274 
A. BOYD. 
of the beam by means of a hanger on which were placed 
known 
weights. 
The deflections at the centre were read 
directly by means of a microscope with a scale in the eye- 
piece, of which one division equals 0°00127 inches. 
The 
modulus of elasticity is found from the formula 
Wa’ 
K= 
60 [ 
where W =central load. 
a= half span. 
w= deflection. 
I=moment of inertia. 
The beam was also fixed (encastré) at each end and loaded, 
the deflections being taken as before. 
The modulus of elasticity in this case is calculated by 
the formula 
where L=span. 
au 
19201 
w=deflection as before. 
The beam was then tested to destruction by placing it 
on knife edges 30 inches apart and loading at centre. The 
results of these tests are given in the following table :-— 
Specimen for 
Wheel, 
Three armed 
Four armed, 
straight and 
curved. 
Four armed, 
jointed. 
Span 
inches. 
1 Knife 
edges. | 
|“ encastre 
Breadth 
in 
inches. 
297-0 | 
228'5 
123°6 | 0°942 
#23°6 
Transverse Tests. 
Depth | 
in 
inches. 
130°00  0:996 | 0-536 
136°25  0°925 | 0°536 
0°500 
| Deflection 
per Ib. 
,°00127 ins. 
on kunife- 
edges. 
2°14 
445 
1°42 
Modulus of 
Elasticity lbs. 
per sq. inch on | 
kuife edges. 
15,846,000 
15,044,000 
15,630,000 
Deflection 
per lb. 
*00127 ins. 
encastre. 
0°492 
0°558 
0°315 
Modulus of 
Elasticity lbs. 
jer square inch, 
encastre. 
Modulus 
of rupture 
lbs per 
sq. inch. 
12,906,000 
38,080 
13,825,000 
12,200,000 | 38,800 
For the six armed wheel the cross breaking test-piece 
was too badly flawed to be of any value, but use may be 
made of the values for the specimen for the three armed 
wheel. 
The wheel was driven from a jack-shaft by means of 
a plaited leather belt which passed round the pulley on 
