286 
TRACTION OF WHEELS AND AXLES. 
were fitted were loaded, to give in each the same weight upon the 
wheels (7 cwt. 1 qr. 21 lbs.), attached, in succession, to a dynamometer, 
fitted to a limber, and carefully drawn at a speed of three miles an 
hour over the same ground. The dynamometer used is one of very 
simple construction, designed by Mr. Butter, Manager R.C.D., in which 
the variation of draught is registered, by a pencil attached to the 
spring of the draught-hook, upon a graduated paper wound round 
a metal cylinder, which latter revolves as the limber is moved forward. 
II. To test Lubrication.— The carriages to which the wheels were 
fitted were firmly fixed, in succession, in such a manner that one wheel 
was driven by a wooden friction pulley made to revolve at a given rate 
by steam shafting; the pulley was arranged to press against the wheel 
with a greater force than the wheel with its maximum load would, in 
ordinary use, bear against the ground, while its speed was such as to 
make the wheel revolve at the rate of 20 miles an hour. The latter 
was thus made to travel under similar, but more severe conditions, to 
what it would if running on a smooth hard road; while the absence of 
minor disturbances inseparable from a road—such as constant varying 
inequalities, dust, &c.—rendered the comparative trial strictly accurate. 
Before starting, each wheel was lubricated with the same quantity of 
the service grease, and arrangement provided for catching any that 
escaped during’ travelling. The latter quantity and the remain was 
measured on the conclusion of the trial. 
The wheels and axles experimented upon were— 
A. The service field wheel and axle of latest pattern (9 or 16-pa\) 
—namely, diameter of wheel, 5 ft.; width of tire, 3 ins.; dish of spokes, 
2 ins.; strut, or inclination outwards of working spoke, nil) pipe-box 
of phosphor bronze, grooved, with recess for 6J ozs. of grease; centre 
of pressure in pipe-box, 5 Jins, from face, and 4Jins. from back; line 
of pressure (wheels level) coincident with central line of working 
spoke; hollow, or downward inclination of under side of axle-arm, 
*4 in. in 10 ins.; weight of wheel, 2 cwt. 1 qr. 2 lbs» 
B. A proposed modification of the service field wheel and axle, 
differing from them in the following particulars :—Strut of working 
spoke, | in.; an additional grease chamber, formed in the outer 
flange, giving a capacity, with the ordinary recess, for 13 ozs. of grease, 
and admitting of the wheel being greased without removal from its 
axle; centre of pressure in pipe-box, 4J ins. from face, 5J ins. from 
back; line of pressure (wheels level) nearly coincident with central line 
of working spoke; hollow, *15 in. in lOins.; weight of wheel, 
1 cwt. 3 qrs. 9 J lbs. 
C. The Madras wheel and axle, differing from the service (A) as 
follows :—Strut, 2 ins.; centre of pressure, 3 J ins. from face of pipe- 
box, and 6 J- ins. from back; line of pressure (wheels level) falling out 
of the working spoke, crossing its face at the edge of the front flange; 
hollow, nil, but an upward inclination of the under side of the arm of 
*36 in. in 10 ins.; weight of wheel, 2 cwt. 1 qr. 6| lbs. 
