[From Lowndes' Engineer's Hand-book,-Liverpool, I860.]

Solid, Rectangular, And Round: To Find Their Strength

Square and rectangular.

(Depth ins.)2 X Thickness ins. / Length, ft. X Tabular No. = Breaking weight, tons.

Round.

(Diameter ins.)3 / Length in ft. X Tabular No. = Breaking weight, tons.

Hollow.

(Outside dia. ins.)3 - (Inside dia. ins.) / Length, ft. X Tabular No. = Breaking weight tons.

Thickness not exceeding

1 inch for iron.

2 ins. for iron.

3 ins. for iron.

3 ins. for wood.

6 ins. for wood.

12 ins. for wood.

Square and Rectangular.

Cast and Wrought Iron

1

•85

•7

Teak and greenheart

•36

•32

•26

Pitch pine, and Canadian oak ....

•25

•22

.18

Fir, red pine, and English oak ....

•18

•16

•13

Round.

Cast and Wrought Iron

•8

•68

•56

Teak and greenheart .

•28

•25

•2

Fir and English oak .

•14

•125

•1

To find the Breaking Weight in lbs. use the Tabular No. below.

Thickness not exceeding {

1 inch for Iron.

2 ins. for iron.

3 ins. for iron.

3 ins. for wood.

6 ins. for wood.

12 ins. for wood.

Square and Rectangular.

Iron......

2240

1900

1570

Teak......

800

710

570

Fir and oak ....

400

355

285

Round.

Iron..............................

1800

1570

1260

Teak......

640

570

460

Fir and oak ....

320

285

230

Though wrought and cast iron are represented in these rules as of equal strength, it should be observed that while a cast iron bar 1 inch X 1 inch X 1 foot 0 inch long, of average quality, will break with one ton, a similar bar of wrought iron only loses its elasticity, and deflects 1-l6th of an inch, yet as it can only carry a further weight by destroying its shape and increasing the deflection, it is best to calculate on the above basis:-

A wrought iron bar 1 in. X1 in.X 1 ft. 0 in. long ]

deflects

1.16

with

1

ton.

1.8

""

1

"

2 1..2

"

2

"

The above rule gives the weight that will break the beam if put on the middle. If the weight is laid equally all over, it would require double the weight to break it.

A beam should not be loaded with more than 1-3 of the breaking weight in any case, and as a general rule not with more than 1-4, for purposes of machinery not with more than 1-6 to 1-10 depending on circumstances.

To find the proper site for any given purpose.

Rectangular.

Weight X Length ft. / TabularNo. X 3 or 4 or 6, etc. according to circumstances =

B D2 ins.

Round.

Solid Rectangular And Round To Find Their Strength 52

= diam. ins.