Noseweight advice

DaveAldi replied on 22/10/2017 12:38

DaveAldi

Posted on 22/10/2017 12:38

I tow a 2013 Coachman Pastiche 560/4 with a MTPLM of 1630kgs. I've recently changed my towcar from a Hyundai Santa Fe (Kerbweight 1977kgs and max noseweight 100kgs) to a Skoda Kodiaq Edition 4x4 (Kerbweight 1798kgs and max noseweight 80kgs). Considering the Kodiaq is the current towcar of the year I have been very disappointed with the towing stability of my outfit and despite careful loading and checking of tyre pressures I've had a few episodes of snaking (between 50 and 60 mph in the absence of strong winds), including one event where the car's towing stability assist activated the ABS to bring it under control. The caravan is fitted with ATC and an Al-Ko stabiliser hitch.

I purchased a noseweight gauge and found that the noseweight of my Coachman when totally emptied for winter (apart from two standard gas bottles in the front locker) was over 100kgs.

Please can anyone offer advice, firstly on whether I'm expecting too much of my towcar at a 90% match (bearing in mind I have 30 years towing experience) and secondly whether it's normal to have to remove gas bottles and add "ballast" behind the axle of an empty caravan to reduce the noseweight to an acceptable level. If I remove the gas bottles from the front locker, where is the safest place to carry them?

Thanks in advance to anyone with useful advice.

167 replies

Lutz replied on 09/11/2017 11:21

Lutz

Caravanner

Posted on 09/11/2017 10:31 by Cornersteady

once again you cannot change the laws physics, laws of physics....

you know how the song goes?

Here is an idea of what you are saying in a different format. A heavy chap (possibly me) sits on a see saw. A very light baby sits at the other end (please no H&S comments) what happens? The baby is held up in the air just like your caravan. Now the weight of the man and see saw is taken on the pivot and the man touching the floor. According to you the baby has now zero weight? The weight of the baby is zero? really?

Posted on 09/11/2017 11:21

But the baby and the heavy chap are both part of the total weight of the see saw. You need to physically pull the end of the see saw where the baby is sitting down in order to get the see saw level again and that is the noseweight. As long as you leave the baby in mid air no force is being applied at the baby's end and therefore there is no noseweight.

lornalou1 replied on 09/11/2017 11:22

lornalou1

Caravanner from Lancashire

Posted on 09/11/2017 11:22

i think what Lutz is saying ( to put it in a simple way) is that if the nose was lifted so that it was directly above the axle then it would have no weight as its on the same centre line/pivot point. I think that if your nose was at your towing height and at the correct weight than 6" higher or 6" lower would not make a difference to the original weight. .

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Lutz replied on 09/11/2017 11:35

Lutz

Caravanner

Posted on 09/11/2017 11:35

I'm not ignoring the weight of the baby at all. Its weight is still being supported by the pivot of the see saw.

Cornersteady replied on 09/11/2017 11:56

Member

Cornersteady

Caravanner from Tyne & Wear

Posted on 09/11/2017 11:56

As long as you leave the baby in mid air no force is being applied at the baby's end

Sorry how can you write that, really no force is being applied at the baby's end

So be clear you are saying there is no vertical force being applied or pushing down from the baby on the see saw seat? No Weight = mass x g? Have you ever drawn a force diagram?

As I said you cannot make the weight of an object disappear just because it is being supported elsewhere (which is what I said a few pages ago). There is always a weight on the nose (just like the baby). What the resultant of that force is of course is a whole different matter. That resultant can be zero but that force is always there. Just because the resultant is zero does not mean you can just ignore it, that is sloppy maths/physics and could lead to serious errors.

If you said the resultant noseweight is zero that is fine and perfectly accurate and in accordance with Newtonian physics. Just saying the noseweight is zero is not.

Cornersteady replied on 09/11/2017 11:59

Member

Cornersteady

Caravanner from Tyne & Wear

Posted on 09/11/2017 11:35 by Lutz

I'm not ignoring the weight of the baby at all. Its weight is still being supported by the pivot of the see saw.

Posted on 09/11/2017 11:59

but how would you calculate the force on the pivot if you don't take the vertical force acting on the baby, if as you say there no force is being applied at the baby's end.

See sloppy wording and which could lead to working leading to errors.

Lutz replied on 09/11/2017 12:24

Lutz

Caravanner

Posted on 09/11/2017 11:59 by Cornersteady

but how would you calculate the force on the pivot if you don't take the vertical force acting on the baby, if as you say there no force is being applied at the baby's end.

See sloppy wording and which could lead to working leading to errors.

Posted on 09/11/2017 12:24

The weight of the baby results in a couple in one direction around the pivot point of the see saw. The weight of the heavy chap results in a couple in the opposite direction. The difference between the two is the moment (or torque) necessary to bring the see saw back to a state of equilibrium. Knowing the length of the lever (in the case of a caravan the distance between the axle and the hitch) one can calculate the force necessary to provide such a moment about the axle. That force is the noseweight. Noseweight is always an applied external force. The forces within the see saw system are of no concern. In the case of a towed caravan the towball only perceives the external force, not what goes on with the caravan chassis.