On Tuesday, December 26, 2017 at 6:36:45 PM UTC-6, Peabody wrote:
I have an old Eureka Model 1406 upright vacuum, the one that exactly imitates
the old Hoover models after their patent ran out. It's really powerful, and
still works great, except that the brush roller is worn out.

The original roller contains both brushes and beater bars. Apparently I can
still get a replacement, but wondered if the vacuum might work better if the
roller was all-brush, with no beater bars. This would be for fairly deep
carpet. I guess I never understood exactly what the beater bar was supposed
to do.

Any opinions would be appreciated.

The alternating brush and metal strips were thought to do a better job of beating dust out of the carpet. They probably work better on deep pile residential carpet than on low pile commercial carpet where the backing might get damaged from the beating. The metal strips cause more vibration in the carpet that helps remove soil. Some are called disturbulators or vibra-groomers.