Mon 30 Aug 2010
Posted by Marcin
Towards the end of yesterday’s blog post, we mentioned our progress on the modern steam engine. This is part of our near-term development program (and part of Proposal 2011) towards upgrading our Power Cubes and the LifeTrac infrastructre to modern steam power. Yesterday we met with Robert Thomas, one of those rare individuals who builds steam and gasoline engines for fun. He built this steam tractor replica (23 hp) of a larger 1920s farm traction engine completely from scratch, including building the steam engine from heavy-walled pipe and cutting the gears:
We began a design session. Our conclusions from yesterday are to produce a proof-of-concept prototype of a modern steam engine involving Arduino to provide electronic steam injection. This is analogous to electronic fuel injection in cars. The concept looks like this. and can download this conceptual diagram in Dia here to collaborate on the design:
It is a single cylinder, 4” bore, single-acting uniflow steam engine. The inlet port is a solenoid valve operated by Arduino, with a sensor on the flywheel to provide timing. The materials cost is under $200.
Our proof-of-concept engine design is comparable to that of the hit-and-miss gas engines from the early 1900s. Actually, we were quite impressed with these when we saw them at the Northwest Missouri Steam and Gas Show last week. These are simple, 1-cylinder, water-box-radiator cooled gasoline engines which fire only when they need to – so in idle – they fire every few seconds. For anybody who lives off-grid – these are a perfect solution for a gas-sippind device that can run all day on about a gallon of gas. Does anybody know their more specific gas consumption rates. Here’s an example of one – in the 4 second clip, the engine fired only once if you listen and watch the air intake valve move:
Here’s a basic diagram of the hit-and-miss:
Our concept simplifies the design tremendously. Strip the design down to a cylinder with flywheel, replacing the mechanical timing linkage with Arduino-controlled steam injection. This can’t get any simpler. People, it looks like we’ve got a workable DIY people’s engine design.
Outstanding questions – especially for the Arduino collaborators – are:
- What kind of position sensor is most suitable for timing purposes in this application?
- What is the maximum RPM that the Arduino sensor feedback loop will allow?
- What is the maximum RPM that the solenoid will allow?
We aim to run the steam engine in a hit-and-miss fashion – without injecting steam at every stroke. This solves the solenoid valve cycling speed issues. The hit-and-miss configuration is a low RPM device to begin with – such as 300 RPM in idle for the red engine above.
We have already showed you a similar concept in a blog post last year – from last year’s Steam Automobile Club of America meeting. This was a steam bicycle with electronic steam injection via hydraulic solenoids:
The steam bicycle above ran at 800 RPM, and there were issues with the solenoid. The developer used a hydraulic solenoid adapted for steam use – but mentioned that he expected issues with solenoid lifetime due to its design for lower temperature operation.
Water corrosion and high temperature issues may be resolved readily by using an external solenoid linked to a proper, steam-handling valve – such as a piston or even poppet valve. We would like suggestions on the best solenoid to use for this purpose, as we have not yet looked into solenoid availability. All that we know is that cycle times for solenoids are on the order of 50 ms, which is perfectly acceptable for a simple electronically-controlled steam engine running in hit-and-miss operation. Regarding the valve itself – this is old technology and requires little development effort.
Our goal with Prototype 1 is to demonstrate a lifetime-design, low-speed steam engine for remote power applications – and we will fuel it with pelletized biomass. It is an efficient uniflow design, and because it is single-acting, it is the least complicated design possible. Our approach here may be a breakthrough for remote power applications. We have not seen any low-cost, workable, affordable, appropriate technology, remote power system out there yet. The closest in this game is the Tinytech rebellion in India.
Prototype II and onwards will feature multiple cylinders and higher speed and power. We are pursuing our usual design-for-hypermodularity. This means that we aim to bring forth a veritable Steam Engine Construction Set, such that anyone can build their own engines. With this in place, you and your grandmother can then birth raw slave-power – while reducing the number of real slaves in the world.
No related posts.