>>96028741 (OP)well they need to have rotary mechanisms to actually build a mech, but they also need no solid ground to put a wheel on
so i guess a species that evolved to float through the atmospheres of a gas giant. they want to colonize further south, but its far too cold for them and heavily arboreal with trees kilometers tall, like a cross between bamboo and seaweed- almost space elevators buoyed up by internal bladders
they need environmentally sealed vehicles to survive and harvest the arborial hydrogen or whatever, but its too dense for wing, rotor or lighter-than-air movement, and there's no ground for wheels or rails, so they need something that can climb with limbs