setting the hands

Frequent setting of the ACCUTRON timepiece is not required because of its unusual accuracy.  Since the setting crown is seldom used, it has been placed on the back of the ACCUTRON case.  Its position is shown in Fig. 1 (left). 

Lifting the setting handle to an up-right position, using the fingernail (see Fig. 2 left) engages the setting mechanism.  When the setting handle is in the up-right position, the hour and minute hands may be set by turning the handle in either direction (see Fig. 3)

Most ACCUTRON models are provided with a spring which returns the setting handle to the flat position and at the same time disengages the setting mechanism after the hands have been set.  After returning tyhe handle to the flat position on models NOT provided with the spring, it is necessary to press in the crown, until a slight snap indicates that the setting mechanism has been disengaged.  This is the same as pressing in the crown of an ordinary watch after setting.  If the setting mechanism is not disengaged, the hour and minute hands will not turn.

The sweep second hand of the ACCUTRON timepiece continues its rotation while the minute and hour hands are being set, so that an exact number of minutes or hours may be added or subtracted.  This feature is particularly useful when traveling from time zone to time zone or when changing to or from daylight saving time.  If desired, the second hand can be set approximately on time by removing the Power Cell and replacing it at the proper time.  With practice, this can result in a fairly accurate setting.  This procedure, although relatively difficult, is the only way to accomplish a result which is not intended as a feature of this timepiece.

The above information applies to all ACCUTRON timepieces except special purpose "hack" models, such as the Astronaut and the Railroad models.  These special models provide for second-setting by stopping the timepiece while the hands are being set.  Those requiring the second-setting feature for some special purpose may have it added to any ACCUTRON model (at extra cost) by sending it to the Bulova Service Department, through the jeweler from whom it was purchased.

Unlike the gears in other precision mechanisms, watch gears are deliberately designed to provide a substantial amount of "backlash".  This back-lash is a basic requirement for reliable operation -- not an unavoidable defect or an indication of inferior workmanship.  The user is not usually aware of backlash in the gear train of a conventional watch.  The ACCUTRON timepiece, unlike conventional watches, has no mainspring to keep the gears under tension at all times, thus masking the effects of backlash.  The result is that ACCUTRON exhibits characteristics during setting which are not typical of conventional watches.  For example, when setting the minute and hour hands ahead, the sweep second hand will appear to jump ahead 5-6 seconds and may then pause for the same few seconds before resuming its rotation.  This is merely visual evidence of the backlash in the ACCUTRON gear train--the second hand having been forced ahead of the gears driving it.  Once the gears have had sufficient time to "catch up" (5-6 seconds), the sweep second hand will resume its rotation and will not have gained or lost time in relation to another timepiece.

Backlash in the ACCUTRON gear train results in another characteristic unlike conventional watches.  A sharp tap on the side of the ACCUTRON case, in the appropriate direction, will cause the sweep second hand to advance some 5 to 6 seconds, after which it will pause for the same 5 to 6 seconds before resuming its normal rotation.  The net effect is, of course, zero since the sweep second hand resumes exactly its previous indication in relation to correct time.  This "phenomenon" is a further evidence of backlash in the gears--not an indication that the mechanism has stopped.

The following simple procedure for setting the ACCUTRON timepiece permits exact synchronization of the minute and sweep second hands:

1.  Turn the minute hand ahead of the desired minute marker, then turn backward to position it exactly over the desired marker when the sweep second hand reaches the "60" second position.

2.  After step 1, turn the setting handle slightly forward before returning it to the flat position, making certain not to turn it far enough to move the minute hand forward.

The first step takes the backlash out of the gear train, permitting the minute hand to start immediately, when the setting mechanism is disengaged.  The second step takes advantage of the backlash between the setting stem and the mechanism which is turned by it--permitting the setting stem to turn slightly in either direction, as the setting handle goes down, without turning the minute hand.

changing the ACCUTRON power cell

Each ACCUTRON Power Cell is clearly marked "ACCUTRON, $1.50 RETAIL" for identification. (Boy, that's been a while ago)

This is a work in progress, more to come shortly