Uhrenfabrik Mühlheim, Müller & Co box clock – servicing the movement

It is time to service this very fine German box clock by U. M. Muller. I have been stalling for too long. I am a little leery because the last time I worked on one of these the strike tension spring broke (my fault) so I made a promise to be more careful this time.

I bought this clock in 2013 and while it has been very reliable and running daily, like all things mechanical it requires attention from time to time.

A little background.

German “box clocks” effectively spelled the end of the Vienna regulator period because they were cheaper to produce, had simpler lines and appealed to the middle class consumer of the 1930s.

U M Muller box clock

According to Schmid’s Lexikon, the original founders of this company in Mühlheim started in 1867. It was acquired by R. Schnekenburger around 1880, then by Gebrüder Müller around 1896 when it became Uhrenfabrik Mühlheim vormals R. Schnekenburger. In 1900 it assumed the name Uhrenfabrik Mühlheim, Müller & Co. or UM Muller.

This U. M. Muller box clock features wood carved inlays on the door, metal dial, wall stabilizers, brass bezel trim, spade and spear hands, beveled glass framed in brass and a fixed wood carved crown. The case reflects excellent quality.

Logos are helpful in dating a clock. U. M. Muller clocks can be dated by the lion logo on the clock face. If the lion’s tail is up it is pre-1930. On this clock the tail is down which puts it is in the mid to late 1930s.

Back of movement

Okay, enough of background; let’s get on to servicing the movement which is the subject of this post.

U M Muller movement, front plate

It is a count wheel strike which is not unusual but to be honest I was a little surprised and expected a rack and snail movement for a 1930s clock.

The movement has been opened at least once, perhaps more. I could not see any obvious signs of repairs, so, perhaps a cleaning or an adjustment was all it required. It was very oily and I suspect it was sprayed with some sort of solvent. Despite the “wet” condition of the movement it is actually in very good condition.

I had two issues with disassembly. One, I could not pull the count wheel off its arbour despite my best efforts, so on it stayed. I simply worked around it. It made for an interesting installation of the cam wheel bushing. Secondly, the strike lifting lever spring snapped when I disassembled the clock. See, this is what I feared!

I salvaged what was left of the spring, which is essentially a stiff, straight wire that hooks onto the strike arbour, but had to drill a new hole in the plate adjacent to the old one to secure the spring. The remaining spring happened to be just long enough to do the job.

Spring repair for U M Muller movement, solder used to secure the spring in place

The movement was disassembled and parts placed in an ultrasonic cleaner. After drying all pivots were polished.


The powerful mainsprings are a weak point in German clocks of this era. Usually when they break they take a few things with them. It is called collateral damage and manifests itself in broken wheel teeth, bent wheels, arbours and so on. As the mainsprings were in top shape with plenty of power, no splits or cracks, they were cleaned and reinstalled in their barrels.

Bushing work

The movement required 3 bushings, the escape wheel front and back and one on the cam wheel, strike side. It was actually not as worn as I expected and likely could have gone on further without stopping but the bushing work and overall servicing including a good cleaning will certainly extend the life of this clock.

The three 2mm diameter bushings required for the plates are some of the smaller ones in my supply. Not a huge problem but they are so small that one snapped out of my tweezers when I grabbed it from the container. It is on the floor….somewhere!

Wheels are in place and ready for the top plate

Otherwise, the bushing work went well.


the movement was assembled and while the time side ran well the strike side was out of adjustment. With count-wheel strikes it generally takes a couples of attempts to get it right but I think I have only one adjustment to make, relocating the stop wheel so that the stop pin is in the 12 o’clock position. I will leave it and test the time side for now.

Next day

This is the day when things go horribly wrong.

I let the mainsprings down and opened the plates to relocate the stop wheel. In my haste to reassemble the movement I bent one of the pivots on the governor. I knew it right away because when I had the plates back together the train would not turn and the fly was “stuck” in one spot. Out came the wheels and once I attached the fly arbour to the chuck of my lathe and gave it a few spins I could see how much it was bent. It was not bent by much, but any amount will stop the train. I straightened it as best I could and it looked pretty good. The pivots are tiny and care must be exercised when moving the wheels around when assembling the plates. It is a hard lesson for all clockmakers.

The lion’s tail is downward

Of course, while straightening the fly arbour the tiny fly retention spring, which is a small wire, flew into the room somewhere. I had to fashion a new fly spring from 19 gauge wire. What else could go wrong! Thankfully nothing else did.

This should have been a relatively easy movement to work on. Instead I seemed to have encountered one problem after another but with each problem I arrived at a solution. Despite my issues this is a well made German movement and really nice to work on.

All is well, the movement is running and striking as it should.