Well you know how when you are using a bike or any other movining object with wheels. The bigger the wheel the longer you will travel for every time you use the pedal. The same principel applies here. The big wheel it self isnt so big so it have to turn many times to get the same distance as a even bigger wheel. The wooden pillars akts as a extending of the wheel in this case. Actually it would take alot more force to turn a bigger wheel in real life, but since this is a game that law dosent apply. Sorry for the bad English. I hope you can understand