Homemade Lathe Sanding Belt Holder

[Toolmaker51]

? Save mount weight and drive by a cable? But even not motorized is very, very good, to impart consistent finish across length by power feed.
If motorized and running against spindle rotation it equals a crankshaft polishing machine, far more compact.
Finally and as LMMasterMariner demonstrates, paper or plastic are superior to rags, when shielding bedways from grinding fines.
I prefer oil-wetted paper, as the abrasive and metal stick for disposal.