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Show STOPPING ELCCTrilC CAPS. It-alta 'if H.Miir 1 1 1 . i ui . .O. oxi I So, totl'. I'rtmljK-l Mm-. Homo etperiiu'-rii.i I bat Imvu b-en math- to ib-termine tho .lisi.-ue-s re quir.-d to ctop an eb-etrie car utid'-r or dinary ei cum --tan' from variuis npt-.-iI.--, bavf fiiriu-li'-d inl'-resting results re-sults ILs to the brake pou'.-r of street cars, as appi-ars by lint annual r-port of (be railroad commiv-ioiiors. In mak- iug the cxporiunM.ls tier following cm-, ditioiis went observed: A man witli a iiiiiiil'-r of surveying litis wa.s Ma-tionetl Ma-tionetl on tlie step i A tin- rear platform ; two olii-rvi-n uitil stop wiitelnrs stotxl upon the platform ; a fourth gavo tho signal for Uu- driver to stop. With the ear running at a uniform speed, it w;ts neeess'iry to doti-ruiine llrsf, tho rate of speed, and, seeond, tho dksLaiu'O ro 4iiired to make a stop. At a given signal the first stop wah-h wa-s start.! and a pin wiu. droppt-d upon the groun.f. At iho expiration ut ton seeonds tho i t-u -rver V 1 1 tl his stop wal'-h gave alio t her signal and stopped Iilh wat'-h. When this signal wils gien a second pin wxs dropped on the ground, tie- seemul stop watch w.i-started w.i-started ajul tint signal given for 1 1 le driver to put on the brakes. When tho car came to rest tho second stop wuleh woj slopj.-d and a third pin was drop-H-d. Tin' time rotpiired to puss over the distance helweeu tho lirst uud Hoeond pins showed the rale of speed. The disl.aiico between tint second sec-ond and third pins was the length of stop. tin u subsequent occasion tho speed win obtained by meiusuriiig the time tiecess.-iry to ptLss over tint distal ten between be-tween given streets. This mot In d of observation was easy to carry out, but wa.", of course, not precise, and tho given lengths of stop wen? slightly greater than tlie distances passed over from tho time the brakes were actually applied to the wheels, owing to tlie fad that a fraction of a second wa-s probably lost iu giving thn signals. A great variation was shown between the dilTerent stops made. "Supposing." say tho experts, "tho friction to bo the sumo, the length of slop should be us the square of the velocity. Really the Iriction is less tho greater the velocity, so that tlie length of stop should bo somewhat, greater than in proportion to tho sqttaro of the velocity. This was shown iu a stop in thirty-six feet at iS.'.i miles per hour, and in a stop in forty-eight forty-eight feet ut miles per hour in- stead of u stop hi 1 11 feet, aa it would ' Ie according to the sqtiaro of the velocity; veloc-ity; or if tin; stop in forty-eight feet be taken us a basis of comparison the stop j from six miles an hour should have I boon made in twelve feet. The grades i In these eases wero not greatly dill'er- ent. Again, comparing t wo ex peri-1 incuts in which tho speed w:ls nearly tho same, tho stop on tho down grade was uiuch better than on the up grade. . Other discrepancies of a similar churac-: ter were noticed." lioston Transcript. |