Means of adjusting ball hich lmit

[dave3609]

Directly I added a motor mover I realised that not only was my payload compromised but my ball hitch limit was exceeded for my VW Passat (75 Kg). Now, in order to reduce the ball load I needed to place my spare wheel in the boot with the power cable. Also I needed to place the awning slightly behind the caravan axle on the floor of the 'van. One solution would be to fit rear spring assisters, but I'd rather manufacturers design in a better payload and nose weight compensation.
It occurs to me this is the case for anyone fitting a Motor Mover plus a heavier duty battery. So why have the chassis manufacturers/caravan designers taken this into account?
Have taken some measurements and done a few static tests on my front drive I calculated that by taking moments about the CG of the 'van an extension of the draw bar by 11" would correct the situation.
So why cannot we purchase 'vans with modified A frames/ draw bars?

 

[ProfJohnL]

Directly I added a motor mover I realised that not only was my payload compromised but my ball hitch limit was exceeded for my VW Passat (75 Kg). Now, in order to reduce the ball load I needed to place my spare wheel in the boot with the power cable. Also I needed to place the awning slightly behind the caravan axle on the floor of the 'van. One solution would be to fit rear spring assisters, but I'd rather manufacturers design in a better payload and nose weight compensation.
It occurs to me this is the case for anyone fitting a Motor Mover plus a heavier duty battery. So why have the chassis manufacturers/caravan designers taken this into account?
Have taken some measurements and done a few static tests on my front drive I calculated that by taking moments about the CG of the 'van an extension of the draw bar by 11" would correct the situation.
So why cannot we purchase 'vans with modified A frames/ draw bars?

Hello Dave,
That's an interesting suggestion. Several continental caravan manufacturers do seem to use longer A frames. It also has some other advantages concerning caravan stability.

Just a thought it might have been better to store the spare wheel and EHU cable behind the axle, this doesn't increase the overall weight , but it does reduce the nose weight.

Spring assisters do not change the nose load capacity of the car, that is a fixed limit determined by the car manufacturer. and relates to the construction of the body and the towbar anchorage points. Spring assisters can also compromise modern cars stability control systems, as the suspension travel is modified and the cars sensors may not provide the desired signals to the ESC system. Even adding aftermarket self leveling kits to cars where similar models may have it as standard can also compromise the ESC system which isn't programmed or calibrated for them. Essentially if the ride height of the car is wrong when hitched up, then its most likely the car is overloaded or something has worn or been damaged.

I suspect that if we did have longer A frames, there would be temptation by UK caravan manufactures and users to try and fill the space with some form of additional storage - which rather defeats object of extending it. But lets see if any manufacture actually tries it.

 

[dave3609]

Thanks for that advice v. useful. I am not sure what Manuf's include in the caravan ULW must look into that. But looks like, to me, Get a motor mover - make sure the nose weight of the car will take it before you buy, In my case that was my mistake. Pity there is no warning of the consequences of fitting one eh?
I'm due for a change so will look for heavier ball hitch weight e.g., Honda CRV=100kg, VW Tiguan = 100Kg or something of that ilk.

 

[Gagakev]

So why cannot we purchase 'vans with modified A frames/ draw bars?

Hello Dave,
That's an interesting suggestion. Several continental caravan manufacturers do seem to use longer A frames. It also has some other advantages concerning caravan stability.

[/quote]

My Fleetwood has the longer A frame which they were known for in there days.
My model was made by Adria in 2008 when they took them over before they discarded the name.
Not sure if the new Adria'a have the longer A frame or not

 

[dave3609]

Yes, the idea of purchasing an extended draw bar solves a lot of problems, not sure of the stability implications tho'. Has anybody done any experimenting on this?
At home on my flat driveway I took the measurements of tow ball to axle, axle to CG motor mover, taking the MTPLM of 'van and weight on hitch laden, weight of mover and larger battery (110 ah). If you take moments clockwise and anticlockwise you can calculate the CG of the van, with is you can then calculate how much longer the ball hitch needs to be to achieve a given weight on the hitch. In my case it was 9" extra for my car having a limit of 75Kg.
Currently, to achieve a nose weight of 75kg (Approx 7%) as recommended by the C C. I place my spare wheel or the awning on the floor of the van just behind the axle. It tows very stable up hill and down hill at French motorway speeds. If I didn't do this I would exceed the cars tow ball limit.

 

[dave3609]

Having said that, Does it really matter? Whilst camping near Venice I observed a British reg'd Skoda Superb who's owner had cleverly made a bracket mounted on his A frame upon which was strapped a moped!!

 

[ProfJohnL]

Thanks for that advice v. useful. I am not sure what Manuf's include in the caravan ULW must look into that. But looks like, to me, Get a motor mover - make sure the nose weight of the car will take it before you buy, In my case that was my mistake. Pity there is no warning of the consequences of fitting one eh?
I'm due for a change so will look for heavier ball hitch weight e.g., Honda CRV=100kg, VW Tiguan = 100Kg or something of that ilk.

Hello Dave,

Your comment above does not make sense. It implies the nose weight generated by the caravan remains fixed. It isn't, Its a variable and it is dependent on how you load the caravan. The CC 7% of actual weight is a recommendation, and it is generally accepted that something between 5 and 7% is usually satisfactory. In practice you only need enough nose weight to keep the outfit stable, and there is no specific formula for that except the EU requires a minimum nose load of 25Kg.

You seem to understand the generated nose weight can be trimmed by positioning of payload within the caravan. items moved rearwards reduces nose weight, and vice--versa.

So provided the actual weight of the caravan is within the cars braked towed weight limit then it is a legal match.
The only practical use of ULW is to establish the available payload allowance, but that must never allow the MTPLM to be exceeded.

Caravans are difficult trailers and add significant additional load and strain to a tow car for that reason Industry advice is to keep the weight of caravan as small as possible and for novices try to keep it below 85% of the towcars ULW, and only approach 100% as experience grows.

 

[dave3609]

Hello John,
Have you read my post 390253?
I do understand n/weight is variable hence my experiment to find out where the hitch should be to achieve my cars Max load.
In practice too, I have fitted a Bulldog stabiliser in addition to my Alko hitch. and I am currently on the lookout for a car with better towing characteristics. Sadly I needed a motor mover due to my parking circumstances which has caused my compromising situation John

 

[intransient1]

Hi Dave,
My last caravan had a 90kg noseweight when it was empty and like you the lint for my vehicle was 75kg.
The guide for loading you van is not hard and fast rule and you distribute the load to make the outfit stable.
My new van is very similar, but I now have a car with 100kg limit, but I still load the van for stability and level towing I hate seeing vans being towed nose down and car front up.
motor movers are quite heavy but are easy to compensate for and save a lot of work.

 

[Dustydog]

Hi Dave
Your thoughts on this very important aspect are to be commended.
Your reference to the Law of Moments is of course important to towing.
Static nose weight is a very important factor. Thus as you say playing around with loading is a basic tool for adjusting the static nose weight.
Subject to the car's listed max nose weight I always go for the maximum allowed.
I shall now upset the Prof.
Since 1998 I have had vehicles with self levelling rear suspension.
Prior to that I fitted Grayston spring assistors to a Cavalier Sri, two Sierras and an Audi A 4 Avant.
They stiffened the back end. Reduced sagging nose high attitude.
I drove all cars solo too and other than a harder ride never had a problem.
I am sure I was stressing the rear springs in a way not envisaged by the designers. Basically suspension was only available through 75% of the spring. The other 25% was held rigid by the spring assistors.
It worked very well indeed on the 80s and 90s technology.
Today? I don't know? I have ESP today but does it ever get used on a 4x4 that rarely burns rubber??

 

[ProfJohnL]

Hello John,
Have you read my post 390253?
I do understand n/weight is variable hence my experiment to find out where the hitch should be to achieve my cars Max load. ....................... Sadly I needed a motor mover due to my parking circumstances which has caused my compromising situation John

Yes Dave I have thread all your posts on this thread. let me try again to explain what troubles me:-

What you may not know is that the nose weight capacity of every car has to be a minimum or greater than 4% of the cars rated braked towed weight limit. This means provided the caravans MTPLM is within the cars rated capacity, the cars towbar will always have the legal minimum capacity for nose weight, especially if you stick the industries 85 to 100% towing ratios guidelines.

Because the caravans nose weight is dependent on how you load the caravan, you cannot know ahead of using the caravan what nose weight you are likely to encounter. So you have to trim the nose weight to match the car.

I have lost count of the number of different caravans I have towed, empty new and loaded ready for holidays, and I have never yet have been unable to trim the nose weight to what I wan't. I may have had to add ballast on new caravans, but for those with personal items, rearranging their position has been enough. Awnings and spare wheels have been common items to move rearwards to reduce nose weight.

Motor movers do not produce a large moment so it should be perfectly possible to offset its effect on nose weight with what you already have in the caravan.

If the addition if a motor mover raises the total weight of the caravan above the tow vehicles limit, then that is not a nose load issue.

 

[ProfJohnL]

................I shall now upset the Prof.
Since 1998 I have had vehicles with self levelling rear suspension.
Prior to that I fitted Grayston spring assistors to a Cavalier Sri, two Sierras and an Audi A 4 Avant.
They stiffened the back end. Reduced sagging nose high attitude.
I drove all cars solo too and other than a harder ride never had a problem.................

hmy: hmy: hmy: hmy: :woohoo: :S :side: :huh: