I have recently come into ownership of a French made, Westminster chime wall clock which doesn't work. The chimes and hour gongs are fine but when trying to wind the mainspring there was no resistance. Having bitten the bullet I have removed the main spring barrel and on opening it found the spring burglars have been and knicked it! I assume it had broken and someone was going to replace it and couldn't fathom out how to do it.
So am missing a main spring. I know it hooks onto the lug inside the barrel and would be 18 mm in width. What I have no idea of is how long it would be and how thick the spring itself. Cousins also quote a diameter which I am also struggling to fathom out what that means. Anyone any idea how long the spring might have been and an average thickness and also what the Diameter bit means. This is my first 3 barrel clock repair having only repaired a long case pendulum wall clock and various alarm clocks bought for peanuts.