Expert: John Newman - 7/26/2010

Question
We have a Seth Thomas Grandmother clock.  It was rebuilt a few years ago and now the time has started speeding up until it can be 15 to 20 minutes fast.  Is there an adjustment I can do to correct this?  Also, my wife says that the chimes do not sound as deep and rich as they used to.  Is there a way to adjust the pitch?

Answer
Mark, I need to know in what time period the clock is running fast.  15 or 20 minutes fast an hour, day or week?  If the pendulum hasn't been swapped, there are usually a couple of reasons for speeding up.  One is that someone has tightened the rating nut on the bottom of the bob, moving the bob up.  As a general rule is that one complete turn affects the time one half minute a day, so for 15 minutes a day, the nut would have to have been turned down (unscrewed about thirty times).  It is unlikely that someone turned it that much to adjust it.  If it was 15 minutes a day fast, it probably mean that the escapement teeth are skipping because of a marginal adjustment when it was rebuilt and is now failing.  That fix would require the services of an experienced clockmaker, as it is a rather critical adjustment.  Check this out and let me know what you find.

John Newman
THE VILLAGE CLOCKSMITH
Old Prattvillage
Prattville, Alabama

Mark, I forgot to address the chime part of your question.  The following is my procedure for aligning chime ans strike hammers:

CHIME AND STRIKE HAMMER ALIGNMENT

First, the chime sound board and chime block screws should be very tight.  
Any looseness will cause diminished sound and quality.  For the preliminary
set up, each chime hammer should be aligned with its respective chime rod.  
The center of the hammer head should be in line with its rod and parallel
to the line of travel.  Another way to look at it is that it should not be
angled off to one side.  At rest, each hammer should be approximately
1/16" to 1/8" from the rod.  Pull the hammer back one hammer length and
release it. It should give a solid strike without double-striking or thudding.  
If it does this, the hammer wire needs to be formed back a little.  If the
volume is reduced too much, it needs to be formed closer to the rod.  
Do this with each of the chime hammers.  When you have completed this
sequence, test it by turning  the minute hand around the quarters letting it
chime on its own.  As the chimes will possibly lift differently than from when
done manually, they might need a little more find tuning.

The strike hammers will be done in a similar way with this exception:  
The four hammers all strike at the same time making the adjustment a little
different.  If  3 of the hammers are at the proper rest position and one is
resting on its rod, when it is formed back the other three might move closer
to their rods and the will  have to be adjusted back a little.   This will
now possibly put the first one out a little. The procedure is to form each
alternately until they all strike with good volume and do not double-strike
or thud.  A good example of this is a four-legged stool with one leg longer
than the other three.  You cut it off and find you have cut a little too much.  
Now you have to cut the other three to match the first one.  Fortunately, we
are not doing any cutting on the hammers. 8>)

John Newman