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grahamf · 09-17-2020, 06:21 AM

Hello, I'm slowly planning on making an ultralight trailer to tow behind my fiesta and I was looking for advice.

My priorities are to make a trailer that is basically just big enough for a bed while making it as light as reasonably possible without compromising too much on integrity. My plan is to base it on a welded aluminum frame using a split torsion axel, with a distribution system that uses a solid aluminum bar core for the axle substitute, a 2" hollow bar from hitch to tail as a spine to support a 1" hollow bar frame, a thin sheet of something rigid for the bed, then a lightweight shell with .75" or maybe .5" angle bar for support and with rigid foam with a truck liner exterior and not sure what for the interior yet. I haven't figured out what i will do for doors as it seems it's best to buy premade.

My current estimate is that the trailer will weigh about 400-600lbs and cost about $2,000-$3,000 excluding doors and fixtures that will likely add another grand. Plus I'll likely need help with the welding as I don't have the right equipment so that will cost more

The pictures are as below. the dark pads are solid aluminum for bolting on the split torsion axel along with the stabilizer jacks (using one in the front instead of a standard jack because the trailer will sit low to the ground - my car is also low profile anyways)

i intend to put two doors on either side that are as big as possible, I don't think i can make them from scratch and be fully weatherproof so I need to find ones that aren't full height and make adjustments to fit them. then add some windows i can open, a roof vent, wiring and bolt on a coupler, and it should all be good to go.

I'm still figuring out exactly how I want to do the upper shell, as I'd like to have rounded edges.

It's still in the planning stage and there's a few things i need to figure out still. I just found these doors which should work...

Desert Flyer · 09-17-2020, 08:27 PM

Kudos on your adventure.

However, as a structural engineer, I don’t like the central-only spine. As you travel over terrain, the action of the wheels and suspension would tend to flex the cross members and subsequently twist that single central spine. Now, if properly designed and welded, taking long term fatigue into account, it can work. The welded connection is the critical link. Whereas, with an A-frame as a tongue flowing into two rails that supports the axle, this stable foundation will minimize member twist and high stresses on their connecting welds.

grahamf · 09-17-2020, 10:02 PM

Quote:

Originally Posted by Desert Flyer

Kudos on your adventure.

However, as a structural engineer, I don’t like the central-only spine. As you travel over terrain, the action of the wheels and suspension would tend to flex the cross members and subsequently twist that single central spine. Now, if properly designed and welded, taking long term fatigue into account, it can work. The welded connection is the critical link. Whereas, with an A-frame as a tongue flowing into two rails that supports the axle, this stable foundation will minimize member twist and high stresses on their connecting welds.

Yeah I was wondering how that would work. I'm looking at using half axles which would mean that forces would get distributed through the entire frame, they should reduce twisting as they operate independently but I'm not sure by how much.

Desert Flyer · 09-18-2020, 09:35 PM

If it were me, I would look into buying a utility trailer frame and axle/wheel that was already designed and fabricated. I think I’ve seen them at Home Depot, Harbor Freight, Tractor Supply, and online like Northern Tool, American Trailer Pros, and trailersplus. They’ve done the hard part. Then you can build on top of them.

Roy-c · 09-19-2020, 05:42 AM

Look into buying a trailer and adding or converting to it in order to have what you want. That will save you a lot of time, work and aggravation in the long run and you will have an engineered frame and running gear to start with. I also think you will be surprised at the cost of having the aluminum welded up by a professional.
Your cost estimate seems very low.