First you would need to remove the movement from the case. You would need to have a set of let down keys. With the let down key held on the winding arbor, release the click on the great wheel ratchet wheel. If you have never done this before, do not attempt. Mainsprings are dangerous and should be handled by someone who is trained to work with mainsprings. More information on this and other clock repair topics are found at: http://www.ticktockpro.com Tick Tock Productions
John Tope, June 2008