Originally Posted by
Kontact
Sure. I think the peak friction coming off the cassette and then back onto the chainring creates a tiny flash of heat sufficient to briefly liquify a very small amount of the wax and cause it to draw into the bearing surfaces.
Hard wax is too soft to serve as a structural bearing when it is only seeing friction on one side of the pin, and other types of steel friction have been shown to produce surprising temperatures. So this is the only scenario that makes any sense to me. In other words, chains are not like bearings and all the contact happens within a few degrees - which would displace all the wax to the other side of the bushing in seconds. Some other mechanism is necessary.
Possibly. I had thought about that possibility in the past, but wasn't sure it would be durable. If my memory is correct, I think my chain waxes on the road bike in dry, clean conditions, and flat land mostly spinning and not high climbing loads, lasted over 1000 miles.
However the wiki on babbitt metal posits a similar theory to some babbitt alloys:
Babbitt metal is most commonly used as a thin surface layer in a complex, multi-metal assembly, but its original use was as a
cast-
in-place bulk bearing material. Babbitt metal is characterized by its resistance to
galling. Babbitt metal is soft and easily damaged, which suggests that it might be unsuitable for a
bearing surface. However, its structure is made up of small hard
crystals dispersed in a softer metal, which makes it, technically, a
metal matrix composite. As the bearing wears, the softer metal erodes somewhat, creating paths for lubricant between the hard high spots that provide the actual bearing surface.
When tin is used as the softer metal, friction causes the tin to melt and function as a lubricant, protecting the bearing from wear when other lubricants are absent.
Internal combustion engines use Babbitt metal which is primarily tin-based because it can withstand cyclic loading.