Solar mantel clock servicing – just one hiccup, well, a couple actually

Solar mantel clock
Solar mantel clock

For today’s post, we are looking at a German time and strike mantel clock with a Hermle movement and sold in Canada under the Solar name. It has a 6″ dial and dark walnut case that would have been around $50 or $60 when new in the 1960s. At about 13” wide by 7” high by and 4” deep it is small by mantel clock standards and would fit just about anywhere in a home or office.

Solar clock
Solar clock, just a little taller than a beer can

It has a type 141 German movement from Hermle with a recoil escapement and 11cm pendulum (200.8 bpm). The half-hour strike on a bell is pretty sound for a mantel clock but is loud enough to be heard across the house. As a testament to its design and durability, this movement is still being produced by Hermle today.

Solar Hermle movement
Solar Hermle movement

This was not a running clock when I bought it but I thought a good cleaning was all it required. Judging from mars and scratches on the backplate of the movement it has been worked on in the past.

I took the movement out of its case to examine it more closely and I was relieved when I saw that the pivots were not plated, the bane of Hermle movements from the 1970s to the late 1980s. In those days Hermle used soft steel pivots for their movements and plated them for hardness. The plating has been known to peel off and this requires repivoting which is a time-consuming process. When there is too much pivot work to be done the movement is simply tossed out. This movement predates the plated pivot period.

I did not see any evidence of bushing work on the movement but one or both mainsprings were replaced as the barrels had numerous scratch marks on them. As is typical of clocks of this period the mainspring barrels can be removed without disassembling the movement. The winding arbours simply pull out once the rachet is removed. Mainsprings on some German clocks are a known weakness.

Hermle movement
Hermle movement, you can see the S on the strike barrel

The movement was in very good condition with minimal wear.

Hermle movement, front plate removed
Hermle movement, front plate removed

The movement was disassembled, parts cleaned in an ultrasonic cleaner, the pivot holes pegged, and the pivots polished. The warning wheel is plastic and did not go into the ultrasonic machine, a cost-savings measure by Hermle no doubt on a part that has almost no load.

Hermle stop wheel
Hermle plastic stop wheel

I assembled the parts to check for wear and found that the movement required two bushings, the star wheel, backplate, and the lower drive wheel rear plate, both quite worn. All other pivot holes were within acceptable tolerances.

Installing two bushings

The starwheel bushing installation was simple enough. The center cannon wheel had to be removed so that the backplate bushing hole could be accessed. Bushing work went without a hitch.

Now for putting that centre wheel back on. An oval tension spring just below it must be tight enough but allow the arbour to move. Attempting to reinstall the brass washer was frustrating and as you can see I made some nasty marks trying to get it back into place (below photo). After several tries, I just could not get it tight enough.

Hermle movement, washer and tension spring
Hermle movement, washer, and tension spring

I attempted to stake the washer but that did not work. None of my stock of brass tubes had the correct inside diameter and I was reluctant to put a lot of work into making a friction washer with my mini-lathe.

Solar washer
Solar center wheel friction washer, not reusable

However, I discovered a simpler solution, a brass Bergeon bushing.

Hermle movement new washer
Hermle movement’s new friction washer is a brass bushing

The arbour is roughly 2.6mm and a bushing with an inside diameter of 2.5mm provided a good friction fit. The bushing is also large enough to cover the tension spring underneath. Perhaps not the intended purpose of a brass bushing but it works! In many other German clocks, there is a pin through the arbour and it can be easily taken off but not on this one.

Reassembly and testing

After test fitting all the parts it is off to the next stage, resembling the movement. When reassembling a rack and snail movement there a number of things to consider but in my view, the three most important steps are ensuring the warning wheel pin is in the roughly 12 o’clock position to permit a half-turn to set up the strike, that the strike paddle is between two star points and not resting on the point of star wheel (a strike train that starts up under load may stall) and that the gathering pallet pin is well clear of the rack teeth. On a typical rack and snail movement, all other adjustments are done outside the plates.

Then comes the testing phase which generally lasts a couple of weeks or more depending on what issues may arise.

In the meantime, I took the opportunity to clean the case and touch up some small chips on the decorator piece under the dial.

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