I'm trying to design a classical treadmill for rodents which has two wheels at the two end and a plain "conveyor" belt in between. What is the best way of designing this if i want to have minimal friction? Do smaller or bigger wheels make the belt easier to get to move when the walking begins? Can this problem be estimated by rolling resistance?
Bigger wheels are better for bearing friction, but if the wheels are too large, then they will have a large mass and large moments of inertia... and the rodents won't be able to get the wheels to move because of that. The truth is somewhere in the middle. Excellent low resistance bearings are easy to come by, these days, and so are lightweight wheels. It might pay off to look at existing products, first. No need to engineer something that can be lifted off somebody else's successful design... unless you want to make money on this, then you better check with a patent attorney