Bears Repeating (no pun)
Clocks of the W113 Era, by Jim Mahaffey
VDO subcontracted the job of building mechanical clock movements to the German firm of Kienzle in about 1958 to about 1975. There were two major patterns of Kienzle movements made. Let's talk about the common, drum-shaped movement. It's a basic Borg-wind, anchor-escapement clock, shock-mounted, built on two nickel-plated brass plates. Winding period is about three minutes (sounds like a muffled jolt.) The balance is not temperature compensated, and usually runs in one jewel. (There are rare examples of two-jewel movements.)
Early movements have all brass gears; later movements have plastic escape-wheels with coaxial aluminum flywheels. There are some basic case patterns: 115 (short case), 114 (long case), 113, 107 (SLs have internal lighting and connector blocks on the back), etc... Adjustment is with a jeweler's screwdriver through a port on the back, covered with a paper tape, usually labeled "VDO."
TO ADJUST, set up the clock on a bench with a 12-volt power supply. Make EXTREMELY small movements of the adjustment pinion, and allow the clock to settle for at least 24 hours between adjustments. To get a really fine adjustment can take a week, and it will be spoiled as soon as the car heats up inside. An inability to achieve adjustment indicates wear on the plates. Altitude compensation for the case is provided by a labyrinth vent, hidden under the plastic tape with fuse specs. One of three nuts on the back of the case is warranty-sealed with a two-part plastic lock.
Normal failures are as follows:
1. The thermal fuse. This fuse is installed as a rivet, made of bismuth/tin alloy, and is intended to prevent fire in the rare event of a failure of a flat, phosphor bronze spring on the wind clapper. These fuses eventually fail out-of-specs. A bronze spring separates the electrodes, and the remains of the fuse are usually evident somewhere in the case. I suggest replacing the fuse with lead-tin solder, with the warning that this voids the purpose of the fuse.
2. Points. Causes stalls at the end of the wind cycle without solenoid meltdown. The precious-metal points can become burned or distorted. Lubricant evaporates and is burned to soot in the points, and this can cause overheating. Metal can also sputter and migrate from point to point. Dress the points with fine abrasive.
3. Flywheel bearing failure. Causes uneven force on the first wheel and stalls between winds. The heavy steel flywheel on the solenoid plate should not wobble on its bearing. For some reason these things wear out prematurely on some cars, particularly on SLs, and it may be high-frequency vibration related. It is held on its shaft by an E-clip. On later models the clip is built with a bronze tail, so you can't lose it. Replace the flywheel. Lubricate this bearing.
4. First and second wheel bearing failure, back plate. Causes the clock to stall between winds. The first wheel takes a severe side load from the winder, and this will eventually doodle out the back bearing. The second wheel can also lose its back bearing. Replace the back plate (with attached balance), or repair the bearings. The bearings respond to shrinkage under a staking punch (with subsequent reaming), or to bushing. As good back plates are becoming rare, I find myself resorting to staking punch more and more.
5. Setting knob (rare). The rubber suspension goes soft, and you can't reach the hands with the setting knob clutch. Use the clock for parts.
6. Front plate bearings (very rare). The wheels wobble on the front bearings. Use the clock for parts.
7. Weathering. Red rouge on a cloth wheel can do wonders for the plating on the brass bezel, and even for scratches on the plastic crystal.
8. Cracked or smashed crystal (very rare). Use the clock for parts. Assure the owner that they're all just alike, and he won't notice the difference if he buys a new one.
9. Previous repair work (more common). Note extra stickers or the absence of the nut seal. Note a promiscuous use of lubricant. Stalls in mid-wind. Clean it thoroughly.
10. Salt water immersion. (More common than you'd like to think.) Excellent source of parts - the brass bearing plates are unaffected. Springs will be ruined.
11. Only seen once: Winding pawl worn out. Clapper spring breakage. Clock possessed by demons.
Suggestions:
Be careful of the cleaning fluid you use to remove old, oxidized lubricant. Most organic solvents will play havoc with the various plastic components. The best is freon, which to my utter dismay is no longer available. Professionals advise the use of detergent in water. Lubricate conservatively, using only fine watch oil. Silicon-based oil is certain not to harm plastic components.
Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America
