Page:Popular Science Monthly Volume 89.djvu/620

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��Popular Science Monthly

��A Simple Tracing Method for Electrical Draftsmen

ATIME-SAVKK for t-loctrical drafts- men is shown iK-rt'vvith. The idea is to draw standard details on a paper, or still better, on a tracing cloth template, repeating each figure to each of the standard scales used in the office.

\\'hcn these figures occur in tracing a drawing, the template is slipped under the tracing cloth so as to bring the proper figure, drawn to the proper scale, into position, when it is traced direct, saving the time necessary to make a

��Lightening Automobiles with Aluminum

��Tlll'^ most pronounced tendency connection with modern auton












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��'Stock drawings or templates to slip under tracing cloth as an aid in drawing in machine parts

��scale drawing of that particular symbol. This idea may be extended as far as profitable, as the templates can be made up as a filler job. — Frank Har.\zim.

��A Table Mat That is Both Decorative and Protective

i.N ingenious device for l.ii)lc - lu.ils

is an embroidcrc-d linen slip, in>ide

1 which isplaci'd a sheet of while asbestos.


��m tomo-

bile develo|)ment is the reduction of car weight that has been made by all leading manufacturers in their recent models. One way of lightening the power-plant is to use small cylinders and obtain the power desired by increasing the piston speed and, of course, the number of ex- [)losions in a given time. The experi- mental work done in connection with high-speed motor design brought out the desirability of using light reciprocating parts. To attain this end, aluminum-alloy pistons were tried instead of cast-iron and these have been so successful that many new engines will be equipped with pistons of the lighter metal. Aluminum parts weigh about one-third as much as cast-iron ones of the same size, so the reduction of recip- rocating weight materially re- duces vibration and makes higher speeds possible.

All of the higher grade engines have always used aluminum crank-cases, but it remained for an ingenious designer to use aluminum for his cylinder-block casting in a iyi6 power-plant. This engine is the nearest ap- proach to the aluminum motor that has ever been made, since e\ery jiart that could be made of that material has I)een con- structed in some alloy of it.

Of course, there are numerous parts where it is not possible or [jractical to use aluminum. The crank-shaft, cam-shaft and con- necting rods, for instance, must be of steel and very excellent metal at that. The wilvesand wrisl|>ins must be of steel and the ll\-\vlieel ol slivl or cast-iron, because this part must be heavy to be efTective. In this engine, even the cylinder-head casting is made of aluminum, the valves seating on cast-iron \alve seats, made solid in the casting b\' the ingi-nioiis process of placing them in till' molil and pouring the molten mclal around them, when the c\liiidi'r- head is cast. The valve-stem guides are


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