[Cranky When Wet]

All very valid points...

With that in mind, Lapidary tumbler drums are typically isolated from bearings... I wish I could comment on the grade of the poly/vinyl liners but I've never tested the units for SW applications.

There are a number of manufacturers worth speaking with i.e. Thumlers, Covington or Lortone (just don't look at the cheap units - they are trash and don't last.)

Covington does make a "Hopper-type" unit for polishing gold/silver castings... Here's a link to see what they look like...
http://www.covington-engineering.com/deluxe_tumblers.htm

One might look at their "Vibratory" Tumblers as well? Tho I'd be concerned about heavier elements sinking to bottom and causing tank troubles... http://www.covington-engineering.com/vibrating_tumbler.htm

I'd personally lean towards Covington for getting answers to technical questions...

I do like your thoughts on using a hopper sporadically :-)

Bunny

Originally Posted by Lampshade

The issue with drums is finding a food safe drum so that the Bearings aren't exposed to the salt, and also made of stainless. Anything else would be pretty scary to use on the tank :S.

My opinion would be a simple hopper with a valve. You need something that will seal off the salt when not in use, if it's in the same area as mixing water, the humidity will make it a salt block in no time. If you made a desenct sized hopper with a small outlet, even a 0.5" opening you could open/close that to add salt. Program it so that the hopper is open for a short period then closed for 20+ seconds to allow the salt to mix. Make it cycle whilever your salinity is low.