noseweight guage

[ProfJohnL]

....
Hi Prof.
It's a very sad day when a newbie on here is told most commercial measures are rubbish. I fully appreciate your point which is valid but you didn't acknowledge my earlier comment that I and indeed others on here have measured our Reich readings against your bathroom scale method. The difference was negligible.
I think it is very unfair to dimiss the Reich as "not fit for purpose"

Maybe it's time for PCv to research the various nose weight measurement methods and publish the result . There's nothing stopping them seeking counsel from Milenco, Reich etc

I encourage new caravanner's to take the technicalities of towing seriously, that does not mean they have to fully understand the underlying principles, but more importantly to know how to mange them sensibly. Nose load we all acknowledge is important from a safety angle, and most would also acknowledge the limits of both car and trailer should be observed, so having the right means of doing that must be important.

If someone makes the effort to purchase a nose weight gauge, they should expect it to be capable of doing the job they are purchasing it for. That should include a reasonable degree of accuracy in displaying the applied load, and that it will facilitate the correct measurement process, Quoting Milenco's usage of BS7961:2004 it calls for an accuracy of +/-2kg especially where there is a legal requirement (regardless of whether there have been prosecutions or not). Any product that fails to do what it should be doing is by definition not fit for purpose.

Of the commercial products available the Reich model is probably the most reliable, as it uses load cell technology. Load cells are a robust technology extensively used in industrial weighing noted for reliability and good repeatable accuracy. so this should give good consistency of measurement.

Another important aspect of load cells is they barely deflect under within range loads. This answers the issue of changing length under load another of the fundamental short coming of coiled spring technologies.

So two up for the Reich, but the third issue is still a significant source of error, and that is the fact it raises the hitch by the height of the device which from observations seems to be about 75mm, which is bigger than the EU permitted range of loaded tow ball heights!

Reich clearly appreciate the force measured is not the the same as the nose load produced directly at the tow ball, because they tell us the device compensates for the height error. This means the variations is enough for them to consider it necessary to make a compensation, and they found it necessary to produce dedicated single and twin axle models. However they don't tell us how the compensation is established or how it is introduced into the device, the absence of any user programmable variables suggests the compensation will most likely be a fixed additional figure of a number of kg.

If the compensation is a fixed parameter, then it can't accurately take into account all the factors that affect the variance in nose load with height. We do know that twin axles can have a very aggressive change in nose load with height, and the direction of change is not certain with out checking the individual caravan concerned.

It is encouraging to see the Reich has produced a limited number of empirical results that have close agreement with the more technically correct bathroom scale on a step method, but that is not enough evidence to confirm a whole hearted approval for all car and caravan combinations, as it fails the at height requirement,

The Reich improves on two out of three point of contention over coiled spring gauges. Whether its inherent inaccuracies are acceptable in law is not known.

I totally agree, the magazines should be supporting best practice, and I also believe we should be doing the same on forums and at the same time discouraging poor and bad practice,

I think PC should review the efficacy of the range of retail gauges and their ability to comply with the EU measurement of nose weight. but will we see a true scientific approach that reports warts and all?

If a jobs is worth doing, its worth doing properly. and that applies to measuring nose load and magazines reviews of consumer products.

 

[colin-yorkshire]

hi John, it is still very funny, but a couple of points,
1. yes the subject has been done to death, the reason it keeps coming up is because people just ask questions without looking on the forum at past threads to see if the answer is there first, the result is the same questions and answers being repeated infinitum.
2. I never said I recommended the lift method only that it worked for me as I knew how much weight I could lift one handed which just happend to be lower than the cars maximum load, I did say once the car was changed I tested it, and in doing so confirmed what I knew all along.
3. I don't know why simple issues seem to get so complicated and bound up in legal jargon and specifications when in fact there is just a simple answer out there,
ok so I go buy an electric kettle, plug it in fill with water it boils and I make my tea.
I do not need to understand how the kettle works or the electrical standard it is certified for or the type of plastic used to make it, and I don't need a temperature gauge to see how hot the water is, it is just a kettle it works so it's good enough for me.

sometimes I wish this forum had a B,S, button then when all this technical gobbledegook come out you could press it and a banner comes up ""this is B*** S***""

 

[Keefanmaxx]

Does all this mean that when I ram my 'Lay-z-spa' hot tub in the gas locker, I need to check my nose weight......... :huh:

Get you ...... That's posh!! :cheer:

Now, as a relative newbie to caravanning I acknowledge the importance of not exceeding the nose-weight, but throughout this topic there have been numerous references to the EU Regulations which, lets face it, only us Brits adhere to strictly while the rest of Europe recognises but subtly sticks two fingers up to.
I have a nose-weight gauge (one of those awfully inaccurate springy types so loved by Prof) which I use as a guide to make sure I'm legal ....... and don't rip the tow-bar off the car!

I do feel somewhat confused though. There is all this talk of the weight being measured at the height of the tow ball, the inaccuracy of bathroom scales and springy devices, the fact that possibly the most accurate device available is inaccurate because it raises the height by 75mm yet when we took delivery of our 'van, we were advised to load so it sat with a slight nose down posture to maintain stability. Surely that means increasing the nose weight??

Oh, and I use my own magazines under the caravan step Prof!!

 

[ProfJohnL]

... when we took delivery of our 'van, we were advised to load so it sat with a slight nose down posture to maintain stability. Surely that means increasing the nose weight??

Oh, and I use my own magazines under the caravan step Prof!!

All EU caravan manufacturers know the the permitted range of height for loaded towballs is 350 to 420mm. The will design their caravan with that range in mind, and the caravan will assume whatever angle that range dictates.

 

[Parksy]

..............I do feel somewhat confused though. There is all this talk of the weight being measured at the height of the tow ball, the inaccuracy of bathroom scales and springy devices, the fact that possibly the most accurate device available is inaccurate because it raises the height by 75mm yet when we took delivery of our 'van, we were advised to load so it sat with a slight nose down posture to maintain stability. Surely that means increasing the nose weight??

Oh, and I use my own magazines under the caravan step Prof!!

To maintain stability it's important to check towing vehicle and caravan tyre pressures, to load the caravan correctly and to anticipate potential risk factors when towing.
I concur with the Prof, the attitude of the caravan in relation to the tow car has no bearing on towing stability.

 

[Parksy]

All EU caravan manufacturers know the the permitted range of height for loaded towballs is 350 to 420mm. The will design their caravan with that range in mind,.............

I'm sure that this is the case Prof.
But you are also trying to tell us, with no substantive evidence to prove your assertion, that noseweight manufacturers such as Reich fail to design their products with the added height of their digital gauge and the EU permitted range of towball height in mind, even though they have stated that this is in fact taken into account within the design structure, as is the difference between s/a and t/a caravans?

 

[WoodlandsCamper]

Bet this front bike rack doesn't help the nose weight. hmy:

 

[Dustydog]

Bet this front bike rack doesn't help the nose weight. hmy:

Simple. Put Lady Squirell's nuts in the rear to balance things up

 

[Sproket]

Bet this front bike rack doesn't help the nose weight. hmy:

Funny how the photo shows it on a continental van with a long 'A' frame ....
Don't think it would fit on more up to date uk vans as they seem to be moving the body as far forward as possible

 

[ProfJohnL]

All EU caravan manufacturers know the the permitted range of height for loaded towballs is 350 to 420mm. The will design their caravan with that range in mind,.............

I'm sure that this is the case Prof.
But you are also trying to tell us, with no substantive evidence to prove your assertion, that noseweight manufacturers such as Reich fail to design their products with the added height of their digital gauge and the EU permitted range of towball height in mind, even though they have stated that this is in fact taken into account within the design structure, as is the difference between s/a and t/a caravans?

Hello Parksy,

I cannot put words into manufacturers mouths, so if you really want to know the answer to that specific question you need to ask them not me. But for evidence and the suspicion it raises look at the gauges, and as none of them include any form of height adjustment feature to allow users to match the towing height, you may draw your own conclusion.

What I can say with total confidence as I have done so on many occasions, unless the measurement height is the same as the towing height, the load the gauge experiences is not the Towed Nose Load. Whilst Rwich do claim to understand there is a difference to be considered, the difference is not a fixed value, it varies depending on the trailers geometry and the way it is loaded. However, I must be fair and in some cases the added value may indeed be correct, but change the dimensions or loading of the trailer and that value will not be 100% correct. The difference may be small on a SA but its not correct, and with TA's the difference is far more complex and can be much bigger and either positive or even change to a negative depending on the combination of the car trailer and loading.

 

[Hutch]

To add to the thread,, this mornining on a levelel driveway, brake off on the van, on bathroom scales, level height to the hitch 75 kg 6 inches higher 75 kgs , 6 inches lower 75 kgs. So in my experiences, negative real problems. Scales made by Salter.
Just be below your tow hitch value.

 

[Gafferbill]

...........if the height measuring device weighed 1kgs you are 1kgs out!
tut tut!!

 

[Sproket]

To add to the thread,, this mornining on a levelel driveway, brake off on the van, on bathroom scales, level height to the hitch 75 kg 6 inches higher 75 kgs , 6 inches lower 75 kgs. So in my experiences, negative real problems. Scales made by Salter.
Just be below your tow hitch value.

Should have wound the legs up ....... :lol: :lol:

 

[Parksy]

I can see where our opinions diverge now Prof.
My understanding is that noseweight is noseweight, no matter what the dimensions of any given trailer may be.
Just to be clear:

• If more weight is added forward this will create an increased downward force via a tow hitch onto the towball of the towing vehicle.
  [*]If weight is subtracted there will be a reduction in the downward force and thus less noseweight.
  [*]The noseweight of a trailer is measured when the trailer (in our case a caravan) is static.
  [*]We already know that according to the EC directives the specified height of any towball or coupling height is between 350mm and 420mm on level ground when applied to a fully laden vehicle via the towing hitch of the trailer.
  [*]A trailer coupling head should be between 385mm to 455mm when the trailer (or caravan) is fully laden.
  [*]Trailer or caravan hitch height varies significantly when the unit is travelling but our concern is to measure the static noseweight within the parameters given.
  [*]There is as far as I'm aware no directive which specifies coupling height for a moving vehicle and towed trailer.
  [*]Surely therefore the Reich gauge (amongst others) measures the static noseweight and if, as they state, that they have accounted for the slight height difference created by the measuring device the static noseweight will change according to how the caravan or trailer is loaded when coupled to a laden towing vehicle on level ground.
  [*]Given that towing height varies within the specified range from vehicle to vehicle as it surely will, the dimensions of the actual measuring device remain the same and the object of the exercise is to measure the static noseweight and make the necessary adjustments accordingly.​

• Apart from the number of axles which Reich have made adjustments for in their design, I fail to see how the dimensions of a trailer or caravan would make any difference if the measurement was taken correctly

 

[ProfJohnL]

Hello Parksy,

THe extensive debate suggest there could be a wide gap between our positions on the subject, but in fact your last post indicates otherwise.

Following the pattern of your points, we agree on the first three but on points four and five, you have given a correct summary but you have missed some important points.

The EU directive that sets this out is:

DIRECTIVE 94/20/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 30 May 1994 relating to the mechanical coupling devices of motor vehicles and their trailers and their attachment to those vehicles

Section 2 covers domestic towing arrangements.

Clause 2.1.1 states

"Coupling balls and towing brackets must be attached to a vehicle of category Ml , category M2 below 3,5 tonnes and category N1 in a manner which conforms to the clearance and height dimensions given in Figure 30. This requirement shall not apply to off-road vehicles as defined in Annex II to Directive 92/53/EEC"

"Figure 30" shows the permitted dimensions and working (Loaded) height for domestic towballs as 350 to 420mm.

There is no reference to the vehicle being fully loaded (i.e at its MAM) only that when the trailer is coupled and it is at towing height, which must be when all luggage and passengers are ready to roll.

The working height is the requirement that both car and caravan manufacturers must design to. In practice it ensures the permitted approach and departure angles and clearances are maintained for trailers to negotiate normal road furniture and unevenness.

Clause 2.2.1 states

"Class B coupling heads are permitted for trailers of the maximum mass up to and including 3,5 tonnes. With the trailer horizontal and carrying the maximum permitted axle load, coupling heads must be attached so that the coupling point of the trailer is 430 ± 35 mm above the horizontal plane on which the wheels of the trailer stand (see Figure 31 )."

Figure 31, is a caravan and the height of the coupling head at 430 +/-35mm

The important point here is the trailer is NOT coupled to a vehicle and it is set horizontally. So this particular aspect has nothing to do with nose load, but it is the reason that many caravans do assume a nose down attitude when coupled, but within the normal range it can also mean a caravan might assume a nose up attitude.

On point six and seven, we agree, The measurement of nose load is always done under static conditions. So the variations under dynamic towing are not a concern as those effects should have been catered for by the designers creating sufficient safety margins.

Its points 8 & 9 where it seems you have not grasped the interaction of chassis and loading on the variance of coupling load with height.

It centers (no pun intended, but it actually quite poignant) on the angular change centered on the axle the chassis moves through when the hitch is raised or lowered. I will only describe the case for the Single Axle. If you have a caravan where the distance (radius) from the axle to the hitch is short, and you raise the hitch by for example 75mm, the angular displacement of the chassis will be greater than if you have a longer radius between the hitch and axle. The Center of gravity which is usually located forward and above the axle, also rotates by the same number of degrees around the axle, and as a consequence it will move closer to and in some cases over and behind the axle, change the nose load from positive to negative. How much it changes is also dependant on how heavy the caravan is and how tall the CoG is over the axle. So a caravan that has a taller or heavier effective CoG will change its nose load more than a caravan with a shorter CoG.

Whilst with an SA the variations in hitch load will be quite close to a linear relationship, that is not the case with TA's where there is a complex interaction between the independent and non linear suspension compliances, and hitch loads not only change far more aggressively, they can also change sign within a few mm of elevation.

So one compensation Reiche approach of a single compensation value cannot be correct for all caravans.

What is unsure is the degree of error it produces, and whether it is significant to the overall nose load value.

As a accepted in an earlier comment, the Reich tow ball device is probably better than any other retail device, but it is not perfect.

 

[gravesyt]

My Reich SA arrived this morning so like a big kid went straight down to the storage site to do some comparisons for MY peace of mind. Knowing the last time I weighed it with tube spring type is was 80kg now with the brake off it was the Reich turn it's reading was 92kg to my horror because my last tow car had a max nose weight was 85kg.
That's why it was 80gk so I would have 5kg leeway How wrong was I. Took the Reich off hitched back up and measured the height again now I weighed it with the scales and a piece of wood cut to the right size now it was 91kg so the Reich is 1kg out on a flat even surface which is good enough for me .

 

[Parksy]

Hello Parksy,

THe extensive debate suggest there could be a wide gap between our positions on the subject, but in fact your last post indicates otherwise.

Following the pattern of your points, we agree on the first three but on points four and five, you have given a correct summary but you have missed some important points.

The EU directive that sets this out is:

DIRECTIVE 94/20/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 30 May 1994 relating to the mechanical coupling devices of motor vehicles and their trailers and their attachment to those vehicles

Section 2 covers domestic towing arrangements.

Clause 2.1.1 states

"Coupling balls and towing brackets must be attached to a vehicle of category Ml , category M2 below 3,5 tonnes and category N1 in a manner which conforms to the clearance and height dimensions given in Figure 30. This requirement shall not apply to off-road vehicles as defined in Annex II to Directive 92/53/EEC"

"Figure 30" shows the permitted dimensions and working (Loaded) height for domestic towballs as 350 to 420mm.

There is no reference to the vehicle being fully loaded (i.e at its MAM) only that when the trailer is coupled and it is at towing height, which must be when all luggage and passengers are ready to roll

The working height is the requirement that both car and caravan manufacturers must design to. In practice it ensures the permitted approach and departure angles and clearances are maintained for trailers to negotiate normal road furniture and unevenness.

Clause 2.2.1 states

"Class B coupling heads are permitted for trailers of the maximum mass up to and including 3,5 tonnes. With the trailer horizontal and carrying the maximum permitted axle load, coupling heads must be attached so that the coupling point of the trailer is 430 ± 35 mm above the horizontal plane on which the wheels of the trailer stand (see Figure 31 )."

Figure 31, is a caravan and the height of the coupling head at 430 +/-35mm

The important point here is the trailer is NOT coupled to a vehicle and it is set horizontally. So this particular aspect has nothing to do with nose load, but it is the reason that many caravans do assume a nose down attitude when coupled, but within the normal range it can also mean a caravan might assume a nose up attitude.

On point six and seven, we agree, The measurement of nose load is always done under static conditions. So the variations under dynamic towing are not a concern as those effects should have been catered for by the designers creating sufficient safety margins.

Its points 8 & 9 where it seems you have not grasped the interaction of chassis and loading on the variance of coupling load with height.

It centers (no pun intended, but it actually quite poignant) on the angular change centered on the axle the chassis moves through when the hitch is raised or lowered. I will only describe the case for the Single Axle. If you have a caravan where the distance (radius) from the axle to the hitch is short, and you raise the hitch by for example 75mm, the angular displacement of the chassis will be greater than if you have a longer radius between the hitch and axle. The Center of gravity which is usually located forward and above the axle, also rotates by the same number of degrees around the axle, and as a consequence it will move closer to and in some cases over and behind the axle, change the nose load from positive to negative. How much it changes is also dependant on how heavy the caravan is and how tall the CoG is over the axle. So a caravan that has a taller or heavier effective CoG will change its nose load more than a caravan with a shorter CoG.

Whilst with an SA the variations in hitch load will be quite close to a linear relationship, that is not the case with TA's where there is a complex interaction between the independent and non linear suspension compliances, and hitch loads not only change far more aggressively, they can also change sign within a few mm of elevation.

So one compensation Reiche approach of a single compensation value cannot be correct for all caravans.

What is unsure is the degree of error it produces, and whether it is significant to the overall nose load value.

As a accepted in an earlier comment, the Reich tow ball device is probably better than any other retail device, but it is not perfect.

I accept he first point you made that I've highlighted and italicised, so the measurement has to be taken 'when the trailer is coupled and it is at towing height, which must be when all luggage and passengers are ready to roll', but with your rather pedantic directive being complied with this would have no bearing whatsoever on the operation or accuracy of any noseweight gauge so your first point is a red herring.
As for your reply about the varying centre of gravity between different trailers, the centre of gravity whatever it may be will remain static when the caravan is not moving.
We are measuring static noseweight so the points about a gauge not recognising different trailer dimensions is another red herring I'm afraid.
Reich have already stated that unlike bathroom scales they use different criteria for s/a and t/a caravans so why is a common or garden bathroom scale and a bit of wood more accurate?

 

[Dustydog]

My Reich SA arrived this morning so like a big kid went straight down to the storage site to do some comparisons for MY peace of mind. Knowing the last time I weighed it with tube spring type is was 80kg now with the brake off it was the Reich turn it's reading was 92kg to my horror because my last tow car had a max nose weight was 85kg.
That's why it was 80gk so I would have 5kg leeway How wrong was I. Took the Reich off hitched back up and measured the height again now I weighed it with the scales and a piece of wood cut to the right size now it was 91kg so the Reich is 1kg out on a flat even surface which is good enough for me .

Thanks for that Gravesyt.
That confirms my own recent experiments that the Reich is accurate albeit on a TA in my case. The yellow milenco spring gauge is long gone.

Prof's point regarding CoG and "Centers" is a complex issue and hard to follow in caravan design. I do have physics O and A Level and have some basic understanding of the Law of Moments, static and dynamic loads.
So how can it be that both I and Hutch have carried out the same experiments over the last few weeks and produced the same results , ie statically the difference over a range of heights makes little or no difference to the readings obtained hmy:
Al-ko and BPW have been making "kit" form chassis for years and whilst I have found in practice a longer caravan with long distances from hitch to axle handles better, or so it seems surely the Law of Moments determines noseweight.
Cof G we all know needs to be kept low.
I'm going back to my kennel and play with the see saw some more

 

[Hutch]

And part of my Aircraft Engineers licence it to calculate the C ofG and weight calculation for the Certificate of Airworthiness.
I think our caravan must be balanced just right, so I am going to my garage and sit in a driptray and play with my nuts.

 

[Gabsgrandad]

Despite your best efforts guys to talk me out of caravanning, I will continue, - but probably taking more headache pills!!! :woohoo: :woohoo:

 

[Gafferbill]

Get one of these German caravans and never bother about nose weight again

 

[Hutch]

You will be telling us to become, Motorhomers, next then we would be worring about how heavy a car we can tow behind without having brakes activated.

 

[ProfJohnL]

Hello Parksy,

"Red Herring" No. to be able to make meaningful measurement you need to
equipment capable of creating the correct conditions in which to make the measurement.

You seem to accept that the true nose load can only be measured with the hitch at towing height. To get true measurement you must therefore measure at the towing height. If the gauge you try to use does not allow you to adjust its length so it you can set the hitch at its towing height by definition it is not measuring the true nose load.

If you use a gauge, even Reich's, where the nose of the caravan does not settle on the gauge at the towing height it makes an erroneous measurement. And we mustn't forget that from both forumites own reports and Milenco's advertising that most coiled spring gauges are wildly inaccurate to boot. it's a potentially serious mismeasurement. However where Reigh acknowledge this and attempt to provide compensation so the reading the device gives is different to what it actually measures.

With regards the caravans centre of gravity. All bodies (including caravans) have a Centre of Mass. This is a notional point in three dimensions relative to the body that represents the averaged mass centre of the object. When the object is stationary and subjected to the force of gravity, it reacts as if gravity is only tugging on the Centre of Mass irrespective of its size and shape. Because we are working on earth and for old school Luddites this point is often called the Centre of Gravity or CoG.

In a caravan it is the action of gravity tugging vertically at the CoG that produce the caravans weight, which is proportionally shared between the road wheels and the hitch. In a single axle caravan if you raise or lower the hitch, then the caravan rotates about its axle, whilst the CoG retains its position relative to the caravan structure, it moves relative to the outside world and to the caravan's point of support on its wheels. Gravity will continue to act vertically on the CoG but the proportions of weight borne by the wheels and the hitch have changed.

This is the reason why hitch loads vary with the height of the hitch. But because of the variables of length of caravan and the effective height of the CoG the proportion of change load change to hitch height is not a constant transformation which is where the Reich approach is not accurate.

THe subject need some proper scientific/engineering study to the scale of errors and then to see if they are significant or not. This would be a perfect subject for PC to consider.

 

[Parksy]

Sigh... :S
The height of any noseweight gauge with the exception of those that fit onto a towball can be adjusted by using similar methods to those that you advocate for bathroom scales, i.e. by raising the hitch head to the correct height using blocks of wood, magazines etc;
This means that the noseweight can be measured at the correct height.
The Reich model compensates for the height differential so why would the end result be inaccurate?
To try to pedantically reinforce whatever point you are trying to prove by stating that measurement and the actual reading is different proves nothing, because it's the reading that matters in the case of Reich.
Why would a hitch height vary when the caravan is standing still?
We know that hitch heights vary when the hitch is raised or lowered but the intention is to measure the noseweight as accurately as is reasonable to expect when the caravan is stationary.
Although the CoG alters proportionately through the arc of hitch movement up or down the height range that matters is between 350mm and 420mm.
Do you know what the error that you claim makes the Reich unfit for purpose would be?
When I notice a caravanner, or some mythical noseweight Gestapo for that matter, using a slide rule with regard to the possibility of a prosecution because of an inherent inaccuracy caused by this narrow arc which would also affect bathroom scales then I'll become interested but like most other caravan owners who tour regularly I do the best that I can with what is commercially available.

 

[Thingy]

DING DING

Ladies and gentlemen
For the technical heavyweight champion of the forum, this is the twelfth and final round.