Vacuum Cleaner Magnetic Separator

I had the idea to tape a few magnets to my vacuum cleaner, one with a bagless pickup cylinder, in order to recover ferromagnetic materials I may have dropped (e.g. paper clips, screws, nuts, ball bearings, other machine parts) and failed to recover otherwise. They worked pretty well, but they automatically arrange (stack), which places the poles at the ends, and concentrates magnetic flux outside of the vacuum's canister. With this doodad, I can trap the magnets in place with the poles pointing inward, so the field should be stronger, and it should better trap our desired pieces. I curved the open side with the magnets to a 2" radius (4" diameter) so it should snug up to the surface of the canister.