223
OF ENGINEERING FORMULÆ.
Resistance of Trains.
Approximate Rule.
V — Velocity of train, miles per hour.
R = Resistance, lbs. per ton of train.
R = 6 + -009 V«.
This is under the assumption that the weather is calm, the
road level, straight, and properly maintained, and the rolling
stock in good order.
Side winds press the flanges of the wheels against the rails
and greatly lucrease the friction; wind, curves, or imperfec-
tions of the road will very largely increase the resistance,
probably by 50 or 60 per cent.
V, miles per hour R, lbs. per ton .. .. 6-9 15 8’0 20 9’6 25 11-6 30 14’1 35 17-0 40 20'4
V, miles per hour R, lbs. per ton .. 45 24-1 • 50 28-5 55 33-2 60 38-4 65 44-0 70 50-1 75 56-6
Resistance Due to Gravitt.
D = Declivity of gradient, feet per mile.
— = Rate of gradient.
R = Resistance in lbs. per ton of train.
—r —I-
Gradient, I In D.feet per mile R, lbs. per ton 20 25 30 35 40 45 50 55 GO
264 211-2 176 150'9 132 117-3 105-6 96-0I88-0
112 89-6 64-0 56'0 49-8 44-8 40-7.31-3 1 I
Gradient, 1 in ro 80 100 120 150 I 200 1 I 300 400 500
D,feet per mile 15’i 66-0 52'8 44-0 35-2 26'4 17 6 13-2 10'6
R, lbs. per ton 32-0 28-0 22-4 18-7 14'91 11-2 7-5 5-ei 4-fi