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Rail bonds
Rail Bonds.
April, 19o4. ]
ELECTRICAL
273
SECTION
Staled 2WeetinF held Thursday, October S, sgo3.
Raft Bonds.
BY W. I~. HARRINGTON. General Manager Camden and Suburban Railway Company.
( Concluded f r o m iO. 230.)
SPECIAL RAIL-BONDING TOOLS.
Figs. 6 7 to 7 r e x h i b i t a series of special rail b o n d i n g tools designed for placing a m a l g a m a t e d bonds. A J A X BOND.
T h e A j a x bond consists of a s h e e t or piece of copper, c o n t a c t i n g with the w e b of rail on each side of joint u n d e r the fish plate or joint, held up and a g a i n s t the web by set screws, c u p p e d h a r d e n e d ends, set screws set in fish plate or j o i n t ; u s u a l m e t h o d is to insert a s h e e t of steel b e t w e e n copper plate and points of set screws. T h e w e b of rail h a v i n g b e e n g r o u n d off and t r e a t e d w i t h Edison-Brown alloys, as well as the side of the copper plate contacting with rail, the result is to all intents and p u r p o s e s a knifeblade switch. In all cases w h e r e the A j a x bond has been installed and action and life observed, it has invariably shown a v e r y s a t i s f a c t o r y condition. T e s t No. I I s h o w s 9 ° per cent. resistance, three years life. It m i g h t be i n t e r e s t i n g here to m e n t i o n o t h e r makes of b o n d s more or less in use, some of which have fallen into disuse, either from inefficiency or interested parties discontinuing manufacturing : J o h n s t o n bond, W e s t E n d bond, Bryan bond, Columbia bond, Channel Pin bond, F o r e s t City bond, S. H. H a r r i n g t o n ball bond, S. H. H a r r i n g t o n diagonal bond, G r a u t e n bond, VOL. CLVII.
NO. 94 ° .
t8
274
Harrzngton
."
[ J. F. I.,
Stern &. Silverman bond, P a y n e w e l d e d bond, A t k i n s o n bond, Syracuse bond. CAMDEN AND S U B U R B A N R A I L W A Y
BONDS.
The C. & S. bonds shown in Fig-. 73 were designed b y the writer and i n t e n d e d to provide large, ample contacts. T h e
FIG. 67.--Portable grinder.
No. I C. & S. b o n d consists of a square copper casting w i t h two grooves for 4 / o B. & S. g a u g e copper w i f e ; casting has a @~-ineh hole in center. A cast-iron c a s t i n g with corr e s p o n d i n g grooves and hole is provided. T h e b o n d is
April. 19o4.]
/~az/ t,'onds.
275
applied by g r i n d i n g off the web of the rail w i t h an e m e r y g r i n d e r and t r e a t e d w i t h Edison-Brown alloys, serving to a m a l g a m a t e the surface of the rail and fill valleys and depressions and irregularities of the surface, the 4 / o wires and the copper c a s t i n g grooves are also treated, the whole is t h e n bolted to the web of the rail with a I-inch bolt, u s i n g
FIc.
68.--Portable grinder.
a lock washer. T h e bond plates are located each side of the fish or j o i n t plate and are connected by two 4 / 0 wires. T h e No. 2 C. & S. bond is similar to the No. I, only t h a t it is l a r g e r and is bolted to the rail w i t h two I-inch bolts. T h e No. 3 C. & S. bond is similar in general design to
276
]farrington
:
[J. F. I.,
the No. i and No. 2, b u t differs in t h a t only one No. 4 / 0 wire is employed, and is t w i s t e d in a cireular loop at ends to fit in a circular groove in bond plates, the copper and iron plates are drawn to the web of the rail by one I-inch bolt w i t h lock washerS.
Fro. 69.--Portable grinder.
T h e No. 3 bond has been principally e m p l o y e d on tee rail, a l t h o u g h it is as well a d a p t e d for girder rail. T h e following cut (Fig. 74) illustrates ten types of bonds tested at random, and shown in detail after h a v i n g been tested. T h e m e t h o d of t e s t i n g (Fig'. 75) was exceedingly
April, x9o4.1
Rail
]3ouds.
2 77
s i m p l e a n d is d e s c r i b e d b e l o w u n d e r C. & S. t e s t i n g . Tl~e c o l u m n m a r k e d " R a t i o of C o n d u c t i v i t y B o n d to R a i l " (Fz¢,--, 7d) s i m p l y i n d i c a t e s t h e p e r c e n t a g e o f r e s i s t a n c e t h a t t h e 3 f e e t of rail, i n c l u d i n g j o i n t , b e a r t o 3 f e e t of s o l i d rail st,c-
FIG.
7o.--Portable drill in operation.
tion. I t w i l l b e n o t e d t h a t t h e t e s t s m a k e a v e r y g r a t i f y i n g showing. No,
i .......................... 2 . . . . . . . . . . . . . . . . . . . . . . . . . 3 ......................... 4 ..........................
P e r Cellt.
Years.
43 55 40 55
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[J. F. I.,
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No
Per cent.
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Years.
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Flo, 7i.--Portable drill.
T h e o t h e r t e s t s s h o w o v e r ]oo p e r cent., r a n g i n g f r o m [25 p e r cent. in test No. [o to 312 p e r cent, in t e s t s No. 6 a n d N o . 7.
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FIG. 72.--The Ajax rail-bond.
I t is well to s t a t e h e r e t h a t it is a w e l l - k n o w n fact, a n d t h e o b s e r v a t i o n of all e n g i n e e r s , t h a t s u c c e s s f u l r e s u l t s can-
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",:R^WN ~ TYPES PLUG
TR[NTON1 BOND: PLUO
U,PLU6. FI(;. 7~.--Ten distinctive types of bonds.
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282
Harrington :
[J. F. I.,
n o t be o b t a i n e d from bonds on track where the rail j o i n t s are not m a i n t a i n e d r e a s o n a b l y tight. A loose rail joint will i m p a i r a n y bond. CONANT'S
METHOD
or
BOND TESTING.
Design of c o n t a c t apparatus. T h e chief problem to be solved is t h a t of making, u n d e r all conditions, good c o n t a c t w i t h the rail at the three test points. T h i s has been accomp l i s h e d as follows : T h e c o n t a c t a p p a r a t u s consists of a c e n t e r pole w i t h steel chisel welded to socket at its lower end, to which are bolted by one thumb-screw, two extension b e a m s r e a c h i n g out on the rail, 3 feet on either side. T h e s e carry two hardened steel chisels w h i c h are s h a r p e n e d so as to bear at their centers. T h e edges are set so as to e x t e n d in the direction of the l e n g t h of the rail, while the center chisel edge is at r i g h t angles to the rail length. T h e extension b e a m s are of v e r y t o u g h a n d elastic wood, of v a r y i n g cross-section, so as to secure the best combination of r i g i d i t y and elasticity. T h e w r o u g h t steel knees, b y m e a n s of w h i c h the extension b e a m s are bolted to the center chisel, are p e r m a n e n t l y f a s t e n e d to the b e a m s in such positions t h a t w h e n the T is placed on the rail, the outer chisels touch first, while the center chisel edge is a b o u t an inch above the top of the rail. T h e n , b y r e s t i n g the hollow of the foot on one side, n e a r the center, the T is s p r u n g down so t h a t center chisel rests firmly on rail. T h i s springing action forces the o t h e r chisels o u t w a r d w i t h a s c r a p i n g m o v e m e n t t h a t cuts t h e m into perfect contact w i t h the rail. An additional m e a n s is provided for i n t e n s i f y i n g this cutt i n g effect, by p u s h i n g the h a n d l e of center pole back and forth b e t w e e n the positions i n d i c a t e d in t h e p h o t o g r a p h b y the d o t t e d pole handles. T h i s causes b o t h o u t e r chisel edges to cut t h r o u g h the scale on the rail p r o d u c e d by the rolling action of the car wheels, b u t does not d i s t u r b the contact of the c e n t e r chisel. As the best q u a l i t y and t e m p e r of steel is used in the construction of the chisels t h e y will r e t a i n their edge during a large n u m b e r of tests.
R a i l Bonds.
April, 19o4.]
283
T h e device for sharpening them is simple and rapid, and consists of a small fiat stone that is furnished with and carried in case of instruments. This cuts very quickly, and to
\
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FIG. 76.--R. W. Conant's T-pole bond tester.
stone up the chisel is but the work of a few minutes, as they do]not have to be removed or in any way disturbed from their places. T h e contact apparatus is portable and self-contained. By
284
Harrington :
[J. F. I.,
loosening one t h u m b - n u t the outer b e a m s are b r o u g h t u p to the center pole, m a k i n g it v e r y easy to carry. Method of testing. W i t h the T-pole connected to instrum e n t and telephone in position, t h e operator places T-pole on rail with rail j o i n t a b o u t a foot from the center chisel. T h e i n s t r u m e n t is s t a r t e d by its release switch at t h e side and the b a l a n c i n g switch is placed on point n u m b e r e d I. A r o a r i n g s o u n d in telephone indicates t h a t b a l a n c i n g switch is to be m o v e d to point of silence. W h e n this h a s been done the n u m b e r at which switch s t a n d s is read off T h i s n u m b e r shows the value of resistance of the rail j o i n t in t e r m s of the s t a n d a r d l e n g t h of rail spanned, which is 3 feet. For example, if the point of no s o u n d is found, t h e n t h e resistance of rail j o i n t is equal to twice the 3-foot l e n g t h m e n t i o n e d above, or 6 feet of rail. T h i s indicates a fair condition of bonding, bad j o i n t s r u n n i n g c o n s i d e r a b l y above this a m o u n t . As it takes b u t a m o m e n t to shift the switch completely a r o u n d its circle, the test of a j o i n t is m a d e v e r y quickly. c. & s. TESTING. C. & S. m e t h o d of testing. T h e m e t h o d e m p l o y e d by t h e C a m d e n & S u b u r b a n R a i l w a y C o m p a n y for all its o r d i n a r y testing, is w i t h a car h a v i n g m o u n t e d t h e r e i n a barrel of water, r h e o s t a t i n c l u d e d in circuit, a W e s t o n a m m e t e r , also a W e s t o n voltmeter, to o b t a i n line voltage. A small t r u c k w i t h wood f r a m i n g h a v i n g two axles and 33-inch wheels on 3-foot centers, w i t h a \Veston m i l l i - v o l t m e t e r located in car and h a v i n g its t e r m i n a l s c o n n e c t e d to the axles of small truck, the ear is r u n so t h a t the small t r u c k will trail b e t w e e n car and power station. As all r e a d i n g s are t a k e n relatively, t h a t is, c o m p a r i n g r e a d i n g s of e q u i v a l e n t j o i n t l e n g t h s and solid rail l e n g t h s , n o t h i n g need be done except to r u n and m a k e notes. If, however, a n y u n u s u a l r e a d i n g arises the joints m a y be tested s e p a r a t e l y by r a i s i n g and i n s u l a t i n g the wheels of the small truck on the rail; measurem e n t s are not desired to be m a d e . In m a n y cases ordinarily all t h a t m a y be used is a Wes-
April, ,9o4.]
Rail Bonds.
285
ton v o l t m e t e r taken a r o u n d b y a m a n and a b o y with leads to c o m p a r e drop a r o u n d joint with solid rail. In addition to the above, at reasonable intervals the bonding of a r a i l w a y should be inspected, tested and reported u p o n with s u g g e s t i o n s from some g o o d recognized engineering expert. F r e q u e n t tests over a s y s t e m is positively necessary, as defects will develop, n o t w i t h s t a n d i n g w h a t form, kind or make of bond is employed. L o a d s will change, service increases or grows, track b e c o m e s worn, special work gives out, u n d e r g r o u n d piping is changed, modified or increased. P e r h a p s one of the w e a k e s t features in b o n d i n g is over railroad crossings, and a r o u n d special track w o r k - - t o o m u c h care cannot be exercised at such places. A s a rule, look for high resistance at such places, and particularly w h e r e low joints are observed. R a i l r o a d crossings and special w o r k are peculiarly easy to guard. It has been the practice of the writer for some years to cross bond from one side of a railroad crossing to the other, u s i n g 4 / 0 i n s u l a t e d W. P. wires in sufficient number, proportioned to the load, and carried u n d e r the railroad tracks in a terra-cotta pipe. As to the question of concealed or e x p o s e d bonds, this q u e s t i o n m u s t be settled p u r e l y by the e n v i r o n m e n t and conditions u n d e r which the track is to be bonded. An e x p o s e d bond, while s u b j e c t to theft on open-track work, has m a n y a d v a n t a g e s w h e n it can be employed, in that it is always s u b j e c t to quick inspection. As the real figure of merit of a bond is its life and low resistance, the exposed b o n d has the a d v a n t a g e of longer life and to all intents and purposes no material difference in resistance in comparison with the concealed. In paved streets, the q u e s t i o n of exposed or concealed b o n d i n g in the writer's opinion is not to be considered, as it resolves itself into solely a question of life, c o n d u c t i v i t y and cost, design b e i n g of last importance, design only e n t e r i n g into the question as a m a t t e r of final detail w h e n considerin K the c h a r a c t e r of joint- or fish-plate. In conclusion, the w r i t e r wishes to emphasize the follow-
286
Appem:i::
."
[J. F. I.,
i n g facts as t h e r e s u l t s of his o b s e r v a t i o n a n d e x p e r i e n c e . (I) I n c o n s i d e r i n g a n y b o n d , o b s e r v e a l w a y s : Obtain actual resistance data.
Figure costs to obtain same. Resistance
Conductivity compared with other bonds. Usually compare 3 feet of rail, including joint, with 3 feet of
solid rail section. Life
~ Study life o[ bonds, behavior under practical operation. Make frequent inspection of bonds in service.
Tests
Have frequent tests made on bonding. Look for trouble at all special work and low joints.
T h e w r i t e r w i s h e s to a c k n o w l e d g e t h e c o u r t e s y a n d kindly spirit shown by the following manufacturers and e n g i n e e r s in f u r n i s h i n g d a t a f o r t h i s p a p e r : Mayer & E n g l u n d , Ohio Brass Company, A m e r i c a n Steel Wire Company, Chase-Shawmut C o m p a n y , H a r o l d P. Brown, R. W. Conant, General Electric Company, A j a x M e t a l C o m p a n y , A l b e r t B. H e r r i c k , H. A. J o h n s o n . I n a d d i t i o n to t h i s p a p e r , t h e w r i t e r w i s h e s to a d d t h e r e t o as a n a p p e n d i x a c o m m u n i c a t i o n f r o m Mr. A. B. H e r r i c k , consulting engineer, d e s c r i b i n g his testing a p p a r a t u s ; an a r t i c l e b y Mr. H a r o l d P. B r o w n , d e s c r i b i n g e v o l u t i o n o f b o n d i n g ; a n d to r e f e r to t h e v e r y c o m p l e t e rail b o n d catal o g u e , d a t e d J u n e I, I9O2 , i s s u e d b y P r o t e c t e d R a i l B o n d C o m p a n y of P h i l a d e l p h i a , w h i c h is r e p l e t e w i t h e n g i n e e r i n g facts and data, and s u p p l e m e n t e d b y an article contained t h e r e i n f r o m t h e p e n of Mr. A. B. H e r r i c k , c o n s u l t i n g e n g i neer, of N e w Y o r k . APPENDIX. ~g. E .
ROCHESTER, 2q. Y., September i4, 19o3. H a r r i n g t o n , ~ I a n a g e r Camden Co° Su3urban R a i l w a y Company,
Camden, W. jr. DEAR SIR :--In answer to your favor of September 8th, I enclose herewith
the photograph of my autographic recording apparatus. The method of operating is as follows : the fall of potential on each rail is taken by two sliding brushes 4 feet apart on each rail. In order that there may always be current present on these rails, a transformer is used which gives me about 200 amperes on each rail. The drop from these rail contacts are taken to two Weston milli-voltmeters, which have a commutator over the scale which they pass, and these hands bridge a spark gap, which spark is conducted to the surface of the record paper, which record paper moves at the rate of i inch
April. 19o4.]
]~az'l ]3'ands.
287
per ioo feet traveled by a test car, and the spark traces the record of the m o v e m e n t of the hands at every instant as the car progresses along the track. The height of the deflection of the mark line on the record, when the brushes pass over a joint in the rails, gives the resistance of the joint in terms of 4 feet of rail. There is also, in order to protect these instruments, an automatic relay which cuts out the instrument when it reads beyond an adjustable point, which is changed depending upon the current density required for the rail to carry at the different portions of the system. W h e n this relay operates, it also moves a pen and indicates a poor bond at that point oll the record, there being provided a pen for each rail. The way these bonds are located on the record is by means of a third pen, which draws a continuous line which is open from one curb to the next in case of street intersections, crossings or special work, and, immediately after this location is given, a number is telegraphed by the side m o v e m e n t of the pen, which corresponds to the number assigned to this intersection or special point of location. In this way any bond can be located by measuring on the scale of I inch to ioo feet on the record. In interurban work when the automatic moves, it also actuates electrically-controlled valve, which squirts whitewash or paint on the track at the poor bonds. Briefly, m y experience in bonding rails is that in the cast weld made since iS98 the bond at the b e g i n n i n g of the pour is of lower resistance than a 9o.pound rail of the same length as the weld. At the end of the pour it runs up to 3 feet of the 5o.pound rail. The electric weld is m u c h more uniform as now made by the Lorain Company, and i,~ less t h a n the equivalent length of rail over which the connection is made. In flexible bonds with solid head terminals, those put in by means of compressor givigg an effect of compression of 3o tons have lower initial resistance t h a n any other mechanical method of connecting the bond to the rail, and when the flexible portion is cast into head portion, it shows greater permanence u n d e r poor track conditions than any other method used in constructing these bonds. The bond soldered to the rail, where the laminations are presented edgewise to the ball of the rail, shows the best form of this construction, but I have not had a life-test on these bonds. Hoping this data will be useful to you, I remain, Yours truly, (Signed) ALBERT B. HERRICK. R A I L BONDS AND E L E C T R I C A L CONTACTS F O R H E A V Y CURRENTS. BY HAROLD P. BROWN. The writer has given very careful study to this subject and, as is shown by papers read before this Institute in '96 and '97, has always advised heavy bonding and low contact resistance. These views were at first received with a smile, since it was only a few years ago that the leading street railway electricians felt perfectly satisfied with their track circuit after burying a No. 2/0 copper wire under the right of way and connecting it to each rail with a No. o tap and a channel pin Many of these gentlemen would tell you seriously that the earth was a " reservoir
288
Appendix
:
[J. F. I.,
of electricity," or a " conductor of infinitely low resistance," and that therefore a No. 2/o wire was more than sufficient to do the necessary work. They were surprised to find after a very short service t h a t t h e i r " s u p p l e m e n t a r y wire " had practically disappeared, and the r e m e d y for this disappearance was supposed to be found in the use of tinned copper wire. Later the " s u p p l e m e n t a r y wire " was definitely abandoned and scraps of No. 2/o trolley wire were used as bonds around the angle plates by means of h a n d y but deceptive channel pins. Still later bonds of wire were made with enlarged terminals whleh were riveted into holes in the rail. This riveting was slow work and gave unsatisfactory results, and the next step in advance was what is k n o w n as the " C h i c a g o " bond, whose enlarged terminal was expanded into a hole in the rail by driviDg a tapered steel pin into a cylindrical hole in the center of the b o n d terminal. At first these pins were driven from the side of the rail opposite the bond which was h e l d in place during the driving by a suitable lever or clamp. The next improvement in this type of bond was driving the pin fr0m the same side of the rail as the bond, and reducing the sectional diameter of the hole through terminal at its outer end. The steel pin t h e n displaced t h e metal on the far side of the terminal and enlarged its external diameter, k e e p i n g it from falling out. An endless n u m b e r of bond terminals have been devised to effect a contact between a copper bond and a steel rail. But nearly all of their inventors did not consider the fact that the ratio of eopper expansion under heat is greater t h a n that of steel. Therefore, if a cylinder of copper is compressed even with hydraulic pressure into a cylindrical hole in a steel rail and the metals heated, the copper m u s t occupy greater cubical space t h a n before. It cannot expand in the direction of the steel walls surrounding it, theregore all of the expansion must take effect in a line parallel with the center of the cylinder, thus increasing its l e n g t h while heated. When, however, the metals are allowed to cool the contraction takes place equally in all directions instead of entirely in one line as did the expansion. Therefore when the cooling is completed the copper cylinder is of less diameter than before. Into this small space moisture is sure to penetrate, forming an incompressible layer of iron oxide. When the next heating takes place tile same process is gone t h r o u g h and t h e copper is still further reduced in diameter. Pinally, t h o u g h the mechanical joint between the bond and the iron may seem perfect, the layer of iron oxide may be so thick as to practically ruin the conductivity of the bond. It is well known that in boiler or girder work, iron rust will inevitably form beneath the head of a steel rivet applied under hydraulic pressure in a steel plate with exactly the same coefficient of heat expansion. But perfection of eontaet between copper and steel is not the only problem in rail bonding, since even with the best type of joints there will be some motion between the rail ends under passing cars and with difference in temperature. It was found that the solid wire bonds crystallized and broke between t h e terminals, therefore the solid wires were replaced by flexible copper strands with enlarged terminals cast or welded on the ends.
R a i l Bonds.
April, I9o4. ]
2S 9
It was t h e n f o u n d t h a t s t r a n d e d copper b o n d s with cast copper h e a d s could be f a s t e n e d m o r e f i r m l y to t h e rails b y s c r e w or h y d r a u l i c c o m p r e s s i o n t h a n c o u l d s i m i l a r b o n d s w h i c h w e r e a p p l i e d b y d r i v i n g t h e conical pin. H o w e v e r , t h e g r e a t r i g i d i t y in t h e t e r m i n a l h a d t h e effect of c a u s i n g t h e s t r a u d s to wear o u t t h e s o o n e r . A s i m i l a r effect was p r o d u c e d w h e n copper b o n d s were w e l d e d to s t e e l rails, w i t h t h e a d d i t i o n a l d i s a d v a n t a g e t h a t w e l d e d steel a n d c o p p e r f o r m a t h e r m o - e l e c t r i c couple, a n d t h e loss d u e to t h e F e l t i e r effect of c u r r e n t t r a n s m i s s i o n was oL'en far g r e a t e r t h a n t h e r e s i s t a n c e loss. R e t u r n i n g for a m o m e n t to t h e m a t t e r of c o n t a c t b e t w e e n two m e t a l surfaces, a n y o n e w h o h a s ever s c r a p e d a slide v a l v e to a fit will a p p r e c i a t e t h e fact t h a t m e t a l p l a t e s , e v e n w h e n g r o u n d to a " t r u e " surface, a r e n o t h i n g m o r e t h a n a series of h i g h p o i n t s s u r r o u n d e d b y d e p r e s s i o n s w h i c h are clearly s h o w n b y t h e m i c r o s c o p e . R e a l i z i n g t h i s fact a n d k n o w i n g t h e h i g h resista n c e of iron o x i d e oll c o n t a c t m e t a l s , in t894 a n i n v e n t o r h i t u p o n t h e s c h e m e of c o a t i n g steel a n d c o p p e r c o n t a c t s w i t h a n a d h e r e n t l a y e r o f a m a l g a m a p p l i e d b y a n a l k a l i n e p r o c e s s . O n t h i s p r e p a r e d s u r f a c e a l a y e r o f a plastic m e t a l w a s p l a c e d a n d as t h i s filled all t h e i n e q u a l i t i e s of t h e c o n t a c t s a n d p r e v e n t e d o x i d a t i o n , c u r r e n t s c o u l d be t r a n s m i t t e d at t h e r a t e of 1,5oo a m p e r e s p e r s q u a r e i n c h of s e c t i o n w i t h o u t c o n t a c t loss. F r o m t h i s s c h e m e w a s e v o l v e d t h e plastic rail b o n d in w h i c h a bit of plastic m e t a l is u s e d to b r i d g e t h e s p a c e b e t w e e n rail a n d a n g l e plate. T h e m e t a l p u t t y is h e l d in p l a c e b y a ease or r i n g of c o r k m a t e r i a l , w h i c h is n o r m a l l y 50 p e r cent. t h i c k e r t h a n t h e s p a c e b e t w e e n t h e rail a n d t h e plate; it is t h e r e f o r e c o m p r e s s e d w h e n t h e p l a t e is b o l t e d d o w n , t h u s effectively seali n g its c o n t e n t s . T h e p l a s t i c m a t e r i a l a d h e r e d to t h e a m a l g a n l a t ~ d s u r f a c e s a n d m a i n t a i n e d a c o n t a c t of low r e s i s t a n c e for y e a r s in s p i t e of t h e m o t i o n d u e to p a s s i n g cars or t e m p e r a t u r e c h a n g e s . T h e w r i t e r was o n e of t h e first to u s e t h i s t y p e of b o n d w i t h s a t i s f a c t o r y r e s u l t s b o t h at t h e o u t s e t a n d a f t e r m a n y y ears of us-~. B o m l s of t h i s k i n d i n s t a l l e d by t h e w r i t e r in I895 s h o w e d in i9oo a n a v e r a g e d r o p of 'ooi volts, w h i l e a r e a d i n g of t h e s a m e l e n g t h of u n b r o k t n rail s e c t i o n g a v e "oo3 volts. T h e f o l l o w i n g letter, d a t e d A u g u s t 2i, i9o3, h a s r e c e n t l y b e e n b r o u g h t to m y notice, w h i c h s h o w s e v e n b e t t e r r e s u l t s after s e v e n y e a r s ' service: " I n A u g u s t , J896 , we r e c e i v e d two p l a s t i c b o n d s as s a m p l e . I h a d o u r f o r e m a n , Mr. H u l l i u , p l a c e t h e m o n a 5 t - p o u n d j o i n t of J o h n s t o n g i r d e r rail. T h e b o n d h a d n e v e r b e e n d i s t u r b e d u n t i l a few d a y s ago. I was at t h e t i m e m a k i n g s o m e t e s t s w i t h a C o n a u t b o n d tester. W h e n i c a m e to t h i s j o i n t I f o u n d t h e r e s i s t a n c e was so m u c h less t h a n in t h e o t h e r s t h a t I d e t e r m i n e d to h a v e it o p e n e d , so I c o u l d a c c o u n t for its low r e s i s t a n c e . A f t e r o p e n i n g it, I d i s c o v e r e d t h a t it was t h e j o i n t w i t h t h e plastic b o n d , w h i c h s h o w e d no m o r e resistance t h a n t h e rail itself. A f t e r h a v i n g b e e n u n d e r s e r v i c e n e a r l y s e v e n years, I f o u n d t h e a l l o y a n d c o n t a c t of b o n d in p e r f e c t order. (Signed) F . A . R o s s , Supl. [~ailway Dept.,
~S~zcratnento tz'lectric, Gas and ~ailway Co." To t h e a v e r a g e e n g i n e e r t h i s t y p e of plastic b o n d does n o t appeal, s i n c e it does n o t s e e m m e c h a n i c a l , a n d it is e v i d e n t t h a t if t h e a n g l e p l a t e g e t s loose t h e m a t e r i a l of t h e b o n d will be lost. VOL. C L V I I .
N o 940.
19
e9o
A~pendi.~" :
[J. F. I.,
It is also evident that any other type of bond with loose angle plate will soon be destroyed. Tile use of this bond and familiarity with the permanence of the plastic alloy contacts led the writer to design a bond composed of an amalgamated copper strip held in contact against the web of rail by screws threaded through the angle plate. One end of the strip was in contact with one rail, and the other end with the second rail. The thrust of the screws was received on a thin steel plate and both the copper plate and the web of the rail were amalgamated and covered with the plastic alloy. This type of Bond has given entire satisfaction after m a n y years of service. A modification of this bond called the solid copper bond has had very extensive use in all parts of the world. In this bond the screws used by the writer were replaced by a pair of strong steel springs of the nut-lock type placed between the inner surface of angle plate and the amalgamated copper strip. The thrust of these springs is taken by a soft steel plate to prevent wearing holes in the copper of bond. To keep grit and dirt away from the contact surfaces and to hold the springs in place before the bond is applied, the conductor strip is attaehed to a plate of cork material overlapping the ends and sides of the conductor. When the angle plate is bolted up, this eork plate is compressed so that it touehes the web of the rail and the sides of lhe bond. A plate of similar cork material is placed between the rail ends, thus sealing the crack which would otherwise admit dirt and let out the plastic covering of the bond. With this type of bond t h e motion of the rail ends under passing cars serves to improve the contact. It is interesting to note that stranded bonds of the crown or horse-shoe type have much Better conductivity and last far longer if their terminals and the holes in the rails are amalgamated and covered with a thin layer of the plastic alloy. During the past few years the short-stranded copper bonds have broken to such an extent that few roads use less than seven inches between centers. With bonds of this length and the modern heavy rails and angle plates, mechanical breakage of the bonds has been greatly reduced. But careful tests show plainly their falling off in conductivity through corroding terminals. Several different types of bond-testing apparatus have been designed in the past few years. One type is attached to a ear which is drawn over the road, and its designer and proprietor is said to record the exact electrical condition of tim bonds in a single round-trip at the rate of 6 or 8 miles per hour. This might be possible with accuracy if the rails were clean and b r i g h t But with the ordinary conditions of track covered with dust and scale, this is impossible. Careful measurements with the milli.voltmeter will show very different results. An ingenious type of telephonic tester has been designed by a Boston engineer, and seems to get the most rapid results with a fair degree of accuracy. But for absolute precision nothing can equal milli-voltmeter measurements of a given length of unbroken rail compared simultaneously with the same length including the bond. Even with this method, it is necessary to amalgamate the three contact spots for the instrument in order to obtain absolute accuracy.
April, I9o4. ]
R ai l Boncls.
2(,I
A steel point forming a terminal of the milli-voltmeter will give results very often proportional with the amount of pressure applied or the number of scratches made in the same place on the rail. The most serious side of this subject to an electric railway is the fact that every year the bonds are losing conductivity either from mechanical or chemical causes : breakage or corrosion. It is now well known that poor bonds often double the amount of power required to operate a given n u m b e r of cars. That being the case, the accurate testing of rail bonds and the replacement of defective bonds is a subject whose impo,.rtance cannot be over-estimated. When defective bonds are found in a paved street or even on exposed track, it is a serious problem to apply a new bond without great expense. To use a flexibe copper bond under the angle plate requires the removal of a large amount of pavement and of the angle plates. This means the loss of fully 50 per cent. of the nuts and bolts, and after the bonding is completed it is almost impossible to replace the plates in the location previously occupied. However t i g h t the nuts may be screwed up, the fins left by the former position of the plates will prevent a tight fit. After the pavement is replaced and a few months have gone by, these fins wear away and the plates get loose, and both joint and bond are soon in bad condition. The flexible copper bond around the angle plate requires a greater amount of pavement removed, the bond is expensive, and when the pavement is replaced, it is easily broken off by the movement of the rail. An ideal bond for this purpose is one which disturbs the least amount of pavement in placing, which can be applied without removing bolts and angle plates, and which will permit a reasonable amount of motion between the rail and plate. This idea is very well fulfilled in what is known as the Plastic Plug bond. Two holes are drilled through one angle plate at each joint, so that the drill passes through the base or foot of angle plate and partly through the base of the rail. After this hole is drilled and amalgamated, a small amount of plastic alloy is placed in it and a T-shaped copper plug driven far enough to dip into the plastic alloy. The top of this T makes an amalgamated contact with the angle plate ; its bottom drops into the plastic alloy in the rail. The bond pernfits a motion between plate and rail of ~4 inch or more in every direction without breaking the electrical contact, and the bonds have great conductivity even after many years' use. I should not advise the use of a smaller size than 3.~ inch diameter for this type of bond. as the ~i inch ~ize does not perufit sufficient motion or expansion and contraction. The 7~ inch size, wherever the rail will permit it, is sttll better. A simpler form of this type of bond is made by drilling a hole parallel with the upper edge of the angle plate, so that half of the hole is in the lower edge of rail top, and the other half in the upper edge of angle plate. After this hole is drilled and amalgamated, a coppe~rod of cylindrical section is driven into it and held in place by burring the rail over top of the rod. As the rail moves on the plate this rod is partly sheared, but not enough is left of the copper unsheared to make the bond of very high conductivity.
292
[J. F. I.,
Notes a n d Comments.
Q u e e r l y e n o u g h , e v e n if t h e m o t i o n be sufficient to e n t i r e l y s h e a r t h e b o n d , a h a m m e r blow will force b o t h p a r t s into i n t i m a t e c o n t a c t a n d r e s t o r e t h e full c o n d u c t i v i t y . O n e f o r m of t h i s b o n d s p l i t s in a d v a n c e t h e c o p p e r c y l i n d e r so t h a t t h e h a l v e s slide o n e a c h o t h e r as t h e m o t i o n t a k e s p l a c e ; b u t t h i s does n o t s e e m to g i v e as s a t i s f a c t o r y r e s u l t s as t h e solid c y l i n d e r . O f c o u r s e o n e i m p o r t a n t p o i n t in f a v o r of t h i s t y p e of b o n d is its c h e a p ness. But w h a t e v e r t y p e of b o n d is u s e d , f r e q u e n t i n s p e c t i o n a n d i m m e d i a t e r e p l a c e m e n t of d e f e c t i v e b o n d s is of t h e u t m o s t i m p o r t a n c e .
A SILVER-LIKE
METAL.
A w r i t e r in t h e A l u m i n u m tUor/d g i v e s t h e c o n s t i t u e n t s o f a h a r d alloy w h i c h h a s b e e n f o u n d v e r y u s e f u l for t h e o p e r a t i n g l e v e r s of c e r t a i n m a c h i n e s . T h e s p a c i n g l e v e r of a t y p e w r i t e r is c o n s t a n t l y h a n d l e d w h e n in use, a n d if m a d e of i r o n or s t e e l a n d n i c k e l - p l a t e d , e v e n h e a v i l y , t h e p l a t i n g s o o n w e a r s off, l e a v i n g t h e m e t a l u n d e r n e a t h e x p o s e d to r u s t a n d corrosion, a c o n d i t i o n w h i c h , o f course, is n o t p e r m i s s i b l e . I f t h e levers a r e m a d e of b r a s s t h e m a t t e r is n o t h e l p e d to a n y e x t e n t , as t h e p l a t i n g w e a r s off t h e s a m e as i r o n or steel a n d l e a v e s t h e b r a s s e x p o s e d , w h i c h is, if a n y t h i n g , m o r e o b j e c t i o n able t h a n i r o n or steel. T h e m e t a l n o w g e n e r a l l y u s e d for t h i s p u r p o s e by t h e v a r i o u s t y p e w r i t e r c o m p a n i e s is " a l u m i n u m s i l v e r , " or " s i l v e r m e t a l . " T h e p r o p o r t i o n s are g i v e n as f o l l o w s : Copper . . . . . . . Nickel . . . . . . . Zinc . . . . . . . . Aluminum . . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . . . . . . . . . . . . . . . . .
. . . .
. . . .
. . . .
. . . .
. . . .
57 oo 2o.oo 2o.oo 3.oo IO0.O0
T h i s a l l o y w h e n u s e d o n t y p e w r i t i n g m a c h i n e s is n i c k e l - p l a t e d for t h e s a k e of t h e first a p p e a r a n c e , b u t so f a r as c o r r o s i o n is c o n c e r n e d , n i c k e l i n g is u n n e c e s s a r y . I n r e g a r d to its o t h e r qualities, t h e y are o f a c h a r a c t e r t h a t r e c o m m e n d s t h e a l l o y for m a n y p u r p o s e s . It is stiff a n d s t r o n g a n d c a n n o t be b e n t to a n y e x t e n t w i t h o u t b r e a k i n g , e s p e c i a l l y if t h e p e r c e n t a g e of a l u m i n u m is i n c r e a s e d to 3-5 p e r c e n t . ; it casts free f r o m p i n h o l e s a n d blowh o l e s ; t h e l i q u i d m e t a l c o m p l e t e l y fills t h e m o l d , g i v i n g s h a r p , c l e a n casti n g s , t r u e to p a t t e r n ; its cost is n o t g r e a t e r t h a n b r a s s ; its color is silver w h i t e ; a n d its h a r d n e s s m a k e s it s u s c e p t i b l e o f a h i g h polish.
NATURAL
BORAX.
T h e m i n e r a l boroealeite f u r n i s h e s t h e b a s e of t h e g r e a t e r p a r t of t h e b o r a x c o n s u m e d in E u r o p e . F i f t e e n p a r t s of finely c r u s h e d ore w i t h 6o p a r t s water, 8 p a r t s s o d i u m b i c a r b o n a t e a n d 2 of c a u s t i c s o d a a r e b o i l e d in a s t e a m - h e a t e d boiler a b o u t t h r e e h o r n s . It is t h e n filtered a n d c r y s t a l l i z e d , y i e l d i n g c r y s t a l s of borax. I t is e s t i m a t e d t h a t IOO p o u n d s of boroealcite will y i e l d f r o m l c o to Io5 p o u n d s of crystallized borax.--t~ngineeri~ and LlIiningJournal.
April, 19o4. ]
ELECTRICAL
273
SECTION
Staled 2WeetinF held Thursday, October S, sgo3.
Raft Bonds.
BY W. I~. HARRINGTON. General Manager Camden and Suburban Railway Company.
( Concluded f r o m iO. 230.)
SPECIAL RAIL-BONDING TOOLS.
Figs. 6 7 to 7 r e x h i b i t a series of special rail b o n d i n g tools designed for placing a m a l g a m a t e d bonds. A J A X BOND.
T h e A j a x bond consists of a s h e e t or piece of copper, c o n t a c t i n g with the w e b of rail on each side of joint u n d e r the fish plate or joint, held up and a g a i n s t the web by set screws, c u p p e d h a r d e n e d ends, set screws set in fish plate or j o i n t ; u s u a l m e t h o d is to insert a s h e e t of steel b e t w e e n copper plate and points of set screws. T h e w e b of rail h a v i n g b e e n g r o u n d off and t r e a t e d w i t h Edison-Brown alloys, as well as the side of the copper plate contacting with rail, the result is to all intents and p u r p o s e s a knifeblade switch. In all cases w h e r e the A j a x bond has been installed and action and life observed, it has invariably shown a v e r y s a t i s f a c t o r y condition. T e s t No. I I s h o w s 9 ° per cent. resistance, three years life. It m i g h t be i n t e r e s t i n g here to m e n t i o n o t h e r makes of b o n d s more or less in use, some of which have fallen into disuse, either from inefficiency or interested parties discontinuing manufacturing : J o h n s t o n bond, W e s t E n d bond, Bryan bond, Columbia bond, Channel Pin bond, F o r e s t City bond, S. H. H a r r i n g t o n ball bond, S. H. H a r r i n g t o n diagonal bond, G r a u t e n bond, VOL. CLVII.
NO. 94 ° .
t8
274
Harrzngton
."
[ J. F. I.,
Stern &. Silverman bond, P a y n e w e l d e d bond, A t k i n s o n bond, Syracuse bond. CAMDEN AND S U B U R B A N R A I L W A Y
BONDS.
The C. & S. bonds shown in Fig-. 73 were designed b y the writer and i n t e n d e d to provide large, ample contacts. T h e
FIG. 67.--Portable grinder.
No. I C. & S. b o n d consists of a square copper casting w i t h two grooves for 4 / o B. & S. g a u g e copper w i f e ; casting has a @~-ineh hole in center. A cast-iron c a s t i n g with corr e s p o n d i n g grooves and hole is provided. T h e b o n d is
April. 19o4.]
/~az/ t,'onds.
275
applied by g r i n d i n g off the web of the rail w i t h an e m e r y g r i n d e r and t r e a t e d w i t h Edison-Brown alloys, serving to a m a l g a m a t e the surface of the rail and fill valleys and depressions and irregularities of the surface, the 4 / o wires and the copper c a s t i n g grooves are also treated, the whole is t h e n bolted to the web of the rail with a I-inch bolt, u s i n g
FIc.
68.--Portable grinder.
a lock washer. T h e bond plates are located each side of the fish or j o i n t plate and are connected by two 4 / 0 wires. T h e No. 2 C. & S. bond is similar to the No. I, only t h a t it is l a r g e r and is bolted to the rail w i t h two I-inch bolts. T h e No. 3 C. & S. bond is similar in general design to
276
]farrington
:
[J. F. I.,
the No. i and No. 2, b u t differs in t h a t only one No. 4 / 0 wire is employed, and is t w i s t e d in a cireular loop at ends to fit in a circular groove in bond plates, the copper and iron plates are drawn to the web of the rail by one I-inch bolt w i t h lock washerS.
Fro. 69.--Portable grinder.
T h e No. 3 bond has been principally e m p l o y e d on tee rail, a l t h o u g h it is as well a d a p t e d for girder rail. T h e following cut (Fig. 74) illustrates ten types of bonds tested at random, and shown in detail after h a v i n g been tested. T h e m e t h o d of t e s t i n g (Fig'. 75) was exceedingly
April, x9o4.1
Rail
]3ouds.
2 77
s i m p l e a n d is d e s c r i b e d b e l o w u n d e r C. & S. t e s t i n g . Tl~e c o l u m n m a r k e d " R a t i o of C o n d u c t i v i t y B o n d to R a i l " (Fz¢,--, 7d) s i m p l y i n d i c a t e s t h e p e r c e n t a g e o f r e s i s t a n c e t h a t t h e 3 f e e t of rail, i n c l u d i n g j o i n t , b e a r t o 3 f e e t of s o l i d rail st,c-
FIG.
7o.--Portable drill in operation.
tion. I t w i l l b e n o t e d t h a t t h e t e s t s m a k e a v e r y g r a t i f y i n g showing. No,
i .......................... 2 . . . . . . . . . . . . . . . . . . . . . . . . . 3 ......................... 4 ..........................
P e r Cellt.
Years.
43 55 40 55
4 3
2 3
278
l~arringtolz
[J. F. I.,
."
No
Per cent.
5
. . . . . . . . . . . . . . . . . . . . . . . . .
66
7
.
9°
3
.
9 II
Years.
43
8
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
.
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.
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.
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.
.
.
.
.
Flo, 7i.--Portable drill.
T h e o t h e r t e s t s s h o w o v e r ]oo p e r cent., r a n g i n g f r o m [25 p e r cent. in test No. [o to 312 p e r cent, in t e s t s No. 6 a n d N o . 7.
1. . . . . . . . . . . . . .
~---t
'
t
k ................
j
Ifl
It
I1
11
t!i
/L
FIG. 72.--The Ajax rail-bond.
I t is well to s t a t e h e r e t h a t it is a w e l l - k n o w n fact, a n d t h e o b s e r v a t i o n of all e n g i n e e r s , t h a t s u c c e s s f u l r e s u l t s can-
f ~
i~
.g
C~ ,LO
d 7~
Z
-
I_:-'
6 l T
i,.
~
',_~
"
,
~
..
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,, ~
",:R^WN ~ TYPES PLUG
TR[NTON1 BOND: PLUO
U,PLU6. FI(;. 7~.--Ten distinctive types of bonds.
i"
!A
.N r_r]~
r_]
S
-I1
c~
282
Harrington :
[J. F. I.,
n o t be o b t a i n e d from bonds on track where the rail j o i n t s are not m a i n t a i n e d r e a s o n a b l y tight. A loose rail joint will i m p a i r a n y bond. CONANT'S
METHOD
or
BOND TESTING.
Design of c o n t a c t apparatus. T h e chief problem to be solved is t h a t of making, u n d e r all conditions, good c o n t a c t w i t h the rail at the three test points. T h i s has been accomp l i s h e d as follows : T h e c o n t a c t a p p a r a t u s consists of a c e n t e r pole w i t h steel chisel welded to socket at its lower end, to which are bolted by one thumb-screw, two extension b e a m s r e a c h i n g out on the rail, 3 feet on either side. T h e s e carry two hardened steel chisels w h i c h are s h a r p e n e d so as to bear at their centers. T h e edges are set so as to e x t e n d in the direction of the l e n g t h of the rail, while the center chisel edge is at r i g h t angles to the rail length. T h e extension b e a m s are of v e r y t o u g h a n d elastic wood, of v a r y i n g cross-section, so as to secure the best combination of r i g i d i t y and elasticity. T h e w r o u g h t steel knees, b y m e a n s of w h i c h the extension b e a m s are bolted to the center chisel, are p e r m a n e n t l y f a s t e n e d to the b e a m s in such positions t h a t w h e n the T is placed on the rail, the outer chisels touch first, while the center chisel edge is a b o u t an inch above the top of the rail. T h e n , b y r e s t i n g the hollow of the foot on one side, n e a r the center, the T is s p r u n g down so t h a t center chisel rests firmly on rail. T h i s springing action forces the o t h e r chisels o u t w a r d w i t h a s c r a p i n g m o v e m e n t t h a t cuts t h e m into perfect contact w i t h the rail. An additional m e a n s is provided for i n t e n s i f y i n g this cutt i n g effect, by p u s h i n g the h a n d l e of center pole back and forth b e t w e e n the positions i n d i c a t e d in t h e p h o t o g r a p h b y the d o t t e d pole handles. T h i s causes b o t h o u t e r chisel edges to cut t h r o u g h the scale on the rail p r o d u c e d by the rolling action of the car wheels, b u t does not d i s t u r b the contact of the c e n t e r chisel. As the best q u a l i t y and t e m p e r of steel is used in the construction of the chisels t h e y will r e t a i n their edge during a large n u m b e r of tests.
R a i l Bonds.
April, 19o4.]
283
T h e device for sharpening them is simple and rapid, and consists of a small fiat stone that is furnished with and carried in case of instruments. This cuts very quickly, and to
\
\
FIG. 76.--R. W. Conant's T-pole bond tester.
stone up the chisel is but the work of a few minutes, as they do]not have to be removed or in any way disturbed from their places. T h e contact apparatus is portable and self-contained. By
284
Harrington :
[J. F. I.,
loosening one t h u m b - n u t the outer b e a m s are b r o u g h t u p to the center pole, m a k i n g it v e r y easy to carry. Method of testing. W i t h the T-pole connected to instrum e n t and telephone in position, t h e operator places T-pole on rail with rail j o i n t a b o u t a foot from the center chisel. T h e i n s t r u m e n t is s t a r t e d by its release switch at t h e side and the b a l a n c i n g switch is placed on point n u m b e r e d I. A r o a r i n g s o u n d in telephone indicates t h a t b a l a n c i n g switch is to be m o v e d to point of silence. W h e n this h a s been done the n u m b e r at which switch s t a n d s is read off T h i s n u m b e r shows the value of resistance of the rail j o i n t in t e r m s of the s t a n d a r d l e n g t h of rail spanned, which is 3 feet. For example, if the point of no s o u n d is found, t h e n t h e resistance of rail j o i n t is equal to twice the 3-foot l e n g t h m e n t i o n e d above, or 6 feet of rail. T h i s indicates a fair condition of bonding, bad j o i n t s r u n n i n g c o n s i d e r a b l y above this a m o u n t . As it takes b u t a m o m e n t to shift the switch completely a r o u n d its circle, the test of a j o i n t is m a d e v e r y quickly. c. & s. TESTING. C. & S. m e t h o d of testing. T h e m e t h o d e m p l o y e d by t h e C a m d e n & S u b u r b a n R a i l w a y C o m p a n y for all its o r d i n a r y testing, is w i t h a car h a v i n g m o u n t e d t h e r e i n a barrel of water, r h e o s t a t i n c l u d e d in circuit, a W e s t o n a m m e t e r , also a W e s t o n voltmeter, to o b t a i n line voltage. A small t r u c k w i t h wood f r a m i n g h a v i n g two axles and 33-inch wheels on 3-foot centers, w i t h a \Veston m i l l i - v o l t m e t e r located in car and h a v i n g its t e r m i n a l s c o n n e c t e d to the axles of small truck, the ear is r u n so t h a t the small t r u c k will trail b e t w e e n car and power station. As all r e a d i n g s are t a k e n relatively, t h a t is, c o m p a r i n g r e a d i n g s of e q u i v a l e n t j o i n t l e n g t h s and solid rail l e n g t h s , n o t h i n g need be done except to r u n and m a k e notes. If, however, a n y u n u s u a l r e a d i n g arises the joints m a y be tested s e p a r a t e l y by r a i s i n g and i n s u l a t i n g the wheels of the small truck on the rail; measurem e n t s are not desired to be m a d e . In m a n y cases ordinarily all t h a t m a y be used is a Wes-
April, ,9o4.]
Rail Bonds.
285
ton v o l t m e t e r taken a r o u n d b y a m a n and a b o y with leads to c o m p a r e drop a r o u n d joint with solid rail. In addition to the above, at reasonable intervals the bonding of a r a i l w a y should be inspected, tested and reported u p o n with s u g g e s t i o n s from some g o o d recognized engineering expert. F r e q u e n t tests over a s y s t e m is positively necessary, as defects will develop, n o t w i t h s t a n d i n g w h a t form, kind or make of bond is employed. L o a d s will change, service increases or grows, track b e c o m e s worn, special work gives out, u n d e r g r o u n d piping is changed, modified or increased. P e r h a p s one of the w e a k e s t features in b o n d i n g is over railroad crossings, and a r o u n d special track w o r k - - t o o m u c h care cannot be exercised at such places. A s a rule, look for high resistance at such places, and particularly w h e r e low joints are observed. R a i l r o a d crossings and special w o r k are peculiarly easy to guard. It has been the practice of the writer for some years to cross bond from one side of a railroad crossing to the other, u s i n g 4 / 0 i n s u l a t e d W. P. wires in sufficient number, proportioned to the load, and carried u n d e r the railroad tracks in a terra-cotta pipe. As to the question of concealed or e x p o s e d bonds, this q u e s t i o n m u s t be settled p u r e l y by the e n v i r o n m e n t and conditions u n d e r which the track is to be bonded. An e x p o s e d bond, while s u b j e c t to theft on open-track work, has m a n y a d v a n t a g e s w h e n it can be employed, in that it is always s u b j e c t to quick inspection. As the real figure of merit of a bond is its life and low resistance, the exposed b o n d has the a d v a n t a g e of longer life and to all intents and purposes no material difference in resistance in comparison with the concealed. In paved streets, the q u e s t i o n of exposed or concealed b o n d i n g in the writer's opinion is not to be considered, as it resolves itself into solely a question of life, c o n d u c t i v i t y and cost, design b e i n g of last importance, design only e n t e r i n g into the question as a m a t t e r of final detail w h e n considerin K the c h a r a c t e r of joint- or fish-plate. In conclusion, the w r i t e r wishes to emphasize the follow-
286
Appem:i::
."
[J. F. I.,
i n g facts as t h e r e s u l t s of his o b s e r v a t i o n a n d e x p e r i e n c e . (I) I n c o n s i d e r i n g a n y b o n d , o b s e r v e a l w a y s : Obtain actual resistance data.
Figure costs to obtain same. Resistance
Conductivity compared with other bonds. Usually compare 3 feet of rail, including joint, with 3 feet of
solid rail section. Life
~ Study life o[ bonds, behavior under practical operation. Make frequent inspection of bonds in service.
Tests
Have frequent tests made on bonding. Look for trouble at all special work and low joints.
T h e w r i t e r w i s h e s to a c k n o w l e d g e t h e c o u r t e s y a n d kindly spirit shown by the following manufacturers and e n g i n e e r s in f u r n i s h i n g d a t a f o r t h i s p a p e r : Mayer & E n g l u n d , Ohio Brass Company, A m e r i c a n Steel Wire Company, Chase-Shawmut C o m p a n y , H a r o l d P. Brown, R. W. Conant, General Electric Company, A j a x M e t a l C o m p a n y , A l b e r t B. H e r r i c k , H. A. J o h n s o n . I n a d d i t i o n to t h i s p a p e r , t h e w r i t e r w i s h e s to a d d t h e r e t o as a n a p p e n d i x a c o m m u n i c a t i o n f r o m Mr. A. B. H e r r i c k , consulting engineer, d e s c r i b i n g his testing a p p a r a t u s ; an a r t i c l e b y Mr. H a r o l d P. B r o w n , d e s c r i b i n g e v o l u t i o n o f b o n d i n g ; a n d to r e f e r to t h e v e r y c o m p l e t e rail b o n d catal o g u e , d a t e d J u n e I, I9O2 , i s s u e d b y P r o t e c t e d R a i l B o n d C o m p a n y of P h i l a d e l p h i a , w h i c h is r e p l e t e w i t h e n g i n e e r i n g facts and data, and s u p p l e m e n t e d b y an article contained t h e r e i n f r o m t h e p e n of Mr. A. B. H e r r i c k , c o n s u l t i n g e n g i neer, of N e w Y o r k . APPENDIX. ~g. E .
ROCHESTER, 2q. Y., September i4, 19o3. H a r r i n g t o n , ~ I a n a g e r Camden Co° Su3urban R a i l w a y Company,
Camden, W. jr. DEAR SIR :--In answer to your favor of September 8th, I enclose herewith
the photograph of my autographic recording apparatus. The method of operating is as follows : the fall of potential on each rail is taken by two sliding brushes 4 feet apart on each rail. In order that there may always be current present on these rails, a transformer is used which gives me about 200 amperes on each rail. The drop from these rail contacts are taken to two Weston milli-voltmeters, which have a commutator over the scale which they pass, and these hands bridge a spark gap, which spark is conducted to the surface of the record paper, which record paper moves at the rate of i inch
April. 19o4.]
]~az'l ]3'ands.
287
per ioo feet traveled by a test car, and the spark traces the record of the m o v e m e n t of the hands at every instant as the car progresses along the track. The height of the deflection of the mark line on the record, when the brushes pass over a joint in the rails, gives the resistance of the joint in terms of 4 feet of rail. There is also, in order to protect these instruments, an automatic relay which cuts out the instrument when it reads beyond an adjustable point, which is changed depending upon the current density required for the rail to carry at the different portions of the system. W h e n this relay operates, it also moves a pen and indicates a poor bond at that point oll the record, there being provided a pen for each rail. The way these bonds are located on the record is by means of a third pen, which draws a continuous line which is open from one curb to the next in case of street intersections, crossings or special work, and, immediately after this location is given, a number is telegraphed by the side m o v e m e n t of the pen, which corresponds to the number assigned to this intersection or special point of location. In this way any bond can be located by measuring on the scale of I inch to ioo feet on the record. In interurban work when the automatic moves, it also actuates electrically-controlled valve, which squirts whitewash or paint on the track at the poor bonds. Briefly, m y experience in bonding rails is that in the cast weld made since iS98 the bond at the b e g i n n i n g of the pour is of lower resistance than a 9o.pound rail of the same length as the weld. At the end of the pour it runs up to 3 feet of the 5o.pound rail. The electric weld is m u c h more uniform as now made by the Lorain Company, and i,~ less t h a n the equivalent length of rail over which the connection is made. In flexible bonds with solid head terminals, those put in by means of compressor givigg an effect of compression of 3o tons have lower initial resistance t h a n any other mechanical method of connecting the bond to the rail, and when the flexible portion is cast into head portion, it shows greater permanence u n d e r poor track conditions than any other method used in constructing these bonds. The bond soldered to the rail, where the laminations are presented edgewise to the ball of the rail, shows the best form of this construction, but I have not had a life-test on these bonds. Hoping this data will be useful to you, I remain, Yours truly, (Signed) ALBERT B. HERRICK. R A I L BONDS AND E L E C T R I C A L CONTACTS F O R H E A V Y CURRENTS. BY HAROLD P. BROWN. The writer has given very careful study to this subject and, as is shown by papers read before this Institute in '96 and '97, has always advised heavy bonding and low contact resistance. These views were at first received with a smile, since it was only a few years ago that the leading street railway electricians felt perfectly satisfied with their track circuit after burying a No. 2/0 copper wire under the right of way and connecting it to each rail with a No. o tap and a channel pin Many of these gentlemen would tell you seriously that the earth was a " reservoir
288
Appendix
:
[J. F. I.,
of electricity," or a " conductor of infinitely low resistance," and that therefore a No. 2/o wire was more than sufficient to do the necessary work. They were surprised to find after a very short service t h a t t h e i r " s u p p l e m e n t a r y wire " had practically disappeared, and the r e m e d y for this disappearance was supposed to be found in the use of tinned copper wire. Later the " s u p p l e m e n t a r y wire " was definitely abandoned and scraps of No. 2/o trolley wire were used as bonds around the angle plates by means of h a n d y but deceptive channel pins. Still later bonds of wire were made with enlarged terminals whleh were riveted into holes in the rail. This riveting was slow work and gave unsatisfactory results, and the next step in advance was what is k n o w n as the " C h i c a g o " bond, whose enlarged terminal was expanded into a hole in the rail by driviDg a tapered steel pin into a cylindrical hole in the center of the b o n d terminal. At first these pins were driven from the side of the rail opposite the bond which was h e l d in place during the driving by a suitable lever or clamp. The next improvement in this type of bond was driving the pin fr0m the same side of the rail as the bond, and reducing the sectional diameter of the hole through terminal at its outer end. The steel pin t h e n displaced t h e metal on the far side of the terminal and enlarged its external diameter, k e e p i n g it from falling out. An endless n u m b e r of bond terminals have been devised to effect a contact between a copper bond and a steel rail. But nearly all of their inventors did not consider the fact that the ratio of eopper expansion under heat is greater t h a n that of steel. Therefore, if a cylinder of copper is compressed even with hydraulic pressure into a cylindrical hole in a steel rail and the metals heated, the copper m u s t occupy greater cubical space t h a n before. It cannot expand in the direction of the steel walls surrounding it, theregore all of the expansion must take effect in a line parallel with the center of the cylinder, thus increasing its l e n g t h while heated. When, however, the metals are allowed to cool the contraction takes place equally in all directions instead of entirely in one line as did the expansion. Therefore when the cooling is completed the copper cylinder is of less diameter than before. Into this small space moisture is sure to penetrate, forming an incompressible layer of iron oxide. When the next heating takes place tile same process is gone t h r o u g h and t h e copper is still further reduced in diameter. Pinally, t h o u g h the mechanical joint between the bond and the iron may seem perfect, the layer of iron oxide may be so thick as to practically ruin the conductivity of the bond. It is well known that in boiler or girder work, iron rust will inevitably form beneath the head of a steel rivet applied under hydraulic pressure in a steel plate with exactly the same coefficient of heat expansion. But perfection of eontaet between copper and steel is not the only problem in rail bonding, since even with the best type of joints there will be some motion between the rail ends under passing cars and with difference in temperature. It was found that the solid wire bonds crystallized and broke between t h e terminals, therefore the solid wires were replaced by flexible copper strands with enlarged terminals cast or welded on the ends.
R a i l Bonds.
April, I9o4. ]
2S 9
It was t h e n f o u n d t h a t s t r a n d e d copper b o n d s with cast copper h e a d s could be f a s t e n e d m o r e f i r m l y to t h e rails b y s c r e w or h y d r a u l i c c o m p r e s s i o n t h a n c o u l d s i m i l a r b o n d s w h i c h w e r e a p p l i e d b y d r i v i n g t h e conical pin. H o w e v e r , t h e g r e a t r i g i d i t y in t h e t e r m i n a l h a d t h e effect of c a u s i n g t h e s t r a u d s to wear o u t t h e s o o n e r . A s i m i l a r effect was p r o d u c e d w h e n copper b o n d s were w e l d e d to s t e e l rails, w i t h t h e a d d i t i o n a l d i s a d v a n t a g e t h a t w e l d e d steel a n d c o p p e r f o r m a t h e r m o - e l e c t r i c couple, a n d t h e loss d u e to t h e F e l t i e r effect of c u r r e n t t r a n s m i s s i o n was oL'en far g r e a t e r t h a n t h e r e s i s t a n c e loss. R e t u r n i n g for a m o m e n t to t h e m a t t e r of c o n t a c t b e t w e e n two m e t a l surfaces, a n y o n e w h o h a s ever s c r a p e d a slide v a l v e to a fit will a p p r e c i a t e t h e fact t h a t m e t a l p l a t e s , e v e n w h e n g r o u n d to a " t r u e " surface, a r e n o t h i n g m o r e t h a n a series of h i g h p o i n t s s u r r o u n d e d b y d e p r e s s i o n s w h i c h are clearly s h o w n b y t h e m i c r o s c o p e . R e a l i z i n g t h i s fact a n d k n o w i n g t h e h i g h resista n c e of iron o x i d e oll c o n t a c t m e t a l s , in t894 a n i n v e n t o r h i t u p o n t h e s c h e m e of c o a t i n g steel a n d c o p p e r c o n t a c t s w i t h a n a d h e r e n t l a y e r o f a m a l g a m a p p l i e d b y a n a l k a l i n e p r o c e s s . O n t h i s p r e p a r e d s u r f a c e a l a y e r o f a plastic m e t a l w a s p l a c e d a n d as t h i s filled all t h e i n e q u a l i t i e s of t h e c o n t a c t s a n d p r e v e n t e d o x i d a t i o n , c u r r e n t s c o u l d be t r a n s m i t t e d at t h e r a t e of 1,5oo a m p e r e s p e r s q u a r e i n c h of s e c t i o n w i t h o u t c o n t a c t loss. F r o m t h i s s c h e m e w a s e v o l v e d t h e plastic rail b o n d in w h i c h a bit of plastic m e t a l is u s e d to b r i d g e t h e s p a c e b e t w e e n rail a n d a n g l e plate. T h e m e t a l p u t t y is h e l d in p l a c e b y a ease or r i n g of c o r k m a t e r i a l , w h i c h is n o r m a l l y 50 p e r cent. t h i c k e r t h a n t h e s p a c e b e t w e e n t h e rail a n d t h e plate; it is t h e r e f o r e c o m p r e s s e d w h e n t h e p l a t e is b o l t e d d o w n , t h u s effectively seali n g its c o n t e n t s . T h e p l a s t i c m a t e r i a l a d h e r e d to t h e a m a l g a n l a t ~ d s u r f a c e s a n d m a i n t a i n e d a c o n t a c t of low r e s i s t a n c e for y e a r s in s p i t e of t h e m o t i o n d u e to p a s s i n g cars or t e m p e r a t u r e c h a n g e s . T h e w r i t e r was o n e of t h e first to u s e t h i s t y p e of b o n d w i t h s a t i s f a c t o r y r e s u l t s b o t h at t h e o u t s e t a n d a f t e r m a n y y ears of us-~. B o m l s of t h i s k i n d i n s t a l l e d by t h e w r i t e r in I895 s h o w e d in i9oo a n a v e r a g e d r o p of 'ooi volts, w h i l e a r e a d i n g of t h e s a m e l e n g t h of u n b r o k t n rail s e c t i o n g a v e "oo3 volts. T h e f o l l o w i n g letter, d a t e d A u g u s t 2i, i9o3, h a s r e c e n t l y b e e n b r o u g h t to m y notice, w h i c h s h o w s e v e n b e t t e r r e s u l t s after s e v e n y e a r s ' service: " I n A u g u s t , J896 , we r e c e i v e d two p l a s t i c b o n d s as s a m p l e . I h a d o u r f o r e m a n , Mr. H u l l i u , p l a c e t h e m o n a 5 t - p o u n d j o i n t of J o h n s t o n g i r d e r rail. T h e b o n d h a d n e v e r b e e n d i s t u r b e d u n t i l a few d a y s ago. I was at t h e t i m e m a k i n g s o m e t e s t s w i t h a C o n a u t b o n d tester. W h e n i c a m e to t h i s j o i n t I f o u n d t h e r e s i s t a n c e was so m u c h less t h a n in t h e o t h e r s t h a t I d e t e r m i n e d to h a v e it o p e n e d , so I c o u l d a c c o u n t for its low r e s i s t a n c e . A f t e r o p e n i n g it, I d i s c o v e r e d t h a t it was t h e j o i n t w i t h t h e plastic b o n d , w h i c h s h o w e d no m o r e resistance t h a n t h e rail itself. A f t e r h a v i n g b e e n u n d e r s e r v i c e n e a r l y s e v e n years, I f o u n d t h e a l l o y a n d c o n t a c t of b o n d in p e r f e c t order. (Signed) F . A . R o s s , Supl. [~ailway Dept.,
~S~zcratnento tz'lectric, Gas and ~ailway Co." To t h e a v e r a g e e n g i n e e r t h i s t y p e of plastic b o n d does n o t appeal, s i n c e it does n o t s e e m m e c h a n i c a l , a n d it is e v i d e n t t h a t if t h e a n g l e p l a t e g e t s loose t h e m a t e r i a l of t h e b o n d will be lost. VOL. C L V I I .
N o 940.
19
e9o
A~pendi.~" :
[J. F. I.,
It is also evident that any other type of bond with loose angle plate will soon be destroyed. Tile use of this bond and familiarity with the permanence of the plastic alloy contacts led the writer to design a bond composed of an amalgamated copper strip held in contact against the web of rail by screws threaded through the angle plate. One end of the strip was in contact with one rail, and the other end with the second rail. The thrust of the screws was received on a thin steel plate and both the copper plate and the web of the rail were amalgamated and covered with the plastic alloy. This type of Bond has given entire satisfaction after m a n y years of service. A modification of this bond called the solid copper bond has had very extensive use in all parts of the world. In this bond the screws used by the writer were replaced by a pair of strong steel springs of the nut-lock type placed between the inner surface of angle plate and the amalgamated copper strip. The thrust of these springs is taken by a soft steel plate to prevent wearing holes in the copper of bond. To keep grit and dirt away from the contact surfaces and to hold the springs in place before the bond is applied, the conductor strip is attaehed to a plate of cork material overlapping the ends and sides of the conductor. When the angle plate is bolted up, this eork plate is compressed so that it touehes the web of the rail and the sides of lhe bond. A plate of similar cork material is placed between the rail ends, thus sealing the crack which would otherwise admit dirt and let out the plastic covering of the bond. With this type of bond t h e motion of the rail ends under passing cars serves to improve the contact. It is interesting to note that stranded bonds of the crown or horse-shoe type have much Better conductivity and last far longer if their terminals and the holes in the rails are amalgamated and covered with a thin layer of the plastic alloy. During the past few years the short-stranded copper bonds have broken to such an extent that few roads use less than seven inches between centers. With bonds of this length and the modern heavy rails and angle plates, mechanical breakage of the bonds has been greatly reduced. But careful tests show plainly their falling off in conductivity through corroding terminals. Several different types of bond-testing apparatus have been designed in the past few years. One type is attached to a ear which is drawn over the road, and its designer and proprietor is said to record the exact electrical condition of tim bonds in a single round-trip at the rate of 6 or 8 miles per hour. This might be possible with accuracy if the rails were clean and b r i g h t But with the ordinary conditions of track covered with dust and scale, this is impossible. Careful measurements with the milli.voltmeter will show very different results. An ingenious type of telephonic tester has been designed by a Boston engineer, and seems to get the most rapid results with a fair degree of accuracy. But for absolute precision nothing can equal milli-voltmeter measurements of a given length of unbroken rail compared simultaneously with the same length including the bond. Even with this method, it is necessary to amalgamate the three contact spots for the instrument in order to obtain absolute accuracy.
April, I9o4. ]
R ai l Boncls.
2(,I
A steel point forming a terminal of the milli-voltmeter will give results very often proportional with the amount of pressure applied or the number of scratches made in the same place on the rail. The most serious side of this subject to an electric railway is the fact that every year the bonds are losing conductivity either from mechanical or chemical causes : breakage or corrosion. It is now well known that poor bonds often double the amount of power required to operate a given n u m b e r of cars. That being the case, the accurate testing of rail bonds and the replacement of defective bonds is a subject whose impo,.rtance cannot be over-estimated. When defective bonds are found in a paved street or even on exposed track, it is a serious problem to apply a new bond without great expense. To use a flexibe copper bond under the angle plate requires the removal of a large amount of pavement and of the angle plates. This means the loss of fully 50 per cent. of the nuts and bolts, and after the bonding is completed it is almost impossible to replace the plates in the location previously occupied. However t i g h t the nuts may be screwed up, the fins left by the former position of the plates will prevent a tight fit. After the pavement is replaced and a few months have gone by, these fins wear away and the plates get loose, and both joint and bond are soon in bad condition. The flexible copper bond around the angle plate requires a greater amount of pavement removed, the bond is expensive, and when the pavement is replaced, it is easily broken off by the movement of the rail. An ideal bond for this purpose is one which disturbs the least amount of pavement in placing, which can be applied without removing bolts and angle plates, and which will permit a reasonable amount of motion between the rail and plate. This idea is very well fulfilled in what is known as the Plastic Plug bond. Two holes are drilled through one angle plate at each joint, so that the drill passes through the base or foot of angle plate and partly through the base of the rail. After this hole is drilled and amalgamated, a small amount of plastic alloy is placed in it and a T-shaped copper plug driven far enough to dip into the plastic alloy. The top of this T makes an amalgamated contact with the angle plate ; its bottom drops into the plastic alloy in the rail. The bond pernfits a motion between plate and rail of ~4 inch or more in every direction without breaking the electrical contact, and the bonds have great conductivity even after many years' use. I should not advise the use of a smaller size than 3.~ inch diameter for this type of bond. as the ~i inch ~ize does not perufit sufficient motion or expansion and contraction. The 7~ inch size, wherever the rail will permit it, is sttll better. A simpler form of this type of bond is made by drilling a hole parallel with the upper edge of the angle plate, so that half of the hole is in the lower edge of rail top, and the other half in the upper edge of angle plate. After this hole is drilled and amalgamated, a coppe~rod of cylindrical section is driven into it and held in place by burring the rail over top of the rod. As the rail moves on the plate this rod is partly sheared, but not enough is left of the copper unsheared to make the bond of very high conductivity.
292
[J. F. I.,
Notes a n d Comments.
Q u e e r l y e n o u g h , e v e n if t h e m o t i o n be sufficient to e n t i r e l y s h e a r t h e b o n d , a h a m m e r blow will force b o t h p a r t s into i n t i m a t e c o n t a c t a n d r e s t o r e t h e full c o n d u c t i v i t y . O n e f o r m of t h i s b o n d s p l i t s in a d v a n c e t h e c o p p e r c y l i n d e r so t h a t t h e h a l v e s slide o n e a c h o t h e r as t h e m o t i o n t a k e s p l a c e ; b u t t h i s does n o t s e e m to g i v e as s a t i s f a c t o r y r e s u l t s as t h e solid c y l i n d e r . O f c o u r s e o n e i m p o r t a n t p o i n t in f a v o r of t h i s t y p e of b o n d is its c h e a p ness. But w h a t e v e r t y p e of b o n d is u s e d , f r e q u e n t i n s p e c t i o n a n d i m m e d i a t e r e p l a c e m e n t of d e f e c t i v e b o n d s is of t h e u t m o s t i m p o r t a n c e .
A SILVER-LIKE
METAL.
A w r i t e r in t h e A l u m i n u m tUor/d g i v e s t h e c o n s t i t u e n t s o f a h a r d alloy w h i c h h a s b e e n f o u n d v e r y u s e f u l for t h e o p e r a t i n g l e v e r s of c e r t a i n m a c h i n e s . T h e s p a c i n g l e v e r of a t y p e w r i t e r is c o n s t a n t l y h a n d l e d w h e n in use, a n d if m a d e of i r o n or s t e e l a n d n i c k e l - p l a t e d , e v e n h e a v i l y , t h e p l a t i n g s o o n w e a r s off, l e a v i n g t h e m e t a l u n d e r n e a t h e x p o s e d to r u s t a n d corrosion, a c o n d i t i o n w h i c h , o f course, is n o t p e r m i s s i b l e . I f t h e levers a r e m a d e of b r a s s t h e m a t t e r is n o t h e l p e d to a n y e x t e n t , as t h e p l a t i n g w e a r s off t h e s a m e as i r o n or steel a n d l e a v e s t h e b r a s s e x p o s e d , w h i c h is, if a n y t h i n g , m o r e o b j e c t i o n able t h a n i r o n or steel. T h e m e t a l n o w g e n e r a l l y u s e d for t h i s p u r p o s e by t h e v a r i o u s t y p e w r i t e r c o m p a n i e s is " a l u m i n u m s i l v e r , " or " s i l v e r m e t a l . " T h e p r o p o r t i o n s are g i v e n as f o l l o w s : Copper . . . . . . . Nickel . . . . . . . Zinc . . . . . . . . Aluminum . . . .
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57 oo 2o.oo 2o.oo 3.oo IO0.O0
T h i s a l l o y w h e n u s e d o n t y p e w r i t i n g m a c h i n e s is n i c k e l - p l a t e d for t h e s a k e of t h e first a p p e a r a n c e , b u t so f a r as c o r r o s i o n is c o n c e r n e d , n i c k e l i n g is u n n e c e s s a r y . I n r e g a r d to its o t h e r qualities, t h e y are o f a c h a r a c t e r t h a t r e c o m m e n d s t h e a l l o y for m a n y p u r p o s e s . It is stiff a n d s t r o n g a n d c a n n o t be b e n t to a n y e x t e n t w i t h o u t b r e a k i n g , e s p e c i a l l y if t h e p e r c e n t a g e of a l u m i n u m is i n c r e a s e d to 3-5 p e r c e n t . ; it casts free f r o m p i n h o l e s a n d blowh o l e s ; t h e l i q u i d m e t a l c o m p l e t e l y fills t h e m o l d , g i v i n g s h a r p , c l e a n casti n g s , t r u e to p a t t e r n ; its cost is n o t g r e a t e r t h a n b r a s s ; its color is silver w h i t e ; a n d its h a r d n e s s m a k e s it s u s c e p t i b l e o f a h i g h polish.
NATURAL
BORAX.
T h e m i n e r a l boroealeite f u r n i s h e s t h e b a s e of t h e g r e a t e r p a r t of t h e b o r a x c o n s u m e d in E u r o p e . F i f t e e n p a r t s of finely c r u s h e d ore w i t h 6o p a r t s water, 8 p a r t s s o d i u m b i c a r b o n a t e a n d 2 of c a u s t i c s o d a a r e b o i l e d in a s t e a m - h e a t e d boiler a b o u t t h r e e h o r n s . It is t h e n filtered a n d c r y s t a l l i z e d , y i e l d i n g c r y s t a l s of borax. I t is e s t i m a t e d t h a t IOO p o u n d s of boroealcite will y i e l d f r o m l c o to Io5 p o u n d s of crystallized borax.--t~ngineeri~ and LlIiningJournal.