Greetings.

Does anyone have a source for carbon discs (1/8" thick by 2-5/8" diameter) for a Carbon Pile Regulator?

Thank you!

Brent,

Not sure if they can provide exactly the material you need, but we have purchased graphite rods from St Mary’s Carbon. https://www.stmaryscarbon.com/.

Richard

Please contact me at the Illinois Railway Museum, coach dept . We have some new and used ones. Thanks Roger

Greetings!

Thank you for the timely responses. We contacted St. Mary's Carbon and they are producing brand new discs per our engineer's drawings/specifications.

That is a very interesting device! Thank you for posting the
picture of it. Not to hijack this thread, but could you
please explain what the specific application for this regulator is?

I am asking because right now I am collecting up as many
ideas as I can regarding various types of voltage and current
regulators.

Chuck

That device acts as a high wattage variable resistor. They were commonly used to adjust the intensity of interior lights in passenger cars. They can also be used to adjust the excitation voltage into a generator field winding. By adjusting the field current at lower power levels is if possible to regulate the much higher power output of a generator. There are other uses, any place you need a rugged, high wattage adjustable resistor.

Each carbon disc acts as a resistor, by compressing the discs together (changing the length of the stack with a lever, spring, bolt, etc.) the discs make better electrical contact.

When the discs make better contact the total resistance of the stack goes down.

If this is in series with a string of electric lights the changing resistance regulates the current and hence the brightness.

In some cases these regulators would be in the electrical cabinet at the end of the car and a knob extending outside the cabinet would allow the Conductor to dim the lights at night.

That is my understanding, I have seen them, but never designed a circuit using them they are way before my time.

See here; http://www.freepatentsonline.com/2427805.pdf

Cheers, Kevin

From Wikipedia:
The amount of current flow through the exciter shunt field is controlled by a resistance, which is made up of carbon discs or a carbon pile packed into a ceramic tube.

The resistance of the carbon disc is varied by pressure change. This pressure is controlled by a magnetic field produced by an electromagnet coil. The current for this electromagnetic coil is supplied through the transformer and rectifier circuit from alternator output to the terminal board. This means that as the load changes the alternator voltage also varies. The strength of the electromagnet also increases or decreases due to this load change, resulting in the change in the compression on springs and thus the resistance of the carbon pile.

Kinda true except it would be a DC generator, not AC (alternator) and thus no rectifier. Old car electrical systems were DC. But the gist of that is correct.