80lbs track hoe uses acetal rollers on steel shafts without any problems.
Your build thread is likely going to be filled with hundreds of pictures, you should look at linking your photos from a photo host site sooner than later.
http://www.rctruckandconstruction.co...ead.php?t=4057
Photobucket is one option, there are other sites out there too, like Flikr or Image Shack. They're all free to use, just sign up & get started.