The Mystery of Turns Per Day

In order to know what Turns Per Day mean, you must know the following facts.

Fact 1
Every watch winder has a motor and this motor turns in a radial motion.


Fact 2
The speed of a motor is determined by its RPM or Revolutions Per Minute.


Fact 3
A watch winder is controlled by a microprocessor and each manufacturer programs its own winding sequence.


Fact 4
Since the motors turn in a specific RPM, and in a specific winding sequence, this results (through mathematical calculations) in a specific Turns Per Day for each watch winder.



All of us know that a watch winder is purely for convenience sake. Furthermore, a good winder keeps the watches mainspring at between 50% to 70% levels and not completely wound! So the TPD is the minimum number of rotations required to keep your watches going.


Some people argue that wearing a watch the whole day will eventually wind the mainspring to its peak level but with the in-built clutch, we ought not to worry that it’ll overwind. I beg to defer.


When Ferrari races in the F1 circuit, it does so at a certain period only. And after the race, it goes for mechanical checks, oil changes, lubrications and whatnots. The same for fine watches too. After a day’s wearing, you would want to put your watch in a ‘spa’ to relax and not abuse the clutch. So a winder which provides high TPDs are not recommended here. Some websites provide excellent databases on these TPDs of individual calibers of watches. This is a great source of information and best to adhere to.


Most users of watch winders are unaware of TPDs and the perils of using a winder with high settings. They remain oblivious to these because of the lack of information, either from the sellers or from the ‘outside world’, the web.


To calculate the TPD of a watch winder, you’ll need to know (besides the facts given above) the motor’s RPM and the winding sequence.


Let me give you a hypothetical example.

A watch winder turns clockwise for 15 minutes, then stops for 15 minutes, then turns counter-clockwise for 15 minutes and stops again for 15 minutes. This is the winding sequence.

A winding cycle is the sum of the winding sequence, which is 60 minutes per cycle.

Let’s say the motor turns at a speed of 7 RPM and the sequence repeats the whole day.

So for 15 minutes, the winder turns a total of 15 x 7 = 105 turns in the clockwise direction and for the next 15 minutes it gives 105 turns in the reverse direction.

In a day of 1440 minutes, the winder makes a total of 1440 divide by 60 minutes = 24 cycles.

Multiply 105 by 24 you get 2520 TPD in a clockwise direction and 2520 TPD in the counter-clockwise direction. This means your watch will receive a total of 2520 x 2 = 5040 Turns in a Day or TPD. You judge for yourself if this is acceptable.

For a watch requiring just 650TPD in a CW direction, you actually receive more than 3.5 times this requirement. This also equates to abusing the clutch. If your watch requires 800TPD in either direction (bi-directional winding), then it receives more than 6 times its requirements.



Let’s have another example.

A watch winder turns clockwise for 5 minutes, then stops for 25 minutes, then turns counter-clockwise for 5 minutes and stops again for 25 minutes. This is the winding sequence.

A winding cycle is the sum of the winding sequence, which is again 60 minutes per cycle.

Let’s say the motor turns at a speed of 7 RPM and the sequence repeats the whole day.

So in 5 minutes, the winder turns a total of 5 x 7 = 35 turns in the clockwise direction and for the next 5 minutes it gives 35 turns in the reverse direction.

In a day of 1440 minutes, the winder makes a total of 1440 divide by 60 minutes = 24 cycles.

Multiply 35 by 24 you get 840 TPD in a clockwise direction and 840 TPD in the counter-clockwise direction. This means your watch will receive a total of 840 x 2 = 1680 Turns in a Day or TPD.

So for a watch requiring just 650TPD in a CW direction, you actually receive just slightly more than 29% of its requirement. This doesn’t subject the clutch to much abuse. If your watch requires 800TPD in either direction (bi-directional winding), then it receives about twice its requirements. Compare this results with the one above.



So how do I know what’s the RPM of my watch winder’s motor?

Get a stopwatch and time the rotation from a starting point and count the total number of revolutions it makes in one minute. As mentioned, RPM means Revolutions per Minute.



Conclusion

In my ten years of designing and fabricating watch winders, I’ve discovered another misguided word commonly used by many people. They say a good winder comes with a speed selector. That’s totally wrong! The speed of the motor ALWAYS remains constant! You can only adjust or select the winding sequence to give you the TPD (Turns per Day). I’ve proven this in my above examples.

You can see many watch winders sold on evil-bay. Some sellers in their sales strategy hide certain information such that we will not know what the resulting TPDs are. They may not even know the actual TPD except what is given by the manufacturer or distributor and take it face-value.

A watch winder may have a preset Turns Per Day or a selection of TPD.

Do you homework folks! And most of all… take care of your fine watches as they are also your hard-earned money!


Do refer to the other sections of this blog for more information about the myths on Turn-and-Rest Winding Sequences, the correct way to place your watch on a winder, and even information on how to build one yourself!


Humbly yours

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