Elevator Systems of the Eiffel Tower Part 3

Such supreme confidence must have rapidly evaporated as events progressed.

Despite the invaluable advertising to be derived from an installation of such distinction, the Otises would probably have defaulted had they foreseen the difficulties which preceded completion of the work.

[Ill.u.s.tration: Figure 24.--General arrangement of Otis elevator system in Eiffel Tower. (From _The Engineer_ (London), July 19, 1889, vol. 68, p.

58.)]

The proposed system (fig. 24) was based fundamentally upon Otis' standard hydraulic elevator, but it was recognizable only in basic operating principle (fig. 25). Tracks of regular rail section replaced the guides because of the incline, and the double-decked cabin (fig. 29) ran on small f.l.a.n.g.ed wheels. This much of the apparatus was really not unlike that of an ordinary inclined railway. Motive power was provided by the customary hydraulic cylinder (fig. 26), set on an angle roughly equal to the incline of the lower section of run. Balancing the cabin's dead weight was a counterpoise carriage (fig. 27) loaded with pig iron that traveled on a second set of rails beneath the main track. Like the driving system, the counterweight was rope-geared, 3 to 1, so that its travel was about 125 feet to the cabin's 377 feet.

[Ill.u.s.tration: Figure 25.--Schematic diagram of the rigging of the Otis system. (Adapted from Gustave Eiffel, _La Tour de Trois Cents Metres_, Paris, 1900, p. 127.)]

Everything about the system was on a scale far heavier than found in the normal elevator of the type. The cylinder, of 38-inch bore, was 36 feet long. Rather than a simple nest of pulleys, the piston rods pulled a large guided carriage or "chariot" bearing six movable sheaves (fig. 28).

Corresponding were five stationary sheaves, the whole reeved to form an immense 12-purchase tackle. The car, attached to the free ends of the cables, was hauled up as the piston drew the two sheave a.s.semblies apart.

In examining the system, it is difficult to determine what single element in its design might have caused such a problem as to have been beyond the engineering ability of a French firm, and to have caused such concern to a large, well-established American organization of Otis' wide elevator and inclined railway experience. Indeed, when the French system--which served the first platform from the east and west legs--is examined, it appears curious that a national technology capable of producing a machine at such a level of complexity should have been unable to deal easily with the entire matter. This can be plausibly explained only on the basis of Europe's previously mentioned lack of experience with rope-geared and other cable-hung elevator systems. The difficulty attending Otis' work, usually true in the case of all innovations, lay unquestionably in the mult.i.tudes of details--many of them, of course, invisible when only the successfully working end product is observed.

More than a matter of detail was the Commission's demand for perfect safety, which precipitated a situation typical of many confronting Otis during the entire work. Otis had wished to coordinate the entire design process through Mr. Hall, with technical matters handled by mail.

Nevertheless, at Eiffel's insistence, and with some inconvenience, in 1888 the company dispatched the project's engineer, Thomas E. Brown, Jr., to Paris for a direct consultation. Mild conflict over minor details ensued, but a gross difference of opinion arose ultimately between the American and French engineers over the safety of the system. The disagreement threatened to halt the entire project. In common with all elevators in which the car hangs by cables, the prime consideration here was a means of arresting the cabin should the cables fail. As originally presented to Eiffel, the plans indicated an elaborate modification of the standard Otis safety device--itself a direct derivative of E. G. Otis' original.

If any one of the six hoisting cables broke or stretched unduly, or if their tension slackened for any reason, powerful leaf springs were released causing brake shoes to grip the rails. The essential feature of the design was the car's arrest by friction between its grippers and the rails so that the stopping action was gradual, not sudden as in the elevator safety. During proof trials of the safety, made prior to the fair's opening by cutting away a set of temporary hoisting cables, the cabin would fall about 10 feet before being halted.

[Ill.u.s.tration: Figure 26.--Section through the Otis power cylinder.

(Adapted from Gustave Eiffel, _La Tour de Trois Cents Metres_, Paris, 1900, pl. 22.)]

[Ill.u.s.tration: Figure 27.--Details of the counterweight carriage in the Otis system. (From Gustave Eiffel, _La Tour de Trois Cents Metres_, Paris, 1900, pl. 22{4}.)]

Although highly efficient and of unquestionable security, this safety device was considered an insufficient safeguard by Eiffel, who, speaking in the name of the Commission, demanded the application of a device known as the rack and pinion safety that was used to some extent on European cog railways. The commissioners not only considered this system more reliable but felt that one of its features was a necessity: a device that permitted the car to be lowered by hand, even after failure of all the hoisting cables. The serious shortcomings of the rack and pinion were its great noisiness and the limitation it imposed on hoisting speed. Both disadvantages were due to the constant engagement of a pinion on the car with a continuous rack set between the rails. The meeting ended in an impa.s.se, with Brown unwilling to approve the objectionable apparatus and able only to return to New York and lay the matter before his company.

While Eiffel's att.i.tude in the matter may appear highly unreasonable, it must be said that during a subsequent meeting between Brown and Koechlin, the French engineer implied that a mutual antagonism had arisen between the Tower's creator and the Commission. Thus, since his own judgment must have had little influence with the commissioners at that time, Eiffel was compelled to specify what he well knew were excessive safety provisions.

This decision placed Otis Brothers in a decidedly uncomfortable position, at the mercy of the Commission. W. E. Hale, promoter of the water balance elevator--who by then had a strong voice in Otis' affairs--expressed the seriousness of the matter in a letter to the company's president, Charles R. Otis, following receipt of Brown's report on the Paris conference.

Referring to the controversial cogwheel, Hale wrote

... if this must be arranged so that the car is effected [sic] in its operation by constant contact with the rack and pinion ... so as to communicate the noise and jar, and unpleasant motion which such an arrangement always produces, I should favor giving up the whole matter rather than allying ourselves with any such abortion.... we would be the laughing stock of the world, for putting up such a contrivance.

This difficult situation apparently was the product of a somewhat general contract phrased in terms of service to be provided rather than of specific equipment to be used. This is not unusual, but it did leave open to later dispute such ambiguous clauses as "adequate safety devices are to be provided."

Although faced with the loss not only of all previously expended design work but also of an advertis.e.m.e.nt of international consequence, the company apparently concurred with Hale and so advised Paris.

Unfortunately, there are no Otis records to reveal the subsequent transactions, but we may a.s.sume that Otis' threat of withdrawal prevailed, coupled as it was with Eiffel's confidence in the American equipment. The system went into operation as originally designed, free of the odious rack and pinion.

That, unfortunately, was not the final disagreement. Before the fair's opening in May 1889, the relationship was strained so drastically that a mutually satisfactory conclusion to the project must indeed have seemed hopeless. The numerous minor structural modifications of the Tower legs found necessary as construction progressed had necessitated certain equivalent alteration to the Otis design insofar as its dependency upon the framework was affected. Consequently, work on the machinery was set back by some months. Eiffel was informed that although everything was guaranteed to be in full operation by opening day on May 1, the contractual deadline of January 1 could not possibly be met. Eiffel, now unquestionably acting on his own volition, responded by cable, refusing all payment. Charles Otis' reply, a cla.s.sic of indignation, disclosed to Eiffel the jeopardy in which his impetuosity had placed the success of the entire project:

After all else we have borne and suffered and achieved in your behalf, we regard this as a trifle too much; and we do not hesitate to declare, in the strongest terms possible to the English language, that we will not put up with it ... and, if there is to be War, under the existing circ.u.mstances, propose that at least part of it shall be fought on American ground. If Mr. Eiffel shall, on the contrary, treat us as we believe we are ent.i.tled to be treated, under the circ.u.mstances, and his confidence in our integrity to serve him well shall be restored in season to admit of the completion of this work at the time wanted, well and good; but it must be done at once ...

otherwise we shall ship no more work from this side, and Mr. Eiffel must charge to himself the consequences of his own acts.

This message apparently had the desired effect and the matter was somehow resolved, as the machinery was in full operation when the Exposition opened. The installation must have had immense promotional value for Otis Brothers, particularly in its contrast to the somewhat anomalous French system. This contrast evidently was visible to the technically unsophisticated as well as to visiting engineers. Several newspapers reported that the Otis elevators were one of the best American exhibits at the fair.

In spite of their large over-all scale and the complication of the basic pattern imposed by the unique situation, the Otis elevators performed well and justified the original judgment and confidence which had prompted Eiffel to fight for their installation. Aside from the obvious advantage of simplicity when compared to the French machines, their operation was relatively quiet, and fast.

The double car, traveling at 400 feet per minute, carried 40 persons, all seated because of the change of inclination. The main valve or distributor that controlled the flow of water to and from the driving cylinder was operated from the car by cables. The hydraulic head necessary to produce pressure within the cylinder was obtained from a large open reservoir on the second platform. After being exhausted from the cylinder, the water was pumped back up by two Girard pumps (fig. 31) in the engine room at the base of the Tower's south leg.

THE SYSTEM OF ROUX, COMBALUZIER AND LEPAPE

There can be little doubt that the French elevators placed in the east and west piers to carry visitors to the first stage of the Tower had the important secondary function of saving face. That an engineer of Eiffel's mechanical perception would have permitted their use, unless compelled to do so by the Exposition Commission, is unthinkable. Whatever the att.i.tudes of the commissioners may have been, it must be said--recalling the Backmann system--that they did not fear innovation. The machinery installed by the firm of Roux, Combaluzier and Lepape was novel in every respect, but it was a product of misguided ingenuity and set no precedent.

The system, never duplicated, was conceived, born, lived a brief and not overly creditable life, and died, entirely within the Tower.

Basis of the French system was an endless chain of short, rigid, articulated links (fig. 35), to one point of which the car was attached.

As the chain moved, the car was raised or lowered. Recalling the European distrust of suspended elevators, it is interesting to note that the car was pushed up by the links below, not drawn by those above, thus the active links were in compression. To prevent buckling of the column, the chain was enclosed in a conduit (fig. 36). Excessive friction was prevented by a pair of small rollers at each of the knuckle joints between the links. The system was, in fact, a duplicate one, with a chain on either side of the car. At the bottom of the run the chains pa.s.sed around huge sprocket wheels, 12.80 feet in diameter, with pockets on their peripheries to engage the joints. Smaller wheels at the top guided the chains.

If by some motive force the wheel (fig. 33) were turned counterclockwise, the lower half of the chain would be driven upward, carrying the car with it. Slots on the inside faces of the lower guide trunks permitted pa.s.sage of the connection between the car and chain. Lead weights on certain links of the chains' upper or return sections counterbalanced most of the car's dead weight.

[Ill.u.s.tration: Figure 28.--Plan and section of the Otis system's movable pulley a.s.sembly, or chariot. Piston rods are at left. (Adapted from _The Engineer_ (London), July 19, 1889, vol. 68, p. 58.)]

Two horizontal cylinders rotated the driving sprockets through a mechanism whose effect was similar to the rope-gearing of the standard hydraulic elevator, but which might be described as chain gearing. The cylinders were of the pushing rather than the pulling type used in the Otis system; that is, the pressure was introduced behind the plungers, driving them out. To the ends of the plungers were fixed smooth-faced sheaves, over which were looped heavy quadruple-link pitch chains, one end of each being solidly attached to the machine base. The free ends ran under the cylinder and made another half-wrap around small sprockets keyed to the main drive shaft. As the plungers were forced outward, the free ends of the chain moved in the opposite direction, at twice the velocity and linear displacement of the plungers. The drive sprockets were thereby revolved, driving up the car. Descent was made simply by permitting the cylinders to exhaust, the car dropping of its own weight. The over-all gear or ratio of the system was the multiplication due to the double purchase of the plunger sheaves times the ratio of the chain and drive sprocket diameters: 2(12.80/1.97) or about 13:1. To drive the car 218 feet to the first platform of the Tower the plungers traveled only about 16.5 feet.

To penetrate the inventive rationale behind this strange machine is not difficult. Aware of the fundamental dictum of absolute safety before all else, the Roux engineers turned logically to the safest known elevator type--the direct plunger. This type of elevator, being well suited to low rises, formed the main body of European practice at the time, and in this fact lay the further attraction of a system firmly based on tradition.

Since the piers between the ground and first platform could accommodate a straight, although inclined run, the solution might obviously have been to use an inclined, direct plunger. The only difficulty would have been that of drilling a 220-foot, inclined well for the cylinder. While a difficult problem, it would not have been insurmountable. What then was the reason for using a design vastly more complex? The only reasonable answer that presents itself is that the designers, working in a period before the Otis bid had been accepted, were attempting to evolve an apparatus capable of the complete service to the second platform. The use of a rigid direct plunger thus precluded, it became necessary to transpose the basic idea in order to adapt it to the curvature of the Tower leg, and at the same time retain its inherent quality of safety. Continuing the conceptual sequence, the idea of a plunger made in some manner flexible apparently suggested itself, becoming the heart of the Roux machines.

[Ill.u.s.tration: Figure 29.--Section through cabin of the Otis elevator.

Note the pivoted floor-sections. As the car traveled, these floor-sections were leveled by the operator to compensate for the change of inclination; however, they were soon removed because they interfered with the loading and unloading of pa.s.sengers. (From _La Nature_, May 4, 1889, vol. 17, p.

360.)]

Here then was a design exhibiting strange contrast. It was on the one hand completely novel, devised expressly for this trying service; yet on the other hand it was derived from and fundamentally based on a thoroughly traditional system. If nothing else, it was safe beyond question. In Eiffel's own words, the Roux lifts "not only were safe, but appeared safe; a most desirable feature in lifts traveling to such heights and carrying the general public."[12]

The system's shortcomings could hardly be more evident. Friction resulting from the more than 320 joints in the flexible pistons, each carrying two rollers, plus that from the pitch chains must have been immense. The noise created by such multiplicity of parts can only be imagined. Capacity was equivalent to that of the Otis system. About 100 people could be carried in the double-deck cabin, some standing. The speed, however, was only 200 feet per minute, understandably low.

If it had been the initial intention of the designers to operate their cars to the second platform, they must shortly have become aware of the impracticability of this plan, caused by an inherent characteristic of the apparatus. As long as the compressive force acted along the longitudinal axis of the links, there was no lateral resultant and the only load on the small rollers was that due to the dead weight of the link itself. However, if a curve had been introduced in the guide channels to increase the incline of the upper run, as done by Otis, the force on those links traversing the bend would have been eccentric--a.s.suming the car to be in the upper section, above the bend. The difference between the two sections (based upon the Otis system) was 789' minus 5435', or 2334', the tangent of which equals 0.436. Forty-three percent of the unbalanced weight of the car and load would then have borne upon the, say, 12 sets of rollers on the curve. The immense frictional load thus added to the entire system would certainly have made it dismally inefficient, if not actually unworkable.

In spite of Eiffel's public remarks regarding the safety of the Roux machinery, in private he did not trouble to conceal his doubts. Otis'

representative, Hall, discussing this toward the end of Brown's previously mentioned report, probably presented a fairly accurate picture of the situation. His comments were based on conversations with Eiffel and Koechlin:

Mr. Gibson, Mr. Hanning [who were other Otis employees] and myself came to the unanimous conclusion that Mr. Eiffel had been forced to order those other machines, from outside parties, against his own judgment: and that he was very much in doubt as to their being a practical success--and was, therefore, all the more anxious to put in our machines (which he did have faith in) ... and if the others ate up coal in proportions greatly in excess of ours, he would have it to say ... "Gentlemen, these are my choice of elevators, those are yours &c." There was a published interview ... in which Eiffel stated ...

that he was to meet some American gentlemen the following day, who were to provide him with elevators--grand elevators, I think he said....

[Ill.u.s.tration: Figure 30.--Upperworks and pa.s.senger platforms of the Otis system at second level. (From _La Nature_, Aug. 10, 1889, vol. 17, p.

169.)]

The Roux and the Otis systems both drew their water supply from the same tanks; also, each system used similar distributing valves (fig. 32) operated from the cars. Although no reports have been found of actual controlled tests comparing the efficiencies of the Otis and Roux systems, a general quant.i.tative comparison may be made from the balance figures given for each (p. 40), where it is seen that 2,665 pounds of excess tractive effort were allowed to overcome the friction of the Otis machinery against 13,856 pounds for the Roux.