Just wondering if a wrong main spring, say with a higher tension or different length would cause a watch to run fast. I have an 11ac watch that i'm certain has the wrong spring in that runsfast, everything else has been stripped, cleaned checked etc etc but I dont have the main spring to fit to try yet. I have one coming but just wondered if anyone else had come across this or if it does even make a difference.
Thanks
GVP
In reply to If you don't get the by JP
Short answer is yes. Without the right one it will never run properly. Any number of factors such as too much or little friction/tension will cause the watch to never run properly. A common phrase in regulation is "it all begins with the mainspring." If you experience a timing problem or amplitude problem, the first place to go is the mainspring. Have you been able to get it on a timing machine?
In reply to Short answer is yes. Without by Aberlow
Thanks everyone. I haven't managed to get it on a timing machine. When i first wind it the balance seems to swing correctly, the further I wind, the faster it spins so I am guessing by what has been said this is the issue.
One other question, would the mainspring from an 11AFC be the same as an 11ac? Just wondering as I have an 11afc mainspring here but dont want to try it if it is just going to turn out to be wrong anyway
OK, I find the correct (maybe) main spring only for it to be broken in it's packet. Onlooking up the spring I have been given three totally different dimensions by 3 different sources, one (bestfit) says it should be 1.30 x 0.9 x 280 x 8 another (cousins uk) says it should be 1.40 x 0.95 x 300 x 8.5 and the other (ranfft) seems odd says 1.35 x 0.10 x 9.0 So which one is it? or is it none?
How can three different places have three totally different sizes?
A too powerful mainspring can even make the escapement 'knock', where it sounds as if it is galloping. Within a small tolerance, it is important to get a mainspring as close to original spec as possible, if a branded part is unavailable.
I tend to go by what bestfit says, but not all mainsprings are created equal. Very old springs are a different steel, and are weaker than modern springs with the exact same measurements. A watch under low power will yield low amplitude at the balance, and actually speed up. The amplitude reading will indicate whether the spring is providing too much power. The only way to know for sure what is going on is to use a timing machine, and the best quality one available, at that. There is an inexpensive Timegrapher availbale online that really is substandard and buggy.