Serious Horological Question

I've been wondering this for a long time now. Most automatic mechanical watches have a power reserve of about 40 hours give or take.

Many mechanical hand wound movements (example a PAM111) have a power reserve of about 56 hours.

Why would a hand wound movement have about 16 hours more power in reserve to run the ebauche than an automatic?

Thanks

Don't know if I can answer the specific question, but I don't think the difference is necessarily based on the movement being hand wound or automatic. I do recall seeing power reserves (quoted in magazines such as WatchTime) on automatics that are longer than 40 hours with a single barrel and my new PanoReserve hand wound has a 42 hour power reserve. I think there are just differences between different movements and manufacturers that account for this variability.

One reason may be that the Panny is so big they can fit a bigger mainspring barrel in the watch compared to a smaller movement/watch.

[Uncle-AJ]

The only thing I can think of is, the spring in a mechanical watch being stronger because it's wound by hand. In an automatic watch the spring is wound by the movement of the balence wheel, which can only wind to a certain tension. I may be wrong, we need Dave Knoll to confirm this theory.

Originally Posted by Uncle-AJ

The only thing I can think of is, the spring in a mechanical watch being stronger because it's wound by hand. In an automatic watch the spring is wound by the movement of the balence wheel, which can only wind to a certain tension. I may be wrong, we need Dave Knoll to confirm this theory.

But Adrian, you can also hand wind your Rolex, so I'm not sure that argument holds water.

I wonder if the mechanism that transfers energy from the rotor to the mainspring reduces the energy the watch can store? Of if in fact the mainspring on autos is built less strong (than hand wound) because the auto can be continually powered-up by the kinetic energy built from the rotor?

Where is Dave Knoll when you need him?

[JJ Irani]

Valid point, Johnny. BOTH movements can be hand-wound to maximum torque...yet one will have a greater PR than the other.

My understanding is that it does have something to do with the frequency of the watch....here let me cite a solid example.

The co-axial movment which OMEGA uses comes in 3 varieties....2500A, 2500B and 2500C.

Whereas the first two beat at 28,800 A/Hr, the 2500C beats at 25,200 A/hr and is currently being used in the new PO. The result is that the PO has a PR of well over 50 hours (I tried it out), but their Aqua Terra with the higher beat co-axial movement goes only for about 47 hours on a full wind (I've tried that out too!).

But, of course, Dave Knoll would be the best person for more technical details.

JJ

Hmmm, JJ you may have a really good point there.

I know that, for example, the Panerai OP XI calibre (hand wound for the PAM111) beats at only 21,600 per hour, which could be why they can go longer, i.e., they aren't using as much energy to beat as fast.

[dman]

Mr. Knoll, paging Mr. Knoll.