the kubota 008 is the smallest digger they make 800kg, if you took the boom and dipper arm off , you could put two of the basic traction units in a SWB transit and still have space above and to the back ,the basic unit would travel down a good sized lead mine adit, no problem say for the back door adit at aberllefenni, the booms are that small on this type of digger two "when men were men" could man handle them in,
the old boys laid miles and miles of compressed air pipes to power drill and winches , would not be a big deal to put in 3 phase cable, only cost !. just sayin it could be done, and whats more recoverable after use,
i reckon id get my 3.5 tonner down a good slate adit,after taking the cab and boom off. would not like to try getting the boom in though :ohmygod: