I’m not quite ready to post more photos from our trip to Spain (but I hope to do so later this week) … and I was thinking about what to post on the blog today, when a post-inspiring comment appeared.
After reading Jill’s story on Royal Mail Coach N205 earlier today, Bill sent the following comment: “Explain more about ‘mail axles’ please, and what makes them distinctive.”
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So … from an article published in the London Mechanics’ Magazine in December 1834:
… The earliest axles for wheel[ed] carriages were made of wood, and of a conical form, for two reasons: first, that it is easiest to fit a nave or box on a conical arm than on one of a cylindrical form; and secondly, in case of wear, the arm may be refitted by the wheel being worked farther up. The same form was continued, for the same reasons, when iron axles were introduced. Since that period, innumerable inventors have tried their heads and hands at the improvement of axles, and scarce a year passes that several patents are not taken out to die a premature death.
The commonest metal axle used at present is of a conical form, with a broad flat ring or washer driven firmly up to the shoulder, against which the wheel-box works. The wheel is secured against coming off by a front washer, behind a strong linch-pin. A thick unctuous grease is used for lubrication, to contain which deep channels are sunk in the box.
The next kind, instead of a washer and strong linch-pin, is provided with a screw-nut, formed to screw on the axle-end, in the direction in which the wheel turns, to keep the wheel on. Through both nut and axle a small linch-pin is driven. Some of these nuts are four-sided, others six- and eight-sided, and are consequently pierced with two, three, or four mortices for the linch-pin, in order to regulate the play of the wheel.
The next kind is the mail axle, so called from having been first used in the Mail Coaches. This axle is provided with a solid flat collar at the shoulder, against which the box of the wheel works. This axle has neither front nut, washer, or linch-pin. The arm is cylindrical, and is cut off flat at the front end; the front end of the box is closely stopped with a plate or screw, between which and the end of the arm there is left a hollow space for the purpose of containing oil, which is supplied by loosening a screw-pin in the front of the box. At the back of the box, near the shoulder, there is a second reservoir for oil. The wheel is retained on the arm of the axle by three or four long bolts, which pass through the nave from front to back, and thence through a circular plate of thick iron as large as the nave, which works against the back of the solid collar. Between the solid collar and the axle-box a thick leather washer is placed to prevent any jar arising. The play of the wheel is adjusted by screwing up the nuts of the long bolts against the circular plate. The advantage of this axle is the security it affords against the wheel coming off, by three or four separate bolts. But it is otherwise very imperfect, as the oil wastes very rapidly when the wheel is in work, and the end of the axle not being secured in front, there is an irregular elastic motion, which causes the arm to wear unequally at the shoulder after a short time, and then the oil disappears still more rapidly. The mail axles are most commonly hardened, both arm and box, to guard against this; but it is of little avail. Mail axles arc supposed to be lubricated with oil; but the fact is, that unless they be oiled every three or four days, they are actually lubricated with water. The process is thus: The front reservoir is level with the bottom of the axle arm, and consequently is level with the drainage or leakage point at the leather washer. When the wheel is in motion it acts as a pump, and in a very short time drains off the oil of the front reservoir into the back, till it overflows; consequently the front is left dry. The bottom of the back reservoir is about an inch below the leakage point, and therefore it does not lose its oil by the same process as the front; but it loses it nevertheless. In the process of washing the wheel, and also in rainy weather, water gets in between the washer and the box. Water being heavier than oil, sinks to the bottom of the reservoir, and the oil flows off. Thus it is, that almost every mail axle which is not oiled every few days, gets rusty and spoiled. While the oil lasts, of course, the friction is less than that of a common axle; and, as before remarked, the security is greater against the wheel coming off, but take it altogether, it is, though a neat-looking, a very imperfect axle.
… to be continued tomorrow with our anonymous 1834 author’s thoughts on Collinge’s Axles.
The Slower Road 