Even such a small mass may be the "straw that broke the camel's back". All vans are inherently unstable and become unstable on the road at a particular speed. The critical speed is a function of the particular arrangement of the van and the current load distribution of mass across the length and breadth of the van. The length of the lever behind the axle group is the most influential component. One way to look at and consider the effect of adding 15 Kg of mass is that the critical speed at which instability occurs will be less than it is now. The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash.

Hi Izabarack, if i took your advice "The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash" and did crash does this mean the 15kg was a bit to much to add.

-- Edited by wombat50 on Saturday 6th of February 2021 12:51:05 PM

Hi Dougwe, i diddnt know that section was there and have now posted the question there. Thanks

Anyone can test this, even using a cutting board & tins of tomatoes or bags of rice etc. If the weight is over the caravan's wheels. The tail will not be wagging the dog.

 

If the van is close to it's balance limit, ie it already is tending toward a rearward bias then the 15kgs could cause sway. There are so many variables here that it is very hard to say one way or another on a forum. Really the only way to test it is to add the 15 kgs and test it out. Just edge the speed up to your normal cruise speed in small increments and feel what the van is doing. If there is no evidence of change in the way the van behaves you are fine. If it starts to feel a little twitchy you know the 15kgs has affected its stability. This is basic test driving techniques.

Izabarack wrote:

---

Even such a small mass may be the "straw that broke the camel's back". All vans are inherently unstable and become unstable on the road at a particular speed. The critical speed is a function of the particular arrangement of the van and the current load distribution of mass across the length and breadth of the van. The length of the lever behind the axle group is the most influential component. One way to look at and consider the effect of adding 15 Kg of mass is that the critical speed at which instability occurs will be less than it is now. The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash.

---

 That.

Impossible to tell if it will be a serious problem, or not, but it will be worse, and you won't be able to tell until it is too late.

Cheers,

Peter

Youll be fine . Just counterweight it with drinks, water etc up front ? Or anything forward of axles, spare tyre etc . 

-- Edited by Aus-Kiwi on Saturday 6th of February 2021 06:16:55 PM

Peter_n_Margaret wrote:

-----------------------------------------------------------------------------------------------------------------------

 It is not about balance or ball weight, it is about yaw inertia.

Cheers,

Peter

---

 Yes, weight forward does not change the length of the lever behind the axle group.

As said above. It has nothing to do with balance. When you balance something it is simply balanced. That it, nothing more, zilch, Nada, 0!

This is how gyroscopes function. We would all be stuffed without gyroscopes. Their mass is at the perimeter.

The further the mass is from the centre the more difficult it is to control.

Get the mass all in the centre so the tow vehicle has more control over the trailer.

 

I have to carry petrol outside the car, but it gets used as the tank empties. Very easy with my holder. The sand tracks & solar panels I put in the car for rough roads. The second spare wheel I can't carry it inside, but it is as central to the car as possible, including 2 x 5L of fuel in the centre of the wheel.

It is all about getting your mass as concentrated as close to the centre as possible. Lower would be better still!

 

Unless there is other stuff mounted on the rear, say 20kg toolbox. More than likely ok. But as mentioned by others no guarantee.

wombat50 wrote:

---

 "The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash" and did crash does this mean the 15kg was a bit to much to add.

---

 Yep, that's right.   One way to test the stability of a van is to steadily increase speed until it sways and gets out of control and you crash.   If you do the test now, you will be able to establish the speed at which the current setup exceeds critical velocity.   Always best to make decisions on changes to van configuration once you have established a baseline.

wombat50 wrote:

---

Hi Whenarewethere, i have seen the examples on you tube with toy cars towing trailers put on a conveyer belt and shifting the load. was trying to find out the approx. added weight at which can cause a change

---

This what you were looking for.

 

Aus-Kiwi wrote:

---

Its only 15kg people !! A few suit cases inside would weigh the same ! Without a thought !! Sheesh ! Mind you if can be fitted in the front ?

---

 Absolutely agree...15kg will have no material effect provided ball weight is around 10%.

That depends entirely on the van. If it is a well designed van with reasonable tow ball weight, the axle group well positioned rear of centre then 15kgs is not going to do much at all. But you can have a van which by it's design is very susceptible to slight shifts in weight. I hired one once that was a bit of a dog to tow. After checking a few things I then shifted a bit of stuff around inside. A 20kg shift from the rear to the front and the van towed quite well.