This antique engineering marvel records spring breakup in Alaska like clockwork


NENANA – To really understand the mechanics of the brilliant contraption that monitors the moment of breakup on the Tanana River, you have to see it in the tower that stands on the shoreline here more than 30 feet above the river.

The ice went out on the Tanana River at 1 p.m. Alaska Daylight Time Monday, meaning that those who held tickets for noon Alaska Standard Time, as the classic does not go in for daylight time, will split a jackpot of $267,444.

I have been writing about the Nenana Ice Classic for 40 years, but it wasn't until Sunday afternoon that I really had a good look at the engineering marvel that stops the clock at the right time.

The old newspaper accounts of what was once known as the Nenana Ice Pool say that Fred Mueller of Nenana, who had an aptitude for mechanics, designed the time-keeping system.

[Nenana Ice Classic tripod goes down]

It is one thing to write, as I and many others have done, that the tripod triggers a mechanism that stops the clock onshore, making a lucky day for a chosen few.

But the clock can't be stopped without a feat of engineering.


Ice Classic officials allowed me to climb the 25-foot ladder inside the guarded tower Sunday afternoon and take a close look at the invention that long ago drew favorable comparisons to the imagination of cartoonist Rube Goldberg.

A Rube Goldberg invention is a machine in which one simple action leads to another and another, so that the actions are as orderly as falling dominoes.

Start with this. The wooden tripod, which tipped a bit toward the shore in the rotting and melting ice and fell over Monday morning, weighs hundreds of pounds.

When the ice begins to move, there is incredible tension on the main cable that connects the black-and-white wooden structure to the tower.

The two hand-wound clocks in the small cabin below the tower are delicate antique instruments that would be destroyed in a second if there was not a way to divert almost all of the force elsewhere.

Back in an era when many skilled craftsmen worked in what was a busy railroad yard and shipyard, Mueller invented a machine that still performs like clockwork.

Four half-inch polyethelene ropes — a slight concession to modernity — run from the tower to the tripod cable. The tripod was about 300 feet from the shore before it fell.

The main rope, subjected to enormous pressure when the ice really moves, runs through a pulley system that extends to the bottom of the tower, connecting to a barrel filled with hundreds of pounds of rocks. As the ice moves, the rope gets tight and lifts the barrel of rocks several feet in the air.

That rope does all the heavy lifting, but the other three slack lines attached to it are no less important.

Dennis Argall, the president of the Nenana Ice Classic board of directors, hooked up the ropes late last week when breakup began to appear imminent.

"The shortest one has a foot of slack. That goes to the siren. That's supposed to go off pretty much after the tripod starts moving," he said Sunday.

One of the other lines, with 3 to 5 feet of slack, connects to the cleaver, which Argall calls "Eldridge," as in onetime Black Panther leader Eldridge Cleaver. "Every so often, we have to sharpen it," Argall said.

The cleaver has an extra weight of about 10 pounds welded onto it, to make sure it gets the job done. A 1958 account said Mueller found inspiration for the "million-dollar knife" in the guillotine.

When the tripod moves about 100 feet, the rope attached to the cleaver pulls a small pin and the cleaver cuts the main rope. The counterweight with the hundreds of pounds of rocks hits the ground with a thud and the tripod goes free. But that's not the important thing.

"As soon as the main line gets cut, it will drop and pull that third line enough to stop the clock," said Argall.

Just a slight movement on a clothesline that runs to a copper wire is all that it takes. The bigger of the two clocks, which has to be wound every eight days, has the words "Nenana: Ice-Break Pool" below the clock face.

The second clock, wound every day, is a ship's chronometer, created by the Elgin National Watch Co. decades before it stopped making timepieces in 1967. A notation in the wooden box says, "Cleaned. April 1945."


A newspaper account two years later by Barrie M. White Jr. in the Boston Globe described a system that is little changed from the one in use today.

He saw the tripod move and pull the main rope tight. "The bucket of rocks started rising and then all of a sudden, clunk went the cleaver, followed in a split second by the pin flying out of the clock and we all rushed over to see the time," wrote White, a future delegate to the Alaska Constitutional Convention.

No one today would build anything like this. Even a backyard inventor would turn to an electronic gadget.

But anyone would be hard-pressed today to build a more elegant and workmanlike machine from simple tools.


Columnist Dermot Cole can be reached at dermot@alaskadispatch.com. 

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Dermot Cole

Former ADN columnist Dermot Cole is a longtime reporter, editor and author.