Engine Design basic questions

[kf2qd]

I would recommend starting with a 2 stroke, fewer parts, and run it on glow fuel, or model airplane fuel. You get to play with fits and different design ideas. I have posted here somewhere a .60 CI 2 stroke that is a nice first project.

 

[Bentwings]

Hi Andrew, On setting the eccentric for a steam engine, you should not go far wrong when set 15 degrees ahead of BDC for exhaust valves just opening... or inlet just opening at TDC? - I have used both as a starting point then tweaked to optimise depending on use of the engine.
Of course, a lot depends upon the geometry of inlet and exhaust opening and closing times, arrangement of eccentric linkage, etc. - Which is why there are so many different geometries of valve gear, Joy, Stephensons, Walschearts, etc...
The Steam equivalent of the piston ported "valve-less" 2-stroke IC engine would always be the Oscillating engine, - which can be made without worrying about valve timings. Just drill ports accurately according to "the book".
N.B. Joining engines in series, as suggested by our old friend Bentwings, can cause some strange effects in flexible couplings by different cylinders getting a bit ahead or behind others, and setting-up some terrible (destructive?) torsional vibrations.... When a resonance occurs they fight each other until the coupling is over-stressed and fails. Far better to have torsionally rigid couplings with "perfect" alignment.

I suggest you do as "a majority" of modellers have done.... Make a small steam engine - and make it run and power something. This will prove your skills at making things like pistons and bores that fit properly, crank-shafts that are not misaligned, valves that seal, bearings that do not rattle or seize, etc.
Then you can use the proven skills to make small IC engines. Start with a piston ported 2 stroke to prove you can make a runner with good compression.
A half-inch to 1 inch bore and stroke is a reasonable starter model - steam or 2-stroke IC - before you get too ambitious and go smaller or bigger! (I started with a 1/2" bore and 3/4" stroke V-twin steam oscillator - because the kit was cheap. Learned a lot!).
Then think about 4-stroke IC valves and valve gears! Modelling is an education in precision manufacture, so always use the best tools and materials you have or can afford.
And always ENJOY the hobby. We all make mistakes - then discuss solutions or lessons learned on this website. A good way to learn is from mistakes - hopefully others' mistakes, not your own.
K2

I have a threaded blocker that is micro adjustable that I can accurately measure the piston TDC and BDC

Then I can measure the exact eccentric position . I managed to get one engine to run on pretty low air pressure , about 30 psi. Steam having more expansion ability could cause this to change I YHINK. The hard part is getting the port location as it is completely enclosed soni have to use a deep method the piston Orr pistons fit pretty snug so by carefully turning the flywheel an listening I can hear the ports start to open or close once I get some relationship I should be able to duplicate it across the engine 2. I also have a “ joining flywheel with longer hub so I can have a more ridged connection. I also have several beam couplings that are pretty flexible so I may use these . I have half a dozen stepper motors I planned as generators forvthe steamer to drive plus some LED lights so the little steamer has a Job”. My whole project has gotten out of hand as I now have 6 model steam turbines set up to drive “ scale” dynamos I’ll have a” desk top power company”. May need more LED” lights my ultra low noise compressor works hard to keep up with the turbines . I have different couplings available as well as some gear belts and spring belts. For speed reducers. The turbines spin at 5400 rpm but are pretty weak so I had planned on a 3:1 reduction this would speed them to increase the drive torque to the dynamos they put out about 12 volts so I still need better speed control for the turbines . I’m thinking of needle valves maybe a gang of small ball valves . The turbines have a Mickey mouse air or steam connector so I’m in process of making a better one for the application. Always something I guess

 

[Bentwings]

Hi Andrew, On setting the eccentric for a steam engine, you should not go far wrong when set 15 degrees ahead of BDC for exhaust valves just opening... or inlet just opening at TDC? - I have used both as a starting point then tweaked to optimise depending on use of the engine.
Of course, a lot depends upon the geometry of inlet and exhaust opening and closing times, arrangement of eccentric linkage, etc. - Which is why there are so many different geometries of valve gear, Joy, Stephensons, Walschearts, etc...
The Steam equivalent of the piston ported "valve-less" 2-stroke IC engine would always be the Oscillating engine, - which can be made without worrying about valve timings. Just drill ports accurately according to "the book".
N.B. Joining engines in series, as suggested by our old friend Bentwings, can cause some strange effects in flexible couplings by different cylinders getting a bit ahead or behind others, and setting-up some terrible (destructive?) torsional vibrations.... When a resonance occurs they fight each other until the coupling is over-stressed and fails. Far better to have torsionally rigid couplings with "perfect" alignment.

I suggest you do as "a majority" of modellers have done.... Make a small steam engine - and make it run and power something. This will prove your skills at making things like pistons and bores that fit properly, crank-shafts that are not misaligned, valves that seal, bearings that do not rattle or seize, etc.
Then you can use the proven skills to make small IC engines. Start with a piston ported 2 stroke to prove you can make a runner with good compression.
A half-inch to 1 inch bore and stroke is a reasonable starter model - steam or 2-stroke IC - before you get too ambitious and go smaller or bigger! (I started with a 1/2" bore and 3/4" stroke V-twin steam oscillator - because the kit was cheap. Learned a lot!).
Then think about 4-stroke IC valves and valve gears! Modelling is an education in precision manufacture, so always use the best tools and materials you have or can afford.
And always ENJOY the hobby. We all make mistakes - then discuss solutions or lessons learned on this website. A good way to learn is from mistakes - hopefully others' mistakes, not your own.
K2

Thanks I’ll try that tip. I’m gettingvreadyvtonrelocatvtobtenn. Due to better med care and be with family more. They may be able to provide a “ get going “ atmosphere so I can get over this fatigue issue. I’m packing steamer and turbines for the move. I will still have a hobby room. And I don’t really need much more than a desk and some storage area some of the bigger tools like drill press and air compressor will go in my sons work are. Me and kitty don’t take much room . I’ll still have a computer table and maybe a push to teach cad to don maybe even grand daughter. Son and I talked about education and in view of grand daughter interest in looking things up and investigating we think maybe journalism might be a good direction It’s a tough field but we think it might be satisfying . Ultimately it will be her choice to go what direction she wants but we hoped provide the drive to follow through on her choice . The same goes for grandson . As he get older. Both at playing sports and son and I big sports people. We think this gives an edge to kids to excell at what ever they do with internal fortitude .