http://www.modeng.johnbaguley.info/locos/25inch/Helen%20Longish/helen.htm
http://www.airheart-brakes.com/pdfs/MasterCylinder_Selection.pdf
https://blog.wcbranham.com/how-to-size-a-caliper-disc-brake
https://cdn2.hubspot.net/hubfs/2024592/Brake_Sizing_Sheet.pdf
https://www.youtube.com/watch?v=SDgn6ilRhKA - Fired heater design course
http://www.chaski.org/homemachinist/viewtopic.php?t=96288 - PTFE valve discussion
https://modeleng.proboards.com/thread/13000/piston-valves-rings - More PTFE valve discussion
https://www.modelenginemaker.com/index.php/topic,5215.0.html?PHPSESSID=9b407b661474ab14881613d99d233d46 - Yet more PTFE valve discussion
https://www.modeng.johnbaguley.info/locos/25inch/Helen%20Longish/helen25.htm - John Baguley's PTFE adventures
https://www.fluidsealing.com/wp-content/uploads/Compression-Packing-Handbook-4th-Edition.pdfÂ
https://www.donashton.co.uk/html/stephenson_s_gear.html
http://www.billp.org/Dockstader/ValveGear.html