What I'm building is very much like the one in the picture but heavier and with bigger wheels and hubs and length sized for 20' logs. It needs to be wide enough to easily straddle the sawmill. It's pretty simple really. I have an empty pallet ready to gather the components on to start building it. Some of the parts I have saved for years for it. The wheels, hubs, spindles and lower frame sections are from a scrapped 12' Kewanee farm wheel disk. I have heavy steel rectangular tube for the bulk of the frame and I already have 2 winches for it.
That is not my sawmill in the picture but my configuration is a bit similar. I'm moving my mill into a smallish garage about the size of that carport that has a garage door on one end and I need to add a little onto the back end for my longer bed (21') and add a garage door there. That arrangement then needs the log arch for log loading from the end.
I'll probably not move the mill before I cut this next batch of lumber but I also need the log arch to assist in getting the logs out of the woods without dragging them through the dirt and gravel (bad for blades) plus I have a rather pesky hill to deal with and the arch will be much safer than dragging logs. Once up the hill and back in civilization
The lumber I am cutting is for the rehab house and is about 1600 board feet of sub-flooring, mostly cottonwood, probably cut 5/4 and lightly planed on both sides (Band-saw mill lumber normally doesn't need a lot of surfacing.). At least half of it (above the half basement) is going down on new engineered "I" beam type joist 16" OC which are of course much wider on top than just dimension lumber joist.
I need to get the sub-flooring cut and stickered in on the drying floor and get forced air moving through it so that it will be dried to a reasonable level by the time I am ready for it, probably this fall. The other half is over a crawl space and is in much better shape. There I may just sister onto the existing joist to double all of those then put down the new sub-flooring. I might even cut those from some maples I have.
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