LUBRICATION AND DUST EXCLUSION.
It is always a mistake to suppose that even a ball bearing can successfully and wisely be run without lubrication, under load, although the feasibility of so doing has been declared on what ought to be pretty fair authority. But the rolling movement can never be made absolutely constant and the sliding perfectly gotten rid of; even if this could be, the contact sides of the balls move in opposite directions, and, therefore, must rub slightly on one another; if the balls are held apart by a perforated collar they cannot touch each other, but they touch the collar instead and rub on that—so a little friction will remain in the most favorable circumstances. By the way, some stick vaseline in bearings, but we must disapprove this; we do not regard that substance as a lubricant in any proper sense, and the very quality of adhesiveness which makes it convenient sometimes for holding balls in place while assembling a bearing also makes its presence objectionable after the assembling is done. It has the property of staying in place and not flowing out, not being fluid; but this property is possessed by other substances—by tar, for instance.
Of course, there must always be an open joint in every bearing (the outer end of the pedal excepted) where a moving part passes a fixed one. Nicety of fit, so that these two parts shall be almost in contact, is the first requisite, and is not to be found on “cheap” wheels, albeit such wheels (on paper) have tool steel and dust-proof bearings, like all others. Hard-rubber washers cannot close these joints; soft rubber would quickly be destroyed by the oil. Felt and velvet have been the only recourse, and this not an entirely satisfactory one, although if dust and mud could be perfectly excluded the oil might retain color almost indefinitely. For this, at the risk of repetition, we must say that the cup adjustment—called disk adjustment generally in England, and sometimes here—is exactly adapted, and that the four-point serves best. These soft packings are still retained by quite a number of makers. For instance, the Monarch puts on the left side of the rear wheel an octagonal-faced dust cap, and next to that a felt washer, and next to that the usual ball retainer; the front hub has this construction on both sides, and the crank bearings are fitted with cup adjustment.