# Help me understand how this is a ball mill? "Working Point" sculpture, Baltimore Museum of Industry **URL:** \ **Category:** Factual Questions\ **Created:** [June 5, 2026, 3:46pm UTC](https://boards.straightdope.com/t/help-me-understand-how-this-is-a-ball-mill-working-point-sculpture-baltimore-museum-of-industry/1030638 "2026-06-05T15:46:50Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [June 5, 2026, 3:46pm UTC](https://boards.straightdope.com/t/help-me-understand-how-this-is-a-ball-mill-working-point-sculpture-baltimore-museum-of-industry/1030638/1 "2026-06-05T15:46:50Z")
I’m somewhat familiar with ball mills (machines for crushing solids into powder using a tumbling drum also containing balls). But I can’t see how this particular item can be a ball mill. It’s old, removed from service, and built into a sort of nonsensical sculpture outside a museum. Here’s a guide showing which part of the sculpture I’m talking about: [https://www.hmdb.org/m.asp?m=131183](https://www.hmdb.org/m.asp?m=131183) And here are some other photos of the sculpture, giving much clearer pictures of the ball mill: [https://www.alamy.com/stock-photo-sculpture-in-baltimore-working-point-by-david-hess-1997-museum-of-26864921.html](https://www.alamy.com/stock-photo-sculpture-in-baltimore-working-point-by-david-hess-1997-museum-of-26864921.html) > **[Working Point (David Hess) — Municipal Art Society of Baltimore City](https://masbaltimore.com/workingpoint/)** > > A “Working Point” by David Hess is a point designated on an architectural or construction drawing that is used as a reference for measurements and calculations. This sculpture is composed of 90 tons of obsolete machinery and equipment from a number... I think ball mills are generally rotating steel tubes, horizontal or a little bit tilted, with powerful means to turn them slowly (like a cement truck), and means to fill or empty them, either in batches or continuously. The tube length is usually bigger than the diameter. There are also ball mills that make the tube orbit around to add centrifugal force to the gravity already acting on the balls. The ball mill I’m talking about here clearly has rotating parts, but not a long tube. It also has what look like spring loaded arms pressing radially inward, if I see it right. I spent a while walking around it trying to make sense of it. Museum staff, at least the folks I found, knew nothing. Googling ball mill images gives me nothing even close. Is it some special kind of ball mill? Is it misidentified? Help assuage my burning curiosity! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 5, 2026, 4:13pm UTC](https://boards.straightdope.com/t/help-me-understand-how-this-is-a-ball-mill-working-point-sculpture-baltimore-museum-of-industry/1030638/2 "2026-06-05T16:13:35Z")
It might just be mislabeled. The part labeled “heat exchanger” looks like it might actually be a ball mill. ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [June 5, 2026, 4:47pm UTC](https://boards.straightdope.com/t/help-me-understand-how-this-is-a-ball-mill-working-point-sculpture-baltimore-museum-of-industry/1030638/3 "2026-06-05T16:47:06Z")
Might be the drive (motor and/or gearbox) for the ball mill rather than the mill itself. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [June 5, 2026, 5:24pm UTC](https://boards.straightdope.com/t/help-me-understand-how-this-is-a-ball-mill-working-point-sculpture-baltimore-museum-of-industry/1030638/4 "2026-06-05T17:24:13Z")
I looked at the photos. (I know very little of ball mills, I get what they are, but I can’t tell you if it’s labelled right) This is an art installation. Not an exact replication of the piece of equipment. And probably parts were removed because it didn’t fit the artists vision. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [June 6, 2026, 7:07am UTC](https://boards.straightdope.com/t/help-me-understand-how-this-is-a-ball-mill-working-point-sculpture-baltimore-museum-of-industry/1030638/5 "2026-06-06T07:07:43Z")
> [@Marvin\_the\_Martian](#): > > Might be the drive (motor and/or gearbox) for the ball mill rather than the mill itself. Yes, this - it looks like that would be the part that you load the drum into - think of it like the yellow part in this mill: > **[What is a Ball Mill? | Economy Ball Mill](https://www.economyballmill.com/blog/what-is-a-ball-mill)** > > Learn what a ball mill is, how it works, and why you should choose Economy Ball Mill for your ball mill solutions across the United States and worldwide.