Courting controversy

[mark_5102932]

My car has a towbar weight of 75 kilos, so I set my caravan with a nose weight of normally 60 - 65 kilos [using bathroom scales on level surface] then I hitch the caravan onto the car and use my bulldog stabiliser which with its leaf spring design acts on the car and pushes the weight of the caravan onto the towbar considerably. Should the weight be remeasured someway as now it must exceed 75 kilos. thanks Mark

 

[WatsonJohnG]

I always thought that it worked the other way.

If the leaf is pushing down on the caravan drawbar then it must be pushing up on the car fixing

Or is that courting even more controversy??

 

[Lutz]

Perhaps it's because you've measured the noseweight while the caravan is standing level instead of with the coupling at the same height as when the caravan is hitched up to the car. If the caravan has a significantly nose down attitude, this could account for a higher noseweight than what you are measuring.

 

[rayc]

Mark, I am not a physics engineer but are you are saying that the noseweight of the van has increased by 10kg or so when you have hitched it to the van, with the stabaliser fitted, compared to when you measured it level without being being hitched up? If so how do you know, how did you measure it?

If you are simply thinking that the stabaliser is somehow taking weight from the car and adding it to the caravan, or vice versa, I am not sure how you would come to that conclusion.

When you lift the blade to lift it into the bracket I guess you place a downward pressure on the towball and when it is place in the bracket there is some force ( the weight of the stabaliser?) shared between the caravan and the car but I don't seee how this has effected the noseweight of the van to any significant effect.

Still I may be wrong and as it hurts my brain to think of these things too much, I think I'll go to the pub.

 

[WatsonJohnG]

When you lift the blade and lower it onto the A-frame bracket it pushes down on the bracket and I would have thought that there is an opposite force pushin up on the car towball.

I agree with Ray that its not going to be much.

A simple way of seeing how little/much difference would be to measure the tow ball height (or a point on the bumper) before/after fitting the blade to the caravan

 

[mark_5102932]

Sorry the way I have written first posting may be a little misleading in that when I talk about 75 Kilos I am only talking about this being the maximum allowable weight on the towbar [ I have not actually weighed this, probably couldn't if i tried anyway] it is just that if the A frame has a weight of say 65 kilos {measured when loaded} then the caravan is coupled to the car {still 65 Kilos}. Then bullbog stabiliser which is effectively fixed onto car via towbar has to be lifted and put onto bracket fixed to A frame {with an amount of lifting force}, it is at this point there is now a force acting down on the A frame which must be transferred onto the towball. I do not have any problems with the way the car sits {citreon C5 self levelling suspension} or for that matter any other problems {car tows van perfectly} it is just a thought that occurred to me and was curious as to other thoughts on this. Anyway thanks for replies so far Mark

 

[WatsonJohnG]

Sorry the way I have written first posting may be a little misleading in that when I talk about 75 Kilos I am only talking about this being the maximum allowable weight on the towbar [ I have not actually weighed this, probably couldn't if i tried anyway] it is just that if the A frame has a weight of say 65 kilos {measured when loaded} then the caravan is coupled to the car {still 65 Kilos}. Then bullbog stabiliser which is effectively fixed onto car via towbar has to be lifted and put onto bracket fixed to A frame {with an amount of lifting force}, it is at this point there is now a force acting down on the A frame which must be transferred onto the towball. I do not have any problems with the way the car sits {citreon C5 self levelling suspension} or for that matter any other problems {car tows van perfectly} it is just a thought that occurred to me and was curious as to other thoughts on this. Anyway thanks for replies so far Mark

When you lift the stabiliser to put it onto the caravan you are pulling up on the tow bar bracket until you release the bar onto the bracket.

That upward force less the bit needed to clear the bracket is now coming from the caravan which is pressing on the tow ball so the equilibrium should be about the same.