nearer the van becomes to its point of equilibrium.

If the down force at that height is 80kg on the towball then the van is no closer to its equilibrium than if it was 80kg at a lower height as long as the weight is measured at the actual towball height when hitched.

The higher the tow ball height the nearer the van becomes to its point of equilibrium

I'm really not sure what you mean by this very loose term or indeed how nearer the van becomes to to it by moving the height of the tow ball or hitch? do you mean the point at which the caravan is in equilibrium? where the net sum of all the forces is zero? that is it's centre of mass or gravity, not usually referred to as the point of equilibrium?

If so this centre of mass (gravity) is somewhere near the axle horizontally and (I have no idea but) anywhere up to a third of the caravan's height vertically from the ground. 

If you raise or lower the hitch from the ground the caravan will pivot around the axle and the hitch therefore moves in a circle around the axle and the centre of mass will also move in a similar circle. 

How does it get any nearer it's centre of mass?

If you raise or lower the hitch from the ground the caravan will pivot around the axle and the hitch therefore moves in a circle around the axle and the centre of mass will also move in a similar circle. 

a very apt description of what can happen when for whatever reason the nose weight albeit temporarily becomes less than its static weight.

Some truth but totally irrelevant since noseweight is measured at towball height of connected outfit and that is the height that it stays at during towing.

Could you give some examples of how nose weight can change during transit? As nose weight is a moment (turning force) either the distance from the centre of mass would have to changed, this could happen when the hitch is compressed (by a cm or two?) or by things moving significantly about in the caravan and altering the centre of mass? Any more? The hitch and tow ball are connected (or should be) and move together so I would say the nose weight is pretty much fixed even if the whole outfit takes off over a bump? 

and you haven't answered how and what do you mean by :

The higher the tow ball height the nearer the van becomes to its point of equilibrium