My robotics team inherited a nice roll around tool box, twice as nice and big as our previous boxes, but I don't know how to load and unload the box for competitions. Our trailer deck is about 18" high. Ramps seem pretty difficult and dangerous due to unpredictable road crown, curbs, and pushing casters up ramps sucks.
Are there any clever mechanisms for this task sort of like a lower height ambulance gurney?
Not all that different, yes. The concept is that one does NOT tilt, nor go up and down ramps, but loads and unloads
level.
That can be done with rails that go in the vehicle, knocked-down.
On-site, pull them out, latch together, let down outrigger jack posts to compensate for terrain & match the vehicle. Really help if the vehicle has arse-end left & right outriggers itself. Roll load out level onto the "structure". Then aside the vehicle.
Crank load to a lower altitude. Or not.
Reverse to load and go.
Four-poster should do yah, and you'll probably have to calculate it and DIY fab it to insure you are not limited to one specific haul vehicle.
Commercial rigs made for various "service" trucks are a tad pricey, and generally leave one end anchored inside the truck - whole deal working like a large "drawer". They start simple...
http://www.800toolbox.com/roller_coaster/roller_coaster
...and get a great deal more complex for specialized tasking. Most render the truck immobile for the task duration.
JMNSHO, but with a "team" involved, a rig one can detach from, drive away to go for parts or chow or run someone to the Hospital seems more useful.
The parts aren't hard to find. I-channel and trailer jacks - manual or powered - some bolting and/or welding, basically.
If the box itself is stout enough? Gurney-style legs
on outriggers, could be directly attached to a permanent reinforced frame.
I wouldn't. Easy to make a separate structure a great deal safer, and the specific box may end up not so "permanent" anyway.