App: find the correct mainspring sizes

[praezis]

More than one time I saw requests for mainspring sizes. There are rules, how to calculate the optimum mainspring for a given barrel. I packed them into a tiny windows app: just enter the barrel diameter and the optimum spring will appear. 

App attached for download (unpack the zip file).

Frank

Mainspring.zip

[dadistic]

Thank you very much for this. Another very useful tool, it will get a lot of use from me. 

[Gary]

Thanks for the app! I am sure I will get a great deal of use. That said as I'm somewhat new to the watch world how do I use it? I am assuming the depth I would use my digital calipers? Then measure the arbor at its widest point and then enter the inside of the barrel diameter to get the three numbers? Just making sure I understood. I do remember seeing three numbers on the right and I'm not sure I understood those number represented!
Thanks again! Great tool!
Gary


Sent from my iPad using Tapatalk

[clockboy]

I have just read (several times) a two of interesting articles on this very subject in this months BHI mag. Choosing the correct mainspring using calculations is complex and confusing with many different views on the subject. For example sometimes suggested mainspring thicknesses are given in terms of fraction of the barrel diameter, e.g. Watters says divide by 100 but then  De Carle suggests to calculate the thickness of a spring divide high grade watches by 96,medium grade by 90 and 84 for low grade watches. But which if any is best and then there is the calculation of the length.  

The first article is by a guy David Boettcher who has a web site www.vintagewatchstraps.com argues that these calculations are incorrect he also argues that the normal rule of thirds is also incorrect. If interested I suggest a visit to his site where he puts his arguments and theories on this and other subjects. He does supply on his site a handy mainspring calculator which you can use but only if you agree with his theory that is. Personally I will stick to my faithful GR book which has not let me down so far.

[praezis]

11 hours ago, Gary said:

Thanks for the app! I am sure I will get a great deal of use. That said as I'm somewhat new to the watch world how do I use it? I am assuming the depth I would use my digital calipers? Then measure the arbor at its widest point and then enter the inside of the barrel diameter to get the three numbers? Just making sure I understood. I do remember seeing three numbers on the right and I'm not sure I understood those number represented!
Thanks again! Great tool!
Gary


Sent from my iPad using Tapatalk

Gary,

for using the app, just enter the internal diameter of the barrel and click "Calculate":  You will get sizes of a good working, correct mainspring.

If your real barrel arbor is different than the shown standard, enter its real diameter.

If  you want another thicckness than proposed, enter it (on right edge you can find thickness of a weak/normal, medium and strong mainspring).

Moving the cursor to an item will show a help-text (on some only). The hight of the spring depends only on the internal hight of the barrel (minus 0.1mm).

Frank

[Gary]

Thank you Frank!
This will be most helpful! I have several old pocket watches that have no identification and had had mainsprings bradded together to put back in them during a repair. I can now get a good estimate on how to select a new mainspring! Exciting !
Thanks again. @clockboy I have read his theories on correct mainspring dimensions and while I'm not knowledgeable enough to know I do wonder how the manufacturers fit (size) the original mainsprings? Is it one of the last considerations in the design, I.e., we now have a barrel with this new design that has a 9.1mm internal measurement now we need a 44 hour reserve, etc...? Just curios as to how it develops. I would not think the movement is built around the barrel and mainspring?
Just thinking. I love this forum!
Cheers!
Gary


Sent from my iPad using Tapatalk

[Gary]

By him, I mean David at vintagewatchstraps


Sent from my iPad using Tapatalk

[clockboy]

4 hours ago, Gary said:

Thank you Frank!
This will be most helpful! I have several old pocket watches that have no identification and had had mainsprings bradded together to put back in them during a repair. I can now get a good estimate on how to select a new mainspring! Exciting !
Thanks again. @clockboy I have read his theories on correct mainspring dimensions and while I'm not knowledgeable enough to know I do wonder how the manufacturers fit (size) the original mainsprings? Is it one of the last considerations in the design, I.e., we now have a barrel with this new design that has a 9.1mm internal measurement now we need a 44 hour reserve, etc...? Just curios as to how it develops. I would not think the movement is built around the barrel and mainspring?
Just thinking. I love this forum!
Cheers!
Gary


Sent from my iPad using Tapatalk

If I could I would post the whole of the article/s but I would breach BHI rules & it 8 pages long. It is complex but to try to summarise it is the amount of "turns" you need the barrel to make for the required reserve. Therefore the spring must have enough length to achieve this. Then there is the amount of strength required and for the strength to be as consistent as possible  from a full wind to its fully unwound state. To achieve all this there needs to be enough room between the arbour & the inner wall of the barrel. As I stated originally it is complex indeed.