"Standy" frame questions

[MatthewWorks]

I think 2x2x.125" tubing is really heavy and overbuilt for your trailer. I suspect that you could go with 2x2x.083" tubing and be just fine, .060" might be too thin. I would say .125" for the tongue extension.

.060" yield is ~30,000psi, and weighs about 1.6 lb per foot.
.083" yield is ~32,000psi, and weighs about 2.1 lb per foot.
.125" yield is ~46,000psi, and weighs about 3.1 lb per foot.

Your trailer isn't going to weigh over 1,800lb, and you're not going offroad rock climbing with it, right? I'm a noob here when it comes to teardrops, but have worked with metal most of my working career.

Hey MadMango - thanks for the reply. The trailer itself normally shouldn't weigh over that, but I do expect to carry somewhere between 800 to 1000 lbs for work, on top of the actual trailer weight. So I'm thinking 1500 lbs trailer, 1000 cargo with a bit of room for fudging the figures.
Honestly, I read the figures above, and they make sense... but yet when it comes to real world applications I feel bloody lost. I'm okay with an extra 100 lbs for the trailer if it makes it solid. No rock climbing (nothing like this craziness http://www.theadventureportal.com/leitners-4x4-custom-off-road-trailer-build/ ) but perhaps the occasional crappy dirt road in Utah, or backwoods wherever. There's life to be had out there.

You may claim to be a noob, but I'm a nooooooooooooooob when it comes to big metalwork. Give me really small scale, expensive metals, and I have a tiny bit of sense of what I'm doing... maybe that's part of why I'm so obsessed about building this. Something new.

Maybe 1/8" thickness all around? Compromise between lightweight and strength?

cheers.

[MadMango]

I don't have any confidence in my welding abilities, I received a mig welder for my birthday a few years ago but haven't used it to make anything too structural. If you consider yourself a welder then you are home free. I still think the .o83" wall thickness will be plenty strong, especially if you are planning to use gussets in the corners. Remember too, your "box" will stiffen the trailer as well. I would wait to hear from some of the actual welders here on what they think.

[MatthewWorks]

I'm starting to think no one really likes frame questions! Or am I so far off-base on my thinking it's too much to answer?

[KCStudly]

3x2x3/16 really isn't that stout for a 2500 lb capacity. Use it for the tongue A-frame and first xmbr. Under sling the A-frame and only weld the crossing joints at the first xmbr along the longitudinal axis, not athwartship. This area is the most susceptible to cyclic stress due to being the point where the relatively flexible tongue (in structural terms) meets the relatively inflexible monolithic structure of the cabin and frame "unit" (the cabin stiffens the main trailer frame significantly). In other words, it has to be beefier than you would think. I would actually consider going bigger for the central tongue member, perhaps 3-1/2 or 4 deep x 2); where the A-frame joins it at the neck becomes a stressed area. If you don't need the extra extension from the central tongue to get your desired turning radius, eliminate it and use a std. 50 deg coupler.

I prefer the frame design that you show further above, with continuous frame rails and outriggers (although with a built up "torque box" floor and adequate bulkheads the cabin box would support the edges of the floor w/o them). Since you will not have the traditional galley wall near the rear hatch opening, and probably want your rear hatch load deck to be as clear and wide as possible, perhaps just have the floor support outriggers at the rear most xmbr (i.e. make the rear xmbr extend out to the walls, but consider deleting the rest of the outriggers). I guess it also depends on how much heavy stuff you plan to load along the wall space outboard of the main frame rail, but usually the box holds the floor up well enough.

The other frame design with interrupted rails and notches in at the wheels is much weaker to my eye.

For wear resistance and durability, contrary to what is normally recommended for a sleeping floor skin, you probably want to go with at least 3/8 inch ply for a built up load deck top skin; heavier if making a single ply floor.

Have to think about cargo tie downs and access to same for securing your load; perhaps a track system.

At the rear, do you plan to have a hatch like a traditional TD, or barn doors? Barn doors might be more practical, but more difficult to achieve with the profile radius. If you flatten the vertical area of the profile below the sleeping deck and only make you access doors as high as the bed, barn doors would be much easier to achieve, leaving the roof structure intact and helping to stiffen the rear "wall" from racking when you open the doors. Of course this assumes that you can slide your cargo in and don't need full vertical access.

BTW, I looked thru your art/craft/jewelry/sculpture pics. Very nice work, good eye for what I would (perhaps naively) call a steam punk look, and a very distinct signature style.

[MatthewWorks]

3x2x3/16 really isn't that stout for a 2500 lb capacity. Use it for the tongue A-frame and first xmbr. Under sling the A-frame and only weld the crossing joints at the first xmbr along the longitudinal axis, not athwartship. This area is the most susceptible to cyclic stress due to being the point where the relatively flexible tongue (in structural terms) meets the relatively inflexible monolithic structure of the cabin and frame "unit" (the cabin stiffens the main trailer frame significantly). In other words, it has to be beefier than you would think. I would actually consider going bigger for the central tongue member, perhaps 3-1/2 or 4 deep x 2); where the A-frame joins it at the neck becomes a stressed area. If you don't need the extra extension from the central tongue to get your desired turning radius, eliminate it and use a std. 50 deg coupler.

Thanks KC for the detailed input. One nice aspect about going back to the first frame design (or a variant thereof) is it would let me have some flexibility for the axle placement. Also, I find myself in love with the word "athwartship". I'm not sure how the length works out for the standard "A" shaped tongue with the first width, I'll have to play with that a bit.
Looks like I'm going heavy with the frame, but I'd rather not worry about it.

I prefer the frame design that you show further above, with continuous frame rails and outriggers (although with a built up "torque box" floor and adequate bulkheads the cabin box would support the edges of the floor w/o them). Since you will not have the traditional galley wall near the rear hatch opening, and probably want your rear hatch load deck to be as clear and wide as possible, perhaps just have the floor support outriggers at the rear most xmbr (i.e. make the rear xmbr extend out to the walls, but consider deleting the rest of the outriggers). I guess it also depends on how much heavy stuff you plan to load along the wall space outboard of the main frame rail, but usually the box holds the floor up well enough.

The other frame design with interrupted rails and notches in at the wheels is much weaker to my eye.

For wear resistance and durability, contrary to what is normally recommended for a sleeping floor skin, you probably want to go with at least 3/8 inch ply for a built up load deck top skin; heavier if making a single ply floor.

Have to think about cargo tie downs and access to same for securing your load; perhaps a track system.

I'm looking to see how low I can go for weight... but I bet it'll remain safe for me to say I'll carry approx 1000lbs of cargo for shows. Funny thing is, I carry about 300 lbs just in weight to hold my tent down at the shows. Sheesh. But those are small (lead filled square steel pipes) so they'll be nice to help even out the loads. Mostly, I believe it can be reasonably distributed in the cargo space.
I love e-track, and might even use it to hold up the bed platform/removable floor.

At the rear, do you plan to have a hatch like a traditional TD, or barn doors? Barn doors might be more practical, but more difficult to achieve with the profile radius. If you flatten the vertical area of the profile below the sleeping deck and only make you access doors as high as the bed, barn doors would be much easier to achieve, leaving the roof structure intact and helping to stiffen the rear "wall" from racking when you open the doors. Of course this assumes that you can slide your cargo in and don't need full vertical access.

As far as the rear... originally I was going to do sort of a double hatch - one opening down for the cargo space only, and one opening upwards for just the living space. Split right at a structural member at the head of the bed. No problem with sliding things in with that sort of space. I can adapt as needed if it changes.
Now... well, my time and budget just seriously tanked. I need to concentrate on my business/making new work for awhile, instead of the camper. Outfitting the cap on my Toyota Tacoma for some extremely minimal camping (with the cargo. Exciting stuff.) -- because that's paid for. First trip happening last weekend of January. Camper will still happening, just on a slower schedule. My dear wife completely agrees it would make our life much better.
Since I have a bit more time, I think I'll take it back to the drawing board and simplify a bit. I thought about a 6x10 cargo trailer conversion... but man, I just want a bit more style. (insert curse word here)

BTW, I looked thru your art/craft/jewelry/sculpture pics. Very nice work, good eye for what I would (perhaps naively) call a steam punk look, and a very distinct signature style.

Ha! Thanks. Seeing what I do, it might make sense why I really want the camper to be aluminum. (I did think about titanium briefly, since that's what I work with the most... but there is a budget, or was...) I'd love for the camper to be built with the same sort of groove/style that I put into the work. Gotta have some fun.

[KCStudly]

I'd love for the camper to be built with the same sort of groove/style that I put into the work. Gotta have some fun.

That would be a great marketing tool that would likely attract more business to your booth; you could write the extra cost off, along with the rest of it, as a business expense. I say go for it, if not in actual Ti, go faux.

[MatthewWorks]

Hey all -
Just wanted to a quick update.

First-- thanks to y'all for answers to so many questions, and playing along with some extravagant ideas.

Life being what it is, I ran out of time and money this winter. Since I work for myself, time needs to be spent working on what actually makes me money, instead of building a camper from scratch. So... that being said... I'll be joining the cargo trailer conversion club. I wanted to have a bit more custom and funk going, but it's good to be realistic on what can get done.

The entire idea has been whittled down, to what fits in the yard, in the kind of road and parking situations we'll be in, etc. I just ordered a 5 x 8 cargo trailer, with one foot extra height (so 6' total), sharp v-nose, side door, and barn rear doors. I'll still be playing with adjustable bed height, having room for cargo, etc. I should be driving down to pick it up in approximately four weeks, and will update a new thread in the appropriate place once things actually happen.

My first trips out on the road this year would have paid for a big chunk of the camper. (in fact, a very cool commission that happened sort of did pay for the trailer, but that's another story) I'll have 25 to 30 days on the road (and needing a place to sleep) before the end of June, next trip out third week of March. So some of this will happen fast fast fast. But, it'll be great to have some camping options while between shows, and having things a bit comfortable at the shows. I'm excited that this is starting to roll along, albeit in a new form.


Cheers.