ELASTIC RADIAL DEFORMATIONS OF FLYWHEELS. 273 
The physical properties of the material of the wheels 
were carefuily determined, test pieces being cast at the 
same time as the wheels. The casts were made of ordinary 
engine casting metal, about half a ton of which was taken 
from the cupola and casts made in the following order :— 
1. Tensile test piece. 
2. Wheel with six arms. 
3. Cross-breaking bar. 
4. Wheel with three arms. 
da. Tensile test piece. 
A second set was then cast. The castings were left in 
the sand till they were quite cold. 
The specific gravity of the material was determined by 
means of a chemical balance, the mean of several deter- 
minations being 7°156. Tensile tests were made on a 
Greenwood and Batley horizontal testing machine of 
100,000 pounds capacity, the extensions being measured by 
means of Martens’ mirror apparatus on a length of eight 
inches. The results are given in the following table :— 
Tensile Tests. 
Diameter Area Extension Modulus of Breaking Load. 
Specimen for Wheel. inc vi | ppers00) Tosa elasticity lbs. |) sense (plan nnn: 
™ pitches || 29 MRCS: | 9 ont mim, per square inch.|rotal Jps,| Per cauare 
ncn. 
Three armed ...0°799 | 0°5022 30 13,300,000)12,375| 24,640 
Fourarmed straight) 0°622 | 0°3028 48°9 13,400,000} 7,750} 25,590 
and curved arms. 
Six armed ... -(OGse | "O:37356 37°5 14,200,000} 9,700| 25,960 
Four armed, jointed) 0°630 | 0°3117 45°5 13,736,000} 8,200| 26,307 
between arms. 
Four armed, jointed) 0°620 | 0°3019 | 49:0 | 14,327,000) 7,770) 25,737 
along arms. | 
The test pieces for the cross-breaking tests were care- 
fully planed on all four faces until their breadth and depth 
were approximately the same as those of the rims of the 
wheels. The tests were carried out ona Hwing apparatus 
for transverse tests, the beam being supported on its small 
face on knife-edges. The load was applied at the centre 
