Slide rules HOME page  COLLECTION  SPECIALISED RULES 
Make  James Noble 
Model  Engineer's 
Notes 1. This slide rule was used engineering calculations. On one face there was a "Routledge" type engineer's rule and on the other face a special slide rule for calculating the weights of steel. 2. The rule is folded at 188 since 1 ft of steel with a with a cross section of 188 mm^{2} weighs 0.1 lb. (304.8 mm * 188 mm^{2} * 17309 lb / m^{3} / 1E6 mm^{3}/m^{3}.) 3. The calculation is done by setting the width in (mm or 1/8") on the C scale against the thickness (in mm or 1/8") on the D scale. Against the length in feet on a A scale read the weight in pounds on the B scale. This works for 1/8" and mm since 1/8" is 3.175 mm and 3.175 squared is 10.08. If the values are entered in 1/8" the result is of course 10 times higher than if entered in mm. 4. The rule also has tables for weights of materials and power of steam engines. 

Front face 

Back face 

Detail  front right
 showing scale folded at 5 and tables. 

Detail  back right  showing scale folded at 1.88 and tables. 

Manufacturing date  Circa 1890. 
Length  12 " (40 cm) 
Material  Boxwood 
Scales  Special on two faces 
Cursor  None 