# i dont understand weights, do you?



## philbre (Nov 13, 2008)

hi there

i just weighed my camper

back 2 wheels 1700kg (max allowed 2120)

front 2 wheels 1760kg (max allowed 1850)

whole body 3440kg (max allowed 3850)

water tank full, diesel full, camper loaded for trip

so far so good

now going to load two bikes onto trailer,
the combined weight of all three is 750 kg, standing alone in my yard, which is also fine coz max allowed on trailer, incl trailer, is 750 kg

have to return to weighbridge to weigh back axle of camper with trailer & bikes attached, to see what new weight is on my back axle

i cant believe the weight would increase by 420kg or would it?


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## sideways (Jun 2, 2008)

As far as i know the 5500kg shown on the second line of your plate is the combined gross weight of your van and trailer allowable. you do not need to weigh again. 750kg for a trailer has something to do with the maximum you can tow unbraked, you can tow a trailer equal to the difference shown on your plate between the gross of your van(3850) and the overall gross of 5500kg,


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## H1-GBV (Feb 28, 2006)

Hi 

Did you ever do "turning effects" or " moments" at school? If not, imagine tightening a nut with your fingers, then undoing it. Then imagine tightening a nut with a spanner, but trying to undo it with your fingers The spanner has a much bigger turning effect (moment, torque) than you can exert. The equation is "moment = force x distance". 

The same happens with your trailer. You have probably loaded it so that it has a "nose-weight" of about 50kg; this helps to prevent snaking, and should be within limits set by your trailer and the tow-bar fitting. However, the towball is situated a distance behind your back wheels. The trailer therefore exerts a greater force than the 50kg nose-weight. 

If you have a large rear overhang, then you can have considerable difficulties staying within legal limits. The "good news" is, of course, that your front axle will be less loaded; however, traction (if front wheel drive) and steering become less positive. Can you move some items inside the van forwards? 

Gordon


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## wakk44 (Jun 15, 2006)

sideways said:


> As far as i know the 5500kg shown on the second line of your plate is the combined gross weight of your van and trailer allowable. you do not need to weigh again. 750kg for a trailer has something to do with the maximum you can tow unbraked, you can tow a trailer equal to the difference shown on your plate between the gross of your van(3850) and the overall gross of 5500kg,


I agree,the figure to look at when towing is the GTW (Gross Train Weight)which in your case is 5500kg.So your GVW is 3440kg + trailer weight of 750kg making a total of 4190kg,which is well inside your max. allowed of 5500kg.


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## sallytrafic (Jan 17, 2006)

I disagree with some of the above replies, it is not just a matter of gross train weight - but you should be OK.

It will depend on two things the downforce on the towbar and the ratio of wheel base to rear overhang.

Say the hitch weight is 50kg. Then that is trying to compress the rear axle into the ground whilst the front axle is lifted.

Now if it has a short wheelbase and a large overhang say wheelbase is 3 meters and overhand two meters. (probably extreme) (measure overhang centre of rear wheel to centre of hitch ball.) and using your actual weights


The sum will be at the rear 1700+(2+3)*50/3 which equals 1783 kg

the front will be 1760-50*2/3 = 1726 kg


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## Pudsey_Bear (Sep 25, 2008)

My brian hertz.

Kev :black:


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## Fatalhud (Mar 3, 2006)

Kev_n_Liz said:


> My brian hertz.
> 
> Kev :black:


Who the chuffs Brian and does he know the answer  

Alan H


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## DTPCHEMICALS (Jul 24, 2006)

Wasn`t Brain on Magic Roundabout, Im confused too.

dave P


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## sallytrafic (Jan 17, 2006)

A famous quote which I once got away with saying to a General!!

"Simple explanations are for simple minds - I have no time for either"

seriously its only arithmetic and its really no use saying

it will add more weight to the rear of your van than you might imagine.


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## Pudsey_Bear (Sep 25, 2008)

I have to disagree there Frank, simple explanations might be for simple minds, but if it gives a better understanding of a problem, that problem might not crop up so often.

After all there was a point when you knew nothing, same for all of us, and if all we ever got was a complicated answer to every question, I think we might all have SLD.

There is a time for a complex technological answer, and it's good to see your grey matter is still working well, but a simpler explanation would have helped me alongside the original one.

Your explanations are usually very precise, which I like, but we don't all operate at the same level, anyway I like simple explanations, I have a simple mind you see.

LICE.

Kev :black:

PS Simple Explanations


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## sallytrafic (Jan 17, 2006)

Come on 

Is there anyone on here reading this topic who can't add, subtract, multiply and divide easy whole numbers with a calculator if necessary. 

I'm sorry but sometimes the simple answer is not useful. Sometimes it is necessary to point out an earlier answer is incorrect or only a partial answer. You can't do that unless you are going to be as precise as necessary.

There are hundreds of times on here that I see stuff that isn't exactly right but I let it go because the answer given will do. 

I spend a great deal of time helping people whose questions show that they are way out of their comfort zone but if you want to understand something you have to be willing to expend a little effort as well.


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## Pudsey_Bear (Sep 25, 2008)

Sorry Frank, it wasn't aimed at you as a person, but the philosophy in your quote.

Kev.


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## macone48 (Mar 14, 2006)

sallytrafic said:


> I disagree with some of the above replies, it is not just a matter of gross train weight - but you should be OK.
> 
> It will depend on two things the downforce on the towbar and the ratio of wheel base to rear overhang.
> 
> ...


Frank says it all, except I really think you should determine/measure your hitch weight ??

As an ex-tugger and now tow a BJ trailer with my TVR on it, I keep an eye on the down load on my tow ball. All too easy to position TVR too far forward, or back and induce snaking !! (even with 4-wheeled trailer!!)

You could use a spring balance and lift the tow hitch to the tow ball height noting the hitch weight. Or put the jockey wheel on a bathroom scales!!
(close enough, usually!!), or a short stick at tow ball height length in the tow hitch and again use bathroom scales.

With both bikes set too far forward you could actually be over loading the tow ball/bracket and rear axle loadings. (all clearly within Train weight!!)

Cheers, Trev


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## sallytrafic (Jan 17, 2006)

The general who first of all asked why x couldn't be done in a Lynx helicopter then when I gave him the correct and to an engineer straightforward answer, said he wanted a simple answer I said big bird that flies in sky fall over and make hole in ground then "simple explanations are for simple minds *I'm sure you * have no use for either."

I did pepper it with a few 'sirs' and a smile my boss who was a major nearly swooned but the general laughed and a week or two later he sought me out to give a staff briefing


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## Pudsey_Bear (Sep 25, 2008)

Nice one Frank, 

You're in the wrong job, then and now probably.

Kev.


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## tinkering (Dec 8, 2007)

*weights*

I am sure that Frank did not mean to course offence by his (simple minds) reference.

He is after all a expert in his field, and has give hundreds of us valued advice on his subject ,mind you sometimes I did not understand a chuffing word he said :lol: :lol: /

Boffins are, quite a lot of the time in a completely different world to us mere mortals  ,having worked with a few over the years, what to them is a perfectly simple technical explanaction ,to us on the production side on the shop floor was a nightmare :lol: :lol: .

Over the years I found that the best thing to do was to nod ones head in agreement, say yes and no when needed ,then when they buggered off back to there carpeted office with there on tap coffee etc,(not forgetting there company cars of course) :lol: :lol: to just carry on and do the job so that it was practical. :wink: :wink:

Take care LES :wink: :wink:


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## sallytrafic (Jan 17, 2006)

I should confess that whilst I can use weight and balance data to trim a helicopter or fixed wing I asked DABurleigh in an MHF thread what the formulae was for loading axles.


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## Pudsey_Bear (Sep 25, 2008)

sallytrafic said:


> A famous quote which I once got away with saying to a General!!
> 
> "Simple explanations are for simple minds - I have no time for either"


Can I say for the sake of those who missed it, I was not and do not want to have a go at Frank, I repeat I was annoyed at the quote which he quoted and clearly says he is quoting, not him personally, there are enough on here having goes at other members, for my part if another member Pees me off I'll tell him via a PM, but try to be constructive about it, it's too easy for someone reading a post without registering what they've read to get the wrong idea, and then exacerbate the situation.

franks a lovely bloke, and very knowledgeable, But I don't get half of what he says, as it's too complicated for me.

Kev :black:


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## carol (May 9, 2005)

Ah but this forum needs all these folk, because most people have experience and knowledge in what was/is their field of work and can pass that on - trouble is mine isn't much use on here (knowledge) that is, apart from any touring we may have done - or of course life experiences.

As in life it takes all sorts to make up a good group - and this forum definitely has a very good group of people with a good knowledge in many things we need help on from time to time, be that motorhomes, electrics, computers whatever... long may it last.

What takes time though is finding out which member has a really genuine knowledge in which field - I have thought we could do with a list, but I can't recall why it was thought not to be a good idea.... so you have to stick with the forum to find out who is who

Carol - who would like to thank them all for helping over the years...


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## philbre (Nov 13, 2008)

sallytrafic said:


> I disagree with some of the above replies, it is not just a matter of gross train weight - but you should be OK.
> 
> It will depend on two things the downforce on the towbar and the ratio of wheel base to rear overhang.
> 
> ...


hi there Sallytraffic

I apprec your explanation & have done some sums

my overhang, distance from centre of back axle to centre of ball hitch is 1.4m

my camper width is 2.4m

my hitch weight is 50kg

So 1.4 + 2.4 = 3.8

3.8 by 50 = 190

190 divided by 3 = 63.3

adding this value to my weight of back axle with no trailer attached = 1700 + 63.3 = 1763.3 kg

so by this calculation, the new weight in my axle with a fully laden trailer should be 1763 kg approx

I now wish I had returned to the weighbridge when laden to contrast this calculated figure with the actual figure

the most important thing is that I am well below the 2120kg allowed


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## goldi (Feb 4, 2009)

I reckon that if youcan easily lift the trailer nose onto the towball your goin to be easily ok



Happy trips 

norm


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## sallytrafic (Jan 17, 2006)

philbre said:


> sallytrafic said:
> 
> 
> > I disagree with some of the above replies, it is not just a matter of gross train weight - but you should be OK.
> ...


Just for the sake of accuracy your *wheelbase* is from front axle to back axle (again wheel centres) not the width as you seem to be saying but from a look at your photos you won't have any problem. You don't have much overhang compared with wheel base.

Looking at your calculation you have divided by 3 at one point you should have divided by your wheelbase.

In all this talk of simplicity the formula is a simplification treating the rear axle as a pivot and ignoring any effect of suspension for example how that pivots. Near enough for our purposes. The dynamic case when you are driving may be different because there will be loading and unloading of the hitch weight as the trailer pitches fore and aft.

As it happens I was passing through Malborough last evening and saw a motorhome that might well have a problem with only a 50kg hook load if indeed anyone makes a towbar for it so great was the overhang. It was a newish looking foreign low profile and it looked as if the wheel base and the overhang where similar. Vehicle C&U regs here limit the overhang to 65% of the wheelbase I understand.

So if you take a vehicle at the limit for overhang and do the sums then at the rear it becomes

Weight = Old weight + Added weight * 100+65/100

So weight on rear axle if the overhang is at the UK limit is the oldweight plus 1.65 times the added weight.


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## philbre (Nov 13, 2008)

sallytrafic said:


> philbre said:
> 
> 
> > sallytrafic said:
> ...


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## philbre (Nov 13, 2008)

sallytrafic said:


> philbre said:
> 
> 
> > sallytrafic said:
> ...


[U][B]Thanx Frank, I stand corrected & now know the difference between my wheelbase & my elbow![/B][/U]
wheelbase = 3.8m

overhang = 1.4m

hitchweight = 50kg

so, 3.8 + 1.4 = 5.2

5.2 by 50 = 260

260 divided by wheelbase = 68

adding this to my unladen back axle weight of 1700 = 1768kg

this should now be approx back axle weight when fully laden with a trailer & 2 bikes whose combined mass is 750kg


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