Speedmaster manual?

[Dirt]

Originally Posted by logo

If arm movements on earth are enough to keep it wound, arm movements in space are too. Here’s the physics:

The energy transferred to the watch mainspring can be expressed as work, W, where we assume perfect energy transfer. So:

W = 1/2 (I•w)^2 , where I is moment of inertia of the rotor, and w is angular velocity of the rotor. This tells us that the angular momentum, L is important (L = I•w).

On earth, angular momentum will depend on wrist movement and (possibly) gravity, and friction in the system. Moving the wrist horizontally on earth, there’s no gravity influence - conceptually, is there any reason to believe that restricting yourself to horizontal movement would preclude watch winding? Next time your watch is dead shake it sideways/horizontally and see what happens…. Moving the wrist vertically, gravity actually counters the rotational energy from wrist movement, eventually bringing the rotor back to resting position. Moving the wrist downward, gravity adds to angular momentum.

However, in a zero gravity environment, the ONLY factor against momentum from wrist movement is friction, which for a watch rotor is extremely minimal. So, you can do napkin math assuming conservation of momentum, meaning that even very slight wrist movements such as what an astronaut experiences during the day will efficiently wind the watch because of Newtons Second Law - object in motion stays in motion unless acted on by an external force (gravity or friction in our case). Slight movement = continued rotation of the rotor, thus winding the watch. I won’t go into more details on the physics, but 100% yes an automatic will wind just fine in space.

There are a few watches that have gone to space just fine that aren’t mechanical wind.

https://www.prestigeonline.com/hk/wa...erstellar/amp/

https://www.hodinkee.com/articles/ei...r-professional

We assume too much, without direct knowledge of how the wearer managed their watch

[logo]

Originally Posted by Dirt

This may be plausible and worth consideration.
I imagine the inertia of the Oscilating weight may be sufficiently reduced so that it may struggle to wind the mainspring whilst on the wrist in space.
The inertia may be reduced but the force required to fully wind the mainspring doesn't change from being here on Earth.
Besides, some people here on Earth aren't able to maintain a wind in an automatic through their day to day activities as it is and the reason why bi-directional winding has become the industry standard.

I suppose that's why one of the key NASA selection criterior stated that watches submitted for evaluation must be capable of being manually wound

Originally Posted by Dirt

We assume too much, without direct knowledge of how the wearer managed their watch

Inertia is not reduced - it is constant, regardless of gravity, unless either mass changes (it doesn’t) or if the geometry of the rotor changes (it doesn’t). It’s a property determined by the sum of each infinitesimally small component of mass multiplied by the squared distance to the axis of rotation.

Force required to wind the mainspring is not applicable - what you mean is the energy/work on the mainspring that is needed to establish a sufficient “charge” is the same as on earth. Force is a linear quantity and a rotor winds via angular motion. In fact in zero gravity, you lose acceleration due to gravity on the center of mass of the rotor and thus there is NO force applied. Movement of the arm creates an angular velocity, which is carried as momentum via the rotor inertia.

I am an engineer. Happy to discuss and theoretically assess these things but please let’s keep the discussion based on real mechanical principles so all those who read the thread in the future are not cluttered by argument that is not grounded in science.

[Tqmb79]

It’s actually better if you ask me. U can wind it daily even if you don’t wear. Takes 30 seconds and keeps it running. Also, movement is sooo much nicer to look at versus a huge disc taking up the whole display. If you are new to watches it will strike you as odd. Once you have automatics and manual wind, you very well may end up preferring manual wind.