“Bollinger-Bagger” model, built in 1839

 © Technisches Museum Wien, Photo: Peter Sedlaczek

In 1839 mechanical engineer and machine manufacturer Samuel Bollinger built the 13 ft (= 411 cm) working model of a steam-powered dredger. 
Vienna’s Polytechnical Institute (the present-day Vienna University of Technology) bought the model for 1,500 florins. The model itself was based on two dredgers of the imperial & royal public treasury (Ärar) used for clearing the seaports of Trieste and Venice. They had been built to plans by W. M. Pirswei and J. I. Ruston. In 1839 the public treasury commissioned Bollinger to build two larger models.

In the early 19th century machine models often had a dual purpose, acting as a design model and a scale model.
As the first director of the Polytechnical Institute, Johann Josef Prechtl (1778 – 1854), remarked, “The models are built to a scale such that all component parts are proportionate and of a size such that even the smallest constituent parts are properly represented in relation to the others; so that every full-sized execution of the machine may be undertaken on the basis of these models.”

A dredger has two modes of operation. Longitudinally it operates in a way similar to a plough; if it is shifted laterally during excavation, it operates with a shearing motion. The bucket-chain excavators used around 1860 were still equipped with a mechanically driven feeding winch, with a ploughing mode of operation. By contrast chain-and-bucket excavators move laterally and therefore have a shearing mode of operation. This allows the excavation of a channel with a predefined length, width and depth.

The model on show at the Technisches Museum Wien (Vienna Technical Museum) illustrates the shape of the bucket-chain dredger. It has a forward anchor and two transverse anchors, which are raised and lowered alternately by two drum winches. The shearing action is achieved by one winch reeling in its chain, causing the bucket ladder with the excavating buckets to be dragged through the dredged bank. Meanwhile the passive winch on the opposite side slackens off its chain accordingly.


Technical data

Model dimensions: 402 x 133 x 128 cm
Drive power (of the original): 12 hp
Scale: 1:8

Inv.Nr. 1651

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