i remember seeing a few threads going alone the lines of what you are asking / thinking of. i want to say one of the threads was more geared to having the person wil-chair roll right up into it. and the person would have access to a steering wheel and some gas/brake pedals (err handles mounted on steering wheel) plus a couple other levers that dealt with a lift / tail gate ramp. other words the person never really got up out of there chair. the entire beast kinda swallowed the chair / chairs. and let the folks go for an off-road drive.
off roading + bumps = hard to handle. more so when ya butt bouncing hard to metal surface. let alone back, feet, legs, arms. then the dust come up from the pull vehicle out in front of you.
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i do not recommend it "saftey wise" but a 3pt hitch carry all. lots of folks on here build a flat top on it to hold some things (generator, air compressor, place for tools or like) and then a few spots for hand tools or long handle tools. was going to say goto local junk yard and get a bench seat (seat going all the way across the vehicle) and toss onto coverall. and then add a couple sides, so no one would be willing to toss there legs over the sides.
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but like many come Halloween. many places for "hay rides" just grab someones flat bed trailer toss some straw balls on it. then toss a sheet or blanket over them. and off they go.
there was a couple trailers i saw that had the deck over wheels. "pain in rear waiting for a step stole to be placed down" vs trailer bed that was set much lower. granted there was still a step stole folks had "children" and there short legs. but was more convient for adults / teens to take a small step down.
if wheel chairs is the issue and spending money, they make some hydraulic trailers. were entire bed lifts up and down to the ground (no ramps needed) the entire bed literately goes down to the ground and you just drive stuff on/off of it without ramps. and then raise the bed back up for traveling.
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i don't remember the correct term... something ya toss on back of say a motor home or a truck via a ball hitch. it has 2 wheels on it. and then ya drive a vehicle up on it. so the front wheels set up a wheel lock. so you can kinda trailer a vehicle behind you. be kinda like a 2 wheel wagon being pulled around via horses. but instead a ball hitch setup for a tractor or vehicle.
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my vote is a standard trailer. for say some dirt bikes utv/atv / 4 wheelers. but modified for wheel chair like doing (lower bed) making sure it has some sort of leaf springs or something for suspension (suspension can be very important). to reduce the hard bumps. and maybe a fold up long ramp in back. for anyone with a walker / wheel chair. to make it for an easier incline up. put something up in front to help block dust / crud from tires.
if there old folks. some sort of shade. some of them don't leave home much and don't get to much sun. and my fry up like nice like a lobster. with a couple hours of direct sun. piece of plywood for top or like. nothing fancy. just something to help keep direct sun off them. so when they do get out / off they have ability to go right back to were the shade is.
