285 
RESULTS OF EXPERIMENTS 
MADE IN THE 
ROYAL CARRIAGE DEPARTMENT 
(July 1877) 
TO ASCERTAIN THE RELATIVE VALUE, IN POINT OE TRACTION, OF 
THE SERVICE, OR SERVICE-MODIEIED, AND THE MADRAS FIELD WHEELS AND AXLES. 
COMMUNICATED BX 
MAJOR W. KEMMIS, R.A. 
With regard to traction, tile value of any particular wheel and axle 
depends upon the amount of ease with which they permit of the carriage 
they belong to being drawn over any ground; and upon the distance 
which they will travel without heating. 
When comparison is made between wheels and axles of the same 
diameters and width of tire, and equally well lubricated; any difference 
of ease in traction will be due mainly to difference in weight of the 
wheels and in the amount of their cone. The resistance due to the 
latter; it is hardly necessary to say; is greater as the conical form is 
more developed; and may be considered constant in amount in any 
particular wheel. This amount varies directly with the width of the 
tire; and inversely with the diameter, and in the field wheel is not 
very great. The resistance due to weight is, in the field wheel, of 
more importance, because it increases directly with the unevenness or 
inclination of the ground; as is readily understood when we consider 
that the weight of the wheels, as well as of the carriage body and load, 
has to be lifted over every obstacle or incline which may oppose their 
motion. This resistance—which wonld be diminished to nil on a 
perfectly hard, smooth, and level road—is always of some amount, as 
in reality there is no such thing as a road of the nature mentioned. • 
With regard to the distance which wheels will travel without heating 
—the dimensions, material, and clearance of their axles, the means of 
protection against grit and the lubricant being the same—it will 
depend mainly upon the amount of the latter which can be stored up 
in the pipe-box, and the rate at which it is expended dne to the 
relative form of construction of the wheel and axle, which may or may 
not give a tendency, as the wheel revolves, to the grease to flow out 
or to be absorbed from undue local pressure and consequent tendency 
to heat at a particular spot. 
In the comparative trial made, the experiments, upon the above con¬ 
siderations, were arranged as follows :— 
L To test Traction .—The carriages (limbers) to which the wheels 
