478 
TRACTION. 
driven, we have the total tractive force of a gun-team for horse artil¬ 
lery as 70 x 6 = 420 lbs. 
For a gun-team of six horses for a field battery, we have 82 x 6 
= 492 lbs., and for a gun-team of eight for the same (making a deduc¬ 
tion of 25 per cent, for the additional pair of horses) 82 x 8 — 41 
= 615 lbs. 
The relation between the tractive force and the load, on level 
ground, is given by the equation* 
P = —“—-- + {W + W) sm c, .(1) 
li 
P (P~- W' sin e) , 0 . 
or W =-i.(2) 
T . jU, . COS 6 + K . sm € 
where P = tractive force in lbs., in the direction of the traces, 
W = weight of carriage body and load in lbs., 
W = weight of wheels, 
r (= AC'*) = mean radius of axle-arm in inches, 
E (= C'B *) = mean radius of wheel in inches, 
p = coefficient of friction between wheel and axle, 
c = angle of slope due to height of obstacle. 
In field artillery carriages, W= 1015 lbs., r=r38", P= 29 , 937 ,/ , 
while /x may be taken as *01; and for ground opposing an average 
resistance to rolling, as already stated, e = 64°. 
Inserting the above values, and making P= 420 in equation (2), we 
get the total load, or weight of carriage complete with its load proper, 
which a gun-team of six horses should, for horse artillery, be required 
to draw, thus 
29 ' 93 ? ( 42 ° “ 1015 ' x * 1132 ) 
” 1-38 X -01 X -9935 + 29-937 X ‘1132 
= 2693 lbs., 
and 7P+ 7T= 3708 lbs. 
= 33 cwt. 0 qrs. 12 lbs., total load. 
In the same manner, making P = 492, we find for a gun-team of 
six horses for a field battery, 
W— 3328 lbs., 
and W + W■=■ 4343 lbs. 
= 38 cwt. 3 qrs. 3 lbs., total load; 
and making P = 615 for a team of eight horses for the same, 
W = 4414 lbs., 
and JP+ JV— 5429 lbs. 
= 48 cwt. 1 qr. 25 lbs., total load. 
* See “Traction,” “Proceedings, Pv.A. Institution,” Vol. IX, p. 138. 
