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          Michaelis's concrete calculator

Michaelis / Kvasnicka reinforced concrete calculator (Dimensator)
Click photo to enlarge
    The copy on this unusual device tells you that it is a Dimensator, produced in Prague by architect V. Kvasnička. The lady who sold it to me, having the advantage that she spoke Czech, added that it is a reinforced concrete calculator, and was made around 1925. Since she could add no more insight, I scoured the web for Mr. Kvasnička and the Dimensator and came up with nothing... Fortunately I mentioned this to my friend Nicola Marras, a fellow collector from Italy, who knew one crucial detail: Kvasnička did not invent this tool – he copied and translated it into Czech from an original devised by one William Michaelis.
Michaelis / Kvasnicka reinforced concrete calculator (Dimensator)
Click photo to enlarge
    Michaelis was a German chemist who played a role in the development of concrete technology: apparently he found in 1893 that hydrated metasilicates form a gelatinous mass that dehydrates over time to harden (hey, don’t expect me to explain this – I assume it’s a good thing for making concrete). Subsequently, soon after the turn of the century, he constructed a set of two calculators for computing the parameters of reinforced concrete, of which I have the Czech copy of one.
    There are two other exemplars of this device that I know of. A German version of one unit is in the collection of Nicola Marras, who provided these two photos of it [1], [2]. And a Spanish version of the two units is exhibited online by Ugo Manieri, also of Italy, who acquired them in Buenos Aires. Manieri’s article provides high resolution scans of the devices and of the Spanish instruction manual. All these units look to be of rougher construction than the Czech version, though the functionality is identical.
    The two-sided device shown here is 18.5 cm long and 6.5 mm thick, probably made of wood on the inside with what looks like shellacked paper (or perhaps celluloid) scales and a celluloid cursor that rotates about a pivot. It comes in a lovely cardboard box that matches its unusual shape, and bears a picture with a recognizable silhouette of Prague castle.
    As for V. Kvasnička – turns out he was Vilém Kvasnička (1885 – 1969), a successful architect with many buildings to his name in Budapest and Prague. He must’ve had good use for the Concrete calculator bearing his name.
Exhibit provenance:
    Ebay, from a seller in Prague.
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