Ricoh R20?

 
Ricoh R20?

Ricoh R20?

Description

The japanese manufacturer Ricoh produced mainly in the 1970ies a number of selfwinding movements, which are mostly unknown in literature and also online.

The 12 3/4 ligne (29mm) selfwinding movement shown here, which has got no date correction pusher, is probably the caliber R20.

base plate

base plate

As common on most japanese movements, the base plate shows a bare but technically well made construction where all important bearings contain rubies. You also see the reserved space of the metal rim of the oscillating weight and the two pits, which are used for fixating the movement in the case by clamps.

base plate with minute wheel

base plate with minute wheel

This movement still uses a center minute wheel - a very classical and proven construction, which was technically no longer state of the art in 1970.

gear train

gear train

As the center minute wheel already implied, the whole gear train does not offer any surprises: With third wheel, center seconds wheel and the escapement wheel it uses the classical gear train.

side view of the gear train

side view of the gear train

The Ricoh caliber shown here has got a speciality: A lateral lever with a very short fork:

lateral lever

lateral lever

Not only the shape of the lever is remarkable, it is responsible, that there are no banking pins on the base plate. Instead, the lever has got a hole, into which a single pin from the main plate intervenes and limits the maximum way of the lever:

lever

lever

The pallet lever, which regulates a swiss lever movement, is driven by a two-leg anular balance, which beats still slowly with 18000 A/h and is secured in two Parashock bearings.

gear train of the selfwinding mechanism

gear train of the selfwinding mechanism

The selfwinding module is placed on top and next to the movement bridge and is constructed as a rocking bar changer: The center, ball beared oscillating weight drives the rocking bar changer, which depending on the rotating direction interferes either directly with the next reduction wheel, or with an 1:1 change wheel inbetween. A click spring ensures, that the reduction wheel can only turn in one direction and so wind the mainspring with two additional reduction steps.

On manual winding, the rocking bar changer decouples the oscillating weight.

inner side of the selfwinding bridge

inner side of the selfwinding bridge

If you look excatly on the inner side of the selfwinding gear bridgt, you can see the ratchet mechanism, which engages with the first reduction wheel and blocks it, when it tries to turn “backwards”. On top left, you see the axle for the last transmission wheel, which interferes with the ratchet wheel.

lower side of the oscillating weight

lower side of the oscillating weight

As already written, the oscillating weight is ball beared. Its sprocket engages with the rocking bar changer of the selfwinding mechanism.

movement view without oscillating weight

movement view without oscillating weight

Except the rocking bar changer and the last, slow turning, transmission wheel, all other wheels of the selfwinding mechanism are ruby-beared.

empty dial side

empty dial side

On the empty dial side you the odd constructed yoke winding system. Its setting lever spring should keep the flying setting lever in position. This one is only beared on its upper side, otherwise, it slips(!) on the dial side into its position, supported by its prolonged arm at 4 o’clock.

On the specimen shown here, this mechanism no longer works, but it is unclear, whether it is just worn out, a bad construction or if some parts are missing.

open calendar mechanism

open calendar mechanism

The calendar mechanism is also an unneccessiary complicated construction: The switching wheel at 12 o’clock has got a moveable mounted finger, which is held in position with a super tiny spring(!). This spring is attached between two micro small holes, one in the finger and the other on the disk, virtually impossible to mount after dissection. On the pro side, this mechanism allowed half-fast correction of the date by turning the hands back and forth a few hours.

Ricoh R20?: Dial side

Ricoh R20?: Dial side

The date ring is Der Datumsring lies relatively far inside this movement and compensates its large diameter.

Technical data

Manufacturer:Ricoh
Caliber:unknown
Size:12 3/4''' (measured: 29.0mm)
A/h:18000
Number of jewels:21
Escapement:Pallet lever
Balance types: Nickel anular balance
Shock protection(s): Parashock 2 (Citizen)
Balance bearing / direction hairspring:Counterclockwise
Moveable stud:yes
Adjust mechanism:Hairspring key
Construction:
  • lever
  • escape wheel, seconds wheel, third wheel
  • center minute wheel
  • mainspring barrel
Construction type:solid construction
Winding mechanism:yoke winding system
Features:
  • SCD (direct center seconds)
  • AUT (selfwinding)
  • QG (date indication (aperture))
  • RDR (date corrector)
Inventory number:18003

Usage gallery

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