A different nose weight question

[Lutz]

Your calculations are a liable to misinterpretation, Prof, as you are using the term vehicular weight in two contexts. Using your notation, it would have been clearer if you had used the terms GVW of the towing vehicle when hitched (= FA + RA) and combined axle load of the solo vehicle (= FA1 + RA1). Otherwise one could be left with the impression that GVW is FA1 + RA1, which is not the case as soon as car and caravan are hitched up.

 

[hortimech]

Now for nose weight Trailer weight - TA = Nose weight

Are you sure about this?

If we agree that:

nose weight = amount of caravan weight transferred to towing vehicle

Then if the caravan is uncoupled from the towing vehicle, one of two things would happen. Either the jockey wheel would be lowered and some of the weight of the caravan would supported by this, or the caravan hitch would come to rest on the ground, this would also also support some of the caravans weight.
Either way the nose weight that you calculated would not be correct.

I would think that a more precise way would be (as you said) to weigh the towing vehicle coupled and uncoupled, and subtract one from the other to get the weight of the caravan transferred to the towing vehicle.

i.e. nose weight = (Front Axle Coupled + Rear Axle Coupled) - (Front Axle Uncoupled + Rear Axle Uncoupled)

 

[Lutz]

Both statements are correct.
Noseweight = (Front Axle Coupled + Rear Axle Coupled) - (Front Axle Uncoupled + Rear Axle Uncoupled)
and
Noseweight = Total trailer weight (including load on the jockey wheel) - Trailer axle load

 

[hortimech]

Both statements are correct.
Noseweight = (Front Axle Coupled + Rear Axle Coupled) - (Front Axle Uncoupled + Rear Axle Uncoupled)
and
Noseweight = Total trailer weight (including load on the jockey wheel) - Trailer axle load

Ok, how do you get an accurate Trailer axle load? To be accurate, the hitch would have to be at the same height as if attached to the towing vehicle, without anything holding it up! so that ALL the weight was only on the two tyres. This is virtualy impossible, so in my opinion (for what it is worth) trying to work out nose weight from weighing the caravan is never going to be any where near accurate.

 

[Lutz]

To measure the trailer axle load is quite easy. Hitch the caravan up to the car and drive over the weighbridge until only the caravan's wheels are standing on it. What you read then is its axle load.

 

[ProfJohnL]

Your calculations are a liable to misinterpretation, Prof, as you are using the term vehicular weight in two contexts. Using your notation, it would have been clearer if you had used the terms GVW of the towing vehicle when hitched (= FA + RA) and combined axle load of the solo vehicle (= FA1 + RA1). Otherwise one could be left with the impression that GVW is FA1 + RA1, which is not the case as soon as car and caravan are hitched up.

Hello Lutz,
You are correct. I should have made it clear that the vehicular weight coupled is differnt to the vehicular weight uncoupled, the difference being the nose weight of any trailer in use.

 

[ProfJohnL]

Ok, how do you get an accurate Trailer axle load? To be accurate, the hitch would have to be at the same height as if attached to the towing vehicle, without anything holding it up! so that ALL the weight was only on the two tyres. This is virtualy impossible, so in my opinion (for what it is worth) trying to work out nose weight from weighing the caravan is never going to be any where near accurate.

It may help to look at this from a slightly differnt perspective. As you agree the nose weight is transfered from the trailer to the cars load, So the cars total weight will be greater when the trailer is hitched, compared to when the same car is solo. The difference will be the applied nose weight. So by measuring the front and rear axle of the car both coupled and uncoupled the results can be subtracted to show the nose weight for the outfit.

 

[colin-yorkshire1]

Hello Colin,
I have to take issue with part of your last posting,
"while most methods will give near enough readings "
The problem is that most methods have so many uncontrolled variables, that those I have seen can be significantly out. Most are uncalibrated, and the one that claims to be calibrated cannot do the measuremnt at the correct height so its readings will also be compromised.

hi again John,
sorry for the delay in answering trouble with me router

got on the other night answered a couple of intro's and off it went again

anyway your quite right of course there is so many variables that any method would be at best be a calculated guess.
however I used the term "near enough" very loosely because I have tried all the methods at my disposal to asertain the average noseweight reading including a coal scale (1 cwt about 50.8kg) suspended from a engine lifting frame with the loading adjusted to 50kg "maximum for the meriva" the difference between the lowest and highest readings using different methods being only 5kg or 2.5kg either way ie" the average".
in the grand scheme of things I would call this "near enough" the method that gave the highest reading was by chance the millenco gauge that is kept in the van, so using this gauge with the noseweight set at 45kg I know there is no way the noseweight could ever be excessive,

 

[ProfJohnL]

The method that we have discussed that VOSA are likely to take where they measure actual axle loads is probably both the simplest and the quickest. Teh gear that VOSA are liekly to use probaly costs thousands, and will be calibrated with proper certification, so they are confident of their recorde results. Such equipment is probabley out reach for most people, but there is a device that will allow you to achive similar results from Reich called the Trailer Weight control.

See
http://www.caseysoutdoorleisure.co.uk/reich-weight-control-1885-p.asp
or
http://www.campervanstuff.com/shop_stuff/index.php?mod=product&id_prd=1002
http://www.campervanstuff.com/shop_stuff/index.php?mod=product&id_prd=1204

This device uses a low profile pad with load cell and mesaument bridge. it has the capacity to measure up 5000Kg which means it can be used for checking your car as well as the caravan, and using the simple calculations prevously described will allow you to check for virtually all loading issues of your outfit.
Its not massive or heavey, it require minimal setting up and provided it has be designed and engineers properly should give a long and reliable working life.

I am considering getting one ( when I can find stock) as it is simpler and safer to use than the stick and scales method.

 

[Sproket]

I bought one like this from a seller on e-bay a few years ago, I do find it usefull for side to side loading, a few mins & your done.