Orfina’s Porsche Design
chronograph in the early 1980s was another functional
(and minimalist design) that used the Lemania
5100.
"Effective,
Precise, and Reliable… In short:
Unbeatable"
Fortis, Sinn, and
Tutima insisted on the continuation of production because
the 5100 is the only calibre that met their military
requirements. The 5100, due to its construction, is the
only chronograph movement that can withstand large shocks
without its chronograph seconds hand stopping. This is
because its chronograph mechanism is driven directly
unlike most other chronographs which use an intermediate
wheel. The calibre easily withstands acceleration in
excess of 7G without appreciable loss of accuracy. Its
ruggedness is legendary; the calibre easily absorbs
shocks and blows. The calibre also maintains its accuracy
over long periods without servicing. Service intervals
from four to seven years have shown to be
sufficient.
“Antiquated
but Reliable”
The Lemania 5100 demonstrates
other unusual constructions. The navette-type chronograph
mechanism is fitted not as usually between the base plate
and the automatic winding system but between the dial and
the base plate instead. The rotor winds in one direction
only over the reduction gear and runs in a hard iron
bearing instead of jewels. The ratchet wheel under the
rotor transfers the rotation of the rotor to a reduced
wheel. The yoke spring on the rotor doubles as a click.
The above clearly shows that the Lemania 5100’s
antiquated construction, while simple, is nonetheless
reliable and functional. The clutch wheel is also made
out of nylon, another tribute to rational production. The
large mainspring barrel continues the rugged design
philosophy of the movement. The balance is also quite
large for a high beat movement running at 28’800A/h.
The calibre uses the reliable and space-saving Triovis
regulator. Kif-Flector shock absorber was chosen instead
of the more usual Incabloc shock absorber seen in ETA
calibre. At 8.2mm, the 5100 is 0.3mm taller than the
ETA-Valjoux 7750. This makes the 5100 the tallest of
today’s chronograph calibre.