Du-fense

When we last reviewed our DUFA friend I noted that the movement looked to be in good shape and I was about to embark on a cleaning.

A practical approach to cleaning starts with a disassembly and simultaneous deep inspection.

Diving in...

It appears that someone tried to make a repair on the movement's suspension spring. You can see the suspension spring glittering above on the upper right. 

Likely the suspension spring broke by some form of rough handling of the pendulum. The home-brew repair effort speaks to the repair person's inexperience with mechanical clocks. Not to sound smug... it's just that the results speak for themselves to the trained eye.

Suspension springs use very thin, highly-flexible "wires" (metal strips), often in pairs. The thinness and flexibility of the suspension wires is key. 

A pendulum must oscillate and be able to receive power from the escapement easily. In most clocks the performance of a pendulum is greatly enhanced by the use of a suspension spring, greatly facilitating the ease of the pendulum swing and helping minimize the amount of power needed to drive it.

Here's the French suspension spring from the dog clock:

The wires on our French example are a little dented but work fine. Those strips are very thin, like 0.05mm and, while not fragile, need to be handled with care and sometimes snap or tear away if a pendulum is manhandled. To be fair, I've broken a French suspension spring myself working on a clock. C'est la guere.

You may recall that DUFAs are German clocks and, along with English clocks, use shorter spring wires but effectively they work just the same as French versions. Replacing a suspension spring is both simple to do and inexpensive. Here's a mess of them being sold on eBay for $40.

And here's how suspension springs are typically installed and suspended in a clock movement. Note how the pendulum leader hooks onto the base of the spring. You can see this too in our top photo.

Here's the repair effort of the suspension spring wires I found in examining our DUFA tall clock.

Turns out that JB Welding the spring wires tends to... ahem... reduce the springy qualities of the spring.

Good thing suspension springs are easy to replace.

OK, enough with my smugness.

Looking over the rest of the movement... it's dusty, tarnished and corrosion lurks a bit but minimally grimy and worn. Promising!

The above shot shows much of the escapement in the movement. The anchor splays in an inverted V left and right. That anchor serves as a pivoted rocker arm, see-sawing the two pallets back and forth with the movement of the pendulum and the escape wheel.

Removing the anchor and related parts from the movement...

Note the suspension "spring" standing straight up on the right.

Below is the anchor up closer. These pallets are adjustable. They are steel slats that are held by screws into place at the ends. They make contact with the teeth of the escape wheel (pointy teeth).

A variation of that pallet design has been incorporated in most modern mechanical wristwatches.

from Luxuo.com

Those pallets in the wristwatch movement are manufactured "jewels" that look like rubies. They are typically used in the pivot holes and sometimes as pallets as the jewels are extremely smooth and resistant to wear. You can see the jeweled pivot holes as well. 

In our our less modern example of the escapement below I'm holding the anchor and you see one end with the grimy pallet extending out. There's an adjustment screw on the end of the anchor. 

Sticky grime on the pallet ends is not unusual. Well-meaning efforts to oil a clock often end up oiling locations that don't need it or now have so much excess oil that it attracts dust/dirt. Time plus excess oil and dust will end up with gunk accumulating in many places on a clock including the ends of the pallets. 

Oiling clock pallets is slightly controversial in the clockmakers community. Some recommend tiny amounts, others, none at all.

Below is the opposite pallet, lightly cleaned, and you can see a very close up view of the pallet "face" which is the part that makes contact with the teeth of the escape wheel.

It is clearly grooved from wear/contact with the teeth. Not dramatic wear but its presence absolutely tells us that this clock did not simply sit unused. While I didn't check this I have no doubt that the width of that wear mark will match the width of the escape wheel teeth. Both pallets had this type of wear.

This clock did run for years. Likely decades.

While I will clean them overall, I will not adjust (unscrew) those pallets unless there is a serious operating problem. These types of pallets are typically factory set and rarely need adjusting. 

The disassembly continued but I'll cover that in another post.

Coming up next the striking mechanism. 

I've never seen anything like it!