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Statement of the case.

tee's damages, and though called profits are really damages ; and unliqui

dated until a final decree is made. 7. Interest upon unliquidated damages is not generally allowable, and should

not be allowed before a final decree for profits.

APPEAL from the Circuit Court for the Southern District of Ohio; the suit being a bill by Whitney for an alleged infringement by Mowry, of a patent which Whitney had for an improvement in the process of making wheels for railcars. The case was thus:

Wheels for rail-cars require to be made in a special way. The “tread” of the wheel, as it is commonly called—that is to say, the periphery—the surface which runs over the rail-must be very hard, or else it will wear out. On the other hand, the interior portions of the wheel, especially the hub, against which there is no friction, but on which there is great strain, need not be so hard, but must be very tough. Now here are requisites which by a law of the metal do not coexist in the same casting. Iron can be very hard only when it exists in a state of laminated crystallization, and then it is brittle. It can be very tough only when it exists in a state of granulated crystallization, and then it is soft. Now how is the “tread” to be made very hard and the interior very tough? This was the first problem in regard to iron car-wheels. And it was thus solved. It had been long observed that where molteri iron was cooled suddenly, it came out solid in the laminated or hard and brittle form, but when cooled slowly it came out solid in the tough and softer form.

The problem, of course, then was to cool rapidly the part of the melted mass of iron which was to make the “ tread” of the wheel, and to cool more slowly the rest which was to make the interior of the wheel; that is to say, the spokes and hub. To do this the moulds into which the molten iron was to be cast were made of sand, surrounded by a circle of iron; this circle, called in the manufacturer's language a “chill.” Iron being a rapid conductor of heat and sand a slow one, the part of the molten mass which came against

Statement of the case.

the iron or chill—the part, in other words, of the molten mass which was to form the tread, was cooled rapidly, and came out in the laminated and hard (though brittle) form; while the parts of the wheel nearer to the hub, and especially the hub itself (which is a very thick part of the wheel, and where a very great strain is put when the rail-car is, in motion), cooling slowly, the requisite toughness was obtained, through this part (and particularly the hub, owing to the greater mass of it) coming out in the granulated and tough (though soft) form. The cut below, which represents a piece fractured from off that part of the wheel including the flange, which runs over the rail, indicates the two forms. The lower part or chilled “tread” (which in the ordinary car-wheel itself is about half an inch deep) being distinguished by its laminated crystallizations and light gray color, and the upper part which runs in the direction of the hub by its granular crystallization, and a deeper gray line.

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This problem, therefore—the problem of obtaining a hard tread, and a tough interior and hub—was solved. The thing desired was attained through the process of a sand mould with an iron chill."

But of this good result in one way, a very bad one in another was the consequence. The wheels had no strength. And here was the cause. A mass of iron in its' molten state

Statement of the case.

is larger than the same mass of iron when cold, Now here the molten iron was poured into the mould at the hub. Thence it flowed out through the sand mould of the spokes to the tread. There it came in contact with the chill, and as soon as it touched the chill it was cooled, crystallized, and reduced in volume almost instantly. The metal immediately behind it, on the contrary, being in contact with the sand, parted with its heat more slowly, and remained in a fluid or semifluid state much longer. Thus it happened that the periphery of the tread cooling and shrinking first, reduced its diameter, while the hub and spokes remaining in a fluid or soft state, presented little or no resistance to the contraction of the tread or rim. But as these spokes and

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hub subsequently parted with their heat, and passed into the solid state, an inherent strain began to be exerted between the rim and hub. The spokes were too short. Restoration of so much of their length as had been diminished by the

Statement of the case.

prior cooling and shrinking of the rim was demanded. All parts of the wheel having passed into the solid state, and become comparatively unelastic, the spokes were severed by mere tensile strain before the temperature of the whole mass was reduced to that of the atmosphère. And the same result followed when, instead of spokes, disks or plates were used on the sides of the wheel, as shown in Figure 3.

To obviate this effect, a rude practice was, on the one hand, to uncover and expose to the air the thick parts of the wheel, sometimes, in addition, pouring cold water on them; while, on the other, the thin portions would be covered with burning fuel or hot sand. Still, however, the wheel would always strain, and usually break.

The great matter pow was to remove this difficulty. One plan was to divide the hub into sections, as shown in Figures 2 and 3, instead of casting it solid. This, of course, relieved the spokes from the tensile strain they were subjected to when counected with the solid hub; the spokes connected with each of the sections being left comparatively free to

contract in length (only, however, it FIG. 4.

may be added) by carrying the section of hub to which they were attached with them.

To restore the requisite strength to the hub, the spaces between these sectious would be subsequently filled with pieces of metal of the exact size of the

spaces, and wrought-iron bands would be shrunk on to each end of the hub, so as to hold firmly together all the sections, and the metal fillings or plates between them. Figure 4 illustrates the metal fillings or plates and bands that would be put into and on the hubs.

Wheels of this description were used till 1840. At that date our roads began to be made more substantial, and higher velocities upon them being demanded, the cast spokewheel, thus filled out at the hub, began to show great defects. The expense of filling the spaces between the sections was considerable. There was difficulty in putting the

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Statement of the case.

wrought-iron bands on the ends of the hub and of boring out the divided hub so as to make it fit well on the axle and to secure it from becoming loose. Yet if these things were not effectually done, the wheel broke or changed its position ou the axle, and the cars were thrown from the track.

To avoid these difficulties other means were employed to compensate for the unequal cooling and shrinking of the parts. These were nearly all con

Fig. 5. fined to making the hub solid, and connecting the hub and rim by a disk or plate, which was generally made double; two plates extending from hub to rim, in form couvex, as in Fig. 5, or otherwise curved, so as to be susceptible, as was supposed, of contracting or expanding in diameter as much as would be required by the unequal cooling and contraction before noticed. In one of these forms the hub was also divided, as shown in Fig. 5, it being expected that with the shrinking of the outer disks it would about close up. These wheels, when skilfully made, were an improvement on the spoke-wheel, with the hub divided into sections, so far as safety was concerned, but they were still faulty.

What, in this obviously not yet perfect art of making castiron car-wheels, was wanted, was some way to make such wheels, having a solid hub, and either spokes, or any desired form of plates, single or double, straight or curved, as represented in Figs. 6 and 7 below, and possessing all the requisites of durability and strength in the respective parts, and yet free from the defects which had attended, up to this time, all wheels yet made; and not requiring the expenditure of special labor upon the mould or pattern before casting, nor npon the finishing of the wheel for use, after it had been cast and cooled; some new and effective device which should eradicate and avnihilate the difficulties which have been already imperfectly described, and which were still bafiling manufacturers and inventors in this art. A new process of

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VOL. XIV.

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