06/06/2016 U29. 18". Compressed Air Tank. Tinplate Clockwork Diving Submarine.
This is the U29, its a small version of its real big brothers in every sense, this boat has a floodable ballast tank in its nose but also takes its own supply of compressed air with it beneath the surface. In the left pic, the first key winds the ballast control timer (up to 60 minutes). The last key winds the motor, the taller of the two middle stanchions is the compressed air filling point, the other is the ballast tank vent pipe. The air tank is charged with a standard bicycle tyre pump.