270 
PROFESSOR OSBORNE REYNOLDS AND MR. J. H. SMITH ON A 
include the specimen to be tested. A pin in this connecting rod at the level of the 
crank shaft gives, by means of a second rod, an oscillatory motion to horizontal 
sliding pieces, introduced as will be seen later (p. 270) for the purpose of having the 
energy of the moving parts invariable. 
The two parts P and Q of the vertical sliding pieces are connected by means of the 
specimen S, which is to undergo the test. The chucks H and J for holding the 
specimen were chased out internally to f-inch Whitworth thread, and the specimen 
was locked by means of two lock-nuts, one at each end. The specimen was prevented 
from rotating by means of a key placed in the lower bearing of the vertical sliding 
piece, which fitted accurately in a key way cut in the moving spindle. The lower 
bearing was bushed to allow of adjustment, and a suitable locking arrangement was 
provided for it. 
All the working parts were well made and exceptionally strong, of mild steel, 
tensile strength 24 tons per square inch ; the pins in the connecting rod were all 
case-hardened and afterwards ground to fit. The greater part of the tool work was 
done by the author in the College Laboratory. 
Energy of the Parts. 
The horizontal sliding piece was introduced in order to make the energy of the 
moving parts constant. Since the vertical connecting rod is 24 times, and the 
horizontal connecting rod 18 times, the throw of the crank, the motions of both 
sliding pieces will be veiy approximately simple harmonic motions, and, as both these 
pieces receive their motion from the same crank pin, the velocity of one will vary as 
the sine, and the other as the cosine of the angular displacement of the crank. The 
sum of the squares of their velocities will be constant. The kinetic energy of the 
parts will thus be constant if the total mass moving in the horizontal direction is 
equal to that moving in the vertical direction. 
The masses of the parts were adjusted to satisfy this condition in the following 
manner:—The connecting rod and the spindles were weighed in the two positions 
shown in fig. 3. 
Firstly, the shorter connecting w>d A was supported horizontally and the load on 
the crank pin weighed; secondly, the longer connecting rod B was supported 
horizontally and the weight on the crank pin again taken. The masses of these 
parts were then adjusted until the loads on the crank pin were the same in the 
two cases. 
The Balancing of the Machine. 
Having adjusted the masses of the horizontal and vertical sliding pieces, it was 
now possible to balance these parts by placing a suitable mass diametrically opposite 
to the crank pin. This balance weight was made in the form of a steel eccentric D 
