I eventually had to revert to a real trailer chassis, simply because the parts for the traditional shepherd's hut were hard to access. As I get my ducks in a row here, I will have all in place so that I can do the more traditional design. Meanwhile, I have done this first step, so I will leave it here for those who want to continue.
The whole culture of tiny houses seems to be all about building on a trailer or constructing a chassis with wheels, but this or any other Tiny House would be just as happy on a foundation, skids, posts or whatever.
In my case we are going to build on a metal 2x4 steel tubing frame that corresponds to a slab, bolting it down to the frame, and placing the whole thing on oak axels and steering mechanism and cast iron or wrought iron wheels.
These wheels will not allow the cart to be taken on the road, except for very slow speeds and over short distances.
The first order of business is to have the basic frame built. It could be made from "I" beam, but I feared the inside corners catching water and mud and eventually rusting. The tubing will be fairly smooth all over. It will have tiny holes here and there to let expanding air out of it while it is heated in the welding process. Those can be filled with silicone, or solder to make it water tight. The whole thing can be powder coated, but well maintained paint will do well also.
Along the edges of the frame, that corresponds to the foundation, bolts can be welded to the outside rim, the head extending down to the bottom of the steel, and extending up far enough to go through the sills and bottom member of the wall framing. The fact that it is on the outside, means that the sills will extend over the edge of the steel so that a hole will accept the bolt.
Alternatively, you can drill right through the steel and put a bolt up through the steel and through the layers of wood. This is easy and tough, but it also opens more places for rust.
Or, a headless bolt or threaded rod could be welded on the top of the steel to go through the wood.
The first option gives you a couple of inches of extra floor space, and since the construction is so light, it will not affect the stability of the building.
You have to do a little planning here. I always see these videos where the people bolt their house down to the trailer, and I wonder..."now how are they going to do repairs once the whole thing is constructed. Are they going to tear the bottom foot of the walls and floor of the house apart just to get at these bolts if they rust, or come loose or squeak?"
I think that the ideal, and this does not work for the welded to the side option, is to start the head of the bolt inside the wall and drop it down through the frame. Access to the nut will allow you to remove the house and put it back and to tighten it as necessary. It must be painted over and over again so the bolt will not rust and freeze up on you.
The other alternative, and the one I plan to use, is to put deep baseboards all around the floors of the building, so that the baseboard can be removed to give access to the bolts. Do not, in this case, put bolts anywhere that they cannot be accessed in this way. Any of the options above can be used with this.
These huts may have the wheels either outside the walls of the house, and up along the siding, or under the walls and the cart. They are a little less stable in wind if they are under the wagon, but screw tie downs will keep either one stable. These are a bit like the screws that you put into your lawn to put a dog chain on. A big augur screws the rod into the ground, and a ring protrudes from the earth to chain the corners of the wagon down to the ground.
After the axels and steering mechanism are made, then brackets to hold the axel and supports for the wheels can be welded to the frame. Do not do all of this till axels are made and ready to be mounted, as they can be hard to make and maintain level from front to back.
I will upload drawings of all this.
The frame will be the length and width of the proposed building (unless you plan to gain a few inches by welding the bolts to the outside as described above.)
These huts can be as small as 6x12feet. This is impossible to live in, and the narrow dimension, while probably perfect for an undernourished 19th century shepherd, would not be useful at all for modern 5'10" and up average people. It would be like sleeping in a loveseat. Sleeping the long way, leaves no room to live.
I think that 8 feet wide is about the minimum for modern Americans, but measure your family and see if other widths would work better. You do not have to be a slave to tradition and sleep with your knees up in a fetal position. Remember though that the wider you go, the more pressure you place on the rigidity of the axels.
I think that 8 feet plus or minus the width of the sills over the edge of the frame is a good number to stick to. If you plan to use a modern trailer, you are only restricted to the width of the trailer you buy or how much you increase the width by welding on extra iron. The wheels can be worked around or over.
Remember to get an accurate estimate of the bearing ability of the trailer's construction. You do not want the trailer bottoming out on the roads, flattening the tires or flexing to the point of cracking walls, floors or framing of your final house.