You can just do things. In this spirit, I am attempting to chronicle building a steam powered Ethereum node, API and website.

Speed: 5300 RPM
Voltage: 10 VDC @ 10 Watts
Voltage no load: 12 VDC
Max Current: 2.4 Amps

So I got 10 watts to work with and that's maxed out. So not much. 
Here's a pic:

To get the 5300 rpms out of the generator, 

½” pulley on the dynamo.  

For our engine, the flywheel is 2.5".  5300/5 = 1060 rpms roughly.

These steam engines typically run at 500 RPMs and the boiler works hard for it. 

So finding an engine with 6.5" dia. flywheel would be ideal. 5300/13 = 410 rpm roughly

Interesting calculations for optimizing generator RPMs based on pulley and flywheel sizes. Efficiency is key in steam engines, and finding the ideal setup is crucial for performance. Great analysis!