GantryCrane prospects
Following this closely, especially recommendations regarding wheels/ casters. I have a shopmade 1/2T that does alright, mobile enough, and I don't transport loads other than by trolley. Mainly, it sits across 16" lathe, to hang chucks and long bar or tube parts.
But I want a 'full size' gantry too, load big parts and tooling where my saws, radial drill, tooling rack and boring mill are. They're in a line on purpose. Plan is not casters but paired Vee groove wheels on trucks, maybe with real stiff short coil springs, haven't hit the right brainstorm for that suspension yet; but the Vee'd wheels would run on inverted angle iron (^ down). Looking to over compensate at 4 to 5 ton load capacity, and a pair of chain falls with trolleys. Going for all the head room possible under 15' ceiling, mainly for column of boring mill. Confident that such trucks will allow safe moves of lighter materials, where pallet jacks or eventually forklift to get big stuff right up to machine base.
Speaking of pallet jacks, if you have room and find a deal, one with load cells and LCD display of weight is all kinds of convenient. Alternate is a floor scale that pop up reasonably priced; but for equal $$, a pallet jack is king.