In 1932, Hilding Carlsson and his mechanical workshop in Umeå received an order for a large two-axle ‘dressine’ from SJ. The dressine was to be used in tourist traffic on the Ore Line and the northernmost part of the Inland Line. It had 14 seats and was box-shaped. The dressine aroused interest at Uppsala-Gävle Railway, which was looking for a cheap vehicle for its Orrskog-Söderfors branch line, and they decided to order a similar vehicle, albeit a larger one. The delivery took place in 1933 and with 24 seats and an engine of 75 horsepower, it was no longer sensible to call it a dressine – now the rail-bus was definitely born!
In 1934, SJ ordered four more two-axle railbuses, one of which was intended for tourist traffic and had a roll-off roof. They became the type Yd (later changed to just Y) and were, as before, box-shaped; but the upper part of the front was tilted slightly backwards. The eye-catching radiator and the high-beam headlights gave the vehicles a distinctive look. This first test order turned out well and Hilding Carlsson delivered a total of about sixty two-axle railbuses to SJ until 1938.
From 1935, Hilding Carlsson changed the design so that the entire front was tilted backwards and thus the classic HC railbus was created. The look became such a strong signature that Hilding Carlsson even used the front in their logo. The railbuses proved to be a good and cheap complement to conventional trains and SJ bought a long line of railbuses during the 1930s and 40s. At first, the railbuses were used mainly in Norrland, but gradually the use also spread to the rest of the country.
Many private railways also bought railbuses from Hilding Carlsson. Normal-gauge lines include TGOJ, Bergslagernas Järnvägar, Gävle-Dala Järnväg and Halmstad-Nässjö Järnväg; but it was above all, the narrow-gauge lines that, with their often poor economy, saw the rail bus as a saviour. Among the buyers were Halmstad-Bolmens Järnväg, Ölands Järnvägar, Gotlands Järnväg, Västergötland-Göteborgs Järnvägar, Mellersta Östergötlands Järnväg and Norsholm-Västervik-Hultsfreds Järnvägar.
In 1937, Hilding launched the bogie railbus. It had more seating and better running characteristics and also the toilet became standard. Initially, the same six-cylinder Scania petrol engine was used as in the two-axle rail buses, but soon it was replaced by a stronger eight-cylinder diesel engine. At the same time, the body was made a little longer and the number of seats was increased. The stronger railbuses meant that the production of trailers took off and different types with varying spaces for passengers, goods and mail were developed. The first two-axle goods trailers had been built in 1934, but now the trailers also got bogies.
The first bogie railbus was bought by Halmstad-Bolmens Järnväg in 1937. The price was about SEK 45,000 in the monetary value of the time. A total of 177 normal-gauge bogie railbuses of type Yo, Yo1 and Yo1s were delivered to SJ between 1938 and 1950. In addition, in connection with the nationalisation of the private railways in the 1940s, SJ had to take over narrow-gauge railbuses with 891 and 1067 mm gauges. Almost all HC vehicles delivered to private railways ended up with SJ, which received a rich assortment of, above all, various trailers.
The railbuses did not have equipment for multiple driving, but sometimes it still happened that trains still ran with several railbuses. Each railbus was then manned with its own driver. The bodies of the railbuses consisted of wood clad with sheet metal. This soon proved to be less successful. The wooden frame required a lot of maintenance and was less resistant to accidents and SJ decided as early as the mid-1940s to instead invest in rail buses with steel bodies. While waiting for a new railbus to be constructed, however, a few more orders were placed and the last wooden railbus was not delivered until 1950. The last series were given a different design with reinforced and enlarged bodies and the standard rail vehicles therefore received the suffix “s” (s = större (larger)).
All HC railbuses had a rather spartan third-class interior (current second-class) with bench seating. Some railbuses or trailers with second class (current first class) were proposed but never built because the vehicles were mainly used in local and regional traffic where the need for different classes was small. However, four of SJ’s bogie rail buses received a more lavish interior for use in express trains on the Östersund-Gällivare section. Even a ‘sleeper’ trailer had been proposed! The colour of SJ’s railbuses was yellowish white with a dark green decorative line under the windows. An exception was the narrow-gauge railbuses on Gotland, which were allowed to retain their dark red private railway colour even after SJ’s takeover in 1948. After the railway on Gotland was closed in 1960, some of the red railbuses were sent to the mainland for use on the Uddevalla-Bäckefors section.
The two-axle railbuses were scrapped in the mid-1950s and many of them were converted into track work vehicles. The service life of bogie rail buses became shorter because most of them could be replaced with the new steel rail buses of the Y6 type as early as the 1950s. By the early 1960s, most HC vehicles had been scrapped, both normal-gauge and narrow-gauge. SJ’s last Hilding Carlsson railbuses, Yo1s 629 and 666, were used until 1969 in internal transports to and from the SJ school in Harlösa in Skåne. A few HC railbuses remain as museum vehicles, including at the Railway Museum, the Veteran Railway Association, the Åmål-Årjäng Railway Society and the Anten-Gräfsnäs Railway. Furthermore, a few were exported to neighbouring Norway and Denmark.