Details of the mail-carrying containers (Büchsen)

The mail was carried through the pipes in cylindrical containers (called Büchse, plural Büchsen). Pneumatic post stationery had to be small and thin, and folded to fit in the cans. The folding was on the vertical axis, twice, so that when the item is opened out it has three vertical fold marks; often the second fold's marks do not show. Pneumatic envelopes were sometimes rolled instead. These creases are helpful in identifying non-Pneumatic Post stationery which has actually passed through the Pneumatic Post, such as express letters sent from Vienna to other places and incoming express mail put into the Pneumatic Post for speedy delivery within the city.

Sketch of a Büchse: the steel container, open at the bottom; the leather jacket; the assembly.

The original steel containers were 158mm long by 53mm outside diameter (Ref: Österreichisches Post, Dr C Kainz, page 114); we cannot find the internal dimensions. [If the wall thickness was the same as for the aluminium containers they’d be 155mm long by 49mm diameter inside.]. They were capped by an outer jacket or casing (Hülse) in the form of a lid made from 3 thicknesses of leather. It was pushed on to the container and enclosed about two thirds of it, thus securing the contents for their journey and providing a seal with the walls of the tube so that the compressed air or vacuum caused the container to travel easily along the tube. Such a can took 20 letters, 25 telegrams, or 30 pneumatic postcards; the weight limit was 10 grams per item. The photographs below (from the Post und Telegraphenmuseum, Vienna) illustrate the several types of containers used. The photo also shows special items of hardware used to stretch the leather casings, to clean the tubes, to remove condensation from the tubes by surrounding a driver with a sponge, and to remove a blockage

During the life of the system (1875-1956) small improvements were often made. In 1891, cans made of the then novel material aluminium were introduced to reduce the dead weight. They were 130mm long by 52mm outside diameter; see Turner "Die Stadtrohrpost in Wien 1875-1956: Technische Beschreibung", his page 74 but document page 9, where he says this is the size of "the latest version". The 1932 "Operations Manual" vol 2 §13a states that the side walls were 2mm thick, the end 3mm: making the internal dimensions 127mm long by 48mm diameter. Indeed, they had a wooden test-piece, 124mm x 48mm dia, which had to fit inside. These cans held 15 letters, 25 telegrams, or 30 cards.

1. Steel container and leather casing. These were the originals; containers made of wrought iron were tried but wore out very quickly. 2. Steel driver with leather tailpiece. 3. Steel container. 4. Steel container. 5. Wooden driver with leather tailpiece. 6. Wooden driver with leather casing and tailpiece. 7. Tube-cleaning driver with sponge washer to absorb condensation. 8. Leather-casing stretcher (with leather casing). 9. Light leather container and casing, introduced from Berlin in 1891: more suited to the vacuum tubes. 10. Rubber casing with steel container. 11. Leather casing with wooden base and steel container. 12. Obstruction remover.

13. Steel container-driver (these were hollow to accommodate mail). 14. Leather container and casing. 15. Leather container-driver. 16. Aluminium container with leather casing: first experimental type. 17. Aluminium container: experience showed that these needed a strongly reinforced base. 18. Aluminium containers with leather casings. 19. Aluminium containers with leather casings. 20. Aluminium Container-driver. 21. Leather container-driver. 22. Tube-cleaning driver - early example. 23. Tube-cleaning driver - later model. 24. Leather container, worn out through use. 25. Steel driver. 26-28. Three casings from the London Pneumatic Post.

Some sections of pneumatic tube with a container in position.

Two Büchses on display in the Vienna Technical Museum.