The Wild Heerbrugg ARK1 (and probably the ARK 2) is similar to the GAK1 / GAK11 but includes a goniometer (horizontal scale and vertical indication through moving mirror). The instrument is hard to find; this is a former Dutch Army version. In a later buy I managed to obtain the documentation and the (modified) converter including the battery. The later buy was no longer working (the gyro would not spin up) but fortunately had an intact wire making this one a working instrument that can actually be used for determining true North.

The converter is modified for the Dutch Army and has a digital stop watch. I am not sure if the converter is still running as I am missing a power cable which I still need to make. The unit also runs on 24V rather than the one for the GAK11 which runs on 12 V. However, the output is the same as essentially this is a GAK11 with a horizontal scale and box compass. The instrument seems to run OK but I still need to work out how to operate it for good results. The modification to the converter is an added stopwatch rather than a separate mechanical one which is in the documentation as an option. The start / stop switch is missing from the converter but seems to be a simple closing contact.

The converter nog only powers the gyroscope but also lights the various scales which are completely unreadable without the light indicating that the instrument was never intended to be used without the converter (and thus the gyroscope). The ARK1 was further developed into the ARK2. Based on available documentation the main difference between the ARk1 and the ARK2 seems to be the vertical scale. Where the ARK1 has a single scale, the ARK2 also has a fine reading for the vertical scale making it more useful as a goniometer / theodolite.

The black and white photographs are from the original Netherlands Army documentation (Codificatiebureau Materieel - CoBuMa) but unfortunately show the device before adaptation. As a result the stopwatch display and start / stop button are not shown but rather the original GKK3. Interesting are the pictures of the internals of the GKK3. There seem to have been two versions one with a large middle section, the other one smaller. The difference is unclear.

Other collections:

Brooke Clarke