Weight Question

[dirvine]

On another web site, it is claimed that when you put a towball weight on your car (does not matter what the weight is) weight comes off the front of the car and as such more than the tow ball weight is added to the rear axle load. The quote is much like the fulcum on a see saw. What has been quoted is that a ball weight of 350kg means about 500kg is loaded onto the rear axle. I failed physics so I am unsure if this is correct. If this is the case then I question if any car could tow a 3.5T van with a notional ball weight of 350kg. Can any of you gurus here answer my question in simple terms. I dont know how you can accurately guess the tare weight on a rear axle unless you drive over a weigh bridge, so just halving the Tare weight would not give an accurate figure, or so i would deduce as I would think more weight would be biased to the front due to the engine and gearbox being more located to the front of the vehicle.Thanks David

[Chops]

David, I don’t believe it to be a massive “see saw” as such’ but yes’ if you put downforce on the rear, I believe it’ll relieve some weight off the front per se.
Dont know if there’s a way of working it out via percentages as such, hopefully someone will be along shortly and fill us in. I think it’s easy to see on older sprung cars where you gain “power steering”.
Personally, I would think that the only real answer would be with a set of scales under each axle/wheel and see where it takes you. Drive through roadside truck scales would probably be ok for this, just a bit of faffing around to disconnect/reconnect.

[PhilipA]

I would have thought that roughly the weight that comes off the front would be proportionate to the distances between the rear axle and the tow ball vs the distance from the rear axle to the front axle.
Lets say the distance to the towball is 1 metre from the rear axle, and the distance from the rear axle to the front axle or more correctly the mid point of the tyre ground contact is 4 metres then the uplift on the front would be 1/4 of the towball weight.
So say the towball weight is 200Kg then the uplift would be 1/4 of that or 50Kg. The drop or lift would depend on the spring rates , so say for example the front spring rates are 100Kg per 25MM X2 , then the uplift would be 6MM roughly. The rear spring rates would also have something to contribute. They are usually harder than the front but the drop would be greater as the distance from the load is less. Lets say rate is 150Kg per 25MM so the drop at the back should be about 25- 30MM.
Regards PhilipA

[Blknight.aus]

you are correct...

the math is simple for static work...

the total weight of the ball is added directly to the rear axle and then you add in a really complicated formula that adds extra weight as a function of the total leverage required to balance that weight including a funky bit that cancels some of it out as the math for the reverse is calculated in to account for the overhang in front of the front axle.... its not fun.

heres the simple way, and remember if you do just this you'll have an answer, it wont be right but it will be pretty close.

add the downforce of the ball to the back axle.

calculate the distance from the hitch to the center of rear axle (set if you have a 6x6) multiply this by the downforce on the hitch to get a number...
calculate the distance from the center of the rear axle (set) to the center of the front axle (use the same units as before) divide the previous number by this measurement.

the number that comes out is how much you need to add onto the back axle and take from the front.

so.... perfect world...

I put 200kg on the hitch
the hitch is 2m from the rear axle
200x2=400.

the front axle is 8m from the rear
400/8=50

the rear axle now has to support the original 200kg + an extra 50Kg of transferred weight. and the front axle is 50kg lighter.

assuming you started out unladen, this is now as simple as plugging those numbers into the unladen axle weight of the landy (which once upon a time were included in the datasheet).

if you have those and extra load the distribution math is pretty easy. each item (and we'll work purely on point load numbers for a single load point about the COG/center of foot print for each item) and in 2d so we dont have to worry about l/right loading)
measure the distance between the 2 axles and then measure out as a percentage where on the distance the center of the load will be, invert the percentage and that is how much of the weight the axle bears...

for example a load placed directly over the rear axle is 100% of the distance away from the front axle so the front axle bares 0% and the rear 100%.

if the load overhangs an axle go through the maths for the towball again using the distance from the center of the load to the axle as the first number.

Add all of those together and you will eventually come up with something thats within a few % of your axle loads.


and then we get into dynamics.................

which is a much longer and requires far more coffee than I've had today.

[Tombie]

What are you actually trying to find out?

The D4 handling dynamics have been designed with the ability to have 350kg on the ball.
Over 250kg you need to reduce internal payload by 100kg to avoid exceeding rear axle weight.

On lesser vehicles you would fit load levellers to compensate for the poor design.

[dirvine]

[QUOTE=Tombie;2935724]What are you actually trying to find out?

It has been quoted to me that when you put 350Kg on a tow ball, because of the see saw effect you are really putting nearly 500 kgs extra on the rear axle. As such you cannot load the car up to 350kg below GVM as the rear axle load has been exceeded. It was said that the New RAM cannot tow 3.5T because of that and neither can a D4. If we want to tow 3.5T then we need to use a DOG trailer. As I cannot find what the rear axle load weight is before a trailer is hooked on, I am just wondering what weight can we put on the ball before the axle load is exceeded. Whilst i read what LR says, that 100Kg seems to be a very "loose" type of figure. How do you remove 100Kg if you have nothing in the back? How much can i put in and still not be over? Then i can fire back with some authority. Physics was never my strong point at school

[Tombie]

[QUOTE=Tombie;2935724]What are you actually trying to find out?

It has been quoted to me that when you put 350Kg on a tow ball, because of the see saw effect you are really putting nearly 500 kgs extra on the rear axle. As such you cannot load the car up to 350kg below GVM as the rear axle load has been exceeded. It was said that the New RAM cannot tow 3.5T because of that and neither can a D4. If we want to tow 3.5T then we need to use a DOG trailer. As I cannot find what the rear axle load weight is before a trailer is hooked on, I am just wondering what weight can we put on the ball before the axle load is exceeded. Whilst i read what LR says, that 100Kg seems to be a very "loose" type of figure. How do you remove 100Kg if you have nothing in the back? How much can i put in and still not be over? Then i can fire back with some authority. Physics was never my strong point at school

Just get your book out - drop it in front of the other persons face and point [emoji6]

Let me hazard a guess - they drive a Toyota? That’s where this generally comes from.


In short they’re wrong, the answer is in the black and white. And you can’t exceed axle weight if the vehicle is empty [emoji6]

[dirvine]

No sure what they drive. I have had a look at my 16.5 D4 handbook and cannot see any reduction mentioned, But it did tell me what to add up when making sure carrying capacity was not exceeded.

[oldyella 76]

We have a registered weighbridge and have weighed many vans and vehicles. It is easy to calculate the weight on the steer with a van attached. We just place the front wheels on the bridge , take the weight, then take the van off. The difference will give you the weight on or off the front wheels. You can then attach the load distributing bars on and then take a weight reading. You can do this with the rear as well. What we have found is that the majority of vans exceed the stated tare weight of the van and also the towball weight when loaded. I have had people having to trade their Prado in on something heavier to tow, upgrade van suspensions, and postpone trips till they redistribute things like water tanks. Had one bloke who had to relocate water tanks from the front of the van to the back to reduce towball weight as with full water and gas the van far exceeded the towball limit. This van could only carry an extra 90 Kgs of bedding, clothes, food or crockery before it exceeded its A.T.M. and this was a new van.
You would be surprised at how many vehicles are overloaded with the tojo/ nissan weights pretty frightening when you weigh individual axles.
The other thing that needs to be considered is how far the towball protrudes out from the rear of the car or the rear axle as the further you go out the more weight you place on that rear axle due to the cantilever effect even though you towball weight hasn't increased.
If anyone wants to play with weights pm me.
Lindsay

[Chops]

We have a registered weighbridge and have weighed many vans and vehicles. It is easy to calculate the weight on the steer with a van attached. We just place the front wheels on the bridge , take the weight, then take the van off. The difference will give you the weight on or off the front wheels. You can then attach the load distributing bars on and then take a weight reading. You can do this with the rear as well. What we have found is that the majority of vans exceed the stated tare weight of the van and also the towball weight when loaded. I have had people having to trade their Prado in on something heavier to tow, upgrade van suspensions, and postpone trips till they redistribute things like water tanks. Had one bloke who had to relocate water tanks from the front of the van to the back to reduce towball weight as with full water and gas the van far exceeded the towball limit. This van could only carry an extra 90 Kgs of bedding, clothes, food or crockery before it exceeded its A.T.M. and this was a new van.
You would be surprised at how many vehicles are overloaded with the tojo/ nissan weights pretty frightening when you weigh individual axles.
The other thing that needs to be considered is how far the towball protrudes out from the rear of the car or the rear axle as the further you go out the more weight you place on that rear axle due to the cantilever effect even though you towball weight hasn't increased.
If anyone wants to play with weights pm me.
Lindsay

Thanks for that tip Lindsay,, sometimes the most practical, easiest of methods eludes us,,, we’ll, me anyway [bighmmm]

As I’ve pointed out before about van weights etc. I think people forget that every item weighs something. It’s a pretty big burly bloke who can carry the weeks grocery shopping on his own,, let alone all the other combined items which are only bought say once a month or so. Pots and pans are weighty too, a few books/magazines nick nacks etc,, boots jackets handbags, etc. It all adds up.

We’ve were informed our van can carry 600kgs, (legally written on the plate) which of course includes almost 200lts of water. It was easy to overload the forward fold camper, and I’m thinking it will be just as easy to overload the caravan. If your only using it for weekend jaunts etc, it’s probably much easier to keep in check. We’ll be living in ours, so some serious consideration, checking and experimenting of weights etc will be undertaken over the coming months.

[Blknight.aus]

[QUOTE=Tombie;2935724]What are you actually trying to find out?

It has been quoted to me that when you put 350Kg on a tow ball, because of the see saw effect you are really putting nearly 500 kgs extra on the rear axle. As such you cannot load the car up to 350kg below GVM as the rear axle load has been exceeded. It was said that the New RAM cannot tow 3.5T because of that and neither can a D4. If we want to tow 3.5T then we need to use a DOG trailer. As I cannot find what the rear axle load weight is before a trailer is hooked on, I am just wondering what weight can we put on the ball before the axle load is exceeded. Whilst i read what LR says, that 100Kg seems to be a very "loose" type of figure. How do you remove 100Kg if you have nothing in the back? How much can i put in and still not be over? Then i can fire back with some authority. Physics was never my strong point at school


thats easy...

you have 2 figures in play.

1. how much you can put in the back
2. how much you can put on the ball.

theres 3 sets of limitations in play.

1. the structural capability of the bodywork/mounts to chassis
2. the structural capability of the tow hitch to the chassis/ the chassis it self
3. the load limit of the suspension.

Landrovers are built to carry the full payload and then have an additional amount of downforce applied to the towball and the vehicle will still be inside its GVM/GCM. in your case that number is 250KG.
the towbar is designed to carry 350KG of downforce

SO (and im making up numbers now for the purpose of an easy demo)

if you have a 1000Kg payload capability you can then drop on 250KG of downforce for free, dont worry about a thing.

BUT...

if you have a 350KG downforce you need to free up the 100KG from the payload.

so you can have 900Kg of payload and then the 350Kg on the ball.

What gets right up the toyosan drivers noses and why they cant wrap their heads around this is simple.

Their vehicles generally make no allowance for towball load, every KG on the ball comes out of the payload.
Same as their allowance for included weight on some models doesnt include an allowance for a driver, fuel, spare tyre.....

[Blknight.aus]

[QUOTE=dirvine;2935726]

Just get your book out - drop it in front of the other persons face and point [emoji6]



Doesn't work.

they either can't read, comprehend or simply ignore the evidence...

its the same at servos.

"you followed me from servo x aren't you going to put more fuel in?"
Nope, tanks are full.
"but its loaded"
yeah and probably a higher GVM than you too, I'm missing your point....
"But that means you did the run on about 15l/100.."
and......
"I cant do that"
so.....
"there's no way that vehicle uses that much fuel"
why not?
"Because my xxx which is newer and better never gets under that and Im looking at 19s"

At which point trying to explain that theres a difference between newer and better as well as a difference between quality and mass engineering is utterly pointless.

[bblaze]

been following that thread on the other forum, whether the guy is right or wrong his approach only gets people offside.
cheers
blaze

[Blknight.aus]

been following that thread on the other forum, whether the guy is right or wrong his approach only gets people offside.
cheers
blaze

got a link?

I had a crap day yesterday and need a laugh..

think he'll mind if we cross post it to the jokes thread here?

[dirvine]

In Grey Nomads Forum under heading of Dodge Ram 1500. My call sign is Walter on that site.

[bblaze]

got a link?

I had a crap day yesterday and need a laugh..

think he'll mind if we cross post it to the jokes thread here?

Dodge Ram 1500 - The Grey Nomads Forum (https://thegreynomads.activeboard.com/t65853068/dodge-ram-1500/)

there you go dave, its a joke
cheers
blaze

[Tombie]

Ah... that peanut... he wacks on regularly. And is totally full of it.

[cripesamighty]

If you get really bored Dave, a few AULROians were trying to explain that modern air-sprung Land Rovers don’t need WDH’s on a Caravaners forum thread. The Landy owners were pushing it uphill because those forum guys just cant comprehend it. Hilarious!

WDH with Air Suspension - "Please Explain!!!!" - Caravaners Forum - Since 2000 (https://caravanersforum.com/viewtopic.php?f=2&t=82056)

[Slunnie]

On another web site, it is claimed that when you put a towball weight on your car (does not matter what the weight is) weight comes off the front of the car and as such more than the tow ball weight is added to the rear axle load. The quote is much like the fulcum on a see saw. What has been quoted is that a ball weight of 350kg means about 500kg is loaded onto the rear axle. I failed physics so I am unsure if this is correct. If this is the case then I question if any car could tow a 3.5T van with a notional ball weight of 350kg. Can any of you gurus here answer my question in simple terms. I dont know how you can accurately guess the tare weight on a rear axle unless you drive over a weigh bridge, so just halving the Tare weight would not give an accurate figure, or so i would deduce as I would think more weight would be biased to the front due to the engine and gearbox being more located to the front of the vehicle.Thanks David

The weight proportions vary a fair bit. The Disco2 for example is about 1.1t on the front and 1.2t on the rear, but a single cab ute with alloy tray will be proportionally very front heavy.

Here are some intersting calculations that I've just done re what the ball weight does to the axle loads. The fellow with this arguement is pretty much on the money but I think his values are a bit out as the RAM proportions are a lot better so the effect on the front end by the ball weight will be a lot less than on a Disco2 or a ute.

http://slunnie.com/coppermine/albums/userpics/10001/IMG-2268.JPG

[Blknight.aus]

The experts then advise that a WDH be used,but all that does is add even more weight to your cars rear axle,as well as increasing your TBO (towball overhang, or distance from rear axle to hitch point). This means that even more weight is transferred from the front axle to the rear.

And I give up... thats not how the physics of them works..
short version.. they create a seperate path of force that levers against the hitch the van and the chassis to create a lifting effect. this takes weight off of the back axle by pushing it onto the front axle of the vehicle and the trailer.


The much-adored McHitch multiplies that weight transfer even further! When the WDH is tensioned in an effort to put some weight back onto the front axle of the car,some weight is indeed taken off the rear axle of the car,and put back onto the front,but there also is weight transferred to the vans axle group,putting you over your ATM

and thats why I give up, hes just contradicted himself in less than 2 lines of text. his example here is also marginally wrong which is seemingly a trifling but it means that his example trailer was already illegal to hook up in the first place.

so lets look at


The 1500 has a rear axle limit of a miserable 1770kg,


The Dodge Ram 1500 has over 1000kg rear axle weight at tare.A towball weight of 350kg transfers around 500kg (+/-) to the rear axle of the car, Add another 100kg for fuel,and already we are up to 1600kg.
nope..
https://www.ramtrucks.com.au/includes/file/RM6199-RAM1500MY19Specifications_V009_2.pdf

Kerb weight includes the vehicle with a full tank of fuel and all standard equipment
I'll just ignore the fact that if you're towing a van the luggage should be in the van and assume that it is so if Ive got 1500kg used of 1770 I have 270 KG to play with.... so unless you're an American couple, a Family of Americans, Samoans, or of other fluffy producing heritage stock 270KG isnt that big a deal. Myself and my partner + the gear we need to go for a week (I'll take out the tent and the food and the water, its in the van in this case) weighs in at ~160KG. take out the weight of the packs and the gear (cause they're in the van) and thats down to 140Kg.

and a quicky from one of the older dodge ram adds "So if you want to tow OR carry a big load then dodge is the truck for you" (its american, its not really a truck, just a big ute, the GVM is way to low to be a truck, a landrover 6x6 is actually a truck)


All my comments are based on the generally accepted 10% towball weight.I sort-of know how the towing ability of a vehicle is calculated,but you may wish to access RV books by Collyn Rivers,a recognised expert in weights wnd dynamics,with over 60 years experience.All will become clear!
From the authors bio....
Author/engineer, Collyn Rivers practices what he publishes. Originally trained (by the UK’s Royal Air Force) as a ground radar engineer, he later worked as a research engineer at Vauxhall/Bedford Motors, then (in Australia) founded and ran Electronics Today International. It was published in seven countries and within seven years became the world’s most successful popular electronics publication. Collyn later started up his own technical publishing company specialising in the RV and solar areas.


the weight on the wheels of the car should be at least 10% more than the weight on the vans wheels (GTM),only a fool would tow a 3150kg GTM van behind a car with GVM of only 3090kg.
I know some farmers and truck drivers that this guy is going to need to have some big long discussions with and tell them how to do their job safely. We've got road trains out here massing over 100T all up and at best maybe 16 of that is the prime mover, lets be really generous and say that the prime mover and the front trailer weigh about 1/3 of the total mass, the next 2 to 7 trailers (I'm including mine specials on closed roads) still hughely out weigh the mover and trailer.

12T tractor hauling 35+T worth of machinery trailer or a string of product bins, every other day.


The only credit I can give him is this...

if you look at his exact arguments and accept all of the situations he presents as being factual and the only examples available he is more or less close enough to correct. However we dont operate in his exceptionally limited range of exposure.

[Blknight.aus]

The weight proportions vary a fair bit. The Disco2 for example is about 1.1t on the front and 1.2t on the rear, but a single cab ute with alloy tray will be proportionally very front heavy.

Here are some intersting calculations that I've just done re what the ball weight does to the axle loads. The fellow with this arguement is pretty much on the money but I think his values are a bit out as the RAM proportions are a lot better so the effect on the front end by the ball weight will be a lot less than on a Disco2 or a ute.

http://slunnie.com/coppermine/albums/userpics/10001/IMG-2268.JPG

Thats very neatly done,

did by chance you ever do ships loading, that looks markedly similar to the diagram maths they use for long point - point loads.

[Blknight.aus]

If you get really bored Dave, a few AULROians were trying to explain that modern air-sprung Land Rovers don’t need WDH’s on a Caravaners forum thread. The Landy owners were pushing it uphill because those forum guys just cant comprehend it. Hilarious!

WDH with Air Suspension - "Please Explain!!!!" - Caravaners Forum - Since 2000 (https://caravanersforum.com/viewtopic.php?f=2&t=82056)

I like WDH when its all set up properly...

I'd argue that they should be used when (ignoring semis) the tow vehicle has less than 1.5X mass of the trailer and high speeds are expected (lets say extended runs over 80 KPH) BUT.....

Landrovers policy is they should not be used as they put the handling dynamics outside of what the computer thinks they will be.

and unfortunately 80% of the ones I have seen havent been setup properly and have the potential to make things worse.

so..

my official what I generally tell people position is..

"if you need a distribution hitch then you're not doing it right"

[Slunnie]

Thats very neatly done,

did by chance you ever do ships loading, that looks markedly similar to the diagram maths they use for long point - point loads.

Thanks Dave, I never did ship loading but it would be exactly the same engineering maths. I did it at Uni.

[Chops]

I know some farmers and truck drivers that this guy is going to need to have some big long discussions with and tell them how to do their job safely. We've got road trains out here massing over 100T all up and at best maybe 16 of that is the prime mover, lets be really generous and say that the prime mover and the front trailer weigh about 1/3 of the total mass, the next 2 to 7 trailers (I'm including mine specials on closed roads) still hughely out weigh the mover and trailer.

12T tractor hauling 35+T worth of machinery trailer or a string of product bins, every other day.


The only credit I can give him is this...

if you look at his exact arguments and accept all of the situations he presents as being factual and the only examples available he is more or less close enough to correct. However we dont operate in his exceptionally limited range of exposure.

If I remember rightly, I think an MF135 weighs in at about two ton,,, we’d have up to three trailers on the back with three apple bins on each. We used to work on an average of just under 500kg per bin (??), not sure what the trailers would weigh in at though, they were single axle, and damn heavy to try and lift up if they fell off they’re stands.
Ive seen longer bin trains, but not towed more than three myself. Seen a few incidents with runaways down hills etc,, always scary to watch.

[gavinwibrow]

Extact of Dave's post

I know some farmers and truck drivers that this guy is going to need to have some big long discussions with and tell them how to do their job safely. We've got road trains out here massing over 100T all up and at best maybe 16 of that is the prime mover, lets be really generous and say that the prime mover and the front trailer weigh about 1/3 of the total mass, the next 2 to 7 trailers (I'm including mine specials on closed roads) still hughely out weigh the mover and trailer.

12T tractor hauling 35+T worth of machinery trailer or a string of product bins, every other day.


Question
So does this all mean that my long term hearsay understanding that subject to all other aspects being covered, a car could pull a directly connected trailer that weighed up to 1.5 times the weight of the car is a furphy? (and that my 3T D4 therefore can't legally tow my 3.5T tandem trailer (as an aside, I follow the European model and have a towball weight of about 7%/200 kilos, rather than the AU 10%/350 kilos)

[Slunnie]

Question
So does this all mean that my long term hearsay understanding that subject to all other aspects being covered, a car could pull a directly connected trailer that weighed up to 1.5 times the weight of the car is a furphy? (and that my 3T D4 therefore can't legally tow my 3.5T tandem trailer (as an aside, I follow the European model and have a towball weight of about 7%/200 kilos, rather than the AU 10%/350 kilos)

I just work off the manufacturers tow rating.

Also, totally agree that 10% ball weight is too high.
I also load based on drop on the towball height measurement - about 1" max which is less than 270kg on the rear axle, so probably about 200kg on the ball.

[Tombie]

Blkknight.

100t combinations? That’s cute [emoji41]
Our combinations are 2-4 trailers and 300t min.

[emoji106]

[Blknight.aus]

Extact of Dave's post

I know some farmers and truck drivers that this guy is going to need to have some big long discussions with and tell them how to do their job safely. We've got road trains out here massing over 100T all up and at best maybe 16 of that is the prime mover, lets be really generous and say that the prime mover and the front trailer weigh about 1/3 of the total mass, the next 2 to 7 trailers (I'm including mine specials on closed roads) still hughely out weigh the mover and trailer.

12T tractor hauling 35+T worth of machinery trailer or a string of product bins, every other day.


Question
So does this all mean that my long term hearsay understanding that subject to all other aspects being covered, a car could pull a directly connected trailer that weighed up to 1.5 times the weight of the car is a furphy? (and that my 3T D4 therefore can't legally tow my 3.5T tandem trailer (as an aside, I follow the European model and have a towball weight of about 7%/200 kilos, rather than the AU 10%/350 kilos)

nope. roughly (and its old school) for cars and body trucks.

2/3of the vehicle weight for unbraked trailers
= weight for override olnly
1.5x vehicle weight with a command brake trailer

[Blknight.aus]

Blkknight.

100t combinations? That’s cute [emoji41]
Our combinations are 2-4 trailers and 300t min.

[emoji106]

yep over 100T all up

I've personally only steered as high as 105T so thought it best for the purpose of the post to limit the info to my personal experience in the same vein as the other forums primary antagonist

[350RRC]

I just work off the manufacturers tow rating.

Also, totally agree that 10% ball weight is too high.
I also load based on drop on the towball height measurement - about 1" max which is less than 270kg on the rear axle, so probably about 200kg on the ball.

I just don't get the 10% ball weight thing.

Have towed many different trailers, loads, etc in many different vehicles over the years.

There has been nothing worse than towing 3,000+ kgs with a truckload of ball weight and having really light steering.

The genuine LR towbar on my 74 2door says max 4,000 kg towing capacity, subject to hitch used and 120 kg max ball weight. I'm happy towing like that. having done it a lot (albeit only up to 3,000 kg).

Brick goes where pointed.

Is the 10% thing just in case you forget to clip the coupling on the ball or something? [thumbsupbig]

Some 'failsafe measure'?

DL

And just for Dave who needs a laugh................... towing 'stories' from the US:

Share your trailer towing horror stories... - Page 4 - Pirate4x4.Com : 4x4 and Off-Road Forum (https://www.pirate4x4.com/forum/general-4x4-discussion/46436-share-your-trailer-towing-horror-stories-4.html)

[gavinwibrow]

nope. roughly (and its old school) for cars and body trucks.

2/3of the vehicle weight for unbraked trailers
= weight for override olnly
1.5x vehicle weight with a command brake trailer


Good, so x 1.5 is not a complete furphy then for my command braked trailer!

[Saitch]

So, if you're in the upper reaches of your weight limit, every time you encounter undulations on a road/track with the van hitched up, it could be very likely that you would be exceeding the defined tow weights when on the downward compression of the rear suspension, therefore, towing illegally.

In my opinion...154077

[350RRC]

Well I've never really thought much about towing a van because I don't have one, but I do get to hear a lot of 'scientific' discussion from a couple of blokes who do.

One of these blokes has a 200 series LC and a big mofo van and is obsessive about the 10% ball weight thing. (he also cleans the stones out of the van tyre treads after a trip)

We only discuss such matters because he didn't believe that a RRC could legally tow 3500 kg or more, till I showed him a pic of the plate on my towbar. Cost him a slab.

He does admit that the 10% thing is only a recommendation, and that he had to get a GVM increase for the 200 when it was still legal to do so to maintain a reasonable payload in the tug, buckling under 300 + kg on the towbar.

A bit of a look around the net reveals the Oz 10% mantra is based on a US study. In the US they can and do go much faster than here.

In Europe the same weight vans are towed with way less ball weight.

Seems like a black art to me.

DL

[DiscoMick]

The dynamics of this are very interesting, and a bit of a mystery to me, so I'm learning from this thread.
The point about semi-trailer and other trucks towing multiple times the prime mover weight certainly shows that a vehicle can tow much more than its own weight if it is set up right.
On trailers, an interesting example is that our camper trailer has, according to the manufacturer, a weight of about 1600kg and a towball of 140kg. However, they offer a extra 100 litre water tank which can be attached to the rear behind the spare tyres. They say adding that 100 litre tank reduces the towball from 140kg to 110kg. So it's interesting to see the effect of where the weight is placed.

[Graeme]

So, if you're in the upper reaches of your weight limit, every time you encounter undulations on a road/track with the van hitched up, it could be very likely that you would be exceeding the defined tow weights when on the downward compression of the rear suspension, therefore, towing illegally.

In my opinion...
Not in my opinion as the manufacturer would have taken that into account in setting the static weight limits.

[Saitch]

Not in my opinion as the manufacturer would have taken that into account in setting the static weight limits.

Whaaat:o?

Manufacturers test their vehicles on the Bruce Highway!!!!

Get out of it, Graeme.[thumbsupbig][biggrin]

[Graeme]

Get out of it, Graeme?

[Blknight.aus]

So, if you're in the upper reaches of your weight limit, every time you encounter undulations on a road/track with the van hitched up, it could be very likely that you would be exceeding the defined tow weights when on the downward compression of the rear suspension, therefore, towing illegally.

In my opinion...154077

Nope the weights are the static limits, the dynamic limits are all worked out from the max static limits.


Not in my opinion as the manufacturer would have taken that into account in setting the static weight limits.

correct.

Some very old vehicles have a normal limit and then special condition limits which allow you to tow a hell of a lot more but under restrictive conditions.

as energy is basically mass x velocity^2 if you cut the speed way down you can push the mass up significantly and retain control.

[Graeme]

Some very old vehicles have a normal limit and then special condition limits which allow you to tow a hell of a lot more but under restrictive conditions.My 1st RRC could tow 8T IIRC (but possibly only 6.5T - another number from long ago) but with a max speed of 40 kph, otherwise 4T.

[cripesamighty]

From an early RRC manual. I don't know what the really early manuals show.
Limited use, low range, under 40kph, max tow weight = 6 tons.
Max trailer weight plus vehicle 8.5 tons.

154104

[Slunnie]

The dynamics of this are very interesting, and a bit of a mystery to me, so I'm learning from this thread.
The point about semi-trailer and other trucks towing multiple times the prime mover weight certainly shows that a vehicle can tow much more than its own weight if it is set up right.
On trailers, an interesting example is that our camper trailer has, according to the manufacturer, a weight of about 1600kg and a towball of 140kg. However, they offer a extra 100 litre water tank which can be attached to the rear behind the spare tyres. They say adding that 100 litre tank reduces the towball from 140kg to 110kg. So it's interesting to see the effect of where the weight is placed.

The semi-trailers dynamics are totally different to a car that is towing, the whole design is just so different and in reality they are not comparable.

For water tanks, I think the best place for them is over the axle and definately not behind the axle.


https://www.youtube.com/watch?v=6mW_gzdh6to

[Saitch]

?

Just a "Turn of Phrase", Graeme. No malice intended.

If static overloading is taken into account by the manufacturers , as explained above by Blknight, then would or would not the same physics apply to the OP's query?
Like others on here, my physics rationale is somewhat lacking.[bigsmile1]

[Pedro_The_Swift]

Thats just wrong Slunnie,, in so many ways.
all it is is an advertising gimmick to sell stuff, scaremongering at its worst.

in all of history nothing has ever been built where the axle is in the middle of the tow length. not even box trailers.


to give an example,, my 30 year old Golf is 4.2m from hitch to the centre of the axles,, and then only another 2.5m to the number plate.
and mine has what I consider a short A frame....


someone somewhere build a toy with those dimensions!! :soapbox::soapbox::soapbox::soapbox:

[Slunnie]

Thats just wrong Slunnie,, in so many ways.
all it is is an advertising gimmick to sell stuff, scaremongering at its worst.

in all of history nothing has ever been built where the axle is in the middle of the tow length. not even box trailers.


to give an example,, my 30 year old Golf is 4.2m from hitch to the centre of the axles,, and then only another 2.5m to the number plate.
and mine has what I consider a short A frame....


someone somewhere build a toy with those dimensions!! :soapbox::soapbox::soapbox::soapbox:
I disagree with that, it's given a really good physics demonstration there. Its not about the axle being 20% further forward or rearward, its a demonstration of how the loading will influence the stability of the trailer. If anything that design is emphasising the situation for the sake of demonstration, but the take aways from that demonstration are still exactly the same, which is not to place the load masses to the rearward extremity otherwise it will induce wagging. We all know that trailers can get the wags on, especially caravans which have long rearward overhangs with weight on the ends and this demonstration is showing what that can do.

[Graeme]

Just a "Turn of Phrase", Graeme. No malice intended.

If static overloading is taken into account by the manufacturers , as explained above by Blknight, then would or would not the same physics apply to the OP's query?
Like others on here, my physics rationale is somewhat lacking.[bigsmile1]
I'm not familiar with the phrase so didn't and still don't know what you meant.

Momentary or cyclic extra load on the tow-bar due to forward/aft rocking on undulating surfaces is not static load and therefore doesn't breach a static load limit, even though I think it is unlikely that LR tested extreme possibilities of vans on badly undulating surfaces and therefore damage to the tow vehicle could occur. Long tow couplings, such as the one that I use on my L322 to clear the bumper, could be a legal issue because LR's maximum ball weight specifications include the maximum distance of the ball from the retaining pin.

[Pedro_The_Swift]

its actually a really bad physics demo,, it has NOTHING to do with the real world.

as stated. Its design premise was to SELL stuff,, ( I saw this demo 30 years ago at the Brisbane Ekka, at an aftermarket/accessory display)
its designed to actually SCARE people into buying goods.

[Tombie]

its actually a really bad physics demo,, it has NOTHING to do with the real world.

as stated. Its design premise was to SELL stuff,, ( I saw this demo 30 years ago at the Brisbane Ekka, at an aftermarket/accessory display)
its designed to actually SCARE people into buying goods.

The machines axle line can be moved, I’ve seen the display also, and they moved it around.

Still an excellent display of the physics in action.

[Odysseyman]

On another web site, it is claimed that when you put a towball weight on your car (does not matter what the weight is) weight comes off the front of the car and as such more than the tow ball weight is added to the rear axle load. The quote is much like the fulcum on a see saw. What has been quoted is that a ball weight of 350kg means about 500kg is loaded onto the rear axle. I failed physics so I am unsure if this is correct. If this is the case then I question if any car could tow a 3.5T van with a notional ball weight of 350kg. Can any of you gurus here answer my question in simple terms. I dont know how you can accurately guess the tare weight on a rear axle unless you drive over a weigh bridge, so just halving the Tare weight would not give an accurate figure, or so i would deduce as I would think more weight would be biased to the front due to the engine and gearbox being more located to the front of the vehicle.Thanks David

Hi David

if you know your ball weight then this simple calculation will tell you what weight will be added to your rear axle.


To calculate the actual ball weight affect on the rear axle; multiply the ball weight by the (vehicle wheelbase plus the rear overhang) and then divide the answer by the wheelbase.
cheers
David

[350RRC]

The machines axle line can be moved, I’ve seen the display also, and they moved it around.

Still an excellent display of the physics in action.

Sometimes when you're trying to find the subtle cause of a cascading problem or you're pressed for time to get to the root cause of an issue it is very helpful to go to an extreme to see what happens.

I don't see that vid as even being close to extreme. It just shows a cause and effect very simply.

DL

[pjh4159]

On another web site, it is claimed that when you put a towball weight on your car (does not matter what the weight is) weight comes off the front of the car and as such more than the tow ball weight is added to the rear axle load. The quote is much like the fulcum on a see saw. What has been quoted is that a ball weight of 350kg means about 500kg is loaded onto the rear axle. I failed physics so I am unsure if this is correct. If this is the case then I question if any car could tow a 3.5T van with a notional ball weight of 350kg. Can any of you gurus here answer my question in simple terms. I dont know how you can accurately guess the tare weight on a rear axle unless you drive over a weigh bridge, so just halving the Tare weight would not give an accurate figure, or so i would deduce as I would think more weight would be biased to the front due to the engine and gearbox being more located to the front of the vehicle.Thanks David
David I cannot see the logic in a statement that putting 350 kgs on the towball means adding 500kgs added to your vehicles weight! Some manufacturers place load carrying reductions greater that the added towball weight when attaching a trailer but I have not seen any similar statement on this by Landrover so I am sure it does not apply in your case. All weights added to a vehicle have to take into account your vehicle GVM, axle loads front and rear and the important GCM of vehicle and trailer combined. GVM means Gross Vehicle Mass or total weight you vehicle can carry legally with front and rear axle loads equal this weight. GCM meaning total weight of the vehicle and trailer be as a maximum weight to be legal on Australian roads.

[alien]

On another web site, it is claimed that when you put a towball weight on your car (does not matter what the weight is) weight comes off the front of the car and as such more than the tow ball weight is added to the rear axle load. The quote is much like the fulcum on a see saw. What has been quoted is that a ball weight of 350kg means about 500kg is loaded onto the rear axle. I failed physics so I am unsure if this is correct. If this is the case then I question if any car could tow a 3.5T van with a notional ball weight of 350kg. Can any of you gurus here answer my question in simple terms. I dont know how you can accurately guess the tare weight on a rear axle unless you drive over a weigh bridge, so just halving the Tare weight would not give an accurate figure, or so i would deduce as I would think more weight would be biased to the front due to the engine and gearbox being more located to the front of the vehicle.Thanks David


David I cannot see the logic in a statement that putting 350 kgs on the towball means adding 500kgs added to your vehicles weight! Some manufacturers place load carrying reductions greater that the added towball weight when attaching a trailer but I have not seen any similar statement on this by Landrover so I am sure it does not apply in your case. All weights added to a vehicle have to take into account your vehicle GVM, axle loads front and rear and the important GCM of vehicle and trailer combined. GVM means Gross Vehicle Mass or total weight you vehicle can carry legally with front and rear axle loads equal this weight. GCM meaning total weight of the vehicle and trailer be as a maximum weight to be legal on Australian roads.
I took advantage of an empty VicRoads certified weigh bridge this weekend with our TVan on behind a 110 Defender.
It produced an interesting result given this discussion with the last figures I’ve supplied.
I run no weight distribution hitch and on coil springs all around. It would be interesting to do a similar test on a vehicle with air bag suspension and one with a weight distribution hitch.

Defender with van attached...
Front axle -1•20
Rear axle- 1•94
GVM. - 3•14
Van axle - 1•10
GCVM -4•24

Van only...
Axle. - 1•10
Hitch. - 0•16
GTM -1•26

Defender only...
Front axle - 1•32
Rear axle. - 1•66
GVM -2•98

The variation on the 110 with the trailer on...
Front axle - Decrease of 0•12
Rear axle. - Increase of 0•28

[Tombie]

That T-van is quite nose heavy given its mass.

[alien]

That T-van is quite nose heavy given its mass.
They all are and it’s often discussed on the Track forum.

[W&KO]

I took advantage of an empty VicRoads certified weigh bridge this weekend with our TVan on behind a 110 Defender.
It produced an interesting result given this discussion with the last figures I’ve supplied.
I run no weight distribution hitch and on coil springs all around. It would be interesting to do a similar test on a vehicle with air bag suspension and one with a weight distribution hitch.

Defender with van attached...
Front axle -1•20
Rear axle- 1•94
GVM. - 3•14
Van axle - 1•10
GCVM -4•24

Van only...
Axle. - 1•10
Hitch. - 0•16
GTM -1•26

Defender only...
Front axle - 1•32
Rear axle. - 1•66
GVM -2•98

The variation on the 110 with the trailer on...
Front axle - Decrease of 0•12
Rear axle. - Increase of 0•28

I’m a fan of weigh bridges and am a regular.

Are the number right

Van TBW is 160kg but it has increased the rear axle weight by 280kg

[alien]

I’m a fan of weigh bridges and am a regular.

Are the number right

Van TBW is 160kg but it has increased the rear axle weight by 280kg
Using a weigh bridge is a daily multiple occurrence for me at work so happy I’ve recorded correct numbers.

I’ve been over the figures a few times and double checked then with another person too.

Yes, the rear suspension is increased by more than just the Tow Ball Weight.

[Slunnie]

I’m a fan of weigh bridges and am a regular.

Are the number right

Van TBW is 160kg but it has increased the rear axle weight by 280kg

That's because the TBW is behind the rear axle and it unloads weight from the front axle onto the rear axle.

[W&KO]

That's because the TBW is behind the rear axle and it unloads weight from the front axle onto the rear axle.

Got it now