. The Street railway journal . r proportion betweenair pressure, cylinder piston area and leverage. First, as to pressure: If more than 2 per cent, brakingpower per lb. of cylinder pressure is attempted, a very *Paper presented at meeting of Central Electric Railway Association,Nov. 21, 1907. November 30, 1907.] STREET RAILWAY JOURNAL. 1059 high braking power power for light cylinder pressures isobtained and, therefore, the cars cannot be handled withoutshocks at low speeds, and either the range between maxi-mum and minimum braking power obtainable must be verynarrow or else wheel sliding will
. The Street railway journal . r proportion betweenair pressure, cylinder piston area and leverage. First, as to pressure: If more than 2 per cent, brakingpower per lb. of cylinder pressure is attempted, a very *Paper presented at meeting of Central Electric Railway Association,Nov. 21, 1907. November 30, 1907.] STREET RAILWAY JOURNAL. 1059 high braking power power for light cylinder pressures isobtained and, therefore, the cars cannot be handled withoutshocks at low speeds, and either the range between maxi-mum and minimum braking power obtainable must be verynarrow or else wheel sliding will result when the maxi-mum power is used. Second, as to area of brake piston: If the ratio of cylin-der piston area to cylinder pressure is excessive, it meanseither a low leverage, which means great shoe movement;or higher leverage with low pressure, which means verynarrow range between maximum and minimum brakingpower. Third, as to leverage: If the leverage is too low, itmeans excessive air consumption and too much shoe move-. Merits of This Truck from a Brake Design Standpoint 1. Inside hung brake shoes. 2. Equalized brake leverage system.—That is to say, it is arranged sothat unequal shoe clearance will not throw all the pressure on one pairof wheels. 3. Radius bar connection to live truck levers.—In addition to its usewhen on a curve, the radius bar construction also eliminates the greatdeflection of weak brake beams, due to the truck levers acting at theircenter. Demerits from a Brake Design Standpoint 1. High truck leverage ratio.—This total ratio is to 1 (i. ,one pound applied at the middle of radius bar gives a total of poundsdistributed at the four-wheel shoes, and therefore necessitates a largemovement of the live truck levers in setting the brake shoes, with con-sequent bad angles and danger of striking an obstruction, since the roomfor movement is generally limited on an electric railway truck. A highleverage ratio is altogether unnecessary on the
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
