Some geographical and technical moments.
From Wikipedia about Surami pass:
Likhi Range or Surami Range is a mountain range in Georgia, a part of the Caucasus mountains. It connects the Greater Caucasus and Lesser Caucasus ranges.
The highest point is 1926 m. above sea level. The lowest and most important mountain pass is the Surami Pass at an elevation of 949 m which links eastern and western Georgia. A railroad (in the tunnel) runs through the pass, as well as the Zestafoni-Khashuri highway.
Surami pass is the part of Baku-Tbilisi-Batumi railway (Transcaucasian railway or Georgian railway).
That pass was very important for oil transportation from Baku to Black Sea ports and different cargos back. In August 1932 the first electric locomotives (8 were bought from US General Electric) opened the railway traffic along the electrified district Khashuri-Zestafoni (63 km, Surami tunnel - 4 km, a lot of turns, level difference - 500 m) instead of steam locomotives. Those US locomotives were named S10-01 - S10-08, where S means Surami; they were equipped with Soviet electric motors (licensed copies of US electric motors). Since 11.1932 till 1933 Soviet Kolomna locomotive factory together with Moscow electric machine engineering factory "Dinamo" produced improved copies of US locomotives under the name Ss11-01 - Ss11-21 (Soviet Surami) - 21 were built. 10.1933-10.1934 - 9 Italian ITBB electric locomotives were bought in addition (Si10-09 - Si10-15; Surami Italian).
Electric locomotives increased the speed along the most hard district from 12-15 km/h to 30-35 km/h, increased the weights of the trains, traffic carrying capacity (2 times), also they used effective regenerative braking which was very important along the dangerous mountain turns. 16 electric locomotives replaced 42 steam locomotives at first.
Specifications of Soviet-built Ss-type: 126 t weight, 16.48x3.05x4.825m; 6x340 kWt electric engines; 65 km/h.
Since 1952 all Surami electric locomotives (which were used also along the Perm railroad, Ural mountains) were reequipped and modernized, they were used till 1960-1979 depending on type.
(modern photo of modernized Ss electric locomotive - only two survived at Perm depot, one of them in bad condition - see Juha's photo)
(old photos of Surami electric locomotives, including my photo above)
To you again, dear Juha!