By HaJo Franken

I saw a picture of this machine for the first time in Wagenbreth-Düntzsch-Gieseler's book The History of the Steam Engine. I was fascinated by the sweeping lemniscate straight line and I thought that this should result in a nice sequence of movements.

In 2007 I took photos of the restored machine in Gera during a visit to the Werdau Steam Days and took the main dimensions, as far as possible. All other dimensions were then reconstructed from the photos.

I also received an excerpt from the invitation of tenders for the restoration from the building regulations office of the city of Gera, which unfortunately only contained a few main dimensions. The aim of the restoration was not to get the machine moving again, but to preserve the state of preservation after removing the dirt, rust and old layers of paint (colourful ‘playground paint’).

It said: "It is to proceed as gently as possible. The bare metal parts are to be processed in such a way that they become metallically bare (rough valleys can remain dark). Under no circumstances are primary products of manufacture and use (grinding marks, burr formation, turning marks, run-in marks, etc to be changed."

Brief history of the Trestle Steam Engine  with lemniscate guidance

of the former Morand & Co. combed wool spinning mill in Gera:

  1. 1833 Manufactured in a French machine factory

  2. 1885 Last day of operation, then installation in the factory's depot

  3. 1937 Donation of the machine to the city of Gera by manufacturer Heinrich Brossen and installation in the courtyard of the adult education centre in Talstraße on the occasion of the city's 700th anniversary

  4. 1999 Dismantling of the steam engine and subsequent restoration

  5. 2000 Installation in the courtyard of the Amthor-Passage

The original engine in the Amthor passage.

After long deliberations on the scale, I decided on 1:10, also because my Sachsenberg, model in the Blankenhain Museum, corresponds to this scale.

The problem was to find a compromise because on the one hand the size of the flywheel with 330mm diameter exceeded the limits of my machines and on the other hand the small dimensions e.g. on the throttle valve my precision mechanical skills were too strained (screws 1.2mm here - I used M2).

Flywheel with square hub attached to the shaft with flat wedges as in the original, is fun to align (four attempts about two hours each).

Lemniscate straight line.


With the centrifugal governor, the speed of the machine can be set to 50-60 rpm


Throttle valve and gate valve


A few more dimensions in mm:

Height 560

Width 360

Flywheel 320 x 8

Column height 340

Cylinder 117 x 18

Stroke 100

Like the original, the valve body with a length of 120 mm contains a double valve. This means that the inlet openings are opened and closed at the top and bottom by means of a slide.

The two slides are connected by a bridge on the original and directly with the slide rod on the model.

Machining was all milling and turning which was not recorded, apart from machining the large flywheel. See separate MEWS article.

See also https://www.hjfmodellbau.de



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