Originally Posted by
Mr Cox
Thanks for the link, I might have read that once or twice before but it doesn't hurt to read through it again...
Interestingly, the counter piston is made conical such that the upper part is too large, this will then compress and seal towards the cylinder.
This CP could possibly be entered in to cylinder from the bottom, if the cylinder is tapered enough, but there is certainly a high risk of catching a the ports...
If There's a high risk of a CP catching on a port, then surely the same risk exists for that happening with a Piston. At the ports the cylinder taper should be such that both of them are "not tight" rather than "loose". After-all Compression starts just after the ports are closed by the piston on the way up.
Also this use of the word "crystal". It describes a substance that exists in a particular structural 3-D "Lattice like" arrangement of its Atoms and Molecules. Materials with such a structure are not necessarily hard. The Carbon based residue left in a model engine running standard diesel fuel blends is not going to be in the form of diamond. It's going to be more like that of soft Graphite.
How do I know this? I studied Metallurgy and Materials Science for three years in my first degree. That was almost fifty years ago, but I don't think things have changed that much.
In passing, I don't think that our friends Fanchi's stuck Contra is due to solidified carbon residue. The problem is more likely to be due to corrosion. Good old rust.