Horology - The Index: Calculate Mainspring Thickness and Length

Calculate the Thickness of an In-Barrel Mainspring if you are replacing with a mainspring of a different width

If you are replacing a mainspring with a different width, then you will want to determine the thickness so as to have the same strength characteristic.

Formulae


T_{MS_n} = ( (	L_{MS_n}	X	W_{MS_o}	) x T_{MS_o}³ )	1 3

	L_{MS_o}		W_{MS_n}


L_{MS_n} =	1	x (	( x D_B² )	-	( x D_A² )	)

	2T_{MS_n}		4		4

where,

T_{MS_n} is the new mainspring thickness
L_{MS_n} is the new mainspring length
L_{MS_o} is the old mainspring length
W_{MS_n} is the new mainspring width
W_{MS_o} is the old mainspring width
T_{MS_o} is the old mainspring thickness
L_{MS_n} is the mainspring length
D_B is the inside diameter of the barrel
D_A is the outside diameter of the barrel arbor