Replies

Possible Cause	Explanation	Likelihood / Typical Fix
Pendulum bob slipped down	Most common after long storage/moving. Bob slides on rod → effective length increases → clock runs slow.	Very high – fixed by raising bob or shortening rod
Old oil gummed up	Dried lubricant adds friction → escapement loses power → behaves like longer pendulum.	High – needs cleaning & oiling
Wrong pendulum reinstalled	Someone in the past replaced with a longer pendulum (common when parts get mixed up).	Moderate – permanent rod shortening fixes it
Change in Earth's magnetic field	Not the cause. Magnetic field changes are far too weak and slow to affect a brass/steel pendulum in any measurable way.	not likely – no effect on mechanical clocks

spokes,

We have an accomplished professional family member who is gone now; he was always a master carpenter, and when in a long retirement, proved his competency by gifting all manner of wonderful carpentry gift items to even extended family.

A few received incredible grandfather clocks.

Apparently, your overall calculus to effect a correction is evident!

Grandfather Clock Diagnosis Table
Why the Pendulum Had to Be Shortened 1 Inch
Possible Cause Explanation Likelihood / Typical Fix
Pendulum bob slipped down Most common after long storage/moving. Bob slides on rod → effective length increases → clock runs slow. Very high – fixed by raising bob or shortening rod
Old oil gummed up Dried lubricant adds friction → escapement loses power → behaves like longer pendulum. High – needs cleaning & oiling
Wrong pendulum reinstalled Someone in the past replaced with a longer pendulum (common when parts get mixed up). Moderate – permanent rod shortening fixes it
Change in Earth's magnetic field Not the cause. Magnetic field changes are far too weak and slow to affect a brass/steel pendulum in any measurable way. not likely – no effect on mechanical clocks

I sprayed the mechanism with wD-40.....was worse.

So I flooded everything with de-greaser spray for car engines (for my 1978 F100 before i sold it)....

But had to double the weight the works the pendulum to about 15 lbs with lead weights from fishing supplies...

The chimes were about 5 lbs of lead..

Both in nice tapered brass canisters .

When I get around to it i will get some sheet brass and fabricate a longer tapered cylinder to accommodate the extra weight for the pendulum mechanism.

Also cut an inch off the pendulum length to get it adjusted to keep good time.

I never made a stand...just mounted the clock box on the wall,,,,(no cats ...dogs ..nor small children to meddle with things)

PS...when the chimes ding..there is a small air paddle that rotates at high speed to control the chimes weight descent.

The clock is smart enough to keep a mechanical memory of the last hour struck.....

So if you wake up in the middle of the night , and want to know what time it is,,,pull on a small string and the clock repeats the last hour struck.

Pretty neat for something over 100 years old that does all this mechanically.

The face of the clock is 10 inches in diameter and the oak box is 18 inches square and 9 inches deep.