The schematic for our Steampunk Geiger counter is shown in figure 2.
I already explained the saw switch function. We apply 18 volts (from two 9V batteries wired in series) to the primary windings of our step up transformer through the saw switch.
The on-off cycling of power to the transformer creates the inductive high voltage generated in the secondary winding of the transformer that passes through a diode D1 and charges capacitor C1. The zener diodes D2, D3, D4 and D5 regulate the voltage to 450 volts for the GM tube.
When the capacitor is charged, we can siphon off 150 volts from the junction of D3 and D4 to light a neon bulb. The neon bulb indicates when we have a full charge on our capacitor, and optimum power going to our GM tube, at which point the user can stop rotating the saw switch.
You can build or buy a Steampunk case for your geiger counter. I decided to buy. I found a suitable SteamPunk design box on ebay, see figure 3. The case was a little small, so it made for a tight fit. This enclosure cost $21.99 with free shipping. Search using terms Steampunk box on ebay.
In our Steampunk Geiger counter, the lever switch will be mounted under the acrylic saw, which are both mounted on the case. The acrylic saw must be able to rotate freely. To create a free spinning saw I assembled the following parts: the acrylic saw, a top brass gear(for decoration only), 8-32 machine screw of suitable length, (2)8-32 nuts (not shown), #8 split lock washer (not shown), flat washer (not shown) a brass tube whose inside diameter allows the 8-32 machine screw to pass through and a thrust bearing, see figure 4.