Question for physicists. Winding in space?

[mansion]

A question for physicists.

Would a Rolex wind in space? I think that it would: the wrist and arm would impart (centrifugal?) force to the winding mechanism in the same way as on Earth.

Gravity is not needed.

Is this indeed the case?

[BiG JeEzY]

Originally Posted by mansion

A question for physicists.

Would a Rolex wind in space? I think that it would: the wrist and arm would impart (centrifugal?) force to the winding mechanism in the same way as on Earth.

Gravity is not needed.

Is this the case?

I am still studying Physics (Mechanics of Fluids and Solids) so I cant give you a physics based answer just yet.

However I will say that a watch with an automatic winding mechanism will NOT be able to wind in space. The Omega watches that went up to the moon before in the late 1960's had manual winding movements in them because of the reason that the rotor from an automatic watch will not be able to oscillate as effectively when the watch is in space. If I am not mistaken, in space, the rotor will not oscillate in the same manner as it will on Earth.

[leopardprey]

No. Rolex Watches have gone in space before and the Perpetual Motion of the Rotar does not work, cause it is gravity driven. GMT II worn on Apollo 13. When using Rolex in space, you must manually wind about every day and a half.

This is one reason why the Omega Speedmasters designed originally for NASA were all Manual Wound watches

[BiG JeEzY]

However there is still gravity in space since planets are able to stay in orbit (the idea that you are weightless and constantly falling in space), just less than there is on Earth (gravity pulls you to the center of the Earth but the Earth stops your fall.)

So the rotor should still be able to wind the watch somewhat since it is gravity driven and there is some gravity in space, just not as effectively as it normally does on Earth and not effectively enough to keep to watch running. It will eventually just stop if you just wear it on your wrist all the time in space.

A Rolex can still be manually wound though so you can go up to space and wear it without having any problems.

[Jedi]

The gravity in space is best described as 'ambient' gravity, ie strong enough to keep you in orbit, but not enough to provide the required effect on Earth-bound mechanisms such as the rotor which is designed to work under the gravitational conditions on the surface of the Earth.

This reply is a bit ad hoc, but I hope it conveys the idea.

[mansion]

... and what about inertia?

If I move my wrist, won't the rotor tend to remain, unmoved? Thus making it 'turn', relative to the rest of the mechanism.

A bit like the coffee in a cup: turn the cup and the liquid remains in its original position.

(Guys, this means 'turn in the plane parallel to the surface'!)

[Alcan]

Originally Posted by mansion

Would a Rolex wind in space? I think that it would: the wrist and arm would impart (centrifugal?) force to the winding mechanism in the same way as on Earth.

Gravity is not needed.

Is this indeed the case?

It is. An automatic watch will work in zero gravity. Although gravity helps to move the rotor when the watch is held in the vertical plane, it does nothing when the watch is held in the horizontal plane.

Rotors are influenced by gravity but more so by inertia, the tendency of an object in motion to remain in motion. Witness the infamous "J.J. brandy swirl" when restarting a Rolex after it's run down. Gravity has nothing to do with that.

Nasa assumed (incorrectly) that an automatic watch wouldn't work in zero gravity.

From TimeZone:

"In 1965 NASA purchased five reputable chronographs (one of which was the Speedmaster) from several jewellery stores in Houston. NASA then proceeded to abuse the watches with tests of extreme environmental conditions. Their aim was to determine if a suitable watch was available for their Space Program. The final three contenders for the "Official" NASA chronograph were a Rolex, Longines Wittnauer and the Omega. The reasons for the Rolex's departure were that it stopped running on two occasions during the Relative Humidity Tests and subsequently failed during the High Temperature Test when the sweep hand warped and was binding against the other hands on the dial. No other tests were run with the Rolex Chronograph."

From WIkipedia:

"Reportedly NASA assumed that the automatic winding mechanism was based on pendulum action like Harwood's original design, requiring either a gravity field or constant acceleration. The weightless environment therefore raised doubts about the ability of an automatic watch to wind itself. In fact a full 360-degree winding mechanism should work even better in low or zero gravity, where the friction experienced by the mechanism is lower. The rotor can thus move longer and transfer more energy into the spring. The rotor is in any case easily activated by momentum and not dependent on gravity."

[SPACE-DWELLER]

Excellent post, Al!

[Jedi]

Why would friction be any less in a zero gravity environment? I'm just working from deduction here, as something like Velcro is friction dependent, and it's used extensively as a secure fastening system in space missions...

[mansion]

A heavy brick will stick more than a light one. And it is heavy becasue of gravity.

With no gravity, it will 'float' above the surface.

[Jedi]

http://www.newton.dep.anl.gov/askasc...9/gen99272.htm

hmmm...

[rundmlee]

The friction force is a function of the coefficient of friction of the materials and the normal force. I would think the coefficient of friction remains constant, whether on earth or in space. However, it's true that if the normal force is mainly gravity, such as a brick on a table, then yes, the overall friction force would be less in space. But, if the normal force is from a spring mechanism and independent from gravity.. then I would think the friction would be the same in space as it would be on earth...

[wandyprawira]

Gravity is just a matter of downward force. Say, if the watch is in space, it means the rotor will only spin if it's given a force, for example: from JJ's brandy shake-like movement. After the force is given, the rotor would continue to spin forever in zero gravity condition unless there was any other force applied in the direction opposite to the rotor movement. This force does exist which is the friction inside the movement itself. At the end, the rotor will stop moving shortly due to friction.

Whereas on earth, the rotor will spin on vertical plane once in a while due to the force it receives from gravity which keep the watch wound everytime.

I would say, just a pure automatic watch will not work in zero gravity condition. Perhaps I am mistaken...

[wandyprawira]

Originally Posted by rundmlee

The friction force is a function of the coefficient of friction of the materials and the normal force. I would think the coefficient of friction remains constant, whether on earth or in space. However, it's true that if the normal force is mainly gravity, such as a brick on a table, then yes, the overall friction force would be less in space. But, if the normal force is from a spring mechanism and independent from gravity.. then I would think the friction would be the same in space as it would be on earth...

The friction inside the movement will be the same. Your formula is correct but I'd say the normal force that you're talking about would be coming from the force exerted by one gear to another gear it's meshing with. Imagine a pair of gears meshing with each other and moving together. One gear will exert force to the other gear and that's exactly where the friction force came into account. Instead of the mass of the gear as the normal force, but rather the movement force itself that creates the normal force (and hence friction).