The chains made with the chain_maker do not actually use ERC, at leas not in respect to the centers of rotation. There is ERC, but it is only used to bend the chain. The trick with the moving centers of rotation is done by the two extra translateY channels, and does not involve any ERC.

When a translate channel is above a rotate channel, the rotation happens from the point at which the item was before the translation was made. The chain links exploit this fact, using one translate channel to move the link, then rotating it, then using a second translate channel to move the link back where it was to start with.