how do i measure noseweight

[Gagakev]

Thanks for your replies folks

Just stood the new po-go style gauge next to the tow ball and guess what, it's nearly the same height!!!(approx 40mm lower)

So thinking when the boot is loaded, caravan hitched up (to work out the correct height) the po-go is going to be too tall, unless it's near perfect when the gauge is compressed with the van attached to it. Time will tell.

Now, the yellow peril, just a thought, if it is designed for purpose surely the height factor would be built into the design to compensate.

Think I'll go back to the bathroom scales with the piece of wood!!

 

[Reg]

I think that the height will make minimal difference to the reading. I personally prefer to use the scales under the jockey wheel as its more secure. If you check the readin with the break on, which for safety you must, then there is a differnce of .1Kg as the leverage is slightly longer (as

 

[Reg]

I hadn't finished!

I think that the height will make minimal difference to the reading. I personally prefer to use the scales under the jockey wheel as its more secure. If you check the reading with the brakes on, which for safety you must, then there is a calculated difference of .1Kg as the leverage is slightly longer (as per my sketch). But the differences are so minimal that they are not worth considering.

 

[Lutz]

The height of the coupling at which the noseweight is measured can have a substantial effect on the noseweight itself on relatively short caravans with a high centre of gravity, especially if lots of heavy items are placed in the overhead lockers. The longer the caravan or the lower the centre of gravity, the less sensitive the noseweight becomes to towball height.

 

[ProfJohnL]

Reg's diagram is very useful. It shows the relationship between force and distance and how it relates to a caravan. It may surprise many of you that in the example given the difference in measuring position gives an difference as big as 8.7Kg! and the example is not unreasonable.

Even though the difference in distance between the jockey wheel and the tow hitch is shown as 0.4M, You can see therefore any thing that changes that distance will affect the accuracy of the reading. For that reason it is important to ensure the jockey wheel is always pointing in the same direction relative to the caravan when taking the reading.

Just as an example and using reg's figures. In the diagram the jockey wheel is pointing forward. Because of the caster of the jockey wheel, its axle can be offset from the main jockey post by 0.120M. (Pneumatic tyred jockey wheels may be greater) So if the wheel was pointing straight back, the jockey wheels axle will be 0.24M (2 x 0.12M) closer to the caravans main axle so the calculations now gives

4 x 75 =300

300/(3.6-0.24) = 89.3Kg

The direction of the jockey wheel can make a difference of 6Kg in this example!

It is advantageous because the jockey wheel won't suddenly slip out of the socket like it did for Steve L, it is easily height adjustable, and you always have it with you, all you need are the scales and a piece of wood to spread the load.

WARNING.

The above method is only reliable for single axle vans as the single axle is the only fulcrum point of the main carriage wheels.

Twin axles have more complex interactions between the suspension of the two axles, and the effective fulcrum point of the main wheels is variable. Here it is better to get a true maximum reading at the hitch, and then repeat the exercise at the jockey wheel to provide the correction figure.

 

[DerekBrad]

It seems to me that Dave has found the easiest solution. Personally, I have never weighed my van in over 30 years of towing, but have always loaded in what I consider to be a sensible, almost intuitive way.Have never experienced any load related problems and have always towed within speed limits.Sorry if this horrifies some my fellow enthusiasts!

 

[Gagakev]

Derek you are not alone, read this written by Nigel D the Editor in this months PC mag

Bit shocked by a poll on PC Facebook group. It asked how often folk weigh their vans. Nine per cent said they do every time they tow but 58% never have!!!

Makes you wonder.

 

[Steve L]

I know we can all get very technical with sketches and theories but all that goes out the window if the measuring device be it, pogo stick, yellow peril or the wifes best scales from the boudoire, are not calibrated and CE marked.

Take the yellow peril I use that fits on the car towball and sit's in the hitch of the trailer. Basically all you have is a couple of plastic mouldings with a spring between them and a plastic pointer that slides up and down a scale of lines and nubers.

Without being calibrated and frequently re- calibrated it is only a comparator.

Once you have loaded your van to the indicated weight and have driven without incident that is then a presumed acceptable load situation. Now one believes that as long as we follow the same indicated weight graduation, then things should remain stable.

So, forget all the technical blurb, as long as you get the confidence that you have towed at the indicated nose weight successfully, then that is basically all we need. A guiding marker stick to idicate devience from the established acceptable tow situation.

I use the bathroom scale method at home and duplicate it using the yellow peril. Sure enough mine happened to read very close to the scales. But when touring, I use the peril as it is less obtrusive and more practical to carry around.

Atb Steve L.

 

[Reg]

Lutz

I take your point about the C of G of the van affecting nose weight in relation to towball height. I can calculate the position of the C of G in the horizontal but not in the vertical.

What is your best guess?

I would think about 70cm from ground but its just a guess.

With that information I can then calculate the effect of raising or lowering the ball on the nose weight. Obviously this will change according to the way the van is loaded but it might give us some idea on the effect.

Reg

 

[Lutz]

I really have no idea how high the centre of gravity of a caravan typically is. Of course it depends on how the payload is distrubuted, especially what heavy items are stored in the overhead lockers. An air conditioning unit on the roof, for example, if fitted, is bound to have a significant effect. I rather suspect that your assumption of 70cm is a bit on the low side. I'd expect it to be between 80 and 90cm.

 

[ProfJohnL]

I really have no idea how high the centre of gravity of a caravan typically is. Of course it depends on how the payload is distrubuted, especially what heavy items are stored in the overhead lockers. An air conditioning unit on the roof, for example, if fitted, is bound to have a significant effect. I rather suspect that your assumption of 70cm is a bit on the low side. I'd expect it to be between 80 and 90cm.

The fact is the CofG will be different for every caravan, and even different for the same van for both outward and return journeys, so there is no simple correction figure that can be applied.

 

[Reg]

Accepting that there will variations from one van to another these findings can only be used as a rough guide but my reason for producing them was to determine whether the change in height of the tow hitch when measuring the nose weight would be devastating.

Draw your own conclusions.

 

[Gafferbill]

.......I hope Julie is following all this!

 

[ProfJohnL]

Accepting that there will variations from one van to another these findings can only be used as a rough guide but my reason for producing them was to determine whether the change in height of the tow hitch when measuring the nose weight would be devastating.

Draw your own conclusions.

Hello Reg,

Thank you for working out the figures. It gives an indication of the scale of changes, and that is useful. I am sure you would agree though that what you have provided is a very specific, and it is not just the assumption of the position of the CoG all the measurements are assumptions, but at least they are measurable.

Now I challenge you to do the same for a twin axle caravan.

 

[Reg]

Oh John!!!!

For me there are too many unknowns. For the single axle it was easy to just go along to the caravan with a tape measure but I just do not have any data on a twin axle.

My thoughts are that if each axle has it's own suspension then this would play a part in the nose weight and this would be a completely different ball game. The front axle springs might absorb some of the load if the CofG changed.

But it's just my guess.

I might just have a look around to see if there is any data............

It sounds er........... interesting......... challenging...... especially when I look outside at this grotty weather!!!!!

Reg

 

[Millerman]

Off I went to storage tonight, armed with the wealth of info this thread has provided.

I previously used the pogo stick thing but have now "upgraded" to the argos bathroom scales. I never was too keen on that setup as I always had visions of the stick moving and the van falling on its nose.

Having removed the two 4.5kg gas bottles I can get my Charisma 550 down to 90kg on the scales, which allowing for the 2kg they are out by (checked against significantly more expensive scales at home) makes 88kg. Is it "reasonable to assume" that the other 3kg would disappear based upon the calculcations above being the difference between jockey wheel and tow hitch? (Tow bar limit 85kg).

Also do I need to put a block of wood on the scales or can I just place the jockey wheel directly on to them?

It was amazing to see the movement on the scales when the power cable was moved further back under the fixed bed - perhaps I'm developing a late interest in physics!

I'm just glad my tow bar limit isn't 75kg or I'd really be struggling - probably have to take the front windows out or something!

 

[ProfJohnL]

Off I went to storage tonight, armed with the wealth of info this thread has provided.

I previously used the pogo stick thing but have now "upgraded" to the argos bathroom scales. I never was too keen on that setup as I always had visions of the stick moving and the van falling on its nose.

Having removed the two 4.5kg gas bottles I can get my Charisma 550 down to 90kg on the scales, which allowing for the 2kg they are out by (checked against significantly more expensive scales at home) makes 88kg. Is it "reasonable to assume" that the other 3kg would disappear based upon the calculcations above being the difference between jockey wheel and tow hitch? (Tow bar limit 85kg).

Also do I need to put a block of wood on the scales or can I just place the jockey wheel directly on to them?

It was amazing to see the movement on the scales when the power cable was moved further back under the fixed bed - perhaps I'm developing a late interest in physics!

I'm just glad my tow bar limit isn't 75kg or I'd really be struggling - probably have to take the front windows out or something!

Well provided you removed the rear windows as well that would reduce the towing drag, and improve you MPG.

 

[ProfJohnL]

Hello Millerman,

Having given some thought to your reply:-

Firstly more expensive scales does not equate to more accurate, so your assumption about the accuracy of the more expensive set at home is uncorroborated. Perhaps the cheaper set are the more accurate? Try comparing the scales with an empty Aquarol to get its tare weight , then filled with a measured 40L of water (1L of water weighs 1Kg so 40Kg) scales should read 40K = the tare weight.

It is probably better to use a piece of wood to spread the load from the jockey wheel to prevent damage to the scales.

It is also wrong to assume that the load imposed at the hitch will be 3Kg less than at the jockey wheel, that all depends on the geometry of your chassis. You either need to check the difference by comparing the two loads, or by working it out using the methods and examples given by Reg, also you need to be aware of the alignment of the jockey wheel relative to the chassis as per one of my later postings.

The need for good measurement becomes more critical the closer the hitch load approaches the upper available limit, as it is an offence to exceed it. As you are working very close to your available limit, the odd Kg may be the difference between legal and points on your licence.

You tell us that by removing the gas bottles you are getting closer to your target nose load. I must tell you that if you intend to carry gas, it must be secured in an upright attitude, and in its properly defined ventilated box. So you need to address the nose load by repositioning the other items in the caravan further away from the front, and may be behind the axle to counter balance the weight of the gas bottle(s).

I have yet to find a caravan that cannot be balanced with the gas bottle(s) in situe, by repositioning other normal items.

 

[Millerman]

Thanks John L.

My assumption re the other scales accuracy is based on SWMBO going to Weight Watchers each week and measuring same as at home!!!

Will leave gas in situ and put more items under fixed bed behind axle.

 

[ProfJohnL]

Hello Millerman,

Having given some thought to your reply:-

Firstly more expensive scales does not equate to more accurate, so your assumption about the accuracy of the more expensive set at home is uncorroborated. Perhaps the cheaper set are the more accurate? Try comparing the scales with an empty Aquarol to get its tare weight , then filled with a measured 40L of water (1L of water weighs 1Kg so 40Kg) scales should read 40K = the tare weight.

It is probably better to use a piece of wood to spread the load from the jockey wheel to prevent damage to the scales.

It is also wrong to assume that the load imposed at the hitch will be 3Kg less than at the jockey wheel, that all depends on the geometry of your chassis. You either need to check the difference by comparing the two loads, or by working it out using the methods and examples given by Reg, also you need to be aware of the alignment of the jockey wheel relative to the chassis as per one of my later postings.

The need for good measurement becomes more critical the closer the hitch load approaches the upper available limit, as it is an offence to exceed it. As you are working very close to your available limit, the odd Kg may be the difference between legal and points on your licence.

You tell us that by removing the gas bottles you are getting closer to your target nose load. I must tell you that if you intend to carry gas, it must be secured in an upright attitude, and in its properly defined ventilated box. So you need to address the nose load by repositioning the other items in the caravan further away from the front, and may be behind the axle to counter balance the weight of the gas bottle(s).

I have yet to find a caravan that cannot be balanced with the gas bottle(s) in situe, by repositioning other normal items.

Sorry finger trouble

"scales should read 40K = the tare weight"

should read

scales should read 40K + the tare weight