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Well, I consider us a friendly bunch, and we try to go the extra mile....... That being said, neither I nor many other members of this forum can read languages other than english, and forcing everyone on the forum to translate everything you post (when you could do that one time yourself) is...

I think it is safe to say that when using a 21:1 compression ratio, diesel fuel will combust when injected into the cylinder at TDC. So does it really matter what that exact temperature is ? Regardless of the temperature, diesel will combust under these conditions, and so that is what is...

I really liked my sandblaster when it worked. I need to rework it, add a cyclone/dust collection system, and dewater the compressed air, and get a new window, and I think I will be on a roll. Nice work ! Now I know what to do to get mine working. .

I just found out that the origins of the Detroit Diesel line of engines originated with GM's purchase of the Winton Company around about 1930. Never knew that. (not my drawing) .

There appears to be a recess in the top of a Detroit Diesel 671 piston, and both the two and four valve heads for the 671 appear to be flat on the surface facing the piston. The injector appears to be directly centered in the cylinder. .

I use the mass function in Solidworks to calculate the mass of various 3D parts, so I can calculate how much metal I will need to cast a part. I can change the material to aluminum, bronze/brass, gray iron, etc. This is very helpful in avoiding short pours, where your crucible does not hold...

I am not sure about the 25 bar, but the answer seems to be to compare the stroke to the head clearance. .

I would not have thought that it would be as simple as a ratio of stroke to head space, but it does seem that way, reading what everyone has posted above. .

Working it as a volume comparision, the total volume at BDC with a 0.267" head clearance would be 74.68 cu in. At TDC, the volume with a 0.267" head clearance (assuming a flat head and a flat piston top, to simplify things) would be 3.7857 cu in. The ratio would be 74:68/3.7857 = 19.7 : 1 So...

Looking at the two extremes, in one ideal case, where there is no clearance, the pressure will approach infinity as the piston approaches TDC. In the other extreme, as the cylinder becomes infinitely long, the pressure approaches zero; ie: no compression is taking place. I seem to recall that...

Seems like you are mixing your units. You are making a ratio between length in mm and volume in cubic mm. I think it would need to be a comparison between two cubic volumes in order to calculate the ratio of minimum to maximum pressure, which I think is the definition of compression ratio ...

This is one of Find Hansen's videos. He lists a bore of 20mm, and a stroke of 40 mm, with a compression ratio of 21:1. Obviously the clearance volume is going to have a big affect on compression ratio, and I seem to recall seeing that diesels had a relatively small clearance space. I will see...

For an engine with a 1" diameter bore, the area of the top of the piston is pie-r-squared, so 0.785 sq.in. Assuming a clearance of 1/16", then the volume at TDC would be 0.04906 cu.in. For a 20:1 ratio, then the volume at BDC would be 0.98125 cu.in. So 1.25" stroke. My math is off...

I like the concept. Very interesting. .

Jason- Really nice build, and great color scheme. I highly encourage the model engine folks to learn the method JasonB uses, ie: find old patent drawings, photos of original engines, etc., create an accurate 3D model, and then build an engine. Putting the design into a 3D model gives a lot of...

Corn cob is another option for removing paint without damaging the metal surface. Must be well-sealed to avoid varmits and moisture absorption. .

Welcome, glad to have you here. Pat J .

You can run gray iron on gray iron also. .

If you will be running the engine with no load, slowly, as a model, then you can get away with things that you cannot get away with if you operate at a faster speed, with some amount of load. Generally the crosshead is constrained one way or another in all four directions, ie...

Welcome, glad to have you. It took me a while to learn machining. I had to learn how to grip a part, and grip it rigidly to it did not flex. Then I had to learn patience when approaching the final part size, and take very light cuts. I am no expert now, but I can do it and get within 1/2 a...