Turntable Caravan

[Gafferbill]

What has puzzled me for a long time is why no manufacturer has used a turntable design for their larger range of caravans.

With 2 axles with 4 tyres carrying the weight and a wheel at each corner of the caravan, this would do away with most of the instability problems associated with the balanced trailer designs we have now.

Worrying about noseweight and small payloads would be a thing of the past.

Surely the caravan could have disc brakes, possibly electrically operated and controlled directly from the tow car.

Rod operated drum brakes must be a thing of the past.

This type of trailer is almost impossible to reverse using the tow vehicle.

However this is no longer a problem because a motor mover could be fitted to the turntable axle and all reversing could easily be carried out by means off this. The increased payload could accommodate larger 12-volt batteries for this purpose.

The front of the caravan would have to have a raised floor to allow the front axle to pivot to provide steering. This area could be a streamlined, windowless storage area extending to the full height of the caravan.

The back of the caravan could have a vista window and contain the lounge area.

The area in between could fit the bathroom bedrooms and kitchen as required.

They say everything goes full circle.... perhaps we should go for a 21st Century design of the original Gypsy caravan.

 

[Chrisbee]

That would require the caravan industry to think "outside the box". No chance!

 

[colin(bridgend)]

I believe caravans were manufactured to this design pre second world war but were not very successful for sales. How would the coupling me made to the towing vehicle as I am sure that with the added weight a normal tow bar and 50mm ball would not be sufficient. For this type of design a fifth wheel coupling would probably be required similar to the prewar photo in this month C&CC magazine of an American outfit.

With modern fifth wheel caravans I cannot see why the caravan wheels could not be set back to the rear of the outfit similar to an articulated trailer on a lorry. Surely this would make for a steadier outfit.

 

[colin(bridgend)]

I believe caravans were manufactured to this design pre second world war but were not very successful for sales. How would the coupling me made to the towing vehicle as I am sure that with the added weight a normal tow bar and 50mm ball would not be sufficient. For this type of design a fifth wheel coupling would probably be required similar to the prewar photo in this month C&CC magazine of an American outfit.

With modern fifth wheel caravans I cannot see why the caravan wheels could not be set back to the rear of the outfit similar to an articulated trailer on a lorry. Surely this would make for a steadier outfit.

should read "... the coupling BE made to the ...." Apologies

 

[Steve L]

This design would require an expensive chassis which would be cost prohibative. Also because of added weight the trailer would be limited to 4X4 towing. But it can be done.

You could adapt conventional over run couplings to work a hydraulic brake master cylinder, which would then operate a conventional car type hydraulic brake system.

You are right to say that a fixed motor mover fitted to the steering axle would make manouvering easy.

Now there are two down sides.

1/ As we already have caravans that are at maximum design length easily towed by large cars and 4X4's, why would we want to change.

2/ Given that some caravan sites already don't allow twin axle caravans with doors on the right, or caravans that look too chromed etc. Why would they accept a caravan that looks like a fair ground showman's home?

Finally I believe that law already exists restricting towing of such vehicle to showmans tractors only.

Atb Steve L.

 

[emmerson2]

If my memory is correct, I believe one of the bigger manufacturers (Sprite, I think), did experiment with a four-wheeler, probably in the early 70s. I saw it on the M4 in Wales. It looked just like the then current Sprite major, but the side panel was cut away, and the front panel shortened to accommodate the front axle. The rear axle appeared to be as normal, simply moved back a couple of feet. I often wonder why it never caught on.

Does anyone else remember this?

 

[Gafferbill]

..since a caravan is bodywork built on a trailer chassis, then think of the caravan that could be built on one of these trailers shown on the website below!

http://www.batesontrailers.com/trailer-detail.asp?ID=78&cat=8
Colin...a standard tow ball would be fine.

The forces applied to the tow ball by today's caravan designs are what cause instability in outfits.

Most of these forces would be reduced to insignificance by the fact that a turntable caravan would have a front axle.

The forces present would be acceleration and deceleration hence the need for better brake design.

 

[Phillipcharnwoodforest]

How would the nose weight be attained?

 

[hgv dave]

hi all

i remember one that i saw about 20 yrs ago at a caravan dealer outside leeds,it was about 20ft long and looked like a normal caravan apart from the front axle

the nose weight would not not be a factor because all of the weight is taken on the front axle

a turntable caravan is not impossible to reverse......it just seems that it is,not so long ago there were many hgvs that used turntables because the maximum length was longer than an artic and was able to carry more.these days the "a" frame has been changed to a normal artic set up,if you look at a wagon and drag outfit now the axles are in the middle of the trailer which makes reverseing far more easier

hgv dave

 

[kennygee]

I disagree with the idea it would be easier to reverse as you would have two pivots to work with. VERY difficult. Ask anyone who works on a farm and has to reverse farm trailers. Ken

 

[Martin_E]

I agree with Kenneth.

Having seen the mess some get into when reversing something as simple as a caravan they wouldn't stand a hells chance of reversing a pivot type trailer.

 

[Steve L]

I agree with Ken and Martin.

Reversing a turntable trailer is a nightmare, and that comes from someone who can park a 6ft 4ft car trailer and his caravan on a six pence. I've had first hand experience using farm trailers when transporting poultry unit frames and cladding from a main road location to the farm tucked away in the hills of Wales.

That is probably why Gaffer started off by suggesting a motormover be fitted to the front axle.

Phil, the nose weight would remain consistant as you have a drawbar with no optional attatchments. There would be axle weights to adhere to, so I guess if your running at 100% loaded, you would need to use a weighbridge.

To be honest, reversing on the highway isn't realy advisable even with a conventional caravan due to volume of traffic and most peoples ability to reverse confidently. Even I prefer to use a roundabout, large carpark or do a diversion route to turn round. The latter usually is less than 2 miles and takes a matter of minuits to do. Plus you see views that you wouldn't normally see. I did one in Scotland with a group of 4 caravans and we U turned a mile up the road on a roundabout, it did cause a stir seeing 4 car & caravan combo's doing a U'y. But it's part of the fun of caravanning.

I think the main negative for a turntable unit will be gaining acceptance from narrow minded site wardens.

Our warden (forest grump) won't let caravans with doors on the right on site, so you could guess what he'd say to a showmans type caravan.

Atb Steve L.

 

[Hoits]

I think that this design would make a lot of sense. Ideally the front steering would be an "ackerman type" with front wheels at the front corners, rather than a turntable, as this would occupy less of the caravan's internal space. Internal design could be improved as there would be no wheel arches in the middle of the van, and the van could be built lower.

Cost would obviously be an issue, but stability and therefore safety should be much improved.

I can't believe that the Warden's attitude should be a significant design factor!, you could always fit a front grill and make it look like a motorhome!

Dave C

 

[metz13]

Hi, Lynton Caravans produced a prototype van of this design back in the seventies, Dad and i had a tow with it, very stable on the road, plenty of room inside, today's designers would have a field day with the available room, sadly weight and cost where to be it's downfall.

 

[Phillipcharnwoodforest]

Phil, the nose weight would remain consistant as you have a drawbar with no optional attatchments. There would be axle weights to adhere to, so I guess if your running at 100% loaded, you would need to use a weighbridge.

Thanks steve and dave just wondered.

 

[DJGB]

It was at the 1985 Earls Court caravan show at the 1986 Lynton Excalibur was launch with a wheel at each corner.

It was tested in Practical Caravan being towed by a Volvo 740.

It cost around

 

[Lutz]

As mentioned at the start of this thread, such a caravan could not be fitted with overrun brakes but would have to have some sort of active braking system of its own. This, in turn, would at least have to receive some sort of proportional signal from the towcar to work simultaneously with the car's brakes. The easiest solution would be an electrical signal, but there wouldn't be enough free pins in the existing 13 pin layout to do that, so a further electical plug and socket would be required. Also, the car's braking system would have to supply the signal, but neither the car industry nor international standards provide for that, so a solution would have to be found for that, too. Currently, trailers over 750kg and up to 3500kg must have an overrun brake and trailers over 3500kg must have an active braking system. It is unlikely that short term agreement could be achieved within the industry on a common active braking system for trailers under 3500kg as the lobby just isn't powerful enough.

 

[emmerson2]

Lutz, why could it not be fitted with overun brakes? It would simply mean that they would be cable operated than rods.

 

[NickinFrance]

Lutz,

Apart from cost, what's wrong with these ?

http://www.easternmarine.com/em_store/trailerbrakes/trailerbrakes_hyd.html

 

[extrucker1]

hi all, been a lorry driver all my life, at one time drove a lorry and trailor. a six wheel lorry pulling four wheel trailor, wheel on each corner. you could stop them all right, they had air brakes. had to reverse them on to loading bays, on to ferries( fred olson boats, felixtow to oslo) only one way on and off. they were ok but not stable at all. used to wobble all over the place. ray

 

[Lutz]

Lutz, why could it not be fitted with overun brakes? It would simply mean that they would be cable operated than rods.

There would be a danger of the trailer itself jackknifing if it were fitted with only an overrun brake.

 

[Lutz]

Lutz,

Apart from cost, what's wrong with these ?

]http://www.easternmarine.com/em_store/trailerbrakes/trailerbrakes_hyd.html

http://www.easternmarine.com/em_store/trailerbrakes/trailerbrakes_hyd.html[/quote
Nothing basically wrong with such a setup, only that it is very complex as one would probably need a separate servo to achieve enough hydraulic line pressure for a disc brake system.

 

[davidnewname]

I was watching on program on the telly the other night and it was showing some old outfits and I noticed that on of them had a pneumatic wheel either side of the A frame when towed by the car....anyone know what that was about?

 

[emmerson2]

Lutz, I don't follow your reasoning re overun brakes. The set-up would be the same as on a twin axle van but with the axles twelve feet apart.All wheels would brake together, so why should it jack-knife?

There were some wide-spread axled trailers around a few years ago,which by some loop-hole in the law were allowed to travel at 70mph. I used one of these for some time, and never had any braking problems.Admittedly the axles were only four feet apart, but the principle's the same. Four-wheeled lorry trailers don't have a jack-knife problem either.

 

[Lutz]

In the case of a twin axle, both axles are always held parallel no matter how well or poor the grip is at each wheel. However, if the trailer has a steerable front axle then there should be a degree of brake proportioning to ensure that its rear axle brakes harder than the front or else the rear end of the trailer could lose grip and swing round. I cannot see how brake proportioning can be achieved with a simple overrun brake, but it wouldn't be a problem with an active hydraulic system.