pondering 4 wheeled caravan?

[jayjay]

Why can't caravans have four wheels like horse trailers do? I'm sure it would make it easier to reverse it, and a lot more stable on the road. I'm talking 4 wheels here with a space in the middle, not like the big caras which are twin axle with two sets of wheels in the middle... is there some reason we only tow on two wheels instead of four?

I was just pondering this question, I don't know the answer but I bet there is one!

[glenw]

Don't horse boxes have central twin axles the same as big caravans????

[jayjay]

they seem to be spaced a little wider, probably because of the weight of the horse!

http://www.ebay.co.uk/itm/IFOR-WILLI...item27c1b4d2e7

But why couldn't we have four wheels spaced like on a car or camper on our caravans?????

[jayjay]

Something like this with a caravan on it!

http://www.jescraft.com/fwt.html

They don't make baby prams with two wheels in the middle! Even the small buggys have three!

[Twolitre]

Something like this with a caravan on it!

http://www.jescraft.com/fwt.html

They don't make baby prams with two wheels in the middle! Even the small buggys have three!

But I recall, from my young daddy days, that to wheel a pram round a tight corner involved tipping it so that one pair of wheels left the ground.
As the axles get further apart tyre wear on bends increases and inevitably as the distance increases one axle eventually has to have a steering facility.
Even caravans with twin axles close together are near to impossible to manhandle except in a straight line because sideways forces on the tyres absorb so much power they cannot be steered.
In fact, without a castor type jockey wheel your little Kip would need a lot of more effort to maneuver.
The trailer you illustrate would become much more complicated for a caravan because it would by Law require suspension and braking systems to be added (weight, complexity and cost) and reversing it by car would require steering techniques to be also reversed from normal practice.
Jim.

[jayjay]

Hi Jim, glad you spotted this one! I was hoping for your imput!

so if the wheels weren't in the middle but four square, then it wouldn't corner properly?

Unless you went very very slowly, as a horse would do with this one!
http://www.ebay.co.uk/itm/Gypsy-Bowt...item19cc4ae62a

I notice that this road worthy one has been put on a single axle chassis:
http://www.ebay.co.uk/itm/Gypsy-bowt...75675299879583

[Twolitre]

Hi Jim, glad you spotted this one! I was hoping for your imput!

so if the wheels weren't in the middle but four square, then it wouldn't corner properly?

Interesting links jayjay.
The first does have a steering front axle which pivots in the centre on a turn table set up (with a central "King Pin" a term carried over to present day vehicles though used differently). The trouble with this setup is that it is very unstable on tight turns becoming virtually a triangle of wheels.
The second I think, though I could be wrong, is a survivor of a fleet of such vans from the Preston area which were hired out to people who fancied a "Gypsy" type break. I remember seeing them quite frequently en-route to the West Coast from Chesterfield in the late 50s- early 60s.
Perhaps someone from that area will rember and confirm or correct me.
Happy New Year, Jim.

By the way, have you ever noticed the swirls of rubber left on roads by articulated vehicles which have executed "U" turns in the road? That is rubber ground off the tyres of close coupled twin axle wheels as they are forced to move sideways.

[derek b]

Why can't caravans have four wheels like horse trailers do? I'm sure it would make it easier to reverse it, and a lot more stable on the road. I'm talking 4 wheels here with a space in the middle, not like the big caras which are twin axle with two sets of wheels in the middle... is there some reason we only tow on two wheels instead of four?

I was just pondering this question, I don't know the answer but I bet there is one!

My thoughts are it's to do with manouverability, wheels in the centre of the trailer means it will pivot about that central point, wheels on each corner means it has to be towed in a curve which requires more room!

derek b and Babs

[jayjay]

Very interesting! And I see why the artics have trouble turning. We have a pie factory here and it's very interesting seeing the artics take the corner at the crossroads in the middle of the village.

Now a caravan with four spaced wheels would actually be - a campervan! LOL!! they have four spaced wheels, the front two are attached to a steering wheel... so what I actually need is one of these, then I'd be away! (it corners well)
http://www.youtube.com/watch?v=4UCZF_UnG10

[Rob B]

Well its not a new idea, one of the earliest forms of caravan was the horse drawn gypsy bow top and they do indeed have 4 wheels spaced apart like on a car.



A lot of the big farm machinery and trailers also have wheels in this kind of arrangement. The problem with it of course, as has already been said is that in order for it to work you need a pivoting front axle to allow it to negotiate bends. On a modern caravan this would add substantial weight, cost and complexity to what is already an expensive and increasingly heavy towing unit. The more moving parts you have leads to more things going wrong as well of course and the need for greater maintenance.

[Twolitre]

O.K. for horses, but on full lock a pivoting axle becomes a virtual tricycle with inherent stability problems! Which is why a certain Mr. Ackermann designed the system now used on virtually every motor vehicle. Though he designed it to make more stable horse-drawn vehicles, long before motor vehicles existed.
Jim.

[Ian.C.S]

Ee knows tha knows does our Jim,ees full of brains from ear to ear tha knows.

[di allen]

Well its not a new idea, one of the earliest forms of caravan was the horse drawn gypsy bow top and they do indeed have 4 wheels spaced apart like on a car.



A lot of the big farm machinery and trailers also have wheels in this kind of arrangement. The problem with it of course, as has already been said is that in order for it to work you need a pivoting front axle to allow it to negotiate bends. On a modern caravan this would add substantial weight, cost and complexity to what is already an expensive and increasingly heavy towing unit. The more moving parts you have leads to more things going wrong as well of course and the need for greater maintenance.

That is one beautiful caravan. I would just love to have that parked on my drive with a horse in the back garden eating the grass. I could even use the manure for my roses!

When I was small the bread and milk were delivered by a horse drawn cart and neighbours used to dive out with their shovels to scoop up the droppings. Biggest cause of squabbles were about whose house the droppings were outside!!!

Di.

[Rob B]

That is one beautiful caravan. I would just love to have that parked on my drive with a horse in the back garden eating the grass. I could even use the manure for my roses!

When I was small the bread and milk were delivered by a horse drawn cart and neighbours used to dive out with their shovels to scoop up the droppings. Biggest cause of squabbles were about whose house the droppings were outside!!!

Di.

They certainly are beautiful.

I quite fancy putting one of these in my garden for use as a den/workshop and occasional guest bedroom.


You can buy them for between £8 and £15k - not cheap but compared to building an extension its a bargain!

[peterholden]

Has anyone noticed that some of the more recent artic trailers have a sort of passive rear steer mechanism to get round some of the problems of "skid" steering round tight corners.

Some of the Citroen Zx cars and some Audis used to have "rearwheel steering" actually done by causing the suspension trailing arm to deform under certain conditions. It was claimed to make them safer when cornering at speed.

And of course some of Pickfords lowloaders have a steerable rear bogey. They carry an extra person as a "steersman"

Peter