How to build an Aluminum trailer frame?

[tsmiley23]

I'm currently building a standie and the question has come into my head of how I might reduce the weight on my next build by building the frame with aluminum. I can weld aluminum, I have a 175 amp TIG but I wonder what aluminum alloy would be best and what my weight savings may be. Here's a picture of my current frame: As seen here the total weight is 680 lbs



The box is 6' 3" by 10' and the main members are 2"x2" x 1/4" square tube and the cross members and perimeter are 2"x2"x1/4" angle. So the question is would aluminum of the same dimensions give me similar strength and what would the weight savings be?

If there is a post discussing this, I haven't been able to find it in my search's, if someone can lead me I'd sure appreciate it.

Thanks for all your help in advance

Terry

Thought this picture might help too:

[Yota Bill]

you could try not overbuilding the frame with such heavy steel. 2"x2"x1/4" wall is pretty heavy stuff for a 6'x10' trailer. How much weight do you plan on putting on it anyway?

Just for example, I built a 7' wide by 14'6" trailer using 2"x1"x3/16" box steel (standing upright) as the main frame, with a deck frame made of 2"x2"x1/8" angle steel (outer perimeter and crossmembers) and 1.5"x1.5"x1/8" angle steel (interior rails), and once it was complete, except for the deck or any wood, it weighed 480 lbs. Thats a savings of 200 lbs, but also 9 inches wider and 4 & 1/2 feet longer.

I calculated what it could safely hold, but I'm not an engineer, and may have done the math wrong somehow, so I wont bother saying what number I came up with for a failure weight rating ( I think I did do something wrong, but its close enough for me). I can safely say it will hold over 2k lbs, and have had a total weight (including trailer) at about 3k from Oklahoma to Michigan, with no concerns (OK, at least no problems..I was concerned, obviously, but more for the tow vehicle). I've had similar weights on it for much more local trips, and there are no signs of stress or any potential failure. Since the camper I plan to build on it is expected to be at about 1400 lbs fully finished and loaded (figured on the heavy side, will actually be a couple hundred under that) it is more then sufficent, and has quite a safety margin as well.

Also, since cost is a concern for anyone, I also spent right around $600 total to buy all new steel, lights and wiring, hitch, suspension parts (excluding axle, springs, and tires) tounge hitch, welding wire, etc. To build something similar from aluminum would cost roughly twice as much.

[tsmiley23]

Yota Bill said: Just for example, I built a 7' wide by 14'6" trailer using 2"x1"x3/16" box steel (standing upright) as the main frame, with a deck frame made of 2"x2"x1/8" angle steel (outer perimeter and crossmembers) and 1.5"x1.5"x1/8" angle steel (interior rails), and once it was complete, except for the deck or any wood, it weighed 480 lbs. Thats a savings of 200 lbs, but also 9 inches wider and 4 & 1/2 feet longer.

Thanks for your input Bill: I like your idea but am concerned with using smaller dimension members. By the time I had my frame welded together I noticed the 2"x2"x1/4" main members had a 3/16" crown. I don't know if I annealed the steel when I welded on the axle but I'm removing this crown using the sheathing and siding. If I jack the trailer off the ground at the corners it bows in the opposite direction and by doing this and attaching the sheathing (1/4" luan) and siding (040 aluminum diamond plate) I hope to reinforce and straighten the frame. I'm not surprised I got some warpage but would a smaller member suffice?

I suppose I should give more design criteria and see if there's a better design available that would incorporate your ideas. As you stated "cost certainly does enter the equation. Here are more design details, 7' foot tall standie, approximately 2000 lb net weight, 500 lb live load, and further design details at this build:

http://www.mikenchell.com/forums/viewtopic.php?p=799463#799463

As I state at this build I took a used trailer that I've owned for 20+ years and rebuilt it using slightly smaller members and basically following the existing design. The original used 2"x3"x1/4" angle throughout and had a raised curb built out of 1-1/2"x 1-1/2" x 3/16 angle. I don't know if it was crowned but it didn't appear to show any adverse effects other than rust and I always used it hard and put it away wet.

Maybe my question should be; How would you design an efficient trailer to fit my needs, rather than modifying my design? I really do appreciate input.