CHAPTER XXI.
ALUMINUM IN CYCLE CONSTRUCTION—STRENGTH OF TUBES.
“We really thought that we were going to pass over a period of three months without having to chronicle the discovery (?) of a method of producing aluminum at a cost of not more than that of first-class steel. The periodical inventor has appeared, and this time he hails from Melrose, Mass., and his name is Washburn. Next!!”—Bicycling World.
Inventors do little harm in periodically making cheap aluminum or increasing its strength without adding to its gravity, but when a large corporation is started, as was done some months ago, with a lot of money and aluminum medals issued, the same being made out of copper, then the matter becomes serious. Probably, next to the hobby of separating water and creating enormous power thereby, the aluminum hobby holds undisputed sway. But as there really is something of interest to cyclists and cycle makers in the subject, there seems a need to touch upon it. Among the articles in the manufacture of which aluminum can be satisfactorily used we find in the catalogue of a well-known smelting firm mention made of bicycles, tricycles, etc. The idea exists in the minds of many that a bicycle made from pure aluminum would be a practical machine and much lighter than one of steel. This notion arises from the fact that aluminum in the pure state has a specific gravity of only 2.5, or about one-fourth the weight of steel. Below we print a letter from the Cowles Smelting and Aluminum Company on the subject.
“Lockport, N.Y., U.S.A., August 20, 1888.
“R. P. Scott, Esq., Baltimore Md.:
Dear Sir,—Replying to your favor of August 16, you can obtain the book on Aluminum, by Richards, from Philadelphia. Aluminum has a great many uses in its commercial state, but a simple pure aluminum casting has not sufficient strength to make it desirable for small parts. If you could have it rolled or hammered to shape, so as to make it rigid, it would become much more tenacious, but to secure strength desired in bicycle parts, your castings would necessarily be so large as to be ungainly, and we doubt if you would attain the most desirable end,—viz., light weight. The alloys of copper and aluminum are much better adapted to your requirements than the pure metal could possibly be.
“Yours very truly,
“The Cowles E. S. and Al. Co.
“Tucker.”
It will be seen that the metal in its pure state lacks strength, and can only be used in the arts to any extent when alloyed with copper about in the proportion of nine of copper to one of aluminum. When alloyed as above, it is about as heavy as steel.
| Pounds per square inch. | |
|---|---|
| Cast brass | 23,000 |
| Annealed brass wire | 49,000 |
| Cast copper | 24,000 |
| Annealed copper wire | 32,000 |
| Gun bronze of copper and tin cast | 39,000 |
| Average American cast iron | 16,000 |
| Good wrought iron | 50,000 |
| Best American wrought iron (exceptional) | 76,100 |
| Iron wire ropes | 38,000 |
| Malleable iron castings | 48,000 |
| Steel plates (rolled) | 81,000 |
| Cast steel average Bessemer ingots | 63,000 |
| ALUMINUM BRONZE. | ||||
|---|---|---|---|---|
| Per cent. of aluminum. | Grade. | Tensile strength per square inch. | Elongation. | Ingots per pound. |
| A 1 | 90,000 lbs. and over. | 0 to 5 per cent. | $0.45 | |
| A 2 | 75,000 to 90,000 lbs. | 10 per cent. and over. | .40 | |
| 10 | A 3 | 65,000 to 75,000 lbs. | 25”” | .37 |
| 71⁄2 | B | 47,500 to 65,000 lbs. | 20”” | .33 |
| 5 | C | 35,000 to 47,500 lbs. | 25”” | .26 |
| 21⁄2 | D | 27,500 to 35,000 lbs. | 30”” | .20 |
| 11⁄2 | E | 20,000 to 27,500 lbs. | 15”” | .16 |
The specific gravity of the A grade is 7.56, that of steel being 7.88. Its coefficient of expansion is small at ordinary temperatures; its electrical conductivity is about 9, and with the lower grades the expansion by heat, specific gravity and heat and electrical conductivity increases the nearer the metal approaches to pure copper. With more than eleven per cent. of aluminum the bronze rapidly becomes brittle. In color, aluminum bronze of the C and D grades is the nearest to gold of any known metal, the higher grades being lighter in hue than the lower. The A grade melts at about 1700° F., a little higher than ordinary bronze or brass. Aluminum bronze shrinks about twice as much as brass.
In working aluminum I have found it to be a splendid substitute for malleable iron, especially in many cases where the iron could not be procured in time, or when it came so warped as to be unfit for use. I have never been able, however, to get castings which would come quite up to the strength claimed for it; the most satisfactory grade was that of ten-per-cent. aluminum, which by the way is very hard to work, especially in drilling. There is no doubt, however, that it can be made to take the place of steel in many instances.
A knowledge of aluminum is a great boon to experimenters, as it will probably come into quite general use with the manufacturer. The ten-per-cent. aluminum finishes very handsomely, and in olden times it would have been a splendid substitute for the brass hubs then so common. As an antifriction metal it is unsurpassed by any of the bronzes. It casts bright and sharp, but shrinks amazingly, although not dangerously; at least I have never had a part of the casting drop off, as in malleable it often does, and though the aluminum sometimes leaves a great depression in the heavy part of the casting, it causes no sponginess underneath. It can be readily bronzed or soldered.
Aluminum bronze drawn into wire will make very good spokes, and it has been used for this purpose to some extent in England. All tendency to rust is obviated, and it saves all nickeling; it resists corrosion sufficiently well to dispense with any covering, but it does not look as well as a nickel finish. No better authority on the subject can be had than that of the Cowles Catalogue; useful information also can be gathered from “Richards’s Aluminum,” and “Thurston’s Material of Engineering.” The last-named treatise speaks on the subject as follows:
“The alloys of aluminum are very valuable. Its remarkable lightness, combined with its strength, makes it useful as a constituent of those alloys in which strength and lightness are the needed qualities. It has a pleasant metallic ring when struck, and confers a beautiful tone when introduced into bellmetal.
“Aluminum may be added to bronzes and brasses with good results. The alloys (copper ninety per cent., aluminum ten per cent.) may be worked cold or hot like wrought iron, but not welded. Its tenacity is sometimes nearly one hundred thousand pounds per square inch. Its specific gravity is 7.7. In compression this alloy has been found capable of sustaining a little more than in tension,—one hundred and thirty thousand pounds per square inch (nine thousand one hundred and thirty nine kilos per square millimetre),—and its ductility and toughness were such that it did not even crack when distorted by this load. It is so ductile and malleable that it can be drawn down under the hammer to the fineness of a cambric needle.
“It works well, casts well, holds a fine surface under the tool and when exposed to the weather, and it is in every respect considered the best bronze yet known. Its high cost alone has prevented its extensive use in the arts. These alloys are very uniform in character and work regularly and smoothly. Even one per cent. of aluminum added to copper causes a considerable increase in ductility and fusibility, and enables it to be used satisfactorily in making castings. Two per cent. gives a mixture used for castings which are to be worked with a chisel. It is softened by sudden cooling from a red heat. Its coefficient of expansion is small at ordinary temperatures.
“It has great elasticity when made into springs; it has been found useful for watches, and has the decided advantage over steel of being little liable to oxidization. Kettles of aluminum bronze are used in making fruit syrups and preserves. Steel containing but .08 per cent. of aluminum is said to be greatly improved by its presence.”
Aluminum bronze, such as would be required for cycle castings, costs from thirty to fifty cents per pound, according to quality and quantity. A valuable alloy of aluminum and iron has recently been made, by which it is maintained that wrought-iron castings are possible. The factory is, I believe, at Worcester, Mass. In our endeavor to learn more upon the subject we have been referred to the United States Mitis Co., No. 26 Broadway, New York, which company has the exclusive right in this country to make Mitis castings, or of granting permission to those who desire to make these castings themselves.