The Tracked Post Bus
1927 · Half-Track Alpine Coach · Work 735 of 1,871
An alpine post bus with rubber crawler tracks of 1927 on a snow-covered pass road in Graubünden in Switzerland, a long-bonneted motor coach, its body deep yellow with plain smooth painted panels, glazed side windows under a folding roof of black canvas, in front two spoked wheels in snow chains, at the rear on each side a track unit, one large spoked wheel between two smaller ones inside a black rubber band forty-two centimetres wide, behind the coach a double track in fresh snow, grey canvas mail sacks on the rear rack, the driver in a fur cap and leather coat seen from behind at the radiator, low winter sun from the left.
- What it was used for
- Post buses with track drive kept winter services running in the Swiss mountains before snow blowers cleared the roads. The Museum für Kommunikation in Bern sets out the sequence: in 1924 a trial with a drive by the Swedish postal works foreman Nyberg on the Chur - Churwalden route; in the winter of 1925/26 regular service Chur - Lenzerheide with 2 plough vehicles and 4 alpine coaches; in 1926/27 six more converted vehicles and about 10 new ones delivered with tracks from the factory. St. Moritz - Maloja and Reichenau - Flims were also worked. The alpine coaches were Saurers; the licensed version of the drive was designed by the PTT together with the federal works at Thun; the rubber tracks were 42 cm wide, 10 cm more than the Swedish model.
- What was new
- What was new for the Swiss post was adapting the vehicle to the snow, taken over from the Swedish Post - and it did not last. The same source calls the Swedish drive tested in 1924 "zu schwach dimensioniert", too weakly dimensioned, for the Chur - Churwalden mountain route; the mechanism was unusable after a short time even once strengthened; on the Maloja road the system reached its limits in heavier snowfall; and maintenance was far more demanding than on cleared roads. The barb: the answer lay not in the vehicle but in the road. First a rotary snow blower borrowed from the army, then from 1927/28 one of the post's own from Hanomag/Saurer. Most Nyberg-drive vehicles were scrapped, converted back or rebuilt around 1933/34; the surviving P 1820 was converted back in 1933. A trial with 2 Citroën Kégresse followed in 1929.