Terrific workmanship, well done!Freezerrr12 wrote: ↑Thu Aug 27, 2020 7:49 pmI would like to address the readers of the forum with a few questions. I really hope to receive answers that will help me in further construction. What can be the maximum mass of moving parts of a steam engine to obtain high revolutions? The parameters are as follows. The weight of one connecting rod with bronze bearings is 5 kg, the weight of a piston with a diameter of 100 mm. together with the piston rod, crosshead - 5 kg. The weight of the piston with a diameter of 170 mm. - 4.5 kg. I designed a 132.5mm piston stroke. Do you think these parameters are outside the optimal range? Do they come out strong? The second question: what should be the area of the steam bypass channels in such cylinders? I will be very grateful for the answers of knowledgeable people. I thank you for your help, I am attaching pictures of pistons and connecting rods for a general idea of my project. My name is Ingvar.

Regarding maximum RPM, all I can say from this distance is, “it depends”. There are plenty of formulas out there for calculating the minimum cross sections of connecting rods and piston rods, the minimum thickness of pistons, etc., but while your engine’s parts look a little heavy, they are not outrageously so. Form follows function, and as the saying goes, if it looks right, it probably is. I would think that your engine will be good for 500 RPM with no issues.

The weight of the reciprocating parts compared to the weight of the complete engine plays a part in how much of the vibration the mass of the engine is able to absorb. While a weight of 5 pounds of reciprocating parts in an engine that weighed 10 pounds would be disastrous, those same 5 pound weights in an engine weighing 100 pounds would be unnoticeable while running at the same speed. In avoiding using aluminum in your engine, it weighs more overall, making it more stable.

I am not sure about your meaning with the term “area of the steam bypass channels”. If you mean the steam ports, the steam should pass through them at 6,000 to 10,000 feet per minute. Take the average piston speed of the piston, at your maximum RPM, which is 5.2 inches stroke times 1,000 strokes per minute, which equals 435 feet per minute piston speed. 435 FPM divided by 6,000 FPM equals .073. So the area through the port should equal the area of the piston (12.17 square inches for the HP) multiplied by .073 , which gives us an area through the port of .89 square inches. If the length of the port is .8 times the bore of the cylinder (3.15 =.8 x 3.94 inches bore) , its height should be (.28 = .89/3.15 port length).

Keep up the good work.