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Answer: Referring to sketch No. I, the full lines represent the part which you show. The sketch has been completed with dotted lines indicating the proper method of wiring to obtain the desired result. One turn of the switch will throw off the light which is burning, and throw on the other, in every case. The wiring shown in sketch No. 2 is entirely correct for the three-way switch as it is used for the purpose of controlling a light from two separate points. The light can be turned on or off from either of the two three-way switches shown.
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The Wesco Supply Co.
St. Louis, U. S. A.
Probable M. E. P. of Steam Engines
Question: Please explain how to find the Mean Effective Pressure of a 6 x 12 steam engine making 250 revolutions per minute, the boiler pressure being 80 pounds by gauge.F. J.
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O, Off on Catalogue Prices
CONSULTING DEPARTMENT-(Continued) Answer: Your question cannot be given an absolute answer, for the reason
tors than those which you have given.
Hereafter we will give to the public
Stradivarius model $65 violin for $32.50. Other
Germany, and Padua, Italy. Ten days' free trial of our instrument. Write for catalogue.
WM. LEWIS Q SON,
know the cut-off, the back pressure, and type of engine. Making certain assumptions, we can give you an approximate answer. If the cut-off is 14, then the ratio of expansion is 4, neglecting clearance. Assuming the back pressure to be 3 pounds gauge, then the M. E. P. can be found by the formula
M. E. P.=p1+hyp. log. R
P= Absolute initial pressure.
p= Back pressure (absolute).
What Is Daus’ Tip-Top?
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for making 100 copies from pen
ship complete duplicator, cap
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The Felix G. L. Daus Duplicator Co. Daus Building, 111 John Street, New York City
THE ENGINE ER
= 56.5—17.7 = 38.8 pounds. We have made no allowances for losses due to compression, clearance, condensa
tion, wire drawing, etc. To allow for is a power plant paper for engineers-for those who install, operate and care for machinery, whether steam, these in a plain slide-valve engine, it is electric, gas or hydraulic.
customary to multiply this theoretical The issues of one year contain about one thousand
M. E. P. by the factor .8, which will pages of reading matter. The articles are in the highest degree educational, and of the most authoritative give us for the probable M. E. P., 38.8 x character. Every phase of every power plant subject is treated in a manner both popular and interesting.
.8 (= 31.04) pounds. ISSUED TWICE A MONTH. ONE DOLLAR A YEAR In the formula used above, you will Write for free sample copy.
find the term “hyp. log. R.” We are to The ENGINEER PUBLISHING COMPANY substitute for this term the hyperbolic 357 Dearborn Street,
CHICAGO, ILL. logarithm, or, as it is sometimes called,
the Napierian logarithm of the factor R. These logarithms will be found in almost
any engineer's handbook. The wonderful new power: maximum efficiency: minimum bulk. Especially adapted for marine or anto use. The best stationary power for electric lighting or other high speed purposes. Catalogue on request if you mention THE TECHNICAL WORLD,
Exhausting Under Water Cushman Motor Co., Lincoln, Neb. Question: Is it possible for two-cycle gas
engines to exhaust under water without seri-
Answer: This is frequently done
without loss of H. P. by extending the SECURED OR FEE RETURNED FREE opinion as to patentability. Send for Guide
terminal under water, with a small vent Book and What To Invent, finest publication is above the water. The vent prevents the sued for free distribution. Patents secured by us advertised free. EVANS, WILKENS & co.
water from drawing back to the muffler No. 600 F Stroot, N. W. Washington, D. C. when the motor stops.
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The Cushman Motor
( Model “H.” Capacity four passengers. Speed up to twentyfive miles an hour. $850. Equipped with tools, oilers, pump, repair kit, brass oil side lamps and brass horn.
( In this model the speed is regulated by the trottle attached to
( Made in our own factory where the facilities are so complete that they involve the making of bolts and nuts even. These exactly fit the spanner wrenches which go with our vehicles.
The tonneau of Model “H” can be readily removed and the vehicle converted into a run-about, Model “G", and at slight expense delivery wagon top can be added. (Send for THE RAMBLERMAGAZINE and other printed matter.
Thomas B. Jeffery & Company MAIN OFFICE AND FACTORY, KENOSHA, WISCONSIN
New York Agency 140 West 38th
Representatives in all leading
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Preparation for College
CONSULTING DEPARTMENT-(Continued) Current of Open and Closed Motor
Question: Upon the name plate of a G. E. 500-volt direct-current compound-wound motor is the following:
"Open....10 H. P.....17 amperes.
Closed....572 H. P.....10 amperes."
Answer: This doubtless refers to the condition of the machine running in the
first place as an open motor, and in the JF Main Building, Armour Institute of Technology
second as an enclosed motor. It will be noticed that a current of 17 amperes is allowed in the first case, or when the machine is running as an open motor; and a current of only 10 amperes, when the machine is running as a closed motor. This discrepancy is, of course, due to the
difference in ventilation, the open motor BY MAIL
being much better ventilated than the Instruction under the direction of the regular
enclosed. teachers in a resident engineering college.
Lessons prepared especially for home study by teachers of acknowledged standing.
Domestic Heating System The full College Preparatory Course covers the entrance requirements of such a college as ARMOUR
Question: I wish to put a heating system INSTITUTE OF TECHNOLOGY, and students
in my house. Kindly give me some rules by satisfactorily completing this course are admitted
which I can determine the size of pipe necesto the college of engineering of that institution without further examination in the subjects taken.
sary, the dimensions of radiators, etc.-H. B. An unusual opportunity for young men of limit
Answer: Your inquiry is entirely too ed means to prepare for entrance to an engineering college without leaving home or interfering indefinite, since there are so many variwith their regular work.
able factors connected with any heating PARENTS wishing to KEEP THEIR
system, and you have omitted to state the CHILDREN AT HOME as long as possible before sending them to college will
exact conditions. The principal points find these courses of great value. There
to be considered are:- First, the system is no breaking of home ties, and the student not only has many of the ad
itself, i. e., whether a furnace, steam, or vantages of a private tutor but also the
hot water is to be used. Second, the sympathy and encouragement of his parents.
location and exposure. Third, the maThis is an excellent opportunity for teachers and terial of which the building is constructothers to take up engineering studies in their own
ed, and the purpose for which it is to be homes and at their own convenience under the guidance of resident school teachers.
used. The following general rules can In addition to the College Preparatory Course be used for rough calculation; but when instruction is also offered in
it comes to actually laying out the plant, Mathematics (Arithmetic, Algebra, Geom
more exact rules which necessitate the etry and Trigonometry), Electrical, Mechanical, Steam, Sanitary and Civil
knowledge of the conditions outlined Engineering: Architecture, Mechanical
above, should be used.
Using steam, one square foot of direct
radiation will supply from 60 to 80 cubic 200 page illustrated Bulletin, giving full infor
feet in ordinary dwellings. If indirect mation as to courses, teachers, methods of study. etc., may be had upon request.
radiation is used, these figures would be
from 40 to 50 cubic feet. If hot water of American School of Correspondence
high temperature is used, one square foot at
of radiation will take care of 50 to 70 Armour Institute of Technology
cubic feet; and if low-temperature hot CHICAGO, ILL., U.S.A.
water is used, these figures should be - Mention The Technical World, Dec. i
from 30 to 50. Mention The Technical World.