Lightweight trailer/floor system?

[loaderman]

To me having a trailer that can carry weight then adding a floor on top does not make sense.

I am building a large foamie (hopefully) around 28' long. And want it to be strong and light. As the trailer often seems to be the heaviest part I am thinking of ways to make it lighter and strong as well

I am thinking double axle with brakes, this would have angle iron on top of the axles, then 2 angle iron going from the axle up in a triangle to the hitch. Basically an A shape all-together.

Then no real metal framework. 1x4 or 1x6 framework, running the length of the trailer 18'. Filled with foam (want it for winter insulation anyway) and skinned on top and bottom with 1/4" ply. The do undercoating or bed-liner on the underside. Basically a big torsion box, bolted to the angle iron on the axles.

Could make the trailer out of angle iron and flat iron with styro filling it in and skin top & Bottom. But it would be heavier, costlier and more difficult.

Any thoughts on this?

[angib]

It sounds like you are still trapped by the idea that the floor must be self-supporting and will have to hold up the walls. The walls are a stronger beam than the floor can ever be , so you need to start looking at how to support the walls on the axles and the coupler and then just hang the floor between the walls.

[loaderman]

good point.
I can see that working with the wheels being outside the walls.
Mine will have the wheels inside the walls. 8.5' wide.
Any ideas?

[Treeview]

I thought that 8' width was max for any vehicle without special use.

[loaderman]

My understanding is that maximum width is 102", or 8'-6"
This is the absolute outside of any lights, window frames, awning or whatever. Most trailers go 8' then have awnings or whatever sticking out past that.

I thinking 8'4" Gives 1" on each side for clearance.

Been thinking abut the walls being the strength. Like a tall box beam basically.

Do a square tubing or angle iron fame, a H that fits just infront to behind the tires. With the angle iron from that to the hitch. could just attach hitch to front of trailer but powers that be probably not like it. Then build your walls with a 2x4" high bottom plate so that you can use joist hangers (custom make for 3/4" material) and hang your floor off the walls with joists running side to side. I'll do a 4" floor so I have r20 styrofoam in there, 1/4" plywood on top and 1/8" on bottom, undercoat or bedliner the bottom.

Basically like a floor hung off a beam in a house, only in this case the walls make a tall box beam.

Kinda a uni-body construction like a car.

[loaderman]

Also if You run a stap from the top of studs that would go on the H on the axles. down to the bottom of the front and back it would carry the front and back

[Treeview]

Tensioned cables can add strength to structures too.

[loaderman]

tree- that is what I was thinking with my metal strap. Kinda like some bridges use.

Had a Farmer friend who wanted to widen his 1 car garage into a two car garage. Didn't want any walls or posts in the center.
The solution was to put a beam there and run a cable on both sides of it. Went from the top at each end then in the center he put a pipe under the beam and the cable went under it. Had held for 20 years when I saw it.

[SteveW]

Tensioned cables can add strength to structures too.

That's what is done on most larger pool enclosures to keep the structure from buckling in high winds..

[chamal]

Hi Fellas,
I am also trying to design my first Caravan/trailer and I want it to be no heavier than 350Kg so that my darling Citroen 2CV (602cc) can tow it with ease.

It would appear my floor idea is called a torsion box, basically I want to get rid of the heavy steel chassis altogether.

I've drawn the floor as a 3"x 1.5" wooden frame 5' x 10' with a 3"x 2" steel spine in the middle, with a 3'3" tongue length and running into the floor 3' sandwiched between 3"x 1.5" timber either side of the steel and bolted through all 3.

I then intended to place 1/2" ply on the top and 3/8" ply on the underside, but reading the earlier post maybe that is overkill, could I get away with a 3/8" ply floor and 1/4" ply underside? or even 1/4" top 1/4" underside. would it be flex resistant or would it be better to run the steel the full length?

once the box is complete I want to drill entrance and exit holes in the underside and squirt expanding building foam into the void,this will act as a glue between the ply wood and will set solid enough to support weight on the floor.
I am using individual hub/suspension units ( I don't know what they are called yet) so no axle.

My next difficulty is where to put the wheels,I guess underneath would be a start lol! My design is a caravan, I think you refer to them as standies, it will be small with a pop up roof and a full size bed at the rear and a forward galley/toilet so the weight won't be concentrated at the rear as with a Teardrop.

I've looked at the design of the "Wanderer" and on the 10' version the wheels seem to be 4' 6"" from the rear of the van.
I understand the Centre of Gravity bit, but I won't know where that is until I've built it, or do I have to work out the weight of everything before I start to build?
I'm a joiner by trade but I've never built a caravan/trailer before.

I bow to the experience of you guys, any advice would be greatly appreciated.

Kind regards Alan

[mezmo]

Hi chamal,

Did you see the "Ultralight Chassis" in the design library?

http://www.angib.pwp.blueyonder.co.uk/t ... tear57.htm

It may be easier to fabricate/use. I like the idea of the wheels
and hitch triangulated with at least some steel. The torsion box base
can support the rest of the TTT body fine. This minimal chassis would
then be attached to the underneath of the torsion box with a wider
spread of attachment points than a single member tongue would have.
If you still want to use the individual suspension units, just have a
cross joist [doubled?] in the torsion box frame 'connect' them as an
axle does in an axle setup.

Cheers,
Norm/mezmo
Norm/mezmo

[chamal]

Hello Norm/Mezmo,

Thank you for your advice, reading Angibs post he states the lightweight frame should not be used on trailers above 8' long and my design is 10' long.
I have designed an 8' version, but reading the post on the "Wanderer" he states that for the small increase in weight and costs, a 10' version makes more sense.
It certainly allows more room and storage space.

I am watching a website passed on to me, I thought my caravan idea of 350 Kg was ambitious, this guy has built a 12' caravan that weighs 120Kg and his next prototype is aimed at 100Kg and BIGGER!! and he tows it with a Honda Goldwing motorbike.
watching his video he is towing at 75mph and the trailer follows beautifully.
If you are interested it is www.goldbrand.info/motorcykelhusvagn2.html

He's certainly got me thinking of weight reduction.

Thanks again, kind regards Alan

[mezmo]

Hi Alan/chamal,

I had mentioned that website to you in the 'newbie' section but your
response there didn't sound like it would be an option for you then.

'Glad to hear you are reconsidering and getting enthusiastic about
his builds. They really show it can be done with the right application
of materials and techniques. His website is at the top of my list for
'inspiration' material.

Good luck planning!

Cheers,
Norm/mezmo

[chamal]

Thanks Norm,
I will be watching to see what "prototype 3" will incorporate, their boat building skills will allow them to attack problems from a different angle.
That foamy stuff they use is called Divinycell but I haven't found a UK supplier yet, it looks as though you can cut it, shape it, sand it etc just like wood, but how strong it is I don't know.
Still designing my caravan, it will be called a Chamal 350, Chamal because my wife's name is Charmaine and I'm Al, not very inventive I know, 350 because that is my goal weight of 350Kg, hopefully LESS!!.
This is a super forum where people share ideas of design and build, I'm still learning the terminology, I think I've figured out a standie and a slouchie, but I haven't got toyhauler yet.
It tickled me how we Brits think on a smaller scale than our American friends, one guy said he was being cautious with his trailer as his tow vehicle was "ONLY" 4 litres, I don't think our trains are that big .
My Citroen 2cv is 602cc, I think that is 30HP, I bet you've got lawnmowers bigger than that.
I'm now learning Sketchup CAD so I can put my drawings on the forum.

REGARDS Al

[angib]

Divinycell is used in boatbuilding and is a proper structural foam used for the core in sandwich structures. It's not too hard to get hold of - it's affording it that is the problem. Proper structural foam costs a proper structural price. £100 ($150) for a single 8x4 sheet isn't impossible.