Places to get materials and related hints

• onlinemetals.comServing the Small Quantity Market with ordering over the internet.
• aeroconsystems A nice looking place to get all sorts of material from, but was particularily recomended for its graphit section Graphite by Rick Topf who had good experience using their surplus grade for Stirling pistons.
• http://www.graphitestore.com has different types of graphite bushing material
• Jerry Howell's menu. Click on the link "Hot-Air Engine Power Pistons" to read about what an experienced builder of hot-air engines has to say. Recommends graphite piston in stainless steel or brass.
• http://www.espi-metals.com/metals/catcarbon.htm Good sourc4e of information about properties of different types of graphite.
• Airpot Cooperation Among others they sell piston/cylinder units of different lengths and diameters with the piston made out of carbon-graphite and the cylinder made out of Pyrex glass. Max operating temperature 260°C
• The Kyocera company has an automotive ceramic division that is making a range of components that are suitable for use in a variety of hot air engines. They have silicon-carbide heater tubes that high conductivity and maintain the same mechanical properties up to 1400- deg C (over 2500 deg F). Their silicon-nitride components can handle thermal shock loads of up to 750-deg C (over 1350-deg F). They are also offering ceramic turbine wheels as well as a range of heat exchangers.
  These new materials and components allow for more efficient hot-air (closed-cycle, heat-exchange, reheat/intercooled Brayton) turbine engines, using higher engine pressure ratios (6:1 or higher), to be developed. Concentrated solar thermal power and biomass combustion can be used as heat sources. In arid regions where steam operation may be a problem, a new generation of higher-efficiency hot-air turbine engines could be used in electrical power generation, possibly even some transportation uses (railway propulsion, marine propulsion).
• chromed and honed steel tubes and rods plus piston gadgets
• A meesage from Rick Topf concerning seals on pistons,30 Jun 2006
  The design of the piston seal(ring) depends on the size of the piston and the pressure it is intended to seal. The Sunpower Ringbom produces substantial pressure so it is most likely going to use a backing to keep it pressed against the cylinder wall. It is also probably not just Teflon, but a fiber reinforced PTFE material like Rulon. This is needed for abrasion resistance. Small or low pressure engines must have lower friction seal designs. One good design is a lip seal with a silicon rubber backing. Look in the photos section of search the message archive for more about these. Teflon and related PTFE products can withstand 400-500 F without melting. They do get a "heat set" that causes the seal to not fit properly after an initial heating. This is why they need a backing ring. Viton is a good choice for its own high temp. abilities. It can be expensive however. I made a engine last winter that use just a viton ring for sealing a 1.25 inch bore. With just the right groove and a very smooth bore it sealed better than Teflon or graphite. Look for help on these from the model steam engine groups.
• Comparing properties of various Teflon compounds, specifically PTFE, FEP, PFA , ETFE. Technical data shown include coefficient of dynamic friction, thermal properties etc. (Might be viewable only with IE).