hello from germany

[angib]

I think that is plenty strong enough. I don't believe you need a plate underneath it, as the axle bracket is big enough to spread the load - but having a plate might make the TuV happier. I do believe you need some plate or big washer on the top to stop the bolt head sinking it - you want to be able to do up this bolt tightly. 50x50mm (or 50mm diameter) in 3mm plate would be enough.

Andrew

[Mini Renegade]

Hi Bernd, welcome to the forum. I lived in Germany for 5 years in the late 1990s when serving in the Army, we were in Fallingbostal, which is half way between Hamburg and Hanover.
I like the lightweight idea, I tried to make mine as light as possible by using 9mm sides which when combined with the cabinets, window frame and door frames is solid.
The only real problem I have encountered is chassis twist when entering through the door, this can be sorted by using corner steadies.

[bernd]

Hi,

Hi Bernd, welcome to the forum. I lived in Germany for 5 years in the late 1990s when serving in the Army, we were in Fallingbostal, which is half way between Hamburg and Hanover.
I like the lightweight idea, I tried to make mine as light as possible by using 9mm sides which when combined with the cabinets, window frame and door frames is solid.
The only real problem I have encountered is chassis twist when entering through the door, this can be sorted by using corner steadies.

Of course i'm interrested in your design, may you provide some pics please? A twisting chassis is no problem, until the joints show wear or breaking, or the trailer shows a instable ride while towing. But where do you think the twisting comes from? Is the torsion box non-continuous?


Frame:



Questions? Comments?

weights are:

axle 50lbs
tongue 22lbs
clampings 6lbs
3 wheels 25.5lbs (now 3, - spare wheel...)
lighting, fenders 7lbs

frame 40lbs

total 151lbs (69kg) now, the rest up to 660lbs (300kg) is for the walls, the roof and bed and ...comfort.


A little built history:

For the crossmembers i decided to glue two pieces of 1*2 timber together as i cancelled the underside covering. It would be too difficult to get a watertight cover on the different hights of the frame parts (ply/timber), so i think it's better to have the frame in free air. Second is, that the TÜV-engineer sees what holds the floor together, and it's easy to inspect for me too. I puzzled two adversatively distorted, knotted battens together to get one straight robust 2*2. That worked out good, was cheap but time consuming. I bought a bundle of 10, length 8feet each, used with almost no waste. The frame is almost precise, despite the workshop conditions. Next time i build a solid flat working platform first... . The glue is PU-MAX from UHU. It has a jelly consistence, is chrystal clear, comes in cartouches and sticks best to skin... . I'm not shure if i like it. Exept the big areas between the plywood parts, where water based glue dries almost never, a D3 PVA glue would have been easier to work with, and it's waterproof too.

Is 1/4 birch ply enough for the floor decking?
I'm not afraid of fexibilities, if it won't break while towing. Insulation will be a layer of XPS on the inside, layed on to allow inspection

How to protect the underside?
Boiled (linseed) oil? I like that stuff, used it in my kitchen on pine ply, even around the sink. Easy to maintain, just wet-sand with that oil, skin friendly... . If dryed out a good base for solvent based paint. I would like to have the underside clean white...
But can i use it for the upper body?

As you see on the pic the axle is right in the middle of the body. I plan plastic boxes as first provisional storage, and "technical modules" of the same size.
One module for example will be 12V battery, charger, 12V outlets for gooseneck lamps, 230v in an out, and the electric fan heater, maybe communication/media/sound. I like to fiddle at home on the workbench. it will be much easier to compress the equipment in a small package, if i can turn the module around, instead of creeping in a build in compartment with the legs hanging in the rain.
Next module is a provisional coffee kitchen, as i cancelled the hatch for the first TÜV-version.
I think about a shower module... porta potti module... Next tear will have a fully funktional popup bathroom...
Clothing stuff will be in bags, on the mattras while towing, or in a big bag net in the back above the feet.

That modules go to the front, and will be the highest pointload on the floor (to come back to the diameter of the floor)


Greetings, Bernd

[angib]

Questions? Comments?

That looks good - strong enough, but not too heavy. I think 1/4" ply is thick enough for the floor, but you will need to be careful not to kneel with all your weight on one knee, in the middle of a floor panel.

As you see on the pic the axle is right in the middle of the body. I plan plastic boxes as first provisional storage, and "technical modules" of the same size.

That is not ideal. Americans typically have 10-15% of the trailer weight on the hitch and while we Europeans run with lighter hitch weights (5-8% is typical), you may not get enough hitch weight with the axle near the middle. If your heavy 'technical' modules are stored at the back of the trailer you might even get a negative hitch weight, which will make the trailer unstable when being towed.

You need to carry out a check on your trailer's balance right now, before you build any more, in case you have to make changes.

I would expect the centre of the wheels to be no more than 45% of the body length from the back, as a maximum, and nearer 35-40% if you are planning to put heavy things at the back. The Design Library menu button at the top of this page has a trailer balance page you can use.

Andrew

[bernd]

Hi,

Andrew, you missed a little detail hidden in plenty of text . The technical modules go to the tongue side, the bed is in the back. At the moment (frame only) the hitch weight is 17lbs. The body will be almost balanced, maybe slightly more weight to the front as there the sidewalls are higher than in the back.

Then i put a mattress in, with only the mattress in i've to put it to the front. Then i load modules/storage boxes to the front, mattress to the back then.
Then i load bags with clothing. For towing the bags lay on the bed, slightly in front of the axle.

You are right, there is at no circumstance plenty of hitch weight, but never negative.

There is no hatch in the back, maybe later, but only for a little coffee kitchen (home is where you get a real good coffee). But until then there will be enough technical module stuff in the front.

The plan is, never to fight against too high hitch weight with counterweight in the back. Lowest possible weight at the rear end will give the lowest inertia in the vertical axis. For towing stability it is not only important to have a propper hitch weight, low weight at the extreme ends of the trailer will help too. All available advice tells me that the "at last 4%, but no more than 55lbs" stated by the authoritys is ok, as long the mass is near the axle, and not at the back- and the frontend of the trailer. This avoids swinging and brings stable towing. 15% hitch weight makes everyting towable, but my front wheel drive...

I would have put the axle slightly more in the back, but then i would have to use a longer 100inch tongue to get propper jack kniving capability. The length of the suspension crankarms and the clamp add to the tongue length. The tonge now is 78inch, which keeps the trailer in the slipstream. I was afraid of shortening a type approved tonge, even if this sounds like childish slavery to the authority.

Greetings, Bernd

[H@nk]

Hallo Bernd,

Nice to have a neighbour on the forum. I am from the "Niederlände".

I like your trailer. I used a complete stripped down trailer from a Alpen Kreuzer. It has brakes, suspension and 4 jacks.
I built something like a T@b, but smaller. Next thing I have to do is covering with epoxy.

[bernd]

Hi Henk,
smaller than a T@b, then it`s more a Dübener Ei? Welcome, there is paved road between us . To visit the most of the community we have to built floats to our trailers, or better wings.

Greetings, Bernd

[Mini Renegade]

hey Bernd, the twist I was talking about is the front corner dipping down as you enter or leave due to having no positive support as an "A" frame would provide.
My chassis is a similar design to yours using a "T" as the main frame, I then had a ladder frame of 25mm angle welded to that. My suspension units are independant torsion units which are bolted to the main cross member.

[angib]

Bernd, OK I missed that - all sounds fine.

Andrew

[H@nk]

Bernd, you are right about the Dübener Ei. The only difference is, I like to shock people with my design,:D
The distance Nieuwerkerk a/d Ijssel, nearby Rotterdam , to your Mannheim must be around 500 KM, so when the MINI T@b is ready, I'll take the short way to you. Take a look at my album, there are pics of the N@b T@b. Its also possible to send an e-mail, then I can write my "best"german to you.

[bernd]

hey Bernd, the twist I was talking about is the front corner dipping down as you enter or leave due to having no positive support as an "A" frame would provide.
My chassis is a similar design to yours using a "T" as the main frame, ...

...almost the same static design. But don't you have an almost closed body on that frame, giving the trailer the stiffness the floor alone doesn't have?
Of course my frame alone behaves like a piece of paper, but if you build a closed suared box out of paper it is stiff, unless you cut too big holes in it. I guess with the front- and backwall, together with the roof as one rounded part it's nearly the same. A problem are may be the doors if they are too big, means, leaving no wall above the floor and under the roof edge. Then there will be variable Parallelogramm instead of the infinite number of triangles given by a flat wall. Another interruption of the Box is the hatch, but at a classic tear the cabinet walls will substitute the missing backwall. In my case there is no hatch and no cabinets in the back, but a backwall. Of course i am worried about my doors as they are directly above the axle, in a thin (lightweight) plywood wall. I hope i can add a sufficiant door framing, especially at the bottom.

An A-frame would be better, if i had the choice... . But it won't compensate a flexing twisting body. The body itself has to be a stiff torsion box.

@ Henk: The "shock" is the massive build up of your mini T@b, instead of the Dübener Ei, made from painted cardboard? ;-) Let's see where we meet. I know beautiful places in nederland, and you may show me more.

@ Andrew: It may look like i have an elaboratively worked out plan, but in fact it isn't. I'm still reading - and relying on that plenty of work you and others have published here.

Not the last I rely on active supervision, that's a great help. Thank you!


Unfortunately it takes time to get the plywood, because the distributor is a cooperative, selling only to members, means woodworking enterprises. It's no problem of quantity, but to keep the wood away from not registered craftsmen. Fortunately i won't have to wait until a buddy is back from vacation, there are craftsmen repairing the house i live in - nice people and good contact, but still it needs time, it's hard to wait.

Has anyone thought about using that superstrong/small Neodymium magnets to pull the circumference of doors/windows tightly into the sealing gasket (weather strip)? That's my idea to avoid multiple catches at thin wobbling doors.

Greetings, Bernd

[angib]

but if you build a closed squared box out of paper it is stiff, unless you cut too big holes in it.

Bernd, I think you are absolutely right - the example we use is the box that new shoes come in - stick the lid to the box and it becomes really stiff against twisting.

I don't think the door openings are much of a problem, as long as they don't cut out all the sidewall - I would always like to see 100mm (or four American inches) left above and below a door, to keep some strength in the body.

Mini Renegade, I'm very surprised you are getting body twist - do you have all your body panels glued/screwed/nailed in place? Until all the faces (front/back/sides/top/bottom) of the box are fixed in place, it won't have the same strength as when it's finished.

Andrew

[Mini Renegade]

Mini Renegade, I'm very surprised you are getting body twist - do you have all your body panels glued/screwed/nailed in place? Until all the faces (front/back/sides/top/bottom) of the box are fixed in place, it won't have the same strength as when it's finished.

Andrew

Andrew, the body is glued, screwed and filleted on all joints and is solid, as Bernd said the chassis is flimsy but with the body on there is no movement apart from the front corner dipping down and trying to lift the opposite corner when entering. I believe that this cannot be rectified without extra side to side bracing. It has a 25mm angle on the chassis and another above the floor in between the roofskin and ceiling/front wall

the pic may explain a bit better.

[angib]

Mini Renegade, the picture you've posted shows no skin on - and like that I would expect the body to be very floppy. High quality joints on spars and even diagonal braces like you've added are just decoration compared to the huge shear strength of (even thin) skins of plywood. It is only when all the skin panels are glued in place that the body becomes resistant to twist.

If you are getting twist after the skin panels are glued in place, that's weird and suggest there's a problem elsewhere. If you're getting twist before the panels are glued in place, that's exactly as expected.

Andrew

[Mini Renegade]

The pic is and old pic, the ceiling and roof skin are glued and screwed in place, the body does twist slightly but no where near as much as before they were fitted. I believe it is due to the front cross member only having one support not 2 as an A frame would provide.