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SE MN | Southern yellow pine is about as strong as you are going to get at the lumber yard but you usually want that treated because it will warp like crazy if it gets wet. The 6X6 posts that they build pole sheds out of are the most common thing that will be readily available. We have a hay rack that uses those for stringers and it is solid. I would double them up in your situation though. Doug fir is very strong but it can't be treated properly so I wouldn't mess with that. The common stuff like hem fir or spruce pine fir is going to be too soft where the stringers sit on the gear.
LVLs or PSLs will be stronger than anything you can get in sawn lumber but I would not want a psl in a situation where there is a lot of movement or shifting and I am not sure I would trust an lvl exposed to the weather, maybe if you painted it. Also, the LVL may have a problem where it bears on the running gear because it is not as strong for crushing as sawn lumber.
My vote is for some home sawn white oak 6x10s.
If you must use dimension lumber, see if you can get treated southern yellow pine 2x10s and nail them up at least 5 wide. Otherwise, untreated doug fir 2x10s five wide would be similar if you don't think that you need the treated wood.
When buying lumber, look at the stamp, if you see "sel str" that means select structural which is rare and very good stuff, otherwise, No 1 is better than No 2.
That should be just enough info to make you dangerous.
Have a good day. | |
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Lumber strength
