Re: Purpose of various steam locomotive parts

Actually, the steam to a dynamo is always turned on all the way. The voltage is a factor of the load and the the speed of the dynamo. If the dynamo is running and you turn the head light on, the electrical load will cause the speed to drop. The governor which is a mechanical mechanism in the dynamo compensates for the speed drop keeping it operating at about the same speed. Bulbs are rated at 34 V. If the governor mechanism gets worn out, the speed and thus the voltage may vary over a wider range which can cause bulbs to burn out prematurly if it runs high. I have never torn a dynamo apart to look at the governor end of things, so am going on what I have been told and from what I have read. I was visiting with Bernie Watts the other day who is the air pump and dynamo guru and he said he recommended setting the governor to maintain 30 volts under load (32 being the nominal std.)as the slightly lower voltage doesn't make much difference on the headlight, but prolongs bulb life.