Effect Of Mainspring.

[fjseal]

Hello all, I am new to the forum.

Bearing in mind that the escapement controls the mainspring, if you put a random spring into a mechanical movement, could the wrong spring cause the watch to run ten minutes a day fast, or is it just likely to be the usual things like hairspring or magnetism.

Thanks.

[Marc]

Hi Fj,

 

It kind of depends on how the rogue mainspring differs from the correct spec.

 

Too thick a mainspring can result in the balance amplitude being so great that the impulse jewel actually bounces off the outside of the pallet fork before the balance reverses its direction of rotation, I believe this is called over-banking. This bounce can impart extra speed to the balance which would speed up the rate and make the watch run fast. This is an easy condition to identify as all you have to do is listen to the watch. In normal operation the tick is nice and even, but if over-banking is happening then it sounds somewhat like a galloping horse. This is not good for the impulse jewel or the pallet fork horns.

 

Too thin a main spring can cause the balance amplitude to be too low. Surprisingly enough, a very low balance amplitude can also result in an increase in rate, as can often be observed in a watch where the mainspring is almost fully unwound.

 

That being said, the first place I look if a watch is gaining unacceptably is the hairspring. Check that no coils are stuck together and that there is nothing fouling the coils in any positions.

[bobm12]

I agree, check the hairspring! Sometimes oil shorts the wire.

[jnash]

I agree, check the hairspring! Sometimes oil shorts the wire.

 

Dont forget magnetism, this causes the coils to stick together therefore speeding up the watch!

[bobm12]

That is correct Geo, I always demagnetize movements before service previous testing with a compass! Good observation!

 

Cheers,

 

Bob

[Geo]

Geo would be Jonathan! :-)

[jnash]

Geo would be Jonathan! :-)

I didn't want to say anything lol

[fjseal]

Thanks for all the replies. Will check your suggestions; magnetizer arrived today. By the way, did you know that each nineteen minutes spent crawling round on the floor looking for 'pinged parts' is one hour and ten minutes less in the gym. Old Horological Formula.

[bobm12]

Sorry, my speed reading sometimes gets in the way! :)

[Marc]

gym?

[bobm12]

 

By the way, did you know that each nineteen minutes spent crawling round on the floor looking for 'pinged parts' is one hour and ten minutes less in the gym.

So it actually saves time. I should be very fit by now! :)