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Metal question

Hi,

I am not an engineer but trying to understand bolt strgth, tensile strength og steel and some other varribles for something I am wanting to construct. I am wanting to build a car dolly and/or dual axle trailer. I have welders and have welded on hobby projects but by no means consider myself an expert welder. My idea is to both weld and bolt a square togther to form the frame. I have some 3 inch square tubing laying around, I believe is is 1/8 thick but not sure. It came from some material stand at work that got cut up.

My idea was to get some scrap 1/8 inch plate and torch cut two ?L? brackets and weld them togther to form a ¼ inch L bracket. These would go on all 4 corners of the square I would bolt each L with bolts through the L and through the 3 inch tubing. Before doing this I would insert a section of black pipe through all pieces for the bolt to ride in. After bolting and everything being square I would weld all joints with 6011 or 6013 rod with either my AC buzzbox or the mIller generator welder I just aquired on DC. (Not welded with it much yet) (I have trouble welding with 7018 for some reason.

My question becomes, what size bolts would be adequate? I get confused when I see specs on bolts such as shear strength, tensile strength, yield strength, etc? I suspect the bolt need only be as strong as the streth of the bolt steel around it. I am having trouble finding the specs for mild steel strength but think it might be around 38,000 PSI? Is this true?

Any help is appreciated!

Reply to
stryped
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I dont like the idea of 1/8" steel on something like this that is mean to carry a load like a car.

And I dont like the idea of you trying to weld it if you are not sure about your welding prowess.

If you screw up on this, you can cause a LOT of damage with a loose car on a dolly or trailer.

If you insist on trying, go down and look at some commercial car dollys or trailers and check out their design and metal thickness in critical areas.

Without making any calculations at all, I wouldnt consider less than 1/4 " wall or maybe a little more depending upon what I was going to haul, and how the calculations came out.

Now, will your insurance company stand behind what you build?

Reply to
hls

Before starting something like this, I would try to find some engineered plans, rather than designing it yourself. This isn't something that you want to have come apart at speed...

nate

Reply to
Nate Nagel

stryped wrote in news:a427ed4f-7167-4ae1-9b17- snipped-for-privacy@x27g2000yqb.googlegroups.com:

Better yet, just buy one second hand locally.

Reply to
chuckcar

by far the best option.

to the o.p., if you really want to build yourself, do a refresher welding course at your local community college. you'll be able to pick the instructors brains about build practices for a project like this - save you a lot of heart ache down the road.

you can also download a set of plans from the net with trailer designs. while they seem simple, a dynamically loaded structure like this should pay proper attention to fatigue as well as just static strength. this is why there is more to it than just welding. ideally, you'll have an engineer design or at least review accordingly. if you don't know someone, this is why it would be important to use a design where it's already been done for you.

Reply to
jim beam

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