229 OJF ENGINEERING FUKMULÆ.
Tikes of Wheels.
Thickness of tire on tread in inches = T.
Minimum thickness to which tire may be turned = t.
4 ft. 81 in. Gauge. Metre Gauge.
Engine. Carriage. Waggon. Engine. Carriage. Waggon.
T, inches .. — 26 2-25 2'25 2 1’77 1-77
t, „ iron = 1 1 J » i i
t, „ steel — I • I i t 8
After carriage tires have been turned to the minimum for
carriages they may be used under goods waggons.
Mild steel tires should be guaranteed for 100,000 miles
with a penalty for all above 20 per cent, that fail under
160,000 miles.
Vickers* Test roii Steel Tikes.
The tire placed vertically on a solid bearing should bear a
series of blows from the fall of a tup weighing 1 ton; 1 st
fall, 5 feet; 2nd, 10 feet; 3rd, 15 feet, to be continued until
partial or complete failure; the tire in its vertical position to
yield 'th of its diameter before breaking.
A piece of the tire thus tested ought to bear a tensile
strength of 47 tons per square inch; the drop test ensures
safety and the tensile strain ensures the necessary car-
burization and consequent durability.
Alloys fob Carriage Bearings.
Copper .. .. Tin .. * . Antimony.. •. Lead Total .. English G.W.E. French. Italian.
22 67 11 82 18 38 25 37
100 100 100