since i can't weld wood, [searched high and low for a "wood rod", but nobody has 'em. ] if i were making some, i would go to my local scrap yard and get used 2x2x1/4" angle, then model the ramps like the ones used with car trailers.
unfortunately, they would be pretty heavy for this old weakling to rassel around into position when needed.
i have a couple of the old style drive on ramps that everyone has, [or has had at one time or other] the bad thing about those is they are [almost] too narrow for today's common tire sizes.
i have been toying with the idea of cutting a pair in two, lengthwise, then adding a section of 1/8" plate with a bunch of dimple die holes, [almost too much work to do] or a piece of perforated metal between the pieces to widen them.
however, that would still not address the approach angle.
as i like to over-engineer things that will support 4000lbs above ME, it still ends up being heavy, weight wise..........