Since 1879
A d d ress y o u r re q u e st to
A. FINKL & SONS CO.
2 0 1 1 S o u th p o rt A v e . • C h ic a g o 14, 111.
Fig. 1— Large marine gear and pinion after shaving. This is a set for a low speed destroyer transmission
IMPACT of the war on production of heavy gears is reflected in the com
plexion of designs as well as in the enor
mity of the production problems to be surmounted. Entirely new transmissions such as those involved in the large land
ing ships have had to be developed and p u t into quantity production without so much as a prototype available. Main propulsion drives for destroyers, cruisers, plane carriers, cargo vessels and a host of new com bat and service vessels are being built in numbers which have defied the most optimistic estimates.
Gear Design Requirements: Gear de
sign may be divided into two broad classes, namely, custom made and stand
ardized. However, the war has led to a dem and for certain single purpose gears in such quantities that the methods used in producing standardized types are being followed.
An example of custom built gearing requiring rigorous design treatm ent is the modem high-speed reducing gear, transmitting large powers from turbines to propellers of naval or mercantile ves
sels. Such gears are of rather impres
sive proportions, the escort carrier drive illustrated in Fig. 3 being 18 x 16 x 10 feet. Thousands of horsepower must be carried with a very minimum of weight and yet the supporting structure must be adequate to maintain precise
By W . P. S C H M I T T E R The Falk Corp.
Milwaukee
gear alignment. The design has met the requirements here in rather ingenious fashion by the employment of skeleton
ized welded constmction.
Pitch line velocities frequently attain values in excess of 3 miles per minute, ne
cessitating the most rigid adherence to precision standards in order that noise, vi
bration, and dynamic tooth loading be maintained at a minimum. Because of this and the absence of major extraneous shock, the emphasis is on surface dura
bility of the tooth profiles and accord
ingly such gears are usually designed
W a r requires m a k in g sp e cial g e a rs on m ass p ro d u c tion basis. H e re a re d e scrib ed som e of the special m a c h in in g a n d production m eth od s successfully d e v e l
o p e d to m eet this ob/'ective
with fine pitches with many teeth in con
tact in the zone of action as is apparent from Fig. 4.
Gear Materials D epend on Size: Gear hardness, heat treatm ent and manufac
turing technique differ radically, depend
ing upon the field to which the product is to be applied and the quantities in which the gears are produced. In the automotive industry, repetitive manu
facture has been developed to the point w here thousands of identical gears are turned out and, consequently, very elab
orate tooling is justified. Morever, ample resources of statistical data permit fore
casting, with sufficient accuracy, the degree and m anner in which a gear will distort under heating treatm ent, the al
lowance which must be made for deflec
tions under load, and reliable estimates of the actual loads imposed under various
Fig. 2 — This 30,000-horsepower double-reduction herringbone gear drive for a destroyer transmission i s n o simple product. M a n y problems are involved in its making
April 16, 1945 127
Fig. 5— Fabricating framework for marine gear housing. Unit is tilted for best welding position in mak- the many fillet welds w ith the
electric arc
Fig. 6— Contact impression on gear after shaving
Fig. 3— Note skeleton frame of this double-reduction drive from turbines to propeller of an escort carrier vessel
conditions. This is not so in the case where industrial gears are manufac
tured in relatively small quantities.
Because of the rigid requirements for the maximum in accuracy, heavy duty industrial gears are usually heat treated before cutting, although applications exist where, because of design or service conditions, it is necessary to use car- burized or fully hardened gears beyond the machinable range. This discussion will deal mainly with gears in which the final cutting and refining of the tooth profiles is not subjected to distor
tion by subsequent heat treatment.
With regard to the choice of alloys, it has been found that any analysis cap
able of being heat treated to the required minimum physicals will conform satis
factorily. It is for this reason that the NE and other lean alloy steels have been
Fig. 4— Turbine reduction drive for single-screw tanker.
Propeller is driven at 96 r.p.m. by three turbines deliver
ing power through the three small gears at left. Covers removed here to show all elements. H igh pressure turbine delivers 2424 b.h.p. at 8012 r.p.m.; intermediate pressure turbine, 2658 b.h.p. at 5033 r.p.m.; low pressure turbine 3122 b.h.p. at 4022 r.p.m. Low speed gear data: Dia
metral pilch 4, 75 and 616 teeth; pitch line velocity 3880 feet per m inute
successfully used for gearing. In the selection of alloys, grades high in car
bide forming elements have been favored in order to secure the maximum re
sistance to abrasive types of profile wear.
For large sections, the alloy content must naturally be increased to obtain the proper response to heat treatment. For sections which cannot be liquid quenched because of the large size or demand for minimum residual stresses to prevent warping after cutting, the physicals must
be obtained by normalizing and tem per
ing. For these applications high alley con
tents are an absolute necessity. The selec
tion of alloy content also is dependent upon the machinability rating of the material at the given production hard
ness because of the critical nature of the gear cutting processes. The use of medium sulphurized steels (0.07 - 0.10 sulphur) has materially aided the gear cutting problem.
Industrial gears of small size are heat treated to maximum hardnesses of ap
proximately 360 brinell by means of a liquid quench. Medium sized gears and pinions are quenched and tempered to a range of 235-270 brinell which gives the best results in production. A range of 260-295 brinell is satisfactorily used when the proper alloy is selected.
F or heavily loaded large pinions rang- ( Please turn to Page 164)
128
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April 16, 1945 129 I
IM$TAWr»SlOUS HXINC preserving a reasonably uniform teeming speed from first to last. Such change has been adopted which achieves reason
able constancy of teeming speed and at
—-From British Steelmaker, Jan. 1945.
nary kind, mounted in the ladle bottom quick-acting bayonet joint or interrupted screw fastening, with wedge-shaped lock forming a continuous passage.
In practice, the first ingots are poured
zles is required, an alternative arrange
m ent is the Bagnall-Bethel multinozzle.
(Fig. 2) The principle is the same as that in the single changeable nozzle, but it is utilized to provide a series of graded nozzles attached one beneath the other, and detached as teeming proceeds.
In the multinozzle, the primary nozzle with bayonet-joint attachment, carrying a secondary nozzle of, say, 114 inches
This nozzle-carrier can be detached quickly by a partial rotation with a
The Bagnall-Bethel patent nozzle, both in the form of the single secondary nozzle, and as the multinozzle, has been thoroughly tested for various types of steel from electrically m elted to open- hearth, in several different melting shops, with uniformly good results.