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Engineering practice and education
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[J. F.I.,
Lan~a:
ENGINEERING
PRACTICE
AND
EDUCATION.
BY GAETANO LANZA, S. B., (2. • M. E., Professor of Theoretical a n d Applied Mechanics, Massachusetts I n s t i t u t e of Technology.
[ Cancluded fi-am ~..56.] S t e r e o t o m y is a species of a d v a n c e d descriptive geometry, and can easily be acquired b y any one who is f a m i l i a r the l a t t e r subject. It bears more especially upon t h e work of t h e e n g i n e e r who is to erect large b u i l d i n g s w h e r e stone plays an i m p o r t a n t part, or m a s o n r y bridges. Of s u r v e y i n g and t o p o g r a p h i c a l drawing, of course, every e n g i n e e r o u g h t to have some knowledge, b u t the principles of s u r v e y i n g are easily l e a r n e d by a n y one who has a scientific t r a i n i n g a n d some skill in h a n d l i n g measuri n g i n s t r u m e n t s , and n i c e t y of execution can only be acq u i r e d by l o n g - c o n t i n u e d practice, a n d the g r e a t e r p a r t of this practice will have to be acquired s u b s e q u e n t l y . Surv e y i n g has s o m e t i m e s been a s s u m e d to be the principal business of the civil engineer, and f r e q u e n t l y a m a n who was m e r e l y a s u r v e y o r has called h i m s e l f a civil e n g i n e e r : b u t the progress of the world is s w e e p i n g this away, and a man who is merely a s u r v e y o r is no l o n g e r considered to be an e n g i n e e r a n y more t h a n a m a c h i n i s t is an engineer. Now, while the m a n who is to build roads or railroads will p r o b a b l y have to use s u r v e y i n g to such an e x t e n t t h a t it will be n e c e s s a r y to give him in the school more t h a n is given in the o t h e r e n g i n e e r i n g courses, n e v e r t h e l e s s his practice will h a v e to be acquired s u b s e q u e n t l y , and the i n s t r u c t i o n in those t h i n g s t h a t he c a n n o t acquire later, or can only acquire later with a g r e a t deal of difficulty, should, on no account, be sacrificed for surveying. W h e n we come to the h i g h e r geodetic work, we h a v e geodesy, a n d n o t e n g i n e e r i n k and hence it will n o t be considered here. T h e n as to shopwork, very s i m i l a r r e m a r k s
Feb., 1895..~
Eng'ineerbzg Practice and Educatiopz.
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to those I h a v e m a d e in r e g a r d to surveying, will apply. It is s o m e t h i n g in w h i c h e v e r y e ~ i n e e r should h a v e s o m e practice, b u t w h i c h should not De g i v e n at the e x p e n s e of more i m p o r t a n t e n g i n e e r i n g work. Indeed, it w o u l d be e x t r e m e l y desirable t h a t this should be acquired at t h e m a n u a l training schools before boeginning an e n g i n e e r i n g course, and w h e n e v e r t h e m a n u a l training schools are e s t a b l i s h e d every. where as a part of the public school system, so t h a t y o u n g men who wish to take an e n g i n e e r i n g course at s o m e engineering school can first a t t e n d the m a n u a l t r a i n i n g school, then the e n g i n e e r i n g schools will not need to teach so m u c h shopwork and w h a t t h e y do teach will b e of a more advanced character. Coming, now, to t h e studies of the second class, we shall find that we m a y divide t h e m into two classes, the first being those r e q u i s i t e for such specialties as can be developed b y a s u i t a b l e addition of certain lines of work, b u t where t h e s e lines of w o r k d e p e n d u p o n the p r e v i o u s training that has been g i v e n ; and second, those w h e r e a considerable k n o w l e d g e of, and hence a drill in, c h e m i s t r y is neces. sary. A m o n g the first I should place: (I) b r i d g e s ; (2) hydraulic e n g i n e e r i n g ; (3) railroad engineering, w i t h special reference to p e r m a n e n t w a y ; (4) railroad engineering, with special reference to m o t i v e p o w e r and rolling stock; (5) marine e n g i n e e r i n g ; (6) mill e n g i n e e r i n g ; (7) naval architecture; (8) electrical e n g i n e e r i n g ; and others as t h e y m i g h t arise. In the second class, on the o t h e r hand, I should place mining, m e t a l l u r g i c a l and chemical engineering, and others as they m i g h t arise. The essential difference b e t w e e n these two classes is that, in the latter, a considerable k n o w l e d g e of c h e m i s t r y is required, and, c o n s e q u e n t l y , that the s t u d e n t m u s t h a v e considerable i n s t r u c t i o n in e l e m e n t a r y c h e m i s t r y and in qualitative and q u a n t i t a t i v e analysis, before he is in condition to discuss the s u b j e c t s p e r t a i n i n g to his special line; and hence, that for t h e s e courses, a certain a m o u n t of c h e m i s t r y beComes one of t h e essential f u n d a m e n t a l s t u d i e s t h a t the student cannot do w i t h o u t , and m u s t be p r o v i d e d for at the
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Lapz~a :
[J. F. 1.,
s t a r t by a s s i g n i n g the necessary t i m e for it in a d d i t i o n to t h a t needed for t h e o t h e r f u n d a m e n t a l studies. W h e n suitable provision is m a d e for this, there remains, of course, less time for o t h e r s u b j e c t s t h a n there is in the o t h e r cases. Of course, the a m o u n t of c h e m i s t r y r e q u i r e d is a m a t t e r of degree. In some lines of m i n i n g e n g i n e e r i n g it is not great, whereas, in m e t a l l u r g i c a l works, or in chemical works, the a m o u n t is decidedly larger. Nevertheless, t h e one who is l a y i n g out a n y of these courses m u s t bear in m i n d t h a t t h e y are i n t e n d e d to fit m e n to do p r i m a r i l y the e n g i n e e r i n g w o r k of such e s t a b l i s h m e n t s , and t h a t it is not n e c e s s a r y t h a t t h e y should h a v e as m u c h c h e m i s t r y as would be required by the analytical chemist. Hence, he s h o u l d b e g i n by c o n s i d e r i n g w h a t is the minim u m a m o u n t of c h e m i s t r y w h i c h it will do to p u t in the course ; p u t t h a t in, and t h e n l e a v e t h e rest of t h e chemistry, w h i c h it m i g h t be desirable to add, to take its chances with the o t h e r professional subjects, according to t h e i r relative i m p o r t a n c e in the special line of work for w h i c h the course is laid out. L e t us assume, now, t h a t we h a v e fixed upon the fundam e n t a l subjects, a n d the time t h a t m u s t be g i v e n to each. W e are prepared, then, to map out the course to be p u r s u e d in the second class, or special line of studies, i n c l u d i n g w h a t e v e r of t h e first class we deem wisest to insert in the list. W e r e I to a t t e m p t to map out the details of w h a t s h o u l d be given in t h e case of each special e n g i n e e r i n g course in these special lines, I should need a whole course of lectures to elaborate it. I shall only say a little, therefore, a b o u t some general rules to be observed in m a k i n g t h e selection: (i) To drill the s t u d e n t in all the details of his profession, or to i m p a r t to h i m experience, is not possible in a school. Experience can only be g a i n e d after the school days are past, and he goes to work. (2) To a t t e m p t to perfect h i m in those t h i n g s t h a t he will h a v e to do w h e n he first goes to work, at the expense of his l a t e r success, is a v e r y short-sighted policy. (3) Hence, the object to be a t t a i n e d should be, first, to so
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arrange this work t h a t he shall h a v e to deal w i t h such cases as are liable to ariae in the practice of his profession, as with the a c t u a l d.;~l[ils of a bridge, of a s t e a m engine, of a locomotive, of a mill, etc., and t h u s become f a m i l i a r with what he is likely to m e e t later on ; and secondly, t h a t he shall be t a u g h t how to go to work oi1 these p r o b l e m s in a scientific m a n n e r , a p p l y i n g the principles t h a t he has previously learned, t h u s t e a c h i n g him w h a t is the relation of his scien{ifie s t u d y to the practical problems he will m e e t later in life. Next, in r e g a r d to the t h i r d class of subjects, or those i n t e n d e d for g e n e r a l i n f o r m a t i o n , it is desirable to insert as much as can be inserted, w i t h o u t sacrificing the accomplishm e n t of the main objects of the course. Such s u b j e c t s are, mainly, linguistic a n d l i t e r a r y studies. The first, however, if confined to the m o d e r n l a n g u a g e s , are also, to a certain extent, professional; for, w i t h o u t m o d e r n languages, some of our most v a l u a b l e e n g i n e e r i n g l i t e r a t u r e is closed to the s t u d e n t . H a v i n g t h u s m a r k e d out the character a n d t h e scope of the s t u d i e s t h a t should enter into an e n g i n e e r i n g course of one or of a n o t h e r kind, it r e m a i n s for me to speak of two subjects, viz.: (I) T h e g r a d u a t i o n thesis, a n d (2) the e x t e n t to u hich l a b o r a t o r y practice in the e n g i n e e r i n g laboratories should be i n t r o d u c e d into the courses. First, as to the g r a d u a t i o n thesis. It has a l w a y s been the c u s t o m for the e n g i n e e r i n g schools to require of the st,~dents, before t h e y are g r a d u a t e d , a thesis. T h e special feature r e q u i r e d of a thesis should be t h a t it shall involve an d e m e n t of original i n v e s t i g a t i o n , and its chief object is to teach the s t u d e n t how to make, and to give h i m practice in m a k i n g , original i n v e s t i g a t i o n on his own account. H e should be m a d e to feel t h a t the problem is his own to solve. He should be e n c o u r a g e d to propose his own plan.~ for the solution, and to s u b m i t t h e m to some one m e m b e r of the corps of i n s t r u c t i o n , who s h o u l d aid h i m w h e n he needs aid, and exercise so close a supervision over his work, t h a t he should be m a d e to do it correctly. If th.is s u p e r v i s i o n is properly m a i n t a i n e d , a large
126
£alCza :
[ J. F. I.,
a m o u n t of i n v e s t i g a t i o n can be a c c o m p l i s h e d in connection w i t h the thesis work. In giving the i n s t r u c t i o n I have outlined above, it should not be m e r e l y class-room instruction, b u t also l a b o r a t o r y work, partly to e m p h a s i z e and illustrate the work of t h e classroom, partly to drill the s t u d e n t in p e r f o r m i n g carefully and a c c u r a t e l y such e x p e r i m e n t a l e n g i n e e r i n g w o r k as he is liable to be called u p o n to p e r f o r m in the practice of his profession, and partly to teach h i m e x p e r i m e n t a l investigation. T h e s t u d e n t will have, of course, in addition to this, labo r a t o r y work in his special line, as in the m i n i n g laboratory, electrical laboratory, industrial chemistry, laboratory, etc., besides, of course, work in the chemical and physical laboratories. I h a v e p r e v i o u s l y called a t t e n t i o n to the process of g r a d u a l d e v e l o p m e n C which has resulted in the e x t e n s i v e int r o d u c t i o n of l a b o r a t o r y practice of a variety of kinds into technical instruction, and therefore to t h e e v o l u t i o n of the e n g i n e e r i n g laboratories. A s to the organization of such laboratories, the principal o b j e c t s to be a c c o m p l i s h e d b y t h e m are three, to wit : (I) To give the s t u d e n t s practice in such e x p e r i m e n t a l work as an e n g i n e e r is c o n s t a n t l y liable to be called upon to p e r f o r m in the practice of his profession, as tests of the s t r e n g t h of materials, e v a p o r a t i v e tests of s t e a m boilers, s t e a m engine tests, calorimetric tests, valve setting, etc.; and to teach him to carry on his work with accuracy, and to take all proper p r e c a u t i o n s to aw-~id error. (2) To give the s t u d e n t o p p o r t u n i t y of carrying on original i n v e s t i g a t i o n in the e n g i n e e r i n g branches, s u c h a s i n v e s t i g a t i o n s in s t r e n g t h of m a t e r i a l s in s t e a m engineering, etc. (3) A n o t h e r i m p o r t a n t function of such laboratories, w h i c h is entirely c o n s i s t e n t with the other two, is t h a t of t a k i n g up and carrying on s y s t e m a t i c i n v e s t i g a t i o n s of e n g i n e e r i n g problems, and this can be done in a laboratory, w h e r e a s it is only w i t h v e r y g r e a t difficulty that it can be
Feb., x895.]
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done in a maclqine shop or a m a n u f a c t u r i n g establishment. By p u b l i s h i n g these results from time to t i m e the labor a t o r y will serve to add g r a d u a l l y to the c o m m o n stock of knowledge,. I recognize v e r y fully the i n c a p a c i t y of the s t u d e n t , as a rule, to o r i g i n a t e and carry on research w i t h o u t aid from his t e a c h e r s ; b u t w h e n this aid is given, a n d the necessary supervision is exercised, a large a m o u n t of research can be accomplished in such laboratories. O r i g i n a l researches should also be carried on by the s t u d e n t s in connection w i t h t h e i r g r a d u a t i n g theses ; some of t h e m are, of course, b e t t e r able to do t h i s k i n d of work than others, b u t all s h o u l d be required to u n d e r t a k e original research, and a careful supervision should be exercised by some one of the i n s t r u c t i n g force, who s h o u l d see to it t h a t w h a t e v e r is done should be properly done, so t h a t the results, as fa'/~s t h e y go, w h e t h e r extensive or not, m a y be of real value. I n a s m u c h as the n u m b e r of i m p o r t a n t i m v e s t i g a t i o n s "which it is possible to take up and carry o u t is so very large that only a few can be u n d e r t a k e n in a n y one laboratory, and, therefore, while there are certain pieces of a p p a r a t u s of so typical and general a character t h a t all e n g i n e e r i n g laboratories need them, and should be p r o v i d e d w i t h the best t h a t their m e a n s will a d m i t of, as for instance, t e s t i n g machines and s t e a m e n g i n e s - - t h e r e m a i n d e r of the apparat:::q :nay vary very considerably in e q u a l l y well-equipped engineering laboratories. Instead, therefore, of l a y i n g down general rules for the e(iuipment and c o n d u c t of such laboratories, it seems to me tha: I shall be b e t t e r able to convey m y ideas by describing to you the e q u i p m e n t of the e n g i n e e r i n g laboratories of the -~Iassaehnsetts I n s t i t u t e of 'I'echnology, and the way in which t h e y are conducted. ~Phe first a t t e m p t at e s t a b l i s h i n g e n g i n e e r i n g laboratories a t t h e I n s t i t u t e was m a d e in the school y e a r ~873 74, w h e n one was e q u i p p e d w i t h the following apparatus, viz.: (a) T w o horizontal t u b u l a r boilers, each 4 feet in diam-
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[J. F. I.,'
eter and E2 feet long, c o n t a i n i n g fifty 3-inch t u b e s ; (b) one small vertical t u b u l a r boiler, 3 feet in diameter, and 7 feet high, c o n t a i n i n g fifty 2-inch t u b e s ; (c) a cast-iron superh e a t e r ; (d) an 8-inch b y 24-inch Harris-Corliss engine, with a brake on t h e fly-wheel; (e) a c o m b i n e d surface c o n d e n s e r and calorimeter w i t h the n e c e s s a r y tanks and scales; (/) also a v a r i e t y of accessory apparatus, as indicators, gauges, etc. F r o m this l a b o r a t o r y there e m a n a t e d an i n v e s t i g a t i o n into s o m e special p r o b l e m s on cylinder condensation m a d e for Mr. George B. Dixwell. F r o m t h e s e small beginnings, partly t h r o u g h g r a d u a l growth, and p a r t l y t h r o u g h considerable c h a n g e s and imp r o v e m e n t s m a d e all at one time, have arisen our p r e s e n t e n g i n e e r i n g laboratories, s i t u a t e d in the E n g i n e e r i n g Building, and o c c u p y i n g two floors, 5o x I 5o feet each. T h e e q u i p m e n t of the L a b o r a t o r y of A p p l i e d Mechanics, z.e., the l a b o r a t o r y for t e s t i n g the s t r e n g t h of materials, e m b r a c e s t h e following a p p a r a t u s : (I) A t e s t i n g m a c h i n e of 3oo,ooo pounds capacity, m a d e b y W i l l i a m Sellers & Company, Incorporated, u n d e r the p a t e n t s of A l b e r t H. Emery, the m a k e r of the G o v e r n m e n t t e s t i n g m a c h i n e of 8oo,ooo p o u n d s capacity at W a t e r t o w n Arsenal. This m a c h i n e has r e c e n t l y been a d d e d to t h e e q u i p m e n t of the laboratory, and it is to be o b s e r v e d t h a t this style of t e s t i n g m a c h i n e is the most delicate and a c c u r a t e in the world. Moreover, the a m o u n t of i n v e s t i g a t i o n in the line of s t r e n g t h of materials of such a c h a r a c t e r as to be of positive value to the engineer, which has been m a d e b y means of the G o v e r n m e n t m a c h i n e at W a t e r t o w n , is far g r e a t e r than that which h a s been a c c o m p l i s h e d by m e a n s of any o t h e r t e s t i n g m a c h i n e in the world. It is provided with suitable holders and m e a s u r i n g appar a t u s to a d a p t it to specimens of different shapes. (2) A n Olsen t e s t i n g machine of 5o,(~oo p o u n d s capacity for d e t e r m i n i n g tensile strength, elasticity and c o m p r e s s i v e strength. This m a c h i n e is furnished with c o m p r e s s i o n platforms, w h i c h d i s t r i b u t e t h e p r e s s u r e e v e n l y over the specimen.
Feb., I895.]
Engineering Practice and Edzlcatzbn.
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(3) A t e s t i n g ~ m a c h i n e of ioo,ooo p o u n d s c a p a c i t y for deter r~kning the t r a n s v e r s e s t r e n g t h and stiffness o f b e a m s up to twenty-five feet in length. By m e a n s of this m a c h i n e tests are also m a d e on the s t r e n g t h of f r a m i n g joints u s e d in practice, and on the s t r e n g t h of the r i v e t e d joints of plat e girders, as well as on other s p e c i m e n s s u b j e c t e d to transverse stress. (4) A t e s t i n g m a c h i n e of 18,ooo p o u n d s c a p a c i t y for d e t e r m i n i n g the t r a n s v e r s e s t r e n g t h and stiffness of b e a m s up to fifteen feet in length. (5) A m a c h i n e of I44,ooo-inch pounds c a p a c i t y for testing the torsional s t r e n g t h and stiffness of s h a f t i n g up to twenty-otle feet in length, p r o v i d e d with a p p a r a t u s for m e a s u r i n g the angle of twist to four seconds of arc. (6) A t e s t i n g m a c h i n e of 25,00o p o u n d s c a p a c i t y for determining the s t r e n g t h of ropes or wire, w h e r e the clear length of the s p e c i m e n can be made as g r e a t as ten feet. By m e a n s of this m a c h i n e tests are m a d e u p o n b o t h long and short splices, and on a v a r i e t y of hitches and holders. (7) A m a c h i n e for t e s t i n g the tensile s t r e n g t h of c e m e n t s and morro"s, w h e r e the clips h a v e been specially d e s i g n e d in such a w a y as to secure an evenly d i s t r i b u t e d pull on the specimen. In connection with this m a c h i n e is a c o m p l e t e ontfi~ of nicely-constructed m o u l d s for m a k i n g the briquettes or specimens, and also all other n e c e s s a r y apparatus, as sieves, tanks, e~c. (8) A m a c h i n e for d e t e r m i n i n g the s t r e n g t h and elasticity of ioi~g s p e c i m e n s of wire. (9) A machine for d e t e r m i n i n g the s t r e n g t h and elasticity of cloth. (~o) A m a c h i n e for d e t e r m i n i n g the effect of r e p e a t e d S~resses on the s t r e n g t h and elasticity of iron a n d steel. (I i) A m a c h i n e for d e t e r m i n i n g the deflection of parallel rods w h e n r u n n i n g u n d e r different conditions. (12) A q u a n t i t y of m e a s u r i n g and o t h e r a p p a r a t u s for d e t e r m i n i n g stretch, deflection and twist. The s t u d e n t s w h o take the s u b j e c t of applied m e c h a n i c s in their senior y e a r are r e q u i r e d to learn h o w to use this apparatus, and the m e t h o d of m a k i n g the different kinds of VOL. CXXXIX. 9
13o
Lanza
:
[J. F. I.,
tests, t h u s l e a r n i n g how tests s h o u l d be made, and alsd a c q u i r i n g a f a m i l i a r i t y with the appearance a n d b e h a v i o r of m a t e r i a l s w h e n s u b j e c t e d to stresses such as occur in practice. Thus, in the school year each s t u d e n t m a k e s t h e followi n g tests in the l a b o r a t o r y : (I) A t e s t to d e t e r m i n e the m o d u l u s of elasticity, the l i m i t of elasticity, and tensile s t r e n g t h of a cast iron or w r o u g h t - i r o n or steel rod or bar, or the transverse s t r e n g t h of a coupling. (2) A test of the deflections and of the t r a n s v e r s e s t r e n g t h of a full-size iron or steel I beam, or of a w o o d e n b e a m subjected to t r a n s v e r s e load. (3) A test to d e t e r m i n e the m o d u l u s of e l a s t i c i t y and the tensile s t r e n g t h of various kinds of wire. (4) A test to d e t e r m i n e the s h e a r i n g m o d u l u s of elasticity and the torsional s t r e n g t h of a shaft. (5) T e s t s of the tensile s t r e n g t h of h y d r a u l i c cement. (6) T e s t s of t h e compressive s t r e n g t h of h y d r a u l i c cement. (7) T e s t s of t h e s t r e n g t h of rope, and t h e loss of efficiency due to different hitches and knots. (8) Besides t h e above the s t u d e n t s m a k e a v a r i e t y of tests of large pieces on the E m e r y t e s t i n g m a c h i n e ; sometimes compression tests of full size columns, or of small blocks, or of c o l u m n s with bolsters, etc., a n d s o m e t i m e s tensile tests of pieces of v a r y i n g shapes and sizes. The hydraulic laboratory contains : (t) A closed tank, 5 feet in d i a m e t e r and 27 feet high, connected w i t h a Io-inch stand-pipe over 7° feet high, so a r r a n g e d t h a t a c o n s t a n t h e a d m a y be kept at a n y desired level. (2) A p p a r a t u s in connection w i t h the t a n k a n d standpipe, for m a k i n g e x p e r i m e n t s on t h e flow of w a t e r t h r o u g h orifices and mouth-pieces, over weirs and in pipes, u n d e r different h e a d s a n d conditions, and on the losses of head occurring u n d e r different circumstances. (3) A s y s t e m of pipes, eonnected both w i t h t h e main pipe and w i t h the pumps, is fitted for the i n s e r t i o n of diap h r a g m s , b r a n c h e s a n d other a p p a r a t u s for s t u d y i n g loss of h e a d and the laws of discharge.
Feb., I895 ]
Engincerinff Practice alzd EducaZiolz.
I3I
(4) A n a t t a c h m e n t to the m a i n tank, c o n t a i n i n g a P i t o t tube for s t u d y i n g the laws of velocity in jets, and a d j u s t a b l e points for the m ' e a s u r e m e n t of the cross-section of jets. (5) A cylindrical steel m e a s u r i n g t a n k of 28o cubic feet capacity. (6)j A six-inch Swain turbine, so a r r a n g e d t h a t it can be run u n d e r different heads, and t h a t m e a s u r e m e n t s can be made of the power exerted, of the efficiency, etc., u n d e r different gates. (7) A 48-inch P e l t o n w a t e r motor, similarly arranged. (8) A V e n t u r i m e t e r and n u m e r o u s hose nozzles for m e a s u r i n g water. (9) A bceir of a d j u s t a b l e w i d t h up to four feet. (to) A h y d r a u l i c ram with a two and one-half inch drive pipe. The s t e a m l a b o r a t o r y contains : (I) A triple-expansion engine, with cylinders of 9 inches I6 inches, and 24 inches diameter, respectively, by 3o inches stroke, a r r a n g e d in such a w a y as to be r u n single, compound or triple, as desired for the purposes of experiment. It is of th. Corliss type, and has a c a p a c i t y of a b o u t ~5o horse-power w h e n r u n n i n g triple, with an initial pressure of I5O pounds in the h i g h - p r e s s u r e cylinder. To it is connected a surface condenser, a n d the other a p p a r a t u s needed to adapt it to the ptIrposes of accurate e x p e r i m e n t . The ends and barrels of the cylinders are s e p a r a t e l y jacketed, so t h a t s t e a m can be let into e i t h e r or both. T h e receivers are also j a c k e t e d so t h a t t h e y can bc used either wilh s t e a m in the j a c k e t s or not. T h e cut-off on all three cylinders can be t h r o w n into connection w i t h the governor, or any of t h e m can be d i s c o n n e c t e d from t h e g o v e r n o r and adjusted bv h a n d at a fixed point. Cans are provided for catching the drip from each jacket, and t h e s e cans are provided with water-glasses so t h a t we can d e t e r m i n e its quantity. The engine i s t h u s fitted to carry on series of e x p e r i m e n t s Under different conditions, and by its use we can obtain results comparable w i t h t h e results t h a t are a c t u a l l y realized on large m a r i n e and s t a t i o n a r y engines. T h e w a t e r consump-
I32
Lalz~t :
[J. F. I.,
tion per horse-power per h o u r varies w i t h the different conditions u n d e r w h i c h the e n g i n e is r u n , "but we have f o u n d it u n d e r some conditions as low as I3" 7 pounds. A very considerable a m o u n t of i n v e s t i g a t i o n has been carried on already, and valuable r e s u l t s have been obtained. (2) A Harris-Corliss engine, w i t h cylinder 8 inches diameter by 24 inches stroke, with a c a p a c i t y of a b o u t I6 horsepower, with an initial pressure of 75 pounds. T h i s engine is a l s o c o n n e c t e d w i t h a surface condenser and a t a n k on scales to w e i g h t h e condensed steam, and, of course, it can be used to m a k e e n g i n e tests ; b u t i n a s m u c h as it is a small engine, it is not economical, u s i n g from 3° to 4o pounds of w a t e r per horse-power per h o u r ; and, now t h a t we have the triple expansion engine, we use the Harris-Corliss machine m a i n l y for valve-setting. Moreover, this HarrisCorliss e n g i n e is the original one t h a t was p u t in t h e laborat o r y when it was first founded, in 1873 , by m e a n s of which the i n v e s t i g a t i o n s were m a d e for Mr. Dixwell. T h e r e is also a n o t h e r eight-horse-power e n g i n e used for valve-setting, etc. (3) Of surface condensers t h e r e are four in all: (a) the one connected w i t h t h e triple-expansion engine, and which is also specially a r r a n g e d for e x p e r i m e n t a l purposes in such a way t h a t t h e c o n d e n s i n g w a t e r can be m a d e to pass once, twice or three t i m e s t h e l e n g t h of the c o n d e n s e r while per. f o r m i n g its f u n c t i o n s ; (b) a smaller surface condenser a t t a c h e d to the Harris-Corliss engine, and (c) and ( d ) t w o o t h e r surface condensers, used in various experiments. (4) A mercurial pressure c o l u m n which e x t e n d s to I6O p o u n d s pressure, by m e a n s of w h i c h our g a u g e s are tested. T h e r e is also a m e r c u r i a l v a c u u m column. (5) A d y n a m i c s t e a m engine indicator tester. (6) Several pieces of a p p a r a t u s for d e t e r m i n i n g t h e quant i t y of s t e a m i s s u i n g from a given orifice, or t h r o u g h a short tube, u n d e r a given difference of pressure. (7) A p p a r a t u s for t e s t i n g s t e a m injectors. (8) A n u m b e r of s t e a m pumps, the l a r g e s t one b e i n g a duplex p u m p 16, IO½-b y i2 inches. (9) A n u m b e r and v a r i e t y of calorimeters.
Feb., I895.]
Enffhteering" Practice and Edztcation.
13 3
(Io) A larg6 s u p p l y of indicators, p l a n i m e t e r s , gauges, t h e r m o m e t e r s , a n e m o m e t e r s a nd o t h e r a c c e s s o r y a p p a r a t u s . (IS) T h e r e ar~ in t he di f f er e nt b u i l d i n g s two 2o8-horsepower s ectio n al boilers, two ioo-horse-power, and one eightyhorse-power h o r i z o n t a l t u b u l a r boilers, a n d a n o t h e r sixtyhorse)power h o r i z o n t a l t u b u l a r boiler at t he shops, and these' are used for m a k i n g boi l er tests ; all t he f o u r t h y e a r s t u d en ts of m e c h a n i c a l , electrical, c h e m i c a l e n g i n e e r i n g and naval a r c h i t e c t u r e , h a v i n g to take p a r t in t h e s e tests. It is b e l i e v e d t h a t t h e s t u d e n t s can b e s t l e a r n to m ake boiler tes ts b y m a k i n g t h e m on large boi l ers p r o d u c i n g a considerable q u a n t i t y of steam. B es id e; all the above, t h e e n g i n e e r i n g l a b o r a t o r i e s . a r e provided w i t h s e ve r al f r i ct i on b r a k e s of d i f f e r e n t capacities; with m a c h i n e r y for d e t e r m i n i n g t he t e n s i o n r e q u i r e d in a belt to e n a b l e it to c a r r y a g i v e n a m o u n t of power, at a g i v e n speed, w i t h no m o r e t h a n a g i v e n a m o u n t of slip ; w i t h a m ach in e for t e s t i n g t h e t r a n s m i s s i o n of p o w e r by r o p e s ; with a n u m b e r of t r a n s m i s s i o n d y n a m o m e t e r s ; w i t h a fourhorse-power gas e n g i n e ; w i t h a c o m p l e t e set of W e s t i n g house air-br ke a p p a r a t u s , i n c l u d i n g t he p a r t s b e l o n g i n g to the car an d to t h e l o c o m o t i v e ; w i t h t he p u m p and e n g i n e e r ' s valve of th e N e w Y or k air-brake ; w i t h a m e a s u r i n g t a n k for large q u a n t i t i e s of water, t hi s t a n k b e i n g p r o v i d e d w i t h a n u m b e r of orifices in t he b o t t o m , and a w a t e r glass on the side ; with a n u m b e r of w a t e r meters, and of weirs of different sizes, for m e a s u r i n g w a t e r ; with a l o c o m o t i v e link model : w i t h a c e n t r i f u g a l p u m p , a g a n g p u m p and a r o t a r y pump ; w i t h a h o t - a i r e n g i n e ; w i t h a p u l s o m e t e r p u m p ; w i t h an e x p e r i m e n t a l g o v e r n o r ; w i t h an oil-testing m a c h i n e ; with a n u m b e r of w a t e r m o t o r s ; w i t h an e j e c t o r ; and with cotton m a c h i n e r y as follows : two cards, a d r a w i n g frame, a speeder, a fly frame, a r i n g f r a m e and a mule, as well as accessory a p p a r a t u s . As to t he work r e q u i r e d of t he students of m e c h a n i c a l , e l e c t r i cal and c h e m i c a l e n g i n e e r i n g , I will say t h a t in t h e second t e r m of t h e i r j u n i o r y e a r t h e y are r e q u i r e d to make, u n d e r careful s u p e r v i s i o n , e n g i n e tests on th e tr ipl e engine. In t he course of t he s e n i o r y e a r the list of tests m a d e by each s t u d e n t is a p p r o x i m a t e l y as follows, viz. :
134
Lanza.
[ 1. F. I.,
T e s t s of the t r a n s m i s s i o n of power ~ b e l t i n g ; test of t h e p e r f o r m a n c e of a surface c o n d e n s e r ; t e s t of a directa c t i n g steam p u m p ; test of the flow of steam ; valve s e t t i n g (plain slide valve); test of a p u l s o m e t e r ; test of a p l u n g e r p u m p ; calibration of orifices for the flow of w a t e r ; determ i n a t i o n of the clearance of an e n g i n e ; use of the different d y n a m o m e t e r s ; valve s e t t i n g (double valve) ; t e s t i n g g a u g e s b y means of the m e r c u r y c o l u m n ; test of some of the boilers; test of t h e s t e a m i n j e c t o r ; test of s t e a m ejectors; use of the different kinds of calorimeters; t e s t of a Swain t u r b i n e ; m e a s u r e m e n t of the flow of w a t e r by m e a n s of orifices and weirs; test of w a t e r m o t o r s ; test of a hot-air e n g i n e ; valve s e t t i n g (Harris-Corliss engine); a n a l y s i s of c h i m n e y g a s ; t e s t of a b a t t e r y of boilers application of Hirn's analysis to the triple-expansion engine in the laboratory; test of the efficiency of a W e s t o n differential pulley block; test of t h e efficiency of jack screws (each test is performed b y a s q u a d of from two to five s t u d e n t s , and t h e results are t h e n worked up and h a n d e d in w i t h i n two or three d a y s by each m e m b e r of the squad); test on exp e r i m e n t a l g o v e r n o r ; tests on the indicator t e s t e r ; tests on the gas e n g i n e ; tests of w a t e r m e t e r s ; calibration of hose nozzles, etc. T h e tests are all m a d e u n d e r such supervision as will insure accurate work, and reliable results. T h e n each s t u d e n t is required to make all the calculations for every test in w h i c h he takes p a r t , and to h a n d t h e m in w i t h i n a week. These reports are e x a m i n e d by c o m p e t e n t instructors who make all the calculations i n d e p e n d e n t l y before examini n g those of the s t u d e n t s . T h e n each s t u d e n t is f u r n i s h e d with the results of all the tests in w h i c h he takes part, and, moreover, t h e r e s u l t s of t h e i n v e s t i g a t i o n s m a d e in the course of the r e g u l a r laborat o r y work of the e n g i n e e r i n g laboratories is r e g u l a r l y published in the 7?chlzology Q u a r t e r @ T h e above is a description of the e q u i p m e n t of, a n d the work done in, these laboratories at the M a s s a c h u s e t t s Insti-
Feb., 1895.]
Water Purificatiall.
135
tute of T e c h n o l o g y . It is plain t h a t s o m e of t he m o s t c o m m o n w o r k of t h e e n g i n e e r in p r a c t i c e will be to m a k e tests of s t e a m e n g i n e s and of s t e a m boilers, to m a k e tests of p o w e r arid to d e t e r m i n e q u a n t i t i e s of w a t e r e i t h e r in h y d r a u l i c wo r k or in w or k on s t eam . Now, t h e y o u n g e n g i n e e r s h o u l d be drilled in d o i n g this work a c c u r a t e l y a n d well, and s h o u l d u n d e r s t a n d w h a t constitutes g o o d w o r k ; m o r e e s p e c i a l l y is t h i s of i m p o r t a n c e because t h e r e are so m a n y so-called e n g i n e e r s w ho m a k e tests c a r e l e s s l y a n d p u b l i s h r es ul t s w h i c h h a v e b e e n obtained--from t e s t s e r r o n e o u s l y made. T o o o f t e n t h e y do not give a d e t a i l e d d e s c r i p t i o n of h o w t h e y m a d e t h e i r tests. Before one can j u d g e of t he c r e d i b i l i t y of t he resul t s of a test, he n e e d s to know h o w t he test was m a d e . T h e s t u d e n t s h o u l d be t a u g h t to do all t h a t he does, well an d t h o r o u g h l y . It will be easy e n o u g h to t e a c h h i m to do r o u g h w o r k w h e n it is r e q u i r e d if he k n o w s h o w to do a c c u r a t e work, b u t if he is a c c u s t o m e d to do r o u g h work it will b e v e r y difficult to m a ke h i m do a c c u r a t e work. WATER
PURIFICATION.*
BY RUDOLPH HERIN(;.
T h e s u b j e c t of t he l e c t u r e w h i c h has b e e n set dow n for to-night is one w h i c h m i g h t o c c u p y o u r t i m e for m a n y evenings, ev en if it s houl d be t r e a t e d, in part, q u i t e superficiallv. T h e r e are m a n y as pe c t s u n d e r w h i c h it m i g h t be considered, and, in or de r t h a t it m a y possibly be of SOme v a l u e to you, it is n e c e s s a r y t h a t we confine o u r s e l v e s to but one aspect, a nd e ve n this one we shall n o t be able to exhaust. Th e use of w a t e r m a y be di vi de d i n t o t h r e e g e n e r a l c l a s s e s - - d o m e s t i c , publ i c and m a n u f a c t u r i n g . In t h e first class we place the w a t e r used for drinking, for c o o k i n g and for w a s h i n g ; t h e s e c o n d class com pr i s e s t h e w a t e r used in A lecture delivered before the Franklin Institute, February 2, I894.
[J. F.I.,
Lan~a:
ENGINEERING
PRACTICE
AND
EDUCATION.
BY GAETANO LANZA, S. B., (2. • M. E., Professor of Theoretical a n d Applied Mechanics, Massachusetts I n s t i t u t e of Technology.
[ Cancluded fi-am ~..56.] S t e r e o t o m y is a species of a d v a n c e d descriptive geometry, and can easily be acquired b y any one who is f a m i l i a r the l a t t e r subject. It bears more especially upon t h e work of t h e e n g i n e e r who is to erect large b u i l d i n g s w h e r e stone plays an i m p o r t a n t part, or m a s o n r y bridges. Of s u r v e y i n g and t o p o g r a p h i c a l drawing, of course, every e n g i n e e r o u g h t to have some knowledge, b u t the principles of s u r v e y i n g are easily l e a r n e d by a n y one who has a scientific t r a i n i n g a n d some skill in h a n d l i n g measuri n g i n s t r u m e n t s , and n i c e t y of execution can only be acq u i r e d by l o n g - c o n t i n u e d practice, a n d the g r e a t e r p a r t of this practice will have to be acquired s u b s e q u e n t l y . Surv e y i n g has s o m e t i m e s been a s s u m e d to be the principal business of the civil engineer, and f r e q u e n t l y a m a n who was m e r e l y a s u r v e y o r has called h i m s e l f a civil e n g i n e e r : b u t the progress of the world is s w e e p i n g this away, and a man who is merely a s u r v e y o r is no l o n g e r considered to be an e n g i n e e r a n y more t h a n a m a c h i n i s t is an engineer. Now, while the m a n who is to build roads or railroads will p r o b a b l y have to use s u r v e y i n g to such an e x t e n t t h a t it will be n e c e s s a r y to give him in the school more t h a n is given in the o t h e r e n g i n e e r i n g courses, n e v e r t h e l e s s his practice will h a v e to be acquired s u b s e q u e n t l y , and the i n s t r u c t i o n in those t h i n g s t h a t he c a n n o t acquire later, or can only acquire later with a g r e a t deal of difficulty, should, on no account, be sacrificed for surveying. W h e n we come to the h i g h e r geodetic work, we h a v e geodesy, a n d n o t e n g i n e e r i n k and hence it will n o t be considered here. T h e n as to shopwork, very s i m i l a r r e m a r k s
Feb., 1895..~
Eng'ineerbzg Practice and Educatiopz.
123
to those I h a v e m a d e in r e g a r d to surveying, will apply. It is s o m e t h i n g in w h i c h e v e r y e ~ i n e e r should h a v e s o m e practice, b u t w h i c h should not De g i v e n at the e x p e n s e of more i m p o r t a n t e n g i n e e r i n g work. Indeed, it w o u l d be e x t r e m e l y desirable t h a t this should be acquired at t h e m a n u a l training schools before boeginning an e n g i n e e r i n g course, and w h e n e v e r t h e m a n u a l training schools are e s t a b l i s h e d every. where as a part of the public school system, so t h a t y o u n g men who wish to take an e n g i n e e r i n g course at s o m e engineering school can first a t t e n d the m a n u a l t r a i n i n g school, then the e n g i n e e r i n g schools will not need to teach so m u c h shopwork and w h a t t h e y do teach will b e of a more advanced character. Coming, now, to t h e studies of the second class, we shall find that we m a y divide t h e m into two classes, the first being those r e q u i s i t e for such specialties as can be developed b y a s u i t a b l e addition of certain lines of work, b u t where t h e s e lines of w o r k d e p e n d u p o n the p r e v i o u s training that has been g i v e n ; and second, those w h e r e a considerable k n o w l e d g e of, and hence a drill in, c h e m i s t r y is neces. sary. A m o n g the first I should place: (I) b r i d g e s ; (2) hydraulic e n g i n e e r i n g ; (3) railroad engineering, w i t h special reference to p e r m a n e n t w a y ; (4) railroad engineering, with special reference to m o t i v e p o w e r and rolling stock; (5) marine e n g i n e e r i n g ; (6) mill e n g i n e e r i n g ; (7) naval architecture; (8) electrical e n g i n e e r i n g ; and others as t h e y m i g h t arise. In the second class, on the o t h e r hand, I should place mining, m e t a l l u r g i c a l and chemical engineering, and others as they m i g h t arise. The essential difference b e t w e e n these two classes is that, in the latter, a considerable k n o w l e d g e of c h e m i s t r y is required, and, c o n s e q u e n t l y , that the s t u d e n t m u s t h a v e considerable i n s t r u c t i o n in e l e m e n t a r y c h e m i s t r y and in qualitative and q u a n t i t a t i v e analysis, before he is in condition to discuss the s u b j e c t s p e r t a i n i n g to his special line; and hence, that for t h e s e courses, a certain a m o u n t of c h e m i s t r y beComes one of t h e essential f u n d a m e n t a l s t u d i e s t h a t the student cannot do w i t h o u t , and m u s t be p r o v i d e d for at the
I2 4
Lapz~a :
[J. F. 1.,
s t a r t by a s s i g n i n g the necessary t i m e for it in a d d i t i o n to t h a t needed for t h e o t h e r f u n d a m e n t a l studies. W h e n suitable provision is m a d e for this, there remains, of course, less time for o t h e r s u b j e c t s t h a n there is in the o t h e r cases. Of course, the a m o u n t of c h e m i s t r y r e q u i r e d is a m a t t e r of degree. In some lines of m i n i n g e n g i n e e r i n g it is not great, whereas, in m e t a l l u r g i c a l works, or in chemical works, the a m o u n t is decidedly larger. Nevertheless, t h e one who is l a y i n g out a n y of these courses m u s t bear in m i n d t h a t t h e y are i n t e n d e d to fit m e n to do p r i m a r i l y the e n g i n e e r i n g w o r k of such e s t a b l i s h m e n t s , and t h a t it is not n e c e s s a r y t h a t t h e y should h a v e as m u c h c h e m i s t r y as would be required by the analytical chemist. Hence, he s h o u l d b e g i n by c o n s i d e r i n g w h a t is the minim u m a m o u n t of c h e m i s t r y w h i c h it will do to p u t in the course ; p u t t h a t in, and t h e n l e a v e t h e rest of t h e chemistry, w h i c h it m i g h t be desirable to add, to take its chances with the o t h e r professional subjects, according to t h e i r relative i m p o r t a n c e in the special line of work for w h i c h the course is laid out. L e t us assume, now, t h a t we h a v e fixed upon the fundam e n t a l subjects, a n d the time t h a t m u s t be g i v e n to each. W e are prepared, then, to map out the course to be p u r s u e d in the second class, or special line of studies, i n c l u d i n g w h a t e v e r of t h e first class we deem wisest to insert in the list. W e r e I to a t t e m p t to map out the details of w h a t s h o u l d be given in t h e case of each special e n g i n e e r i n g course in these special lines, I should need a whole course of lectures to elaborate it. I shall only say a little, therefore, a b o u t some general rules to be observed in m a k i n g t h e selection: (i) To drill the s t u d e n t in all the details of his profession, or to i m p a r t to h i m experience, is not possible in a school. Experience can only be g a i n e d after the school days are past, and he goes to work. (2) To a t t e m p t to perfect h i m in those t h i n g s t h a t he will h a v e to do w h e n he first goes to work, at the expense of his l a t e r success, is a v e r y short-sighted policy. (3) Hence, the object to be a t t a i n e d should be, first, to so
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arrange this work t h a t he shall h a v e to deal w i t h such cases as are liable to ariae in the practice of his profession, as with the a c t u a l d.;~l[ils of a bridge, of a s t e a m engine, of a locomotive, of a mill, etc., and t h u s become f a m i l i a r with what he is likely to m e e t later on ; and secondly, t h a t he shall be t a u g h t how to go to work oi1 these p r o b l e m s in a scientific m a n n e r , a p p l y i n g the principles t h a t he has previously learned, t h u s t e a c h i n g him w h a t is the relation of his scien{ifie s t u d y to the practical problems he will m e e t later in life. Next, in r e g a r d to the t h i r d class of subjects, or those i n t e n d e d for g e n e r a l i n f o r m a t i o n , it is desirable to insert as much as can be inserted, w i t h o u t sacrificing the accomplishm e n t of the main objects of the course. Such s u b j e c t s are, mainly, linguistic a n d l i t e r a r y studies. The first, however, if confined to the m o d e r n l a n g u a g e s , are also, to a certain extent, professional; for, w i t h o u t m o d e r n languages, some of our most v a l u a b l e e n g i n e e r i n g l i t e r a t u r e is closed to the s t u d e n t . H a v i n g t h u s m a r k e d out the character a n d t h e scope of the s t u d i e s t h a t should enter into an e n g i n e e r i n g course of one or of a n o t h e r kind, it r e m a i n s for me to speak of two subjects, viz.: (I) T h e g r a d u a t i o n thesis, a n d (2) the e x t e n t to u hich l a b o r a t o r y practice in the e n g i n e e r i n g laboratories should be i n t r o d u c e d into the courses. First, as to the g r a d u a t i o n thesis. It has a l w a y s been the c u s t o m for the e n g i n e e r i n g schools to require of the st,~dents, before t h e y are g r a d u a t e d , a thesis. T h e special feature r e q u i r e d of a thesis should be t h a t it shall involve an d e m e n t of original i n v e s t i g a t i o n , and its chief object is to teach the s t u d e n t how to make, and to give h i m practice in m a k i n g , original i n v e s t i g a t i o n on his own account. H e should be m a d e to feel t h a t the problem is his own to solve. He should be e n c o u r a g e d to propose his own plan.~ for the solution, and to s u b m i t t h e m to some one m e m b e r of the corps of i n s t r u c t i o n , who s h o u l d aid h i m w h e n he needs aid, and exercise so close a supervision over his work, t h a t he should be m a d e to do it correctly. If th.is s u p e r v i s i o n is properly m a i n t a i n e d , a large
126
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[ J. F. I.,
a m o u n t of i n v e s t i g a t i o n can be a c c o m p l i s h e d in connection w i t h the thesis work. In giving the i n s t r u c t i o n I have outlined above, it should not be m e r e l y class-room instruction, b u t also l a b o r a t o r y work, partly to e m p h a s i z e and illustrate the work of t h e classroom, partly to drill the s t u d e n t in p e r f o r m i n g carefully and a c c u r a t e l y such e x p e r i m e n t a l e n g i n e e r i n g w o r k as he is liable to be called u p o n to p e r f o r m in the practice of his profession, and partly to teach h i m e x p e r i m e n t a l investigation. T h e s t u d e n t will have, of course, in addition to this, labo r a t o r y work in his special line, as in the m i n i n g laboratory, electrical laboratory, industrial chemistry, laboratory, etc., besides, of course, work in the chemical and physical laboratories. I h a v e p r e v i o u s l y called a t t e n t i o n to the process of g r a d u a l d e v e l o p m e n C which has resulted in the e x t e n s i v e int r o d u c t i o n of l a b o r a t o r y practice of a variety of kinds into technical instruction, and therefore to t h e e v o l u t i o n of the e n g i n e e r i n g laboratories. A s to the organization of such laboratories, the principal o b j e c t s to be a c c o m p l i s h e d b y t h e m are three, to wit : (I) To give the s t u d e n t s practice in such e x p e r i m e n t a l work as an e n g i n e e r is c o n s t a n t l y liable to be called upon to p e r f o r m in the practice of his profession, as tests of the s t r e n g t h of materials, e v a p o r a t i v e tests of s t e a m boilers, s t e a m engine tests, calorimetric tests, valve setting, etc.; and to teach him to carry on his work with accuracy, and to take all proper p r e c a u t i o n s to aw-~id error. (2) To give the s t u d e n t o p p o r t u n i t y of carrying on original i n v e s t i g a t i o n in the e n g i n e e r i n g branches, s u c h a s i n v e s t i g a t i o n s in s t r e n g t h of m a t e r i a l s in s t e a m engineering, etc. (3) A n o t h e r i m p o r t a n t function of such laboratories, w h i c h is entirely c o n s i s t e n t with the other two, is t h a t of t a k i n g up and carrying on s y s t e m a t i c i n v e s t i g a t i o n s of e n g i n e e r i n g problems, and this can be done in a laboratory, w h e r e a s it is only w i t h v e r y g r e a t difficulty that it can be
Feb., x895.]
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done in a maclqine shop or a m a n u f a c t u r i n g establishment. By p u b l i s h i n g these results from time to t i m e the labor a t o r y will serve to add g r a d u a l l y to the c o m m o n stock of knowledge,. I recognize v e r y fully the i n c a p a c i t y of the s t u d e n t , as a rule, to o r i g i n a t e and carry on research w i t h o u t aid from his t e a c h e r s ; b u t w h e n this aid is given, a n d the necessary supervision is exercised, a large a m o u n t of research can be accomplished in such laboratories. O r i g i n a l researches should also be carried on by the s t u d e n t s in connection w i t h t h e i r g r a d u a t i n g theses ; some of t h e m are, of course, b e t t e r able to do t h i s k i n d of work than others, b u t all s h o u l d be required to u n d e r t a k e original research, and a careful supervision should be exercised by some one of the i n s t r u c t i n g force, who s h o u l d see to it t h a t w h a t e v e r is done should be properly done, so t h a t the results, as fa'/~s t h e y go, w h e t h e r extensive or not, m a y be of real value. I n a s m u c h as the n u m b e r of i m p o r t a n t i m v e s t i g a t i o n s "which it is possible to take up and carry o u t is so very large that only a few can be u n d e r t a k e n in a n y one laboratory, and, therefore, while there are certain pieces of a p p a r a t u s of so typical and general a character t h a t all e n g i n e e r i n g laboratories need them, and should be p r o v i d e d w i t h the best t h a t their m e a n s will a d m i t of, as for instance, t e s t i n g machines and s t e a m e n g i n e s - - t h e r e m a i n d e r of the apparat:::q :nay vary very considerably in e q u a l l y well-equipped engineering laboratories. Instead, therefore, of l a y i n g down general rules for the e(iuipment and c o n d u c t of such laboratories, it seems to me tha: I shall be b e t t e r able to convey m y ideas by describing to you the e q u i p m e n t of the e n g i n e e r i n g laboratories of the -~Iassaehnsetts I n s t i t u t e of 'I'echnology, and the way in which t h e y are conducted. ~Phe first a t t e m p t at e s t a b l i s h i n g e n g i n e e r i n g laboratories a t t h e I n s t i t u t e was m a d e in the school y e a r ~873 74, w h e n one was e q u i p p e d w i t h the following apparatus, viz.: (a) T w o horizontal t u b u l a r boilers, each 4 feet in diam-
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[J. F. I.,'
eter and E2 feet long, c o n t a i n i n g fifty 3-inch t u b e s ; (b) one small vertical t u b u l a r boiler, 3 feet in diameter, and 7 feet high, c o n t a i n i n g fifty 2-inch t u b e s ; (c) a cast-iron superh e a t e r ; (d) an 8-inch b y 24-inch Harris-Corliss engine, with a brake on t h e fly-wheel; (e) a c o m b i n e d surface c o n d e n s e r and calorimeter w i t h the n e c e s s a r y tanks and scales; (/) also a v a r i e t y of accessory apparatus, as indicators, gauges, etc. F r o m this l a b o r a t o r y there e m a n a t e d an i n v e s t i g a t i o n into s o m e special p r o b l e m s on cylinder condensation m a d e for Mr. George B. Dixwell. F r o m t h e s e small beginnings, partly t h r o u g h g r a d u a l growth, and p a r t l y t h r o u g h considerable c h a n g e s and imp r o v e m e n t s m a d e all at one time, have arisen our p r e s e n t e n g i n e e r i n g laboratories, s i t u a t e d in the E n g i n e e r i n g Building, and o c c u p y i n g two floors, 5o x I 5o feet each. T h e e q u i p m e n t of the L a b o r a t o r y of A p p l i e d Mechanics, z.e., the l a b o r a t o r y for t e s t i n g the s t r e n g t h of materials, e m b r a c e s t h e following a p p a r a t u s : (I) A t e s t i n g m a c h i n e of 3oo,ooo pounds capacity, m a d e b y W i l l i a m Sellers & Company, Incorporated, u n d e r the p a t e n t s of A l b e r t H. Emery, the m a k e r of the G o v e r n m e n t t e s t i n g m a c h i n e of 8oo,ooo p o u n d s capacity at W a t e r t o w n Arsenal. This m a c h i n e has r e c e n t l y been a d d e d to t h e e q u i p m e n t of the laboratory, and it is to be o b s e r v e d t h a t this style of t e s t i n g m a c h i n e is the most delicate and a c c u r a t e in the world. Moreover, the a m o u n t of i n v e s t i g a t i o n in the line of s t r e n g t h of materials of such a c h a r a c t e r as to be of positive value to the engineer, which has been m a d e b y means of the G o v e r n m e n t m a c h i n e at W a t e r t o w n , is far g r e a t e r than that which h a s been a c c o m p l i s h e d by m e a n s of any o t h e r t e s t i n g m a c h i n e in the world. It is provided with suitable holders and m e a s u r i n g appar a t u s to a d a p t it to specimens of different shapes. (2) A n Olsen t e s t i n g machine of 5o,(~oo p o u n d s capacity for d e t e r m i n i n g tensile strength, elasticity and c o m p r e s s i v e strength. This m a c h i n e is furnished with c o m p r e s s i o n platforms, w h i c h d i s t r i b u t e t h e p r e s s u r e e v e n l y over the specimen.
Feb., I895.]
Engineering Practice and Edzlcatzbn.
I29
(3) A t e s t i n g ~ m a c h i n e of ioo,ooo p o u n d s c a p a c i t y for deter r~kning the t r a n s v e r s e s t r e n g t h and stiffness o f b e a m s up to twenty-five feet in length. By m e a n s of this m a c h i n e tests are also m a d e on the s t r e n g t h of f r a m i n g joints u s e d in practice, and on the s t r e n g t h of the r i v e t e d joints of plat e girders, as well as on other s p e c i m e n s s u b j e c t e d to transverse stress. (4) A t e s t i n g m a c h i n e of 18,ooo p o u n d s c a p a c i t y for d e t e r m i n i n g the t r a n s v e r s e s t r e n g t h and stiffness of b e a m s up to fifteen feet in length. (5) A m a c h i n e of I44,ooo-inch pounds c a p a c i t y for testing the torsional s t r e n g t h and stiffness of s h a f t i n g up to twenty-otle feet in length, p r o v i d e d with a p p a r a t u s for m e a s u r i n g the angle of twist to four seconds of arc. (6) A t e s t i n g m a c h i n e of 25,00o p o u n d s c a p a c i t y for determining the s t r e n g t h of ropes or wire, w h e r e the clear length of the s p e c i m e n can be made as g r e a t as ten feet. By m e a n s of this m a c h i n e tests are m a d e u p o n b o t h long and short splices, and on a v a r i e t y of hitches and holders. (7) A m a c h i n e for t e s t i n g the tensile s t r e n g t h of c e m e n t s and morro"s, w h e r e the clips h a v e been specially d e s i g n e d in such a w a y as to secure an evenly d i s t r i b u t e d pull on the specimen. In connection with this m a c h i n e is a c o m p l e t e ontfi~ of nicely-constructed m o u l d s for m a k i n g the briquettes or specimens, and also all other n e c e s s a r y apparatus, as sieves, tanks, e~c. (8) A m a c h i n e for d e t e r m i n i n g the s t r e n g t h and elasticity of ioi~g s p e c i m e n s of wire. (9) A machine for d e t e r m i n i n g the s t r e n g t h and elasticity of cloth. (~o) A m a c h i n e for d e t e r m i n i n g the effect of r e p e a t e d S~resses on the s t r e n g t h and elasticity of iron a n d steel. (I i) A m a c h i n e for d e t e r m i n i n g the deflection of parallel rods w h e n r u n n i n g u n d e r different conditions. (12) A q u a n t i t y of m e a s u r i n g and o t h e r a p p a r a t u s for d e t e r m i n i n g stretch, deflection and twist. The s t u d e n t s w h o take the s u b j e c t of applied m e c h a n i c s in their senior y e a r are r e q u i r e d to learn h o w to use this apparatus, and the m e t h o d of m a k i n g the different kinds of VOL. CXXXIX. 9
13o
Lanza
:
[J. F. I.,
tests, t h u s l e a r n i n g how tests s h o u l d be made, and alsd a c q u i r i n g a f a m i l i a r i t y with the appearance a n d b e h a v i o r of m a t e r i a l s w h e n s u b j e c t e d to stresses such as occur in practice. Thus, in the school year each s t u d e n t m a k e s t h e followi n g tests in the l a b o r a t o r y : (I) A t e s t to d e t e r m i n e the m o d u l u s of elasticity, the l i m i t of elasticity, and tensile s t r e n g t h of a cast iron or w r o u g h t - i r o n or steel rod or bar, or the transverse s t r e n g t h of a coupling. (2) A test of the deflections and of the t r a n s v e r s e s t r e n g t h of a full-size iron or steel I beam, or of a w o o d e n b e a m subjected to t r a n s v e r s e load. (3) A test to d e t e r m i n e the m o d u l u s of e l a s t i c i t y and the tensile s t r e n g t h of various kinds of wire. (4) A test to d e t e r m i n e the s h e a r i n g m o d u l u s of elasticity and the torsional s t r e n g t h of a shaft. (5) T e s t s of the tensile s t r e n g t h of h y d r a u l i c cement. (6) T e s t s of t h e compressive s t r e n g t h of h y d r a u l i c cement. (7) T e s t s of t h e s t r e n g t h of rope, and t h e loss of efficiency due to different hitches and knots. (8) Besides t h e above the s t u d e n t s m a k e a v a r i e t y of tests of large pieces on the E m e r y t e s t i n g m a c h i n e ; sometimes compression tests of full size columns, or of small blocks, or of c o l u m n s with bolsters, etc., a n d s o m e t i m e s tensile tests of pieces of v a r y i n g shapes and sizes. The hydraulic laboratory contains : (t) A closed tank, 5 feet in d i a m e t e r and 27 feet high, connected w i t h a Io-inch stand-pipe over 7° feet high, so a r r a n g e d t h a t a c o n s t a n t h e a d m a y be kept at a n y desired level. (2) A p p a r a t u s in connection w i t h the t a n k a n d standpipe, for m a k i n g e x p e r i m e n t s on t h e flow of w a t e r t h r o u g h orifices and mouth-pieces, over weirs and in pipes, u n d e r different h e a d s a n d conditions, and on the losses of head occurring u n d e r different circumstances. (3) A s y s t e m of pipes, eonnected both w i t h t h e main pipe and w i t h the pumps, is fitted for the i n s e r t i o n of diap h r a g m s , b r a n c h e s a n d other a p p a r a t u s for s t u d y i n g loss of h e a d and the laws of discharge.
Feb., I895 ]
Engincerinff Practice alzd EducaZiolz.
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(4) A n a t t a c h m e n t to the m a i n tank, c o n t a i n i n g a P i t o t tube for s t u d y i n g the laws of velocity in jets, and a d j u s t a b l e points for the m ' e a s u r e m e n t of the cross-section of jets. (5) A cylindrical steel m e a s u r i n g t a n k of 28o cubic feet capacity. (6)j A six-inch Swain turbine, so a r r a n g e d t h a t it can be run u n d e r different heads, and t h a t m e a s u r e m e n t s can be made of the power exerted, of the efficiency, etc., u n d e r different gates. (7) A 48-inch P e l t o n w a t e r motor, similarly arranged. (8) A V e n t u r i m e t e r and n u m e r o u s hose nozzles for m e a s u r i n g water. (9) A bceir of a d j u s t a b l e w i d t h up to four feet. (to) A h y d r a u l i c ram with a two and one-half inch drive pipe. The s t e a m l a b o r a t o r y contains : (I) A triple-expansion engine, with cylinders of 9 inches I6 inches, and 24 inches diameter, respectively, by 3o inches stroke, a r r a n g e d in such a w a y as to be r u n single, compound or triple, as desired for the purposes of experiment. It is of th. Corliss type, and has a c a p a c i t y of a b o u t ~5o horse-power w h e n r u n n i n g triple, with an initial pressure of I5O pounds in the h i g h - p r e s s u r e cylinder. To it is connected a surface condenser, a n d the other a p p a r a t u s needed to adapt it to the ptIrposes of accurate e x p e r i m e n t . The ends and barrels of the cylinders are s e p a r a t e l y jacketed, so t h a t s t e a m can be let into e i t h e r or both. T h e receivers are also j a c k e t e d so t h a t t h e y can bc used either wilh s t e a m in the j a c k e t s or not. T h e cut-off on all three cylinders can be t h r o w n into connection w i t h the governor, or any of t h e m can be d i s c o n n e c t e d from t h e g o v e r n o r and adjusted bv h a n d at a fixed point. Cans are provided for catching the drip from each jacket, and t h e s e cans are provided with water-glasses so t h a t we can d e t e r m i n e its quantity. The engine i s t h u s fitted to carry on series of e x p e r i m e n t s Under different conditions, and by its use we can obtain results comparable w i t h t h e results t h a t are a c t u a l l y realized on large m a r i n e and s t a t i o n a r y engines. T h e w a t e r consump-
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Lalz~t :
[J. F. I.,
tion per horse-power per h o u r varies w i t h the different conditions u n d e r w h i c h the e n g i n e is r u n , "but we have f o u n d it u n d e r some conditions as low as I3" 7 pounds. A very considerable a m o u n t of i n v e s t i g a t i o n has been carried on already, and valuable r e s u l t s have been obtained. (2) A Harris-Corliss engine, w i t h cylinder 8 inches diameter by 24 inches stroke, with a c a p a c i t y of a b o u t I6 horsepower, with an initial pressure of 75 pounds. T h i s engine is a l s o c o n n e c t e d w i t h a surface condenser and a t a n k on scales to w e i g h t h e condensed steam, and, of course, it can be used to m a k e e n g i n e tests ; b u t i n a s m u c h as it is a small engine, it is not economical, u s i n g from 3° to 4o pounds of w a t e r per horse-power per h o u r ; and, now t h a t we have the triple expansion engine, we use the Harris-Corliss machine m a i n l y for valve-setting. Moreover, this HarrisCorliss e n g i n e is the original one t h a t was p u t in t h e laborat o r y when it was first founded, in 1873 , by m e a n s of which the i n v e s t i g a t i o n s were m a d e for Mr. Dixwell. T h e r e is also a n o t h e r eight-horse-power e n g i n e used for valve-setting, etc. (3) Of surface condensers t h e r e are four in all: (a) the one connected w i t h t h e triple-expansion engine, and which is also specially a r r a n g e d for e x p e r i m e n t a l purposes in such a way t h a t t h e c o n d e n s i n g w a t e r can be m a d e to pass once, twice or three t i m e s t h e l e n g t h of the c o n d e n s e r while per. f o r m i n g its f u n c t i o n s ; (b) a smaller surface condenser a t t a c h e d to the Harris-Corliss engine, and (c) and ( d ) t w o o t h e r surface condensers, used in various experiments. (4) A mercurial pressure c o l u m n which e x t e n d s to I6O p o u n d s pressure, by m e a n s of w h i c h our g a u g e s are tested. T h e r e is also a m e r c u r i a l v a c u u m column. (5) A d y n a m i c s t e a m engine indicator tester. (6) Several pieces of a p p a r a t u s for d e t e r m i n i n g t h e quant i t y of s t e a m i s s u i n g from a given orifice, or t h r o u g h a short tube, u n d e r a given difference of pressure. (7) A p p a r a t u s for t e s t i n g s t e a m injectors. (8) A n u m b e r of s t e a m pumps, the l a r g e s t one b e i n g a duplex p u m p 16, IO½-b y i2 inches. (9) A n u m b e r and v a r i e t y of calorimeters.
Feb., I895.]
Enffhteering" Practice and Edztcation.
13 3
(Io) A larg6 s u p p l y of indicators, p l a n i m e t e r s , gauges, t h e r m o m e t e r s , a n e m o m e t e r s a nd o t h e r a c c e s s o r y a p p a r a t u s . (IS) T h e r e ar~ in t he di f f er e nt b u i l d i n g s two 2o8-horsepower s ectio n al boilers, two ioo-horse-power, and one eightyhorse-power h o r i z o n t a l t u b u l a r boilers, a n d a n o t h e r sixtyhorse)power h o r i z o n t a l t u b u l a r boiler at t he shops, and these' are used for m a k i n g boi l er tests ; all t he f o u r t h y e a r s t u d en ts of m e c h a n i c a l , electrical, c h e m i c a l e n g i n e e r i n g and naval a r c h i t e c t u r e , h a v i n g to take p a r t in t h e s e tests. It is b e l i e v e d t h a t t h e s t u d e n t s can b e s t l e a r n to m ake boiler tes ts b y m a k i n g t h e m on large boi l ers p r o d u c i n g a considerable q u a n t i t y of steam. B es id e; all the above, t h e e n g i n e e r i n g l a b o r a t o r i e s . a r e provided w i t h s e ve r al f r i ct i on b r a k e s of d i f f e r e n t capacities; with m a c h i n e r y for d e t e r m i n i n g t he t e n s i o n r e q u i r e d in a belt to e n a b l e it to c a r r y a g i v e n a m o u n t of power, at a g i v e n speed, w i t h no m o r e t h a n a g i v e n a m o u n t of slip ; w i t h a m ach in e for t e s t i n g t h e t r a n s m i s s i o n of p o w e r by r o p e s ; with a n u m b e r of t r a n s m i s s i o n d y n a m o m e t e r s ; w i t h a fourhorse-power gas e n g i n e ; w i t h a c o m p l e t e set of W e s t i n g house air-br ke a p p a r a t u s , i n c l u d i n g t he p a r t s b e l o n g i n g to the car an d to t h e l o c o m o t i v e ; w i t h t he p u m p and e n g i n e e r ' s valve of th e N e w Y or k air-brake ; w i t h a m e a s u r i n g t a n k for large q u a n t i t i e s of water, t hi s t a n k b e i n g p r o v i d e d w i t h a n u m b e r of orifices in t he b o t t o m , and a w a t e r glass on the side ; with a n u m b e r of w a t e r meters, and of weirs of different sizes, for m e a s u r i n g w a t e r ; with a l o c o m o t i v e link model : w i t h a c e n t r i f u g a l p u m p , a g a n g p u m p and a r o t a r y pump ; w i t h a h o t - a i r e n g i n e ; w i t h a p u l s o m e t e r p u m p ; w i t h an e x p e r i m e n t a l g o v e r n o r ; w i t h an oil-testing m a c h i n e ; with a n u m b e r of w a t e r m o t o r s ; w i t h an e j e c t o r ; and with cotton m a c h i n e r y as follows : two cards, a d r a w i n g frame, a speeder, a fly frame, a r i n g f r a m e and a mule, as well as accessory a p p a r a t u s . As to t he work r e q u i r e d of t he students of m e c h a n i c a l , e l e c t r i cal and c h e m i c a l e n g i n e e r i n g , I will say t h a t in t h e second t e r m of t h e i r j u n i o r y e a r t h e y are r e q u i r e d to make, u n d e r careful s u p e r v i s i o n , e n g i n e tests on th e tr ipl e engine. In t he course of t he s e n i o r y e a r the list of tests m a d e by each s t u d e n t is a p p r o x i m a t e l y as follows, viz. :
134
Lanza.
[ 1. F. I.,
T e s t s of the t r a n s m i s s i o n of power ~ b e l t i n g ; test of t h e p e r f o r m a n c e of a surface c o n d e n s e r ; t e s t of a directa c t i n g steam p u m p ; test of the flow of steam ; valve s e t t i n g (plain slide valve); test of a p u l s o m e t e r ; test of a p l u n g e r p u m p ; calibration of orifices for the flow of w a t e r ; determ i n a t i o n of the clearance of an e n g i n e ; use of the different d y n a m o m e t e r s ; valve s e t t i n g (double valve) ; t e s t i n g g a u g e s b y means of the m e r c u r y c o l u m n ; test of some of the boilers; test of t h e s t e a m i n j e c t o r ; test of s t e a m ejectors; use of the different kinds of calorimeters; t e s t of a Swain t u r b i n e ; m e a s u r e m e n t of the flow of w a t e r by m e a n s of orifices and weirs; test of w a t e r m o t o r s ; test of a hot-air e n g i n e ; valve s e t t i n g (Harris-Corliss engine); a n a l y s i s of c h i m n e y g a s ; t e s t of a b a t t e r y of boilers application of Hirn's analysis to the triple-expansion engine in the laboratory; test of the efficiency of a W e s t o n differential pulley block; test of t h e efficiency of jack screws (each test is performed b y a s q u a d of from two to five s t u d e n t s , and t h e results are t h e n worked up and h a n d e d in w i t h i n two or three d a y s by each m e m b e r of the squad); test on exp e r i m e n t a l g o v e r n o r ; tests on the indicator t e s t e r ; tests on the gas e n g i n e ; tests of w a t e r m e t e r s ; calibration of hose nozzles, etc. T h e tests are all m a d e u n d e r such supervision as will insure accurate work, and reliable results. T h e n each s t u d e n t is required to make all the calculations for every test in w h i c h he takes p a r t , and to h a n d t h e m in w i t h i n a week. These reports are e x a m i n e d by c o m p e t e n t instructors who make all the calculations i n d e p e n d e n t l y before examini n g those of the s t u d e n t s . T h e n each s t u d e n t is f u r n i s h e d with the results of all the tests in w h i c h he takes part, and, moreover, t h e r e s u l t s of t h e i n v e s t i g a t i o n s m a d e in the course of the r e g u l a r laborat o r y work of the e n g i n e e r i n g laboratories is r e g u l a r l y published in the 7?chlzology Q u a r t e r @ T h e above is a description of the e q u i p m e n t of, a n d the work done in, these laboratories at the M a s s a c h u s e t t s Insti-
Feb., 1895.]
Water Purificatiall.
135
tute of T e c h n o l o g y . It is plain t h a t s o m e of t he m o s t c o m m o n w o r k of t h e e n g i n e e r in p r a c t i c e will be to m a k e tests of s t e a m e n g i n e s and of s t e a m boilers, to m a k e tests of p o w e r arid to d e t e r m i n e q u a n t i t i e s of w a t e r e i t h e r in h y d r a u l i c wo r k or in w or k on s t eam . Now, t h e y o u n g e n g i n e e r s h o u l d be drilled in d o i n g this work a c c u r a t e l y a n d well, and s h o u l d u n d e r s t a n d w h a t constitutes g o o d w o r k ; m o r e e s p e c i a l l y is t h i s of i m p o r t a n c e because t h e r e are so m a n y so-called e n g i n e e r s w ho m a k e tests c a r e l e s s l y a n d p u b l i s h r es ul t s w h i c h h a v e b e e n obtained--from t e s t s e r r o n e o u s l y made. T o o o f t e n t h e y do not give a d e t a i l e d d e s c r i p t i o n of h o w t h e y m a d e t h e i r tests. Before one can j u d g e of t he c r e d i b i l i t y of t he resul t s of a test, he n e e d s to know h o w t he test was m a d e . T h e s t u d e n t s h o u l d be t a u g h t to do all t h a t he does, well an d t h o r o u g h l y . It will be easy e n o u g h to t e a c h h i m to do r o u g h w o r k w h e n it is r e q u i r e d if he k n o w s h o w to do a c c u r a t e work, b u t if he is a c c u s t o m e d to do r o u g h work it will b e v e r y difficult to m a ke h i m do a c c u r a t e work. WATER
PURIFICATION.*
BY RUDOLPH HERIN(;.
T h e s u b j e c t of t he l e c t u r e w h i c h has b e e n set dow n for to-night is one w h i c h m i g h t o c c u p y o u r t i m e for m a n y evenings, ev en if it s houl d be t r e a t e d, in part, q u i t e superficiallv. T h e r e are m a n y as pe c t s u n d e r w h i c h it m i g h t be considered, and, in or de r t h a t it m a y possibly be of SOme v a l u e to you, it is n e c e s s a r y t h a t we confine o u r s e l v e s to but one aspect, a nd e ve n this one we shall n o t be able to exhaust. Th e use of w a t e r m a y be di vi de d i n t o t h r e e g e n e r a l c l a s s e s - - d o m e s t i c , publ i c and m a n u f a c t u r i n g . In t h e first class we place the w a t e r used for drinking, for c o o k i n g and for w a s h i n g ; t h e s e c o n d class com pr i s e s t h e w a t e r used in A lecture delivered before the Franklin Institute, February 2, I894.