Teardrops n Tiny Travel Trailers

Hello, this is the design i'm currently working on for my tiny trailer, it's designed to hold a double/full sized mattress and my initial estimate is $2,000CAD/$1,600USD for all parts (before shipping and screws and bolts and other fiddly bits) and should weigh about 200lbs or a little more

basic design uses 2x2x.125" aluminum square tube as the frame on top of torsion split axles and 8" wheels (to ensure the tounge weight is about right but the wheels don't interfere with the door, there will be fenders i just didn't model them)
that gets bolted onto a 1/2" 5x8 foot marine plywood floor (maybe I can use regular plywood and just seal it to save weight) with a shell made of 1.5" ridged foam that's reinforced with poor man's fiberglass (and maybe something on the inside that's ridged and light like thin wood paneling)
Doors are pre-made and just need to be popped right in https://www.teardroptrailerparts.com/doors.html
What are your thoughts on the basic design?

Doors
mattress
walls
Axles
outer coating (tinted orangey red to match my car then sprinkled with copper paint)
stabilizer jacks
fenders

I mostly just wanted to get a sanity check for glaring mistakes as I largely have been planning things on my own but pulling information from any sources I can. I do largely think I got the basics down up until I'm in a less stressful financial situation and can play with the materials more. Since i'm getting prebuilt doors (or prebuilt door and window if i just make a twin bed sized version) that just pop into place I don't anticipate needing a wooden shell in something this small (but i could be wrong) providing I'm using PMF and truck liner and thicker foam which will also ensure it's well insulated in cooler and wetter weather, maybe with a battery powered electric blanket for heat.

basic design uses 2x2x.125" aluminum square tube

I'm not an engineer, but that seems awful light for the tongue. If it were steel, I'd say it was light but okay. It wouldn't take much to bend it.

Hopefully, someone with a bit of structural knowledge will chime in.

Tony

as far as i can tell it might be, but yeah i'm just going off load tables which wouldn't be as accurate as someoen who knows the metal properties better. the trailer itself weighs 200lbs and the axles are only rated for 600lbs so it won't have a lot of weight behind it. I mean I can likely jump it up to 1/4" thick tubing without having to completely overhaul the design.

The long un-laterally-braced tongue that raises concern for me. Also might want "no step" signs on tongue.
Are you in a state where registering will require inspection?

The tongue and the two parallel bars will be screwed to the wood flooring at 6 or 12 inch intervals which should secure it very well, the tongue might be slightly shorter so the coupler ball is right at the intersection of the two angle walls (to make backing up easier as you can tell if you are about to jacknife easily.)

https://assignedvin.ca/ looks like I do have to go through some steps to get the trailer registered, and it will be inspected.

I thought the 84 was inches and looks like 48" of tongue unsupported. Just seems possible to bend right at point it is under cabin if you loaded it at all or stepped on it. I know its light and you won't put anything in it while towing, but pictures on this site of heftier steel tongues bending at that point.

yeah sorry it is in inches. Measuring in the program the lengths are 26" from edge of the shell to the tip of the bar and 42" from the tip to the cross beam, and I'll shorten it a little so the total length includes the coupling; but yeah I see your point. If i load the trailer correctly there should never be a lot of weight on the tongue (and the front jack will sit just beneath the floor on the tongue). I was doing my best to guess at what the bare minimum would be needed for the frame but I suppose I overshot a little and should switch back to .250" for the bars, might as well make them all .250", and yeah I can add a do not step warning to the tongue.

I'm generally the critic of over building, advocating strong enough, not just strongest. And the impact from a pothole bounce can be a multiple of the load. Test it. Clamp some two-by to the tube approximating the underfloor, and support at axel and hitch points and jump on it.

I applaud you not over building. Much more elegant. Regrettably, we probably cant keep building and testing like Space-X can.

The tongue and the two parallel bars will be screwed to the wood flooring ...

Bolts maybe?

Tony

QueticoBill wrote:I'm generally the critic of over building, advocating strong enough, not just strongest. And the impact from a pothole bounce can be a multiple of the load. Test it. Clamp some two-by to the tube approximating the underfloor, and support at axel and hitch points and jump on it.

I applaud you not over building. Much more elegant. Regrettably, we probably cant keep building and testing like Space-X can.

to be fair the most expensive components - axle, doors, jacks - can be unbolted and removed from a broken or failed attempt and attached to a new shell later on. Does mean a loss of ~500 per attempt tho

tony.latham wrote:

The tongue and the two parallel bars will be screwed to the wood flooring ...

Bolts maybe?
Tony

...yeah, maybe. Assuming I find some that sit sorta flat so they don't dig into the mattress or person

one thing, when using canvas and waterproof glue as pmf for the outside, using truck liner instead of paint at the end is fine?

I wish the design resources included a very simple frame that imho would suit your intents better. Basically a triangle. Instead of a center piece and two parallel at side, a triangle with axel as base and hitch as apex. The "corners" just hang over diagonals. Actually less material and more rigid.

QueticoBill wrote:I wish the design resources included a very simple frame that imho would suit your intents better. Basically a triangle. Instead of a center piece and two parallel at side, a triangle with axel as base and hitch as apex. The "corners" just hang over diagonals. Actually less material and more rigid.

i mean, i did see that, but the angles that tongue hitches come in is somewhat limited, and the front corners and entire back half of the trailer would be unsupported - and i don't trust 1/2" plywood or even 3/4" plywood that much. the designs I saw using the triangle also had a frame of parallel bars running under the body which makes the weight saving a smidge moot.

Build deck of 1/4" ply on 1 or 1 1/2" foam. Roughly as strong as two-by and weight like 1/2" ply.

The frame I recall was just triangle and axel was the base. I really miss that collection of designs.

In my design work if using aluminium its generally larger than steel by half or more - 3" instead of 2" - for portable staging for instance. Don't use it often as generally triple the price for half the weight.