Conservation in action: The German 25 cm trench mortar (Minenwerfer ) 1917

In 2004 a former member of the Royal Armouries staff collected this German 25 cm trench mortar from a Farm in Norfolk, where for a number of years it had been exposed to the elements and was in need of some tender loving care.

conservation2

conservation1

On site at Royal Armouries Fort Nelson in Portsmouth, the trench mortar remained in the Artillery Hall, where it continued to suffer from the adverse conditions until Mick Cooper (Fort Nelson Technician)  began the lengthy conservation process last year. Mick jumped at the opportunity to restore the rare object, and was not deterred by its level of degeneration.

On initial inspection, due to the extensive level of corrosion, the mortar had completely seized.  To aid in the dismantling process, a releasing agent was used. The Mortar was dismantled into three main sections: the gun, the chassis and the wheels. PH neutral chemicals and sensitive abrasive cleaning techniques were primarily utilised to remove the corrosion, however due to the extent of the decay, grit blasting was applied to larger areas. The chassis had deteriorated extensively, both the rear end and the middle section were missing. New rear chassis sections were reconstructed out of fiberglass.

The wheels comprised of different sections and materials, including a metal tyre and wheel hub, and wooden spokes and fellies. Once removed from the metal tyre, the wooden spokes were initially rubbed down and put in the freezer for a minimum of one month to kill all bugs and termites.

Mick sourced wood to manufacture the five fellies and two spokes which had rotted and obtained a high level of satisfaction in applying his previously learnt wheelwright carpentry skills into practice.  The metal tyre and wheel hub were fortunately intact. Sensitive abrasive techniques were used to remove any traces of corrosion.

When all areas had been successfully stripped back and restored where appropriate, a zinc phosphate primer and authentic paint was carefully applied to all metal and wood surfaces.conservation5

conservation4

Now, fully reconstructed, the 25 cm Minenwerfer looks robust. It is carefully positioned in the Voice of the Guns to prevent future risk of corrosion.

25 cm trench mortar (Minenwerfer )
25 cm trench mortar (Minenwerfer )