I am currently planning on building a set of welding tressles using 100x50 channel and 50 x 50 box for the legs. for the bracing i puzzled wether to use 50x50 box or 50x50 angle. please see pic attached and share what you think.
Welderpaul has some trestles that are box section ( 120mmx90mm ish 12ish wall) with a simple vertical down section sat on top of a horizontal piece and he has put stupid weight on them and have never moved
Most of our ones that are for general use are 50x50 box, with 70/80 box tops....about 1-1.2m long.. put plenty of weight on them without a problem.
The thing with trestles, is you want them nice and strong, yet you don't want them so heavy you struggle to move them.
Some of the heavy duty ones we have are too heavy to move very far without using the forks, very similar to the ones in MK's picture above.
id go 100x50 top with 50x50 legs down to 50x50 feet. bung a few littel braces in with a bit of 50x10 welded across the top so the box dosent dent when bounceing beams over on them. pair of them will copewith a ton bounceing around on them
My thoughts are if you need to clamp down work to trestles you need them heavy enough not to lift when you get a bit of weld twist going on
but the other thing is if the job is quite thick, uni beam gives you the option to clamp under the top lip or if you need to bolt down it is easy to drill holes in the beam with short bolts also when end capped perfectly at 90deg you can clamp vertical down pieces to the end caps and not have to check for square but the main thing is you get less weld twist in the top beam when making the trestles using uni beam. I think for ease I would go for one vert leg 70x70 ish with flat box foot at either end but with a little flat strip across at the very end to stop centre rocking, on scrap or swarf etc .