Expert: William J Perkins - 6/6/2007

Question
QUESTION: Ihave a Viking Grandmother clock that I built from a kit in
the late 60's . It has a series 111 movement with a brass
pendulum bob & a wooden pendulum rod. The problem is that
once the pendulum is started it works find then after a while the bob starts hitting the side of case and will continue to do so untill you stop it. I have checked the level of the clock and tried adjusting the adjustment screw
and also adjust the suspension arm & it does not help.DO you think I need a new suspension spring? Or do you have any other suggestions?If I need any kind of parts please advise tel. # and who I can talk to.
Thanks

ANSWER: Does the bob hit both sides or just the one?

---------- FOLLOW-UP ----------

QUESTION: Yes it does hit both sides

Answer
Something has happened to cause an increase to the arc of the pendulum.  Coming immediately to mind is a change of pendulum or the bite of the verge has been altered.  A remote possibility is that the pendulum spring has significantly weakened or is broke on one side.
If the pendulum was replaced go back to the original.
If the bite has altered, this can happen from a hold down screw becoming loose.  If you don't know how to make this adjustment provide me with all the information stamped on the backplate of the clocks movement.  This will identify to me the exact movement involved, which in turn would enable me to provide appropriate instructions.
A pendulum spring problem can be hard to detect.  If your spring is made up of two pieces fixed between the top and bottom hanger, you would look to see if one of the pieces has broken.  If your spring is one piece fixed between the two hangers, look for a kink or wear through.  With either of these conditions replace the spring.  
Sure hope this helps you WJP