Ball weight... how do you calculate

Hi Steve,

Thanks for the info and thanks to the rest of the wise people that frequent this forum. Had a look at you rig profile, can you tell me the make, size and weight of your van.

Cheers

Graham

goodday graham
the van is a paramount "delta"17'6 internal about 2t+ loaded
when looking at vans dont be fooled by the sales people and van weights and ball weights as they are all done when van is empty it all changes when tanks are filled stuff put under the bed and if the water tanks are both in front of the axle it adds a lot to the ball weight when full
have a look at the hayman reece site it gives some goood tips and also how to get the ball weight properly with house hold scales

steve

Easier said than done sometimes. My ball weight was in excess of 300kg and would have surely stuffed most bathroom scales. Better option is to go to caravan repairer and ask them to tell you unless you can lift the front of the van by hand, then you would be sure not to stuff a set of bathroom scales.
I personally prefer a bit of extra weight on the ball as I think the trailer tows better this way as opposed to tail heavy. So long as the vehicle is set to cope with this and you don't go stupid all should be OK.

Regards Trevor.

Yota - assume you mean a kitchen scale?

Ball weight in excess of 300kg's - strewth! If mine weighed that much I'd think I'd gladly stuff anything. A man's not a wheelbarrow.

re: the kitchen scale - thanks but I think I'll politely 'pass' on the next cake you bake then:-)

Much childish giggling going on here. bbbbbwahahahahahhaha:-)))

You may find this helpful

Click on this and it will take you to the Hayman Reese site which will help with the way to determine the drawbar weight on the towball
vis GTW, TW capacities

link text

Cheers aston

"2. A simple 'home made' solution is using bathroom scales. If you are worried about going over the scale limit, use two. Put a piece of timber between them and rest the jockey wheel on the timber. Add together the reading of the two scales"

The Jockey Wheel will show more weight. The reading needs to be directly UNDER the ball housing.

Hi Lone Wolf. I'm not going to claim to be an expert, but here is my understanding:

100% of the weight of the van is transmitted to the ground, no more no less. It is transmitted through any load bearing point. In this case we have 4 wheels (I think) and a jockey wheel (or tow ball if attached to the vehicle). Providing the jockey wheel is set so the van coupling is at the same hight as it would be when attached to the vehicle, the weight transmitted through the jockey wheel will be the same as transmitted through the ball to the vehicle. For the purpose intended 'near enough should be good enough' as far as hight of the ball is concerned.

Put another way. The weight on the wheels will not have changed, so the balance must be on the jockey wheel, or tow ball.

Regardless of whether the wheel is resting on the ground, one scale, 2 scales or 10 scales, the same weight must be transmitted to the ground. In this case it is via the scale(s) which will accurately measure the weight. For it not to measure accurately, the missing (or extra) weight has to get to the ground somehow. It could only be via the wheels. But how could that be so?

Happy for you to correct me with better science, but that is my understanding.

I weighed my ball weight using this method. I later was able to borrow a hydraulic jack with a weight scale. Measured weight was within 5KG in 240KG or about 2%. Close enough for my purposes.

Check out Aston's link to the Hayman Reese web site (above). They use the same 'science' as me, but being smarter, they use one scale and a brick (rather than 2 scales). If you place the tow ball exactly half way between the scale and brick, you multiply the measured weight by 2 to get the actual weight (the other half of the weight is carried by the brick. Place it 2 thirds of the way towards to the brick, multiply by 3 etc. Using this method you could theoretically measure any weight, regardless of the capacity of the scale.

Actually Norm, that is a good call, and I had to think it through...

My reasoning, and may I please re-iterate, my own reasoning, is due to simple leverage.

If I move my trailer, and lift it with the handle, which is very close to the ball coupling, I am lifting around 27 kg.

If I do the same thing, but move my hand in towards the trailer, by about a metre ( where my jockey wheel is), I struggle. If I keep moving back, and try to lift at one of the wheels, I'm battling with 120 kg ( approx.)

Bit like pushing open a door in your house with the handle, and then doing it again at the hinge... leverage.

Anyway, it's late, and I'm splitting hairs... lol.

Cheers

Wolfie

I'll back you up on that one Wolfie, it is indeed the lever arm length principle that applies here.
As you say, some jockey wheels are fixed far enough back from the coupling to give a very wrong reading.
And no, you're not splitting hairs at all her.
Klaus

Lone Wolf and V8, of course you are right if the jockey wheel is set well back. But this is true no matter what scale you use. A common method of measuring ball weight is to get the jockey wheel onto a weigh bridge, but leave the wheels just off.

Only way to solve the leverage effect, if it is large, is to rest the coupling on something, like a couple of bricks, then deduct the weight of the bricks. Pretty simple.

That used to be the case. Caravans were made in batches and one or two were weighed and the whole batch would be plated the same, but the are not allowed to do it anymore.

Each individual unit must have it's tare weight stamped on the plate.
(so Jayco tell me)

That may be true but do the manufacturer's use weighbridges which would be regularly calibrated or do they use their own which have probably never been check calibrated since purchase 10 years ago and could now be reading 100kg or more incorrect ???

Cheers

Darryl
Brisbane

An interesing aside to this, is what information the manufacturer of the vehicle provides to the purchaser.
In 1997 I bought a new Toyota diesel tray back. Now this is a vehicle designed to carry loads and presumably also built to tow. But what does the owners manual say about permissable loads, trailer weights etc.?
Apart from a GVM of 3150kg., absolutely nothing.
I also have a Landrover Discovery, also bought new 1997 which in its owners manual gives max. figures for ball weight, allowable towed weights (various brake combinations), max allowable weight over front axle, rear axle and GVM. It also recommends that levelling aids should not be used.
This is the sort of information I believe all manufacturers should provide, it corresponds to the sort of questions frequently asked and relieves the sales person of that responsibility
kesh