I am very close to replacing the mainspring on a Ansonia time-only movement

One more shot is what it deserves. It had been running fairly well since I serviced it three years ago it but in the last few weeks it has decided to run for about 5 minutes and stop and I think I know the reason why.

Ansonia Drop Extra wall clock
Ansonia Drop Extra wall clock

This Ansonia Extra Drop time-only Rosewood veneered wall clock was manufactured in the early 1880s by what was then known as the Ansonia Brass and Copper Company.

The brass dial bezel is the only significant part missing. Minor items such as the verge, hands, pendulum bob, suspension spring/rod, and the drop access door were easily sourced. I made the drop access door later on.

Here is an article I wrote in 2018 wherein I assess the case and movement for the first time. At the time I was challenged by the prospect of putting a rusty old movement back in running condition and giving it a new life.

It was in poor condition when I bought since it literally came out of a barn and it is just pure luck that it runs at all.

The symptoms? If wound halfway it would run 3-4 days and stop. If wound tight it would not run at all because surface rust and other contaminants caused the coils to bind together. This is very typical of old clocks that have not been running for years. A movement that is “overwound” is a myth. It is the combination of old oil, rust and dirt that seizes the mainspring.

Rusty mainsprings

For some clockmakers any rust on a mainspring means that is it tossed it out because the mainspring is inherently weaker. This particular mainspring has surface rust on the outer two coils and rust on the edges of the spring. Otherwise, it has no cracks or splits and has plenty of power.

Yes, it was seized

Generally, to remove rust, repairers often apply a liquid gel, black tea, or even use electrolytic rust removal.

If I were in the business of clock repair, I would certainly replace the mainspring and pass the cost on to the customer. However, the original mainspring is part of the history of the clock and I don’t think the amount of rust is enough to prevent me from reusing as long as it is cleaned properly. As far as I am concerned, replacing a mainspring is the last resort.

Servicing yet again

Now that I have it apart why not throw the parts into the ultrasonic for a good cleaning. After everything was dry I inspected the parts, polished the pivots, and pegged the pivot holes.

I released the mainspring but this is how it came out of the case

I gave special attention to the mainspring. After inspecting it (yet again) I used a Brillo pad, steel wool and a microfiber cloth to eliminate the roughness as much as possible.

Ansonia mainspring cleaned up and ready for installation

Following the cleaning I applied a thin film of Keystone mainspring oil. I then reassembled the movement and oiled it prior to placing it on the test stand.

Ansonia movement on the test stand

While on the stand I gave the mainspring a few turns, put the movement in beat and it ran well for a couple of days which is what I expected.

On day 4, it was time for the ultimate test, to wind it fully till it winds no further. I was hoping for a good result and it ran the full 8-day cycle. The mainspring just might be “clean” enough that it will now run without stopping.

I will monitor the results of this little experiment for a while longer but for now things very good.

Another mainspring saved from the recycle bin.