Service: Roamer MST 372 Shock Resist

This is a nice Roamer dress watch with an MST 372 movement. This movement was produced with several types of shock protection systems. This one has Shock-Resist and that places the watch in the mid to late 1940s.

It has a US import code on the balance cock; FXU. That means that this watch was imported to the USA from Switzerland and was therefore intended for the US market.

FXU has Roamer and Meyer & Stüdeli listed so the movement is correct (at least the balance cock is).

The movement ran very erratically and setting the time was rough.

When I removed the hands, I found out why the Timegrapher showed me a snowstorm on the screen. The hour hand and the minute hand actually stuck together because of severe magnetism.

I used my Elma Antimag to demagnetize the hands and I demagnetized the trays with parts before I put them in the watch cleaning machine.

Disassembly

Before you start working on a mechanical movement, make sure to remove all the power from the mainspring. This is to prevent any damage while working on the wheel train.

Move the click away from the ratchet wheel while letting the crown slip between your thumb and index finger.

Lift the balance and the pallets.

Roamer MST 372

Balance and pallets removed

Turn the movement around and lift the cannon pinion. You won’t be able to remove the center wheel later if you forget this.

I noticed that the cannon pinion post was very dry. That and the fact that the setting wheel post wasn’t lubricated were the reasons why setting the time was so rough.

Lift the wheel-train bridge to expose the wheel train.

Remove the escape wheel, 4th wheel, and the sweep second wheel.

Roamer MST 372

Wheel-train bridge, escape wheel, 4th wheel, and sweep second wheel removed

Remove the ratchet wheel and the crown wheel (with the crown wheel shim).

Lift the Barrel bridge.

Roamer MST 372

The ratchet wheel, crown wheel, and the barrel bridge removed

Remove the center wheel cock and the center wheel. Finally, lift the main barrel.

Roamer MST 372

The center wheel cock, center wheel, and main barrel removed

When I opened the main barrel, I noticed that it still had the original (blue) mainspring.

Those old mainsprings are made of carbon steel. They don’t have the S-shape and they’re most likely “set” to some degree. That means that the metal has lost the elastic limit and they’re stuck in the compressed form.

I removed the blue mainspring and ordered a new white alloy one.

Roamer MST 372

Old blue mainspring. Notice that it doesn’t have the s-curve

Flip the movement around and begin with the bottom plate.

Roamer MST 372

Pre-clean the pivot holes and bearing jewels with a peg wood.

Clean all the parts in the watch cleaning machine.

Assembly

Start with the main barrel, the center wheel, and the center wheel cock.

Roamer MST 372

Main barrel, center wheel, and center wheel cock reinstalled

Refit the escape wheel, 3rd wheel, and sweep second wheel.

Reinstall the wheel-train bridge.

Roamer MST 372

The rest of the wheel train and the wheel-train bridge reinstalled

Install the barrel bridge, the crown wheel, and the ratchet wheel.

Roamer MST 372

The barrel bridge, ratchet wheel, and crown wheel fitted

Turn the movement around and start with the motion works and the keyless works.

I took extra care to correctly lubricate the cannon pinion post and the winding wheel because setting time was very rough.

I use Moebius 9501 to lubricate the keyless works and motion works (not the minute wheel).

Roamer MST 372

The bottom plate almost completely reassembled. I always install the hour wheel and washer just before I fit the dial

Flip the movement to the top plate and reinstall the pallets and the balance.

Roamer MST 372

Pallets and the balance reinstalled

As you might have noticed, the regulator is almost completely to the ‘slow’ side.

That’s because someone has shortened the hairspring or it might have left the factory this way.

You can see that there’s a long end of hairspring at the other side of the studholder. There is always a little end of hairspring but this piece is extremely long. That means that the effective length of the mainspring is shorter and a shorter hairspring equals a higher rate.

I had to move the regulator to the ‘slow’ side to counter this effect and increase the effective length of the hairspring.

It can’t really hurt but it would’ve been nice if the regulator was more in the middle of the balance cock.

Roamer MST 372

Roamer MST 372 freshly serviced

Do you have a similar Roamer? Or a different style with the same movement? Let me know in the comments below.

Founder & editor of WahaWatches. I’ve been collecting watches for years. My favourite part is to pull them to bits.

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2 Comments

  1. Gorgeous watches! Roamer is very interesting and classically beautiful. They are not Longines, not Omega, not Zenith … But they are not worse than them. And they look, often, much more interesting. And how much more reliable.

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