Mike is sorta right, not enough room to fit the boiler in the cab!
Actually, its a combination of cost and mess - having seen what happens when a hydraulic line leaks, and I want to be able to run this one around in the house. Also wanted to see if it could be done - kind of a middle ground between the pure hydraulic machines and the plastic-geared 'toy' ones. The gearmotors and leadscrews are an interesting combination, seen them used in some of the builds here (especially in truck dump beds). It seems to have enough power in initial tests, but it could always be converted to hydraulics later on if need be.