I only feed round bales in the winter so it is not worth it to me to spend a lot of money building a bale mover. I remember folks asking how others move bales out onto pasture. Here is a picture of how I do it with a forecart. I back the cart up to the flat end of a bale, stick a bar a couple feet into the opposite flat end and run a come-along from the bar to the hammer strap. the bale will pivot up on the cart as you winch it in. My bales are smaller, about 200 pounds, I am not sure how well this would work with the big bales.
Just wanted to share.
PS: I have scoot runners bolted to the rims if you are trying to figure out what happened to the rims.