2. First Last and Always
Every Body Home
Safe and Healthy
Every Day!
Safety
3. • The manuals contain warnings.
• The warnings are in boxes and
contain a safety message
preceded by a warning symbol
and a signal word (danger,
warning and caution).
Warning
Safety
Always read the safety information
before operating the rig or
beginning maintenance work!
12. Safety
Signs Warning sign
• Danger of scalding
and pressure
Warning sign
• Danger of air pressure
Warning sign
• Danger of moving
and rotating parts
13. Safety
Signs Warning sign
• Danger of swinging
and crushing parts
Warning sign
• Danger of tipping
when moving rig
Warning sign
• Tipping risk during
drilling
15. Safety
Signs Warning sign
• In the event of a breakdown
or during service work the
boom falls diagonally
Warning sign
• High tension
Warning sign
• Danger of crushing
injuries
16. Safety
Signs Warning sign
• Maximum load for
service platform.
Warning sign
• Refrigerants under pressure
Warning sign
• The rig's operating cycles are
preprogrammed and can start
automatically without the
presence of an operator.
28. To ensure optimal utilization of the rig and its equipment, it is of
utmost importance that daily maintenance is carried out in
accordance with our recommendations.
The objective for the daily inspection of the rig is to:
• detect faults at an early stage
• facilitate servicing
• allow scheduled maintenance and planned
reconditioning work to be performed
• prevent costly secondary damage
• prevent breakdowns
• prevent personal injury
Note:
Do not operate the rig or the rig equipment until all faults have been
rectified.
Daily Inspection
29. Daily Inspection
• Always begin by making a proper
work area or heading inspection.
• Check the overall condition of the
equipment.
• Check safety devices
• Check hoses and cables
• Check oil levels
• Check the lubrication points.
• Keep your eyes open for possible
leakage and wear.
• Pay attention to any faults in the
function of the controls.
Checklist
30. Daily Inspection
Before performing an equipment
inspection it’s important to identify
and correct any hazards in the area
where the equipment is parked by
completing an inspection of that area
and recording the inspection on your
5 point card.
Think about these points:
• What is my work area?
• What is a heading?
• What hazards did I find?
• What did I do to correct those
hazards?
31. Daily Inspection
Overall visual inspection of the carrier, boom,
screen handler, and bolt unit.
Is the unit clean?
Is there any new
damage?
Are there any
obvious leaks?
Is it safe to continue with
the equipment
inspection?
32. – To be able to see wear
– To be able to see damages
Cleaning – Between shifts
Daily Inspection
33. Left Side
While this cover is open you can :
– Check the condition of the
A-40 box
– Check the hose reel gear box
oil level
– Inspect the condition of the
hoses
– Inspect the batteries
– Turn on the master switch
Daily Inspection
34. Daily Inspection
Pull out the hose reel and inspect the
valves underneath it may be necessary
to wash out this area from time to time.
This is also where the “Y” trap for the
water inlet is located.
Left Side
35. – Water inlet strainer
– Clean by opening blue
valve
Water System
Daily Inspection
37. Daily Inspection
NOTE: The bolt rack is no longer
attached to this unit.
From this location you can inspect :
– The tire, lug nuts, wheel, and final
drive
– Inspect the A-50 low voltage
electrical box and make sure the
connectors on top are attached and
locked
– Inspect the engine for leaks, fan
belts, and motor mounts (when
possible)
– Inspect the duct work for possible
leaks and loose hardware.
Left Side
38. – Engine oil level
– Pull out the A-50
box to check the
engine oil
Diesel Engine Oil Level
Daily Inspection
39. – Hydraulic oil level
– Top up if necessary
Hydraulic System
Daily Inspection
40. Daily Inspection
Inspect the electric power pack for damage
Make sure all mounting bolts are tight
Inspect the 480 connector to ensure it is not
Loose or damaged
Note: Do not grease the grease zirks on the
electric motor. This is done during PM by the
maintenance electrician
Left Side
41. • Attached to the bottom of the power
pack is the;
Percussion Pump
Positioning and Feed
Pump
Rotation Pump
and Compressor Pump
• Check for leaks at each section
• Inspect all hoses and fittings
• Ensure all electrical connections are
intact and not damaged
Daily Inspection
Left Side
42. Checking Transmission Oil Level
Daily Inspection
Note
Allow the oil to reach
normal operating
temperature (80-95 °C)
before checking the
level.
1. Check the oil with the
dipstick (A) while the
engine is idling, 800-850
rpm.
2. Top up as needed
through the filler pipe (A)
to the “full” mark on the
dipstick.
Left Side
43. Daily Inspection
Be sure to visually inspect articulation
pins and steering cylinders for leaks,
loose or missing bolts, and broken or
damaged grease hoses.
Ensure that the articulation lock
is available and in good repair.
Left Side
44. Daily Inspection
Inspect the cab for damage
that may have occurred
during the last shift
Inspect the windows, hand
holds, latches, hinges, and
footsteps to ensure the safety
of all persons entering or
exiting the cab.
Also be sure to fill the ECL
lubrication system (Rock Drill
Oil)
Note: Operators have been using Gojo
and Citrol to remove the acid from the
windows. It is your responsibility to
wash your equipment at least once per
shift.
Left Side
46. Daily Inspection
1 Attachment plates
2 Rear boom cylinders
3 Telescope devices
4 Rotary actuator
5 Feed holder
6 Tilt cylinder
Boom Components that need to be
Inspected and Greased Each Shift.
47. Daily Inspection
(A) Bolt carousel
(B) Bolting arm 1
(C) Bolting arm 2
(D) Bolt tool (Driver)
(E) Drill-steel support (Centralizer)
(F) Intermediate drill-steel support
(Not Used)
(G) Three-position mechanism (drill-
steel movement)
(H) Cartridge injection nozzle (Not
Used)
(J) Stinger
(K) Rock drill
48. The feed chain, feed rails, feed motor, sensor cables, and hoses
also need to be inspected once each shift to reduce downtime.
Note: The bolt unit should be washed
once each time you load the carousel.
Daily Inspection
49. – 7 lubrication points for bolt
arm / jaw
– Wash down Bolting unit
– Lubricate
Bolt Arm
Daily Inspection
50. Daily Inspection
– Guide rails and slide
pieces
– Check for wear on slide
pieces and slide rails.
Adjust if necessary
Feeder
51. Daily Inspection
– Rock drill accumulator
charge pressure
– Press in the pin on the
test valve. If the
accumulator is charged,
the pin will stick out by
4.5 mm and give a firm
resistance when
pressed in
Feeder
52. – 1 lubrication points
to the front chain
sprocket wheel
– Wash down Bolting
unit
– Lubricate
Daily Inspection
Feeder
53. Daily Inspection
– 4 lubrication points
on the chain
tension cylinders
– 2 lubrication points
to the rear chain
sprocket wheels
– Wash down Bolting
unit
– Lubricate
Feed Drive Unit
54. – Machine cradle
– If necessary, adjust the
cradle to the correct
height and centre
directly on the beam
Clearance 5-7 mm
Machine Cradle
Clearance 1 mm
(Check clearance entire
Length of the feed beam.)
Daily Inspection
55. – 4 lubrication points
– Bushing halves
– Lubricate
– Check for wear and
replace as necessary
– Adjust the drill-steel
support central
position as necessary
– Adjust the drill-steel
support opening as
necessary
Drill Steel Support
Daily Inspection
(Click here to play video)
56. Front boom lift
Rear boom lift
Boom telescope
Rear
screen
rotation
Front screen
rotation
Screen
tilt
Screen jaw
Boom swing
Inspect and grease the screen handler
Daily Inspection
57. Daily Inspection
•Inspect the swellex
pump
•Inspect the cab for
damage that may
have occurred during
the last shift
•Inspect the windows,
hand holds, latches,
hinges, and footsteps
to ensure the safety of
all persons entering
or exiting the cab.
Right Side
•The tire, lug nuts, wheel, and final drives
58. Daily Inspection
– Oil reservoir
– Check the oil level
in the oil reservoir
(See instruction on
how to check)
Compressor
59. – Coolant level
– Check to see if the radiator is dirty
– Top up if necessary
– Call the lube truck. This is a sealed
radiator and needs to be bled when
filling.
Diesel Engine Coolant Level
Daily Inspection
60. – Nozzles/Hoses
– Powder container
– Check that nozzles
are clean and the
protective caps are
fitted and tight
– Check that there is
no damage to the
powder container
Fire Fighting System
Daily Inspection
61. Daily Inspection
– Inspect the fire extinguisher
– Wipe all areas of cabin
to remove grease, oil
mud and dust
NOTE: Do not wash out cab with water
62. – Sweep floor area
to include upper
level in drivers
compartment
– Blow out heater before
sweeping
Daily Inspection
64. What is RCS ?
Advanced Drill Control Man Machine Interface
Options
Software
RCS – Rig Control System
65. RCS - Rig Control System
Access Levels
There are several access levels
to RCS:
This is to prevent inexperienced
personnel from entering RCS
and changing parameters and
settings.
It also avoids unneeded site
visits to restore settings
accidentally changed.
Three access levels are built in:
Operator, local service staff, and
Atlas Copco service staff.
66. RCS (Rig Control System) is a
control system that governs and
monitors the rig. It is intended for
the following use:
• Checking necessary and essential
parameters
• Conveying necessary information
to the operator
• Executing orders given from the
operator panel
RCS - Rig Control System
67. A. Left-hand lever
B. Left button unit
C. Emergency stop button
D. Right button unit
E. Drilling lever
F. Right-hand lever
G. Buttons for navigating
through the menu system
H. PC card holder
I. Display screen
J. Buttons for direct
selection and screen
settings
RCS - Rig Control System
Operator Panel Overview
68. A. Escape - Move one step to the
right in the menu structure.
B. Left arrow - Move the cursor to
the left of the display screen.
C. Up/down arrow - Move the cursor
up/down on the display screen.
D. Right arrow - Move the cursor to
the right of the display screen.
E. Enter - Confirm selected icon,
cursor position and accept a
value.
F1 Direct selection - Bolting/Drilling.
F3 Direct selection - Parameters.
G. Screen brightness - Brighter
screen.
H. Screen brightness - Dimmer
screen
RCS - Rig Control System
Navigation Buttons
71. Controls
Overview Operators Cabin
Air conditioning control panel (option)
Hydraulic panel (A71) for
reeling units, jacks, etc.
Electrical panel (A74) for work
lights and interior lighting
Control panel (A70)
Panel (A76) for RCS system
on/off and searchlight
79. It is essential that the service brakes and park brake be
properly maintained at all times.
Test the park/emergency and service brakes at the
beginning of each shift, and before driving down
ramps.
If the machine fails any part of the brake system tests,
do not operate the machine until corrective action has
been taken.
Inform your supervisor immediately if the machine fails
a brake test.
WARNING!
Brake Test
80. Brake Test – Parking Brake
• Make sure that the parking brake is applied
• Start the diesel engine and engage 2nd gear
• Gradually increase engine rpm to maximum
• Check the rig for movement. If the rig moves the brakes must
be adjusted without delay
– Note
Do not continue this check for longer than 4 seconds at
most
Controls
81. Controls
• Start the diesel engine
• Depress the brake pedal and hold it down
• Release the parking brake
• Engage 2nd gear
• Gradually increase engine rpm to maximum
• Check the rig for movement. If the rig moves the brakes must
be adjusted without delay
– Note
Do not continue this check for longer than 4 seconds at
most
Brake Test – Service brakes
82. Controls
• Press the button to check the interlock chain.
The interlock chain senses the engine oil
pressure, hydraulic pressure in the brake
circuit, the transmission oil pressure and the
cable reeling unit limit switch.
• Pressing the button will apply the parking
brake.
Test Button, Interlock Chain
85. Operating Panel
Controls
Activate and deactivate boom
1. Activate the boom by pressing button (26).
Note:
Button (26) will light up to indicate the boom
is active. When the boom is activated the
hydraulic pump will also start, which is
Indicated by the button (31) lighting up.
2. Inactivate the boom by pressing button (26)
again.
Note:
Button (26) will go out to indicate the boom has
been inactivated.
Figure: Right button unit
86. Operating Panel
Controls
Activate and deactivate boom
3. The hydraulic pump is turned off by
pressing button (31).
Note
If nothing is operated within 40 seconds after
activation, the lever functions will be
disengaged and the boom must then be
reactivated before use.
Figure: Right button unit
88. Controls
Operating Panel
Raising and slewing
the boom
• The right lever with rocker
switch “NOT” actuated is
used for raising and slewing
the boom.
Figure: Raising and slewing
the boom
90. Controls
Operating Panel
Rotation and feed extension
• The left lever with rocker switch
“NOT” activated is used for
rotation and feed extension.
• Feed extension is used to bring
the feeder up to the rock face.
Figure: Rotation and feed extension
91. Controls
Operating Panel
Feed lookout cylinder and
boom telescope
The left lever is used for operating
the feed lookout cylinder and boom
telescope.
The upper or lower part of the
rocker switch should be depressed
and remain depressed throughout
the lever movement.
The feed lookout cylinder is
normally locked. Before it can be
operated, the feed cylinder lock
button (right-hand keypad) must be
pressed in.
Figure: Feed lookout cylinder
and boom telescope
95. Drilling & bolting
Bolt arm 1
• 0=jaws closed
• 1=jaws open
Left Side
Bolt arm 2
• 0=jaws closed
• 1=jaws open
Bolt arm 2
• 0=arm in carousel
position
• 1=arm in drill center
Bolt arm 1
• 0=arm in carousel
position
• 1=arm in drill centre
Bolt arm 1
• 0=guide position inactivated
• 1=guide position, condition:
jaw 1 must be closed
Bolt tool
• 0=extended
• 1=contracted
Bolt arm, bolt
selection
• 0=long bolt*
• 1=short bolt*
Bolt arm 2
• 0=guide position inactivated
• 1=guide position, condition:
jaw 2 must be closed
96. Drilling & bolting
Left Side
Carousel rotation
anticlockwise
• 0=inactivated
• 1=activated
Carousel rotation
clockwise
• 0=rotation
• 1=rotation
Auto and manual
• 0=automatic
• 1=manual
Bolting operation
position
• 0=inactivated
• 1=activated
Drilling operation
position
• 0=inactivated
• 1=activated
Injection operation
position
“NOT USED”
Percussion and water
• 0=inactivated
• 1=activated
Manual air flushing
• 0=inactivated
• 1=activated
97. Drilling & bolting
Left Side
Three-position mechanism
in bolting position
• 0=inactivated
• 1=bolting position
Three-position mechanism
in drilling position
• 0=inactivated
• 1=drilling position
Three-position mechanism
in injection position
• 0=inactivated
• 1=injection position
Three-position mechanism
in injection position
• 0=inactivated
• 1=injection position
Locked collaring
• 0=inactivated
• 1=activated
Intermediate drill-steel
support “NOT USED”
Drill-steel support
• 0=closed
• 1=open
99. Drilling & bolting
Right Side
Boom
• 0=unallocated
• 1=allocated
Pump stop
• 0=pump turned on
• 1=pump switched off
Network handling or
charge cage is
activated
Network manager
• 0=network failsafe inactive
• 1=network failsafe active
Direct menu for statistics
Extension drilling
• 0=deactivated
• 1=activated
The following buttons
are not used;
30, 33, 34, 35, 36, 37
38, 39, 40, 41
100. Drilling & bolting
Before Drilling & Bolting
1. Turn on the power to the rig by setting the battery
switch (S300) to position (1).
2. Connect the rig to the main power:
a) Connect the cable to the main power.
b) Make sure the trailing cable is firmly attached to the rib.
101. Drilling & bolting
Before Drilling & Bolting
Turn on the electric cabinet:
• Start the power with the remote
power button
• Check that the indicator lamps
on the electric cabinet work
• Connect to water supply
Note:
Be sure to blow out hoses
before connecting to machine.
102. Drilling & bolting
Before Drilling & Bolting
Set Up
Note
It is vital that the rig is correctly set up each time it is
erected. See safety Rig stability.
1. Move the rig into position for drilling and bolting.
2. Set up the rig in such a way that the largest possible
area of coverage is obtained from one position.
3. Set up the rig on its jacks:
a) Start with the front jacks and then the rear jacks.
b) Make sure the rig is level using the rig's spirit level.
103. Drilling & bolting
Before Drilling & Bolting
Control system
1. Turn on the power to the control system:
a) Press button (1) on the computer switch located on the operator
panel.
b) Make sure the control system starts properly
1 2
Panel (A76) for RCS system on/off and searchlight
104. Drilling & bolting
Before Drilling & Bolting
Fill The Bolt Carousel
The bolt carousel holds a maximum of ten bolts. Each bolt must be
placed in a separate slot.
1. Maneuver the bolting unit to a suitable working height for loading
the bolt carousel.
Figure: Bolt carousel
105. Drilling & bolting
Before Drilling & Bolting
Fill The Bolt Carousel
2. Turn knob (C) clockwise to move allocation out from the cab,
this means that nobody in the cab can control the bolt carousel.
Rotate the bolt carousel anticlockwise by pressing in button (A)
until the first slot is in filling position.
Figure: (OLD) Button panel for rotation of bolt carousel
106. Drilling & bolting
Before Drilling & Bolting
Fill The Bolt Carousel
2. Turn switch (A) to position (1) to move allocation out from the
cab, this means that nobody in the cab can control the bolt
carousel. Rotate the bolt carousel anticlockwise by pressing
switch (B) down until the first slot is in filling position. The switch
is a three position switch which returns to the neutral position
when released.
Figure: (NEW) Button panel for rotation of bolt carousel
A
B
107. Drilling & bolting
Before Drilling & Bolting
Fill The Bolt Carousel 3. Place the bolt in the carousel.
4. Rotate the carousel until slot two is
in position for a bolt to be inserted.
5. Continue inserting bolts until the
bolt carousel is full.
6. Then rotate the carousel
anticlockwise (so that there will be
room for the bolt gripper jaws
beneath the bolts).
7. Turn knob (C) anticlockwise or
place switch a in position (0) to
move allocation back to the cab.Figure: Bolt in slot
109. Drilling & bolting
Drilling & Bolting
Selecting work mode
Before drilling can start, the “drilling”
work mode must be selected with button
(19) on the operator panel.
When switching from bolting to drilling,
the control system will perform an
automatic cradle change, which means
that the rock drill is moved from parked
position to drill center and the three-
position mechanism places the drill
steel into the drill-steel support.
The carousel will also rotate automatically so that a new bolt is fed
into the bolt arm/arms.
110. Drilling & bolting
Drilling & Bolting
Adjusting the water mist
Knob (1) adjusts the quantity of water for drilling with water mist
(water injection). The quantity of water in the flushing air should be
sufficient to prevent dust during collaring and drilling. Normally, a
larger quantity of water is required at the start of a hole.
112. Drilling & bolting
Drilling & Bolting
Figure: Lever Sectors
Lever function when drilling
• Sector S7
– Rotation and flushing
• Sectors S1 and S4
– Collaring
• Sectors S10 and S13
– Reverse feed and rotation
• Sectors S2 and S5
– Feed forward
113. Drilling & bolting
Drilling & Bolting
Figure: Lever Sectors
Lever function when drilling
• Sectors S11 and S14
– Reverse feed
• Sector S9
– Rotation right
• Sectors S3 and S6
– Feed forward and rotation right
• Sectors S12 and S15
– Reverse feed and rotation right
• Sector S8
– Neutral
115. Drilling & bolting
Drilling & Bolting
Selecting work mode
Before bolting can start, the
“bolting” work mode must be
selected with button (15) on the
operator panel. When switching
from drilling or injection to
bolting, there will be an
automatic cradle change so that
the bolting tool is moved to drill
center and the three-position
mechanism moves the drill steel
away from the drill-steel support.
117. Drilling & bolting
Drilling & Bolting
Lever function when bolting
• Sectors S2 and S5
– Feed forward for all types of bolt.
• Sectors S11 and S14
– Reverse feed for all types of bolt
• Sector S7
– Swellex chuck pressurized
• Sector S9
– Swellex bolt pressurized
118. Drilling & bolting
Drilling & Bolting
If in drilling position and bolting has just been selected, all bolting
unit movements will be stopped. Manual mode will be selected
automatically after restarting the system and the button for the
“bolting” work mode will flash.
Select first automatic mode with button (11) and then the “bolting”
work mode with button (15). The system will then complete the
sequence and move to the correct position to start bolting.
If the emergency stop is activated
during a cradle change!
119. Drilling Bolt Holes
1. Move the feeder to the rock face with lever (A).
2. Apply the stinger to the rock with lever (F).
3. Check that the settings in the Parameters
menu are correct. The Parameters menu is
described in more detail in operator's
instructions Control system.
4. Select “drilling” work mode with button (19).
The cradles will now be switched if the rock
drill is not already in the drill center.
Meanwhile, the carousel must also rotate so
that a new bolt is positioned in the bolt
arm/arms.
Drilling & bolting
120. Drilling Bolt Holes
Drilling & bolting
5. Select long or short bolt with button (5)
on the operator panel.
• Depressed button = short bolt.
• Raised button = long bolt.
6. Check that automatic mode has been
selected. The LED on button (11) must
be off.
121. Drilling Bolt Holes
Drilling & bolting
7. Carry out a careful and straight collaring
by:
a. Moving lever (E) straight to the left,
start of rotation and flushing.
b. Move the lever slowly forward, start
of feed and low percussion.
c. Once the drill bit has got a grip,
switch to full drilling by moving the
lever further forward. After a short
time, drilling will go to locked mode,
whereupon the lever can be released.
122. Drilling Bolt Holes
Drilling & bolting
Note
Drilling can be stopped at any time, even
when in locked mode. With the lever in
neutral, sector S8, all the drilling functions will
be stopped if one of the thumb switches is
pressed.
8. Once the rock drill has reached the desired
hole depth according to the setting in the
Parameters menu, drilling will stop. If auto
air flushing has been selected the hole will
be flushed clean.
The rock drill then reverses to the rear end
position with or without air flushing
depending on the settings that were made
in the Parameters menu.
123. Bolting
Drilling & bolting
1. After the hole has been drilled and the
rock drill has reversed to the rear end
position, select the “bolting” work
mode with button (15) on the operator
panel.
The cradles should now be switched
automatically so that the bolt tool is in
drill center.
124. Bolting
Drilling & bolting
The cradles should now be switched automatically so that the bolt
tool is in drill center.
If the Drilling menu is on the screen, it will change to the Bolting
menu automatically. Installation of the bolt can be overseen from
this menu.
125. Bolting
Drilling & bolting
The Bolting menu shows symbols for the functions gripping (A),
swelling (B) and drainage (C). The circle under each symbol indicates
whether the function is active or not. The illustration below shows
gripping (A) active while all the other functions are inactive.
When switching to bolting, the gripper function must already be
activated.
126. Bolting
Drilling & bolting
Feed the bolt forward into the hole by moving lever (E) to sector
S2/S5. As the bolt is being fed forward, the bolt arm/arms should be
moved out of the way automatically.
Feed the bolt completely into the hole so that the bolt washer makes
contact with the rock, but avoid pressing too hard with the bolt tool.
127. Bolting
Drilling & bolting
Swell the bolt by moving lever (E) to sector S7. The circle under the
symbol (B) is now highlighted in yellow and the lever can be released.
Check on the Swellex pressure gauge in the bolting menu that the
right pressure (300 to 320 bar) has been attained.
128. Bolting
Drilling & bolting
The pressure will be drained automatically once the bolt has finished
swelling and the circle under symbol (C) will turn yellow. After
draining, feed back the bolt tool by moving lever (E) to sector S13 or to
any one of the other lever sectors that gives reverse feed.
Return the stinger with lever (F) and pull back the feeder with lever (A).
130. Button 27 Network manager
0=Inactivated network manager
1=Activated network manager
Network Manager
The network manager is operated
with the left (A) and right (F) levers
and activated with pushbuttons 28
and 33 on the right-hand keypad.
Button 32 Network gripper
0=Network failsafe inactive
1=Network failsafe active
131. Network Manager
Shaded arrow indicates the lever button must be pressed, open arrow
controlled without lever button.
• Lever movement 1 = Boom swing to the
left (anti-clockwise).
• Lever movement 2 = Boom swing to the
right (clockwise).
• Lever movement 3 = Rear boom lift
down.
• Lever movement 4 = Rear boom lift up.
• Lever movement 5 = Network tilt
(up/down).
• Lever movement 6 = Network tilt
(down/up).
132. Network Manager
• Lever movement 1 = Front boom
lift down.
• Lever movement 2 = Front boom
lift up.
• Lever movement 3 = Rear network
rotation (anti-clockwise).
• Lever movement 4 = Rear network
rotation (clockwise).
• Lever movement 5 = Boom
telescope out.
• Lever movement 6 = Boom
telescope in.
• Lever movement 7 = Front network
rotation (anti-clockwise/clockwise).
• Lever movement 8 = Front network
rotation (clockwise/anti-clockwise).
