The Model 84 with a calendar, and an unusual one. It switches instantaneously and carries an A.M./P.M. dot alongside the date numeral, because the ring indexes three quarters of a space at midnight and a quarter at noon.
The Timex M-85, caliber 880/881, is a 13½ ligne electric calendar watch movement. The basic movement is the same as the M-84, however a sophisticated calendar mechanism has been added to the dial side. The calendar mechanism is unique in that it is instantaneous, taking only seconds to switch the date, and because it provides a dot as an A.M./P.M. indicator along with the date numeral.
When the date numeral is viewed through the dial window, this dot is displayed either above or below the numeral. If the dot is below the numeral it indicates A.M.; if above, it indicates P.M.
Setting the date: The date can be set manually by rotating the hands. For quick setting, move the hands counterclockwise to approximately 9:00 and then clockwise to just past 12:00.
Note: The movement underneath is the Model 84. See the Model 84 guide for the electric movement, its contact system and its train.
Everything below the numbered parts is the Model 84 electric movement.
Model 85 · Exploded View
100Plate Assembly
255Hour Wheel
2535/1First Date Holder
2535/2Second Date Holder
2539/1Date Indexing Lever
2552/1Date Cam
2557/1Date Ring
2575Date Indexing Lever Spring
2576Date Click
52535/1Date Holder Screw
52535/2Date Holder Screw
How the Date Switches
1 · The Drive
The pin on the date cam is driven by the hour wheel. At 12:00 the lobe of the cam is in a position to allow the date indexing lever to drop off, move to the right, engage and advance the date ring. Since the indexing lever is under spring tension by means of the indexing spring, this action is instantaneous.
The click (2576) holds the date ring in position. This click is also under spring tension by means of the indexing spring.
Because the date cam is driven directly by the hour wheel, instead of through a reduction gear as in most watches, the advancing action of the date ring occurs at both 12 midnight and 12 noon. The shape of the teeth on the index lever and date ring is such that each indexing will not move the date ring forward one full space: only three quarters of a full space at 12 midnight, and one quarter of a full space at 12 noon. In this way Timex has been able to provide the A.M./P.M. indicator on the date ring.
Fig. 85.3 · Calendar
Because the date cam is driven directly by the hour wheel instead of through a reduction gear, the date ring advances at both 12 midnight and 12 noon. The teeth are shaped so each indexing moves the ring only three quarters of a space at midnight and a quarter of a space at noon, which is how the A.M./P.M. indicator works.
2 · Midnight to Noon
From 12 midnight to 12 noon the date is displayed in the window with a small dot below the numeral.
Fig. 85.3 · Midnight to Noon
3 · Noon to Midnight
At 12 noon, instead of switching to a new numeral, the date ring only indexes a quarter space: the numeral moves to the lower portion of the window and a new dot appears above it, indicating P.M.
1 · a · Date cam 2552/12 · b · Second date holder 2535/2 with screw 52535/23 · c · Date click 25764 · d · Date indexing spring 25755 · e · First date holder 2535/1 with screw 52535/16 · f · Date indexing lever 2539/17 · g · Date ring 2557/1
The hour hand: The hour hand is placed in a precise angular position with the slot in the hour wheel so date switching occurs at 12 o’clock. If you remove the hand from the hour wheel, note this position so it can be replaced the same way.
Cleaning & Lubrication
All cleaning and lubricating points indicated for the M-84 should be followed for the M-85. In addition, lubricate the bearing of the date cam 2552/1 as well as the outer edge which bears against the date indexing lever, the guide pins of the date indexing lever 2539/1, the bearing and working surfaces of the date click, and the working surface of the date indexing spring 2575.
Caution: Since the watch contains permanent magnets, no attempt should be made to demagnetize it.
This guide is based on the original Timex factory service manual for the Model 85 movement.
