Caravan Stability, a hypothetical thought.

iana · Guru

Caravan Stability, a hypothetical thought.

Roy E · Senior Member

Hello Guru,
Interesting thought but how about this; Sloping front of van deflects air upwards and in accordance with Newton's third law of motion, van will react by gaining weight at front equivalent to weight of air deflected upwards.
Conversely, as air is deflected downwards at rear of van, rear of van will follow Newton's third law too and rise in reaction.
This may be somewhat difficult to measure at 90 kph.
Cheers,
Roy.

Relax-n · Guru

Tooo early, now my brain hurts.......

iana · Guru

Oww come on, the morning is the best time to think!, I been up and thinking since 4:30, that's a good nights sleep for me.

iana · Guru

We measure the ball weight when the van is stationary, to date I have never heard of any comment of ball weight when moving. A load cell connected there would be interesting.

Rob Driver · Guru

My view would be that towball weight may or may not vary, depending on the speed and shape of the van and we also need to consider the aerodynamics of the tow vehicle as well, but the overall stability is more affected by side wind pressures than the forces generated by towing at our generally accepted towing speeds.

We generally have a brick towing a brick at relatively low speeds.

Regards

Rob

-- Edited by bentaxlebabe on Wednesday 11th of December 2019 09:33:41 AM

Whenarewethere · Guru

Then factoring in a water tank 50% full, braking, accelerating, up hill, down hill.

Rob Driver · Guru

The forces of varied air pressure are more than likely all over the vehicle and the van at speed.

With the large vans that many of us spend a lot of time living in there is not a lot of aerodynamics that may be able to be built in due to the shape required for us to maximise living space inside.
Teardrops and other similar designs allow for a little change is shape to assist stability, but with any item that is towed and is connected to the towing vehicle in most cases by a 50 mm ball does not stand much of a chance when the forces of varying air pressure are applied to the side of the van.

We are trying to balance the weight and these other forces on this tiny ball area.

This is what can happen when a side force is applied to a van.

www.facebook.com/DashCamOwnersAustralia/videos/221019952116680/

Regards

Rob

iana · Guru

Stability would be effected by the distance the center of gravity is in front of the main fulcrum i.e. somewhere over the wheels, and should be positive weight, i.e. 10% of the weight of the van. If the center of gravity moves back and behind the fulcrum point you are in trouble. That's the way I see it anyhow.
So any turning moment rearwards I think would reduce the ball weight. As you say "Whenarewethere" just going up a hill or an incline.
The wind force at 100kpa would be considerable over the area, so I think this could influence ball weight on some models of vans.

I guess what I am saying is if this is the case, an aero foil mounted on the front top of the van giving negative lift could be quite beneficial, the force it applies would increase with speed.

-- Edited by iana on Thursday 12th of December 2019 09:12:47 AM

Iva Biggen · Senior Member

I think instability in towing a van may be caused by a number of small things that at times could add up to disaster.

Weight and weight distribution.
Tyre pressures
Weather and road conditions and surfaces.
Mechanical problems.
Etc Etc.

Even the reported 10% heavier for the tow vehicle over the van weight may not be enough in some circumstances.

But probably the biggest problem is the actual nut behind the wheel.
The vehicle may be set up as recommended by all the experts but it doesnt take a real lot for the whole thing to come undone.
In my opinion the video from Rob above indicates to me that the driver of the van that rolled had little to no idea on how to correct that sway.
I do believe that fortunately there were no serious injuries in that incident, but it was a serious roll over just the same.

Cheers

Ivan