If I leave home with a ball weight of, say, 250kg, and drive for weeks over some of our bad roads, over bumpy bridges, causeways and other 'undulating' roads, does my caravan ball weight remain at exactly 250kg for the entire trip. I maintain that it would be impossible to stay at 250kgs and yet we are told to NEVER exceed the ball weight. As an example of what I am saying, I had a 2kVA Yamaha generator in a rear locker of my van when I hit an almost unnoticeable causeway. On arrival at my destination, the generator was now on its side which suggested to me that the back of the van would have almost lifted off the road to flip that heavy generator onto its side. When your tow vehicle and caravan buck badly, and I am sure we have all experienced it on some of our bad roads, I suggest that the ball weight could go from 250kg to almost zero to maybe 500kg or more. There is no way known that the ball weight would remain at exactly 250kg for all scenarios. To take the enormous stresses of a bucking caravan, the tow bar and associated gear would need to withstand well in excess of 250kg, maybe up to several tonne for a short time. I realise that one should leave home with the correct ball weight for safety reasons, and if one is pulled up and weighed it will show the correct weight but let's face it, the towing gear can cope with well in excess of the legal ball weight. Has any research been done on ball weights? What are the thoughts on this?
outlaw40 said
05:40 AM Apr 21, 2019
Wow ! thats overthinking to the next level. your theory could be applied to any part of the caravan or tow vehicle , but thats not how it works . the weights are static weight calculations so when you are stopped. on a lighter note a mental image of a scallie running alongside of you on the highway trying to stick the scales under your wheels just entered my mind .
Olive Oil said
05:52 AM Apr 21, 2019
Water tank levels would have a major affect on ball weight. Levels are constantly changing on any trip.
Peter_n_Margaret said
09:00 AM Apr 21, 2019
The design criteria for a tow bar require that it is capable of a down load of 50% of the maximum tow rating - that is 1.75T for a 3.5T rated tow bar.
It must also withstand that same load in a transverse (sideways) direction and a load of 1.5 times the tow rating (5.25T for a tow rating of 3.5T) in a longitudinal direction.
Cheers,
Peter
iana said
09:05 AM Apr 21, 2019
I think Captain old chap you are so right, while the van and towing vehicle are in motion the tow ball weight is for ever changing.
The way I see it, tow ball weight is not an absolute rule, the rule really is center of gravity. And you want the center of gravity to be forward of a line drawn up from the pivot point about the vans wheels. The further forward the G of G is from that vertical line (within reason), the better the stability of the van is. As the C of G moves back to the centerline of the pivot point from the wheels the less stable the van becomes, and if the C of G moves behind, the van is unstable.
Measuring the ball weight is just an indication of where the C of G is. When you go up a hill the C of G will move back, and vis versa when going down hill. Bumps are just little hills.
The maximum ball weight is that number stamped on the tow bar compliance plate, the tow bar has been tested and certified to be able to handle the load and stresses on it for that figure.
Whenarewethere said
09:31 AM Apr 21, 2019
The ball weight would be the starting point. As you drive over undulating surfaces the ball weight increases & decreases.
I don't tow but the specs for my car, it has a massive tow ball weight of up to 350kg, 2000kg for on road towing, but only 750kg for off road towing.
Common sense is tie & bolt everything in place like cars on a ship. Take it easy with your rig over challenging surfaces. Go a bit slower & let the tyres down a bit of doing a lot of rough roads.
Half full tanks of water would be a big issue with the water shifting over every bump & braking. Multiple smaller tanks would be better where you can empty 1 tank at a time.
BW said
09:49 AM Apr 21, 2019
Mine being only a small rig , I would not have anything in the caravan tank and only carried water bottles, usually putting them in places to even the weight. the tank being on the front side of van wheels , added to the weight on the tow ball. Also turfed the great big stove and bought a twin burner took a big slab of weight off.
Craig1 said
08:07 PM Apr 21, 2019
" on a lighter note a mental image of a scallie running alongside of you on the highway trying to stick the scales under your wheels just entered my mind "
What a great fate for the older scallies ! Not sure about the new ones
-- Edited by Craig1 on Sunday 21st of April 2019 08:08:18 PM
swamp said
06:16 PM Apr 22, 2019
Hi
Some ball weight specs are reduced when going offroad by some car makers .
Peter_n_Margaret said
06:29 PM Apr 22, 2019
All towing limits are also reduced for the 50mm ball rating of 3.5T if the tug has a GVM of more than 5T (from memory) on a sliding scale.
BW, I assume that you are aware of that?
Cheers,
Peter
yobarr said
07:40 PM Apr 22, 2019
Peter_n_Margaret wrote:
All towing limits are also reduced for the 50mm ball rating of 3.5T if the tug has a GVM of more than 5T (from memory) on a sliding scale. BW, I assume that you are aware of that? Cheers, Peter
Hi Peter...As usual,you are correct,this time with your 5 tonne GVM figure.It is a reducing scale,where a vehicle with a GVM of 6500kg is limited to towing a 2972kg ATM trailer if a 50mm ball is used.Cheers.
Noelpolar said
06:43 PM Apr 23, 2019
FWIW..... when talking "shock loadings" brought about by causeways or wash aways etc ones is probally operating outside the rating intent of the vehicles standard ratings .By that I mean if ones was towing in a "off road" way....some ratings might be reduced by say 50% for this type of use... so 250kg ball weight max might need to be 125kg max.
If I leave home with a ball weight of, say, 250kg, and drive for weeks over some of our bad roads, over bumpy bridges, causeways and other 'undulating' roads, does my caravan ball weight remain at exactly 250kg for the entire trip. I maintain that it would be impossible to stay at 250kgs and yet we are told to NEVER exceed the ball weight. As an example of what I am saying, I had a 2kVA Yamaha generator in a rear locker of my van when I hit an almost unnoticeable causeway. On arrival at my destination, the generator was now on its side which suggested to me that the back of the van would have almost lifted off the road to flip that heavy generator onto its side. When your tow vehicle and caravan buck badly, and I am sure we have all experienced it on some of our bad roads, I suggest that the ball weight could go from 250kg to almost zero to maybe 500kg or more. There is no way known that the ball weight would remain at exactly 250kg for all scenarios. To take the enormous stresses of a bucking caravan, the tow bar and associated gear would need to withstand well in excess of 250kg, maybe up to several tonne for a short time. I realise that one should leave home with the correct ball weight for safety reasons, and if one is pulled up and weighed it will show the correct weight but let's face it, the towing gear can cope with well in excess of the legal ball weight. Has any research been done on ball weights? What are the thoughts on this?
It must also withstand that same load in a transverse (sideways) direction and a load of 1.5 times the tow rating (5.25T for a tow rating of 3.5T) in a longitudinal direction.
Cheers,
Peter
The way I see it, tow ball weight is not an absolute rule, the rule really is center of gravity. And you want the center of gravity to be forward of a line drawn up from the pivot point about the vans wheels. The further forward the G of G is from that vertical line (within reason), the better the stability of the van is. As the C of G moves back to the centerline of the pivot point from the wheels the less stable the van becomes, and if the C of G moves behind, the van is unstable.
Measuring the ball weight is just an indication of where the C of G is. When you go up a hill the C of G will move back, and vis versa when going down hill. Bumps are just little hills.
The maximum ball weight is that number stamped on the tow bar compliance plate, the tow bar has been tested and certified to be able to handle the load and stresses on it for that figure.
The ball weight would be the starting point. As you drive over undulating surfaces the ball weight increases & decreases.
I don't tow but the specs for my car, it has a massive tow ball weight of up to 350kg, 2000kg for on road towing, but only 750kg for off road towing.
Common sense is tie & bolt everything in place like cars on a ship. Take it easy with your rig over challenging surfaces. Go a bit slower & let the tyres down a bit of doing a lot of rough roads.
Half full tanks of water would be a big issue with the water shifting over every bump & braking. Multiple smaller tanks would be better where you can empty 1 tank at a time.
" on a lighter note a mental image of a scallie running alongside of you on the highway trying to stick the scales under your wheels just entered my mind "
What a great fate for the older scallies ! Not sure about the new ones
-- Edited by Craig1 on Sunday 21st of April 2019 08:08:18 PM
Some ball weight specs are reduced when going offroad by some car makers .
BW, I assume that you are aware of that?
Cheers,
Peter
Hi Peter...As usual,you are correct,this time with your 5 tonne GVM figure.It is a reducing scale,where a vehicle with a GVM of 6500kg is limited to towing a 2972kg ATM trailer if a 50mm ball is used.Cheers.