Medicare Technology ENIGMA ENERGI+ User guide

Enigma Energi Owners Handbook Page 1 of 22 Part Code: Z20942
ENIGMA ENERGI+ POWERCHAIR
OWNER’S HANDBOOK

Enigma Energi Owners Handbook Page 2 of 22 Part Code: Z20942
CONTENTS
1. Contents
2. Introduction
3. Personal Safety
4. Parts Description
5. Control Functions Operation
6. Adjustments for Comfort
7. Transportation, Assembly and
Disassembly
8. Battery Charging
9. Care and Maintenance
10. Service Record
11. Warranty
12. Troubleshooting
13. Kerb Climber (Optional)
14. Specification
INTRODUCTION
The Enigma powerchair has been designed for a single occupant user mass of up
to 135Kg. The design of the powerchair assumes that the user has limited mobility
but has the physical, visual and cognitive ability to operate the powerchair safely.
The powerchair is suitable for everyday indoor and outdoor use. It is suitable for
use on outdoor pavements, patios, paths, gravel and similar environments. It is not
suitable for fields, ditches or similar. If the powerchair is used in heavy rain or in
the wet for prolonged periods, the user and powerchair should be protected with a
rain cape.
All Enigma powerchairs are manufactured to the highest standards and are CE
compliant. Medicare Technology is an ISO 9001 and ISO 13485 accredited
medical device manufacturer.
The Enigma powerchair is a robust and visually appealing product whilst being a
cost-effective solution to mobility problems. The attributes of this powerchair are
its versatility and comfort. Using tried and tested industry electronics gives a
highly reliable product.
It is essential that you read this manual before using your Enigma powerchair. If
you have any questions about the manual or the powerchair in general, please
contact the outlet where you purchased the powerchair.

Enigma Energi Owners Handbook Page 3 of 22 Part Code: Z20942
PERSONAL SAFETY
GENERAL OPERATING SAFETY PROCEDURES
•Make sure that the powerchair is switched off before mounting or
dismounting from the chair.
•For your health and comfort, make sure that you adopt a comfortable
posture and that you can operate the controller unit with ease.
•Make sure you are visible when using the chair at night or in poorly lit
conditions.
•Be careful when driving your powerchair as evening falls. It has not been
designed for use at night or for use in severe weather conditions such as
rain, snow, etc).
•Ensure that all modifications made to the powerchair are authorized by
Medicare Technology. Unauthorised modifications may reduce the
performance of the powerchair, invalidate warranty, or result in injury or
damage.
•There is a risk of trapping with power chairs. Ensure all clothing is kept
away from moving parts (e.g. wheels and motors)
•Drive on the pavement and pedestrian areas only. The powerchair can be
used to cross the road on a single carriageway where there is no pavement.
•Do not take the powerchair on escalators
•Do not use a mobile phone or other wireless communication devices whilst
driving as they could interfere with the powerchair controls. Always switch
off the powerchair before using a mobile phone.
EMERGENCY BRAKING
•To apply emergency braking whilst using the power chair release the grip
on the control joystick.
•You can also apply emergency braking by turning off the powerchair.
However, this is an abrupt braking method and should only be used as a last
resort.
•There is a brake at each side of the wheel. These brakes should only be used
when the powerchair is stationary and when in freewheel mode.

Enigma Energi Owners Handbook Page 4 of 22 Part Code: Z20942
PERSONAL SAFETY (CONTINUED)
TURNING AND USING ON A GRADIENT GUIDELINES
•Avoid sharp turns at high speed as this could result in the powerchair
tipping over. This is especially relevant when turning on a gradient.
•The powerchair has been designed for use on gradients up to 1 in 6 (10º).
However, other factors such as the surface of the gradient or the attributes of
the user can vary this figure. If you are in any doubt about going up or down
a gradient please find an alternative route.
•Please slow down when driving on gradients.
EMERGENCY FREEWHEEL
•Warning: The powerchair has a freewheel option device fitted on the top of
each motor. Always re-engage the emergency freewheel device after use.
Failure to do so may result in injury.
OBSTACLES AND KERBS
•Be careful when driving to avoid obstacles which could come in to contact
with the powerchair, in particular the front castors. If you cannot avoid an
obstacle, then negotiate it slowly with care.
•Repeated heavy impacts could reduce the performance of the powerchair
and may result in damage or injury.
•If you have a kerb climber installed, please refer to the separate kerb
climber section before using.
ELECTROMAGNETIC INTERFERENCE (EMI) FROM RADIO WAVES
1. Powered wheelchairs may be susceptible to electromagnetic interference
(EMI) which is interfering electromagnetic energy (EM) emitted from
sources such as radio stations, TV stations, amateur radio (HAM)
transmitters, two-way radios and mobile phones. The interference (from
radio wave sources) can cause the powered wheelchair to release its
brakes, move by itself, or move in an unintended direction. It can also
permanently damage the powered wheelchair’s control system.

Enigma Energi Owners Handbook Page 5 of 22 Part Code: Z20942
PERSONAL SAFETY (CONTINUED)
The intensity of the interfering EM energy can be measured in volts per metre
(V/m). Each powered wheelchair can resist EMI up to a certain intensity. This is
called its “immunity level”. The higher the immunity level, the greater the
protection. At this time, current technology is capable of achieving at least a 20
V/m immunity level, which would provide useful protection from the more
common sources of radiated EMI. This powered wheelchair model as shipped,
with no further modification, has an immunity level of 20 V/m without any
accessories.
There are a number of sources of relatively intensive electromagnetic fields in
the everyday environment. Some of these sources are obvious and easy to avoid.
Others are not apparent and exposure is unavoidable. However, we believe that
by following the warnings listed below, your risk to EMI will be minimized.
The source of radiated EMI can be broadly classified into three types:
1. Hand-held portable transceivers (transmitter-receivers with the antenna
mounted directly on the transmitting unit). Examples include citizens
band (CB) radios, walkie talkies, security, fire and police transceivers,
mobile phones and other personal communication devices.
2. Medium range mobile transceivers, such as those used in police cars, fire
engines, ambulances and taxis. These usually have the antenna mounted
on the outside of the vehicle.
3. Long-range transmitters and transceivers, such as commercial broadcast
transmitters (radio and TV broadcast antenna towers) and amateur (HAM)
radios.
Because EM energy rapidly becomes more intense as one moves closer to the
transmitting antenna (source), the EM fields from hand-held radio wave sources
(transceivers) are of special concern. It is possible to unintentionally bring high
levels of EM energy very close to the control system of the powerchair while
using these devices. This can affect powered wheelchair movement and braking.
Therefore, the warnings listed overleaf are recommended to prevent possible
interference with the control system of the powered wheelchair. Following the
warnings listed below should reduce the chance of unintended brake release or
movement as a result of EMI:

Enigma Energi Owners Handbook Page 6 of 22 Part Code: Z20942
PERSONAL SAFETY (CONTINUED)
1. Do not operate hand-held transceivers-receivers, such as citizens band
(CB) radios, or turn ON personal communication devices, such as mobile
phones, while the Powerchair is turned ON.
2. Be aware of nearby transmitters, such as radio or TV stations, and try to
avoid coming close to them.
3. If unintended movement or brake release occurs, turn the Powerchair OFF
as soon as it is safe to do so.
4. Be aware that adding accessories or components, or modifying the
Powerchair, may make it more susceptible to EMI (there is no easy way to
evaluate their effect on the overall immunity of the Powerchair).
5. Report all incidents of unintended movement or brake release to the
Powerchair manufacturer and note whether there is an EMI source nearby
PARTS DESCRIPTION

Enigma Energi Owners Handbook Page 7 of 22 Part Code: Z20942
PARTS DESCRIPTION (CONTINUED)
CONTROL FUNCTIONS OPERATION
On / Off Button
Horn
Battery Gauge
Speed / Profile Indicator
Increase Speed / Profile
Decrease Speed / Profile
Joystick Control Panel (shown above)

Enigma Energi Owners Handbook Page 8 of 22 Part Code: Z20942
Charger and
Programmer socket
Control Panel
(see previous
diagram)
Joystick
1. Joystick. The primary function of the joystick is to control the
speed and direction of the wheelchair. The further you push the
joystick from the centre position the faster the wheelchair will
move. When you release the joystick the brakes are automatically
applied.
2. On / Off button. This button switches the powerchair on and off.
Do not use the on/off button to stop the wheelchair unless there is
an emergency. (If you do, you may shorten the life of the
wheelchair drive components). The battery gauge shows you that
the wheelchair is switched on. It also indicates the operating status
of the wheelchair.
3. Increase Speed / Profile. Press this button to increase the
maximum speed of the wheelchair.
4. Decrease Speed / Profile. Press this button to decrease the
maximum speed of the wheelchair.

Enigma Energi Owners Handbook Page 9 of 22 Part Code: Z20942
5. Speed / Profile Indicator. This shows the maximum speed of the
wheelchair. The more LEDs are lit, the faster the maximum speed.
The wheelchair can be configured to use drive profiles. However,
this is not included by default. For more information about drive
profiles, contact your dealer. If the speed indicator ripples, this
means the wheelchair is locked. By default the locking function is
disabled.
To unlock / lock the wheelchair:
•Switch the wheelchair on
•Hold down the on/off button for 1 second (lock only)
•Deflect the joystick forwards until the control system bleeps
•Deflect the joystick backwards until the control system bleeps
•Release the joystick. There will be a long bleep and the
wheelchair will be unlocked / locked.
6. Horn. Press this button to sound the horn. The horn will stop when
you release the button.
7. Battery Gauge. This shows the battery power level of the
wheelchair.
•The more LEDs that are lit, the more power is left in the battery.
The LEDs will be lit constantly when the wheelchair is operating
normally.
•If the LEDs on the battery gauge are stepping up (i.e. the number
of LEDs lit quickly increases then resets to 1), the battery charger
is connected and the wheelchair drive inhibited.
•If the battery gauge is flashing slowly then the wheelchair is
operating normally, but the batteries need recharging as soon as
possible.
•If the battery gauge LEDs are flashing rapidly this indicates a fault
with the wheelchair. If you have a problem with your wheelchair
consult the table overleaf. If the problem persists after you have
followed the advice overleaf then restarted the wheelchair, contact
your dealer.

Enigma Energi Owners Handbook Page 10 of 22 Part Code: Z20942
Display Notes
1 Bar
The battery needs charging or there is a bad connection to
the battery. Check the connections to the battery. If the
connections are good, try charging the battery.
2 Bar
The left hand motor has a bad connection. Check the
connections to the left hand motor.
3 Bar
The left hand motor has a short circuit to a battery
connection. Contact your service agent.
4 Bar
The right hand motor has a bad connection. Check the
connections to the right hand module.
5 Bar
The right hand motor has a short circuit to a battery
connection. Contact your service agent.
6 Bar
The wheelchair is being prevented from driving by an
external signal. The exact cause will depend on the type of
wheelchair you have, one possibility is the battery charger is
connected.
7 Bar
A joystick fault is indicated. Make sure that the joystick is in
the centre position before switching on the control system.
8 Bar
A control system fault is indicated. Make sure that all
connections are secure.
9 Bar
The parking brakes have a bad connection. Check the
parking brake and motor connections. Make sure the control
system connections are secure.
10 Bar
An excessive voltage has been applied to the control system.
This is usually caused by a poor battery connection. Check
the battery connections.
10 Bar +
S
p
eed
This is where the Speed Indicator and 10 bars are lit.
A communication fault is indicated. Make sure that joystick
cable is securely connected and not damaged.

Enigma Energi Owners Handbook Page 11 of 22 Part Code: Z20942
ADJUSTMENTS FOR COMFORT
To adjust the leg rests:
To attach the leg rest, slide the leg
rest on to the frame as shown in the
diagram. Then swing the leg rest until
it locks in position.
To swing the leg rest, pull up the
button (arrowed) and swing the leg
rest in or out. When the leg rest is
swung out approximately 45º it may
be removed.
To adjust the height of the arms:
Push the button (arrowed) whilst
adjusting the pad height.
Adjusting the tautness of the seat
and back canvasses:
•Remove the cushions.
•You will then see a number of
straps which determine the
tautness of the canvas. Adjust
these until you are comfortable,
then secure the straps with
Velcro.

Enigma Energi Owners Handbook Page 12 of 22 Part Code: Z20942
ASSEMBLY, DISASSEMBLY AND TRANSPORTATION
ASSEMBLING POWERCHAIR
FOR OPERATION
•Unfold the powerchair and lock the
frame in position by pushing down
on the sides of the seat with the
palms of your hand.
•Place the battery tray into position,
ensuring the tray locks in to place.
Pull out the tray by pulling the
fabric handle on the rear of the tray.
•Insert the batteries and then connect
the batteries together (Please see the
section on BATTERY CHARGING
AND CARE). Slide forward the
tray back underneath the seat
canvas
•Connect the controller to the
batteries and check that the
controller is connected to the
motors (Please see the section on
BATTERY CHARGING AND
CARE)
•Fold out the footrests until they are
locked in place.
•Pull up both push handles and
ensure that the half fold back
mechanism locks securely (if half
fold back mechanism is fitted).
•Make sure that the motors are
placed in gear
•Make sure that there is sufficient
power in the batteries
DISASSEMBLING THE
POWERCHAIR TO TRANSPORT
•Switch off the powerchair.
•Fold and remove the footrests by
turning them backwards whilst
pushing the lever at the same time
•Disconnect and remove the
batteries
•Slide out the battery tray then lift
up to remove. Lift up the 4
brackets which the tray sits on.
•Fold the back posts using the half
fold back mechanisms (if fitted).
To use the half fold mechanism,
push the plastic lever and pull the
push handles down and towards
you.
•Unlock the sides of the seat by
lifting the seat canvas centre
holding both the front and rear
edges of the canvas
•Fold the chair and transport
Under no circumstances should the
wheelchair be used as a seat in a
motor vehicle. The wheelchair user
should transfer to a normal vehicle
seat and the wheelchair should be
safely stored away. The wheelchair
has not been designed to be used as
a seat in a motor vehicle, and failure
to follow the above instructions
could result in injury.

Enigma Energi Owners Handbook Page 13 of 22 Part Code: Z20942
BATTERY CHARGING
CONNECTING THE BATTERIES,
MOTORS AND JOYSTICK
All electrical parts
connect through the VR2
power module mounted to
the side of the
powerchair.
Connect the powerchair
up following the wiring
diagram on the right.
CHARGING THE BATTERIES
The batteries require charging on a regular basis to minimise the risk of you
being stranded due to the batteries being flat. Ideally, you should charge the
batteries whenever the powerchair is not in use to make sure that there is always
the maximum available range for the powerchair.
The information gauge supplied on the joystick displays the amount of charge
left in the batteries. This gauge however should only be used as an approximate
guide. The battery is at full charge when all the lights are lit and the number of
lights lit will reduce once power is used.
When the leftmost red LED starts flashing, recharge the powerchair batteries as
soon as possible, as this is a warning that the powerchair is running low on
power.
To charge the batteries:
•Turn off the powerchair
•Insert the round plug from the charger into the joystick and switch the
charger on. The charging socket is located at the front of the joystick unit.
•Charge the batteries for at least 12 hours for maximum capacity
MOTOR 2
MOTOR 1 24V BATTERY
SUPPLY
JOYSTICK
CONTROL
VR2 POWER MODULE
BATTERY
CHARGER

Enigma Energi Owners Handbook Page 14 of 22 Part Code: Z20942
BATTERY CHARGING (CONTINUED)
CHARGER OPERATION
•Both the charger’s LEDs will illuminate when charging.
•The red LED is lit whenever the charger is switched on.
•The other LED will illuminate when connected to the powerchair.
•The other LED is lit amber when bulk charging and then green when
trickle charging (after bulk charging has finished).
Warning: Please note the fan inside the charger will be activated accordingly
when you switch on the charger. If you find the fan does not work
when the amber LED is lit, DO NOT use the charger. To do so may
result in the charger overheating and risk of fire.
BATTERY CHARGING GUIDELINES
1. Do not disconnect the charger cord if charging is not complete. The
battery life will be seriously shortened or decayed if the battery is
repeatedly used without being fully charged. Ensure you always charge
the battery fully every time.
2. Always charge the batteries until the charger LED light turns green. This
means that bulk charging is complete. Never stop charging before the
LED turns green.
3. Ideally, leave the charger switched on for at least two hours after the LED
has turned green. During this time this charger will trickle charge the
battery to optimise its performance.
4. If you do not use your powerchair for a long time, still charge the batteries
at least once a week to keep the batteries in a usable condition.
5. The ambient temperature will affect charging time. Charging time will be
longer in the winter.
6. After charging, do not leave the charger plugged in to the powerchair, as
this will cause a power drain on the powerchair and temporarily reduce its
range.
7. The batteries carry a one year manufacturer’s warranty. This warranty
only covers issues relating to manufacturing faults, and not faults relating
to failure to recharge the batteries as instructed above.

Enigma Energi Owners Handbook Page 15 of 22 Part Code: Z20942
BATTERY CHARGING (CONTINUED)
8. Charge in a well ventilated space where it is not directly exposed to
sunlight. Do not charge in surroundings where it is humid or damp. Do
not cover whilst charging.
9. Do not charge in temperatures less than -10°C or higher than +50°C as the
charger may not work well and the batteries or powerchair may become
damaged.
10. When a battery is new off-the-shelf it is approximately two-thirds of its
optimum capabilities. During the first 3 – 6 months of use the batteries
will improve to a peak point at which they will remain for 50% - 60% of
their expected lifespan (if maintained and charged correctly, as described
in this manual). At this point the batteries will begin to deteriorate until
they will require replacing. It is for this reason that the batteries must be
correctly charged at all times else the peak point reached may not be the
batteries’ optimum capacity and their lifespan may be dramatically
reduced.

Enigma Energi Owners Handbook Page 16 of 22 Part Code: Z20942
CARE AND MAINTENANCE
CLEANING THE POWERCHAIR
Wipe the powerchair as least once a
week with a damp cloth and dust the
powerchair and motors should they
require it.
TYRE WEAR AND PRESSURES
Make sure that the air pressure of the
tyres on the rear wheels is checked
regularly. The correct air tyre pressures
are stated on the side of the tyres. The
default tyre pressure is 40 PSI.
Also, regularly check the tyres for
signs of wear such as significant
scuffmarks and reduced tyre tread.
NOTE – NEVER INFLATE THE
TYRES WITH A COMPRESSED AIR
PUMP
OTHER ITEMS TO CHECK
Check the electrics on the powerchair,
especially the battery connections,
battery connections to the controller
and the controller connections to the
motor.
Check the upholstery for signs of wear,
tear and slackening. Failure to do this
could lead to a bad posture and
eventual discomfort.
Check the charger. If the fan on the
charger is not working whilst the
amber light is lit, do not use the
charger as this may lead to
overheating.
There is a red LED present on the
charger to show operation. If this
LED does not illuminate the charger
is faulty.
BATTERY CARE
The batteries are maintenance free
and there is no need to inspect the
battery liquid or refill with water.
Recharge the battery to its full
capacity every time.
To ensure optimum performance and
longevity of your batteries recharge
them after every use. Do not fully
discharge the battery, as this does not
improve battery performance and will
reduce the life of your batteries.
The batteries carry a twelve-month
warranty which is conditional on the
batteries being used and recharged in
the correct way.
REGULAR SERVICING
The powerchair should be serviced
annually by an approved Medicare
Technology service agent. A service
log should be filled in this book once
the approved service agent has
completed the service.

Enigma Energi Owners Handbook Page 17 of 22 Part Code: Z20942
SERVICE RECORD
YEAR 1 2 3 4 5 YEAR 1 2 3 4 5
ServiceDates ServiceDates
Controller Motors
On/Off switch Wiring
Jo
y
stick Mountin
g
Joystick Gaitor Function
Output Plu
g
NoiseLevel
Seal Commutator Cleaned
Operation Brushes
Dynamic Braking Upholstery
Static Braking Seat
Batteries Back
Type(SLA/AGM/Gel) Armpads
Container Electrics
Connections Condition of Loom
Wirin
g
A
udible Warnin
g
s
Batter
y
Test Char
g
er
Wheels Charger Connections
T
y
re Pressure Test Run
T
y
reWear TestRuncomplete
Wheel Bearings List Items Repaired
Wheel Fasteners
Lubricated / Greased
Chassis / Frame
General Condition
Castor Assemblies
Manual Brakes
Lockin
g
Mechs
Service Year 1 Year 2 Year 3 Year 4 Year 5
Dealer
Sign / Date
Customer Name Date of Purchase
Address Colour
Serial No.
Options Included
Postcode

Enigma Energi Owners Handbook Page 18 of 22 Part Code: Z20942
WARRANTY
There is a comprehensive twelve-month warranty from the date on which your new
powerchair is delivered. The warranty covers the powerchair for repairs or replacement
during this period. For more detail, please see the warranty conditions below:
1. Any work or replacement part installation must be carried out by an authorised
Medicare Technology dealer / service agent.
2. To apply the warranty should your powerchair require attention please contact the
outlet from which you purchased the powerchair.
3. Should any part of the powerchair require repair or full or part replacement, as a
result of a manufacturing or material defect within the warranty period, parts will be
supplied free of charge. Note: The guarantee is not transferable.
4. Any repaired or replaced parts will be covered by the balance of the warranty period
on the powerchair.
5. Parts replaced after the original warranty has expired will be covered by a three-
month warranty.
6. Consumable items supplied will not generally be covered during the normal
warranty period unless such items require repair or replacement clearly as a direct
result of a manufacturing or material defect. Such items include (among others):
upholstery and tyres.
7. The above warranty conditions apply to brand new powerchairs. Second-hand
powerchairs supplied directly by Medicare Technology carry a six-month warranty
period. If you are unsure whether your powerchair is covered contact your dealer.
8. Under normal circumstances, no responsibility will be accepted where the
powerchair has required assistance as a direct result of:
a. the powerchair part not having been maintained in accordance with the
manufacturers recommendations
b. failure to use the manufacturer’s specified parts
c. the powerchair or part having been damaged due to neglect, accident or improper
use
d. the powerchair or part having been altered from the manufacturer’s specification
or repairs having been attempted before the dealer is notified
9. The frames on Enigma aluminium powerchairs have a five-year warranty.
In the event of your powerchair requiring attention, please contact your service agent /
dealer and give all relevant details so they can act quickly.
The manufacturer reserves the right to alter without notice any weights, measurements or
other technical data shown in this manual. All figures, measurements and capacities
shown in this manual are approximate and do not constitute specifications.

Enigma Energi Owners Handbook Page 19 of 22 Part Code: Z20942
TROUBLESHOOTING
Symptom Possible Remedies
Chair does not move
after direction from
joystick
Check the powerchair is turned on.
Check the batteries are charged up.
Check all the connections are linked correctly.
Check the manual brakes are not applied.
Check the motors are in gear.
Chair does not move
when pushed
Check the manual brakes are not applied.
Check the motors are set to freewheel.
Chair moves in
opposite direction to
that intended
Check the leads from the controller to the motors are
connected correctly (Try swapping the leads over).
Wheels squeak Check the tyre pressure
Controller does not
light up when turned
on
Check the powerchair is turned on.
Check the batteries are charged up.
Check all the connections are linked correctly.
Please also refer to the section about the Controller Information Gauge on page
8 of this manual.

Enigma Energi Owners Handbook Page 20 of 22 Part Code: Z20942
KERB CLIMBER
The Energi powerchair is available with an optional kerb climber which allows
the powerchair to mount kerbs up to 4” (100mm) high. The bracketry to fit the
kerb climber is now available as standard with all new Energi powerchairs.
The kerb climber is installed using the two ‘R’ clips provided. Insert the kerb
climber in to the two aluminium brackets located on the inside of the
powerchair frame by the front castors. Secure by inserting the two ‘R’ clips
through the holes in the kerb climber bar and aluminium brackets.
Recommendations for Use
•Approach the kerb head on.
•Apply power slowly whilst mounting the kerb to minimise disruption to
yourself and the powerchair. Repeated fast impacts with the kerb climber
could damage the powerchair.
•Wherever possible, use lowered kerbs to climb the pavement rather than
the kerb climber.
•Try to avoid obstacles (large stone chips, etc) which could cause impact
with the kerb climber. Such collisions could cause the kerb climber to
move when not required and reduce the life of the kerb climber.
SPECIFICATION
Model PCP18
Operating Dimensions
(L x H x W)
114cm x 66cm x 96cm /
45” x 26” x 37¾”
Folded Dims
(L x H x W)
84cm x 39cm x 80cm
33” x 15½” x 31½”
Seat Dimensions
(D x H x W)
40cm x 47cm x 46cm
15¾” x 18½” x 18”
Total Weight 59.6kg / 131lb
Carry Weight 27.8kg /61lb
Motor 2No. 320W 24V D.C.
Battery 2No. 12V 34AH
Cruising Range 15 – 20 miles / 24 – 32km
Max. User Mass 135kg / 21 stone