Ball Clocks

I had never heard of a ball clock until the ACM Ball Clock problem was discussed on comp.lang.apl. After I posted a summary of the problem on my web site, I started getting inquiries from people who were looking for ball clocks. This page is a repository of information about ball clocks.
If you have something to add, please send e-mail to People occasionally write asking if I know of any other sources for ball clocks. Sorry, I don't; if I did I would put it on this page! Please let me know if you find any other sources.

What Is A Ball Clock?
The clock described in the ACM programming problem has three tracks that hold ball bearings. Once a minute, a rotary arm lifts a ball up and drops it in a channel where it rolls onto the topmost track. When five balls have accumulated in the top track, the weight of the balls tips the track down. One ball rolls down to the middle track, and the rest roll to the pickup queue at the bottom of the clock. The middle track thus has a ball for every five minutes of time. When the twelfth ball rolls onto the middle track, it dumps one ball onto the bottom track and sends the rest to the pickup queue. So the bottom track has a ball for each hour. Each track is labeled with hours or minutes. To read the time, you look at the bottom track and read off the hour, then you add the minutes shown on the top two tracks.
Clock Vendors
September 2000 Flash: They're back! The fall issue of the Edmund Scientific catalog includes the latest reincarnation of the Arrow clock. A new twist is that the clock can be run off either A/C or batteries. (I guess the batteries are for when you take the clock with you camping.) To order, call 1-800-728-6999 and ask for item number #V82-445, or visit their website at
April 2000 Update: Around 1997, some factory in China must have produced a single large run of ball clocks, apparently using the same molds as the Arrow clocks that were sold in the 1970s and '80s. The clocks were available in novelty stores everywhere, but they eventually sold out and are now hard to find. You can check the vendors listed below, but I think it's unlikely that any of them have any clocks left. Your best bet is to check Internet auction houses such as eBay, Yahoo! Auctions, or Amazon Auctions. On eBay, search for "ball clock" or, if you get tired of looking at spherical clocks and clocks with balls in place of numbers, try a more specific search. For the record, here's the information about places that used to sell ball clocks:

Michael Robb wrote on April 9, 1997, and gave the following source for a ball clock:
  The Lighter Side
4514 19th Street Court East
P.O. Box 25600, Dept L9704
Bradenton, Florida 34206-5600
  Phone: 1-941-747-2356
FAX: 1-941-746-7896

The catalog number is 11016 and the price is $49.98.
I actually bought one of these. It's called "As Time Rolls On" and is made of plastic in China. It works fine, but beware that it's not a quiet timepiece. Every five minutes it sounds like someone is rattling a box of marbles. My boys, who are 6 and 9 years old as I write this (fall 1997), adore the clock. They especially love watching the "big dump" at 1:00, when all the balls roll back to the pickup queue.

Ron LaPedis wrote on April 15, 1997 and said that The Sharper Image in California sells the ball clock pictured on the ball clock problem page. It's apparently the same "Time Rolls On" model, but they sell it for $40. Their phone number is 800-344-4444. Ask for item number WR102.

Ron also gave the following source:
  The Edge Company
PO Box 826
Brattleboro, VT 05302
Phone: 1-800-732-9976
FAX: 1-802-257-2787

The product number is #TM-2005 and they sell the clock for $49.95. (Thanks to Jan H. for correcting the URL.)

Still another reference from Ron is:
Box 12700
Scottsdale, AZ 85267
Phone: 1-602-483-3711
FAX: 1-602-483-6116

They sell parts for the Arrow Mfg. ball clock made in the 1970's and 80's. Although the website claims they don't sell complete clocks, Bob Swan says they do and that he bought one from them. (Timesavers also sells the "Golden Hour Mystery Clock," something I remember from my grandparent's house. It has the hands mounted in the middle of a round pane of glass with no visible linkage driving them.)
David MacMillan says that Steven Berger of Timesavers has indicated that a similar clock, constructed of wood, is available in Europe for DM175.
Public Clocks
George Rhoads has created a number of rolling ball sculptures (some of which may be clocks) that are installed in public places. For more information, visit George's web site, or see the article "Clumper Upper to Wok Dumper to Chute to Helix to Block" in the October 1988 issue of Smithsonian magazine. Here's an excerpt:
The paths taken by George Rhoads' flashing little sound-making balls are varied and magical, making art of hypnotic movement. They've been showing up all over North America these past few years -- these intriguing machines with acrobatic balls that move around metal tracks and make noises as they go. There's a highly conspicuous, popular one called 42nd Street Ballroom in the Port Authority Bus Terminal in New York City. There are two in Terminal C at Boston's Logan International Airport and two more in the mammoth West Edmonton Mall in Alberta. You can also encounter them in shopping centers in New Haven, Connecticut; Pittsfield, Massachusetts; Rochester and Watertown, New York; and Kamloops, British Columbia, among other places in North America. There is a big one in the Boston Museum of Science, and there was in the recent past a gallery full of them at the Queens Museum in Flushing Meadow on Long Island. To the man who made them, artist George Rhoads, they are "audiokinetic sculptures" that generate sounds as they move.

Another installation is (or was) at The Tech Museum of Innovation in San Jose, California.
What A Clock!
My friend Jeff Chilton brought this amazing creation to my attention: The Clock of the Long Now. It's a clock that eats Y2K problems
for breakfast—it represents dates using five digit years, not four like the rest of us myopic short-thinkers, and it's designed and built in a way that hopefully will allow it to continue functioning for 10,000 years. The half-scale prototype shown at right, which was finished in 01999 (hah! looks like a Volvo odometer), is on display at The Science Museum in London, and the Long Now foundation has obtained a site in Nevada for the full-scale clock.
In a time when we seldom think past the next weekend, and practically no one ever thinks past, say, their grandchildren's lifetimes, it's a mind-bending experience to consider posterity on the Long Now scale. Yes, elaborate clocks and modern Rosetta Stones aren't that important by themselves, but they are important if they catalyze a hopeful optimism that maybe we'll still be around as a species in 10,000 years and that perhaps we should be striving toward that goal instead of living day-to-day with a sort of Malthusian pessimism.
Jeff said one of the early designs involved rolling balls (obligatory on-topic connection), but they seem to have disappeared from the current design. I particularly like the equation of time cam, a deeply mathematical three-dimensional surface that could hold its own as sculpture in a modern art museum.

Further Reading
Harley Mayenschein invented the ACM-style ball clock in the 1970s and founded the Idle Tyme Corporation in 1978, which manufactured ball clocks made of wood. I learned this when Patrice Gunville, Harley's daughter, wrote me in July 1998 to correct my mistaken claim that George Nelson invented the ball clock. (Nelson's clock is just a conventional clock with balls on radial spikes replacing the numbers.) Her letter has more information about her father and the early history of his ball clock.
David MacMillan has an excellent and extensive website devoted to Rolling Ball Sculptures, Clocks, Etc. His site has pictures of ball run sculptures by George Rhoads and others, descriptions and pictures of many types of ball clocks (including excerpts from Harley Mayenschein's ball clock patent), and numerous links to related sites. David has even set up a mailing list for the discussion of ball clocks and sculptures.
Helge Rustad has built two ball clocks, a large one made of Lego and a smaller one built of wood, plus several other delightful homemade projects (including a ping-pong-ball computer). See his home page for pictures and more information.
David Ralston, a sculptor and clockmaker, has built a large ball clock out of stone billiard balls and brass stock. Another amazing clock, the Sand Wheel, is something like an endless circular hour glass.
Tod Flak built a very nice looking ball clock of his own. Entirely handcrafted out of cherry wood, except for the custom-programmed 8031 microcontroller! (Todd's site has been dead for a while, but maybe it will resurface some day.)
Stuart Singer has a page devoted to ball clocks, including some product literature from the old Arrow clocks and information about the new battery-powered series of Time Machine clocks, which includes a seconds indicator.

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