To the best of my knowledge the OS was the only diesel to use a classical 'fence' baffle-and it was a resounding debacle for OS-who undoubtedly lost a lot of money on it....I suspect (quite apart from the problems of keeping the contrapiston alignment correct at diesel running head clearances (which are about half or less compared those of a glow of the same size) the baffle would a others have suggested act as a hotspot and cause preignition leading to poor power and overheating. Some diesels DID use a step baffle-where the edge of the piston is machined away to form a step-the Mills 75 being a good example-and others such as the ED Comp Special had a scallop out of the piston crown which achieved the same sort of effect.
I'm not sure I'd agree with gcb about the role of the baffle though-the PRIMARY role of the baffle is to prevent the incoming fuel charge from the transfer port escaping out the exhaust by deflecting the incoming fuel jet upwards whilst at the same time deflecting the hot exhaust gases downwards and outwards in the opposite direction. Effectively its an wedging action separating two hot and cold gas streams.... Any swirling motion occurs later and is as much affected by head shape geometry as by the baffle.
In any case, the conical piston achieves the same effect as a baffle and is applicable to a range of porting arrangements not just cross flow....
ChrisM
'ffkiwi'