For  steel  wire  rope  the  test  loads  are  given  below.  These  are
calculated  on  the  assumption  that  the  breaking  strain  equals
7/4  C*  in  tons  and  that  a  factor  of  safety  of  3  is  used.  Should
the  rope  be  known  to  be  of  a  superior  quality  to  this,  the  test
loads  may  be  altered  accordingly.
Test  Loads  for  Steel  Wire  Rope.
Circumference  in  inches.
Loads  in  cwts.
1

14i

H

83

2

58

2h

90

3

130

It  will  not  be  easy  to  apply  test  loads  to  3-inch  ropes  and
upwards  on  account  of  their  magnitude.  If  it  is  not  possible
the  ropes  mtist  be  carefully  examined  throughout  their  length
for  signs  of  weakness.  The  circumference  of  worn  ropes  should
be  accurately  measured  and  the  working  load  reduced  accordingly.
For  hemp  cordage  the  test  loads  are  given  in  the  following
table.  In  this  the  loads  are  calculated  from  the  two  formulae:
C^  cwt.  and  2  C^  cwts.  The  actual  load  to  be  applied  in  each
case  must  be  determined  between  these  limits  according  to  the
condition  of  the  cordage.
Test  Loads  for  Hemp  Cordage.
Loads  will

vary  according

to  condition  of

Circumference  of

cordage.
From —

To—

cwts.
cwts.
1

H

2k

u

2|

5i

2

5

10

2i

8

16

3

Hi

22h

H

15i

31

4

20

40

Sec.  V.  ACCEssoKiES  required  for  bridging.  69


Section  V.— ACCESSORIES   REQUIRED   FOR   BRIDGING
OPERATIONS.
1.  Blocks  are  used  for  the  purpose  of  changing  the  direction  of  Blocks,
ropes  and  of  gaining  power  at  the  expense  of  time.     They  are
identified  by  their  material,  number  of  sheaves  and  length   of
shell.
The  main  parts  of  a  block  are  the  strap,  pin,  shackle  or  hook,
shell  and  sheave.
