1: Follow the 2:1 rule! If either the drive force (Fa) or applied
load force (Fs) are a greater distance than twice the bearing
length (w,x), then troublesome binding or chattering can occur.
This distance is measure from these forces to the rail closest
to the drive force. I’d recommend you always spread these
bearings as far apart as your design allows.
The bearing sets will chatter as they slide in one, or both directions when carrying a cantilevered load, or the bearings may not move at all if they’re being moved by a highly offset drive force.