A sketch caught my eye - I simply had to build a model ! This was a strange thing - there is nothing known about the date, when the sketch 1 was made nor whether this engine has actually been built. I finally think that the sketch has been made in the 1850s. If you like to read more, there are further details here.

The engine is single acting without expansion. The piston rod may swing in the piston, which is quite unusual for a steam engine, and is directly coupled with the shear’s arm. A slide valve, which is actuated by some levers, controls the steam flow. The construction seems to me very massive and very straightforward. 1881 Trappen described one of his constructions like so 2:

Es galt vor allen Dingen eine möglichst einfache, dabei solide und compendiöse Maschine zu bauen, die ohne Gefahr starke Stösse bei hoher Umdrehungszahl auszuhalten im Stande war.

In my translation:

Primary goal was to build a engine as simple as possible, but solid as well as compact, which could stand heavy blows at high rpms without danger.

Though written in a different context, this seems to me to fit well to his steam driven plate shear.

The model is at scale 1:16. It is powered by compressed air (Piston diameter 24 mm).

You may find a video of the model on my YouTube-channel.

Powering a shear by a steam engine became obsolete with the quickly upcoming hydraulics, but the lever shear type (today often referred to as »alligator shear«) remained. In a 1919 published catalogue of the Mesta Machine Works 3, an american steel mill supplier, an impressive picture was published. The shear was able to cut 6 1/2”, i.e. 165 mm cold square bars. It was fitted with a clutch, so that the lever may be stopped at its upper position in order to handle the material to be cut safely. The bottom knife was in line with the main pins centerline. This was called »Low Type«.

The »High Type« on the other hand had the lower knife located above the center line of the main pin and was used to cut plate material - quite like in Trappen’s sketch.

Stand 6.7.2020