2. BASIC MECHANICAL SYSTEMS
2.1 The basic elements of mechanical systems
The front cover of this volume shows a Bedford van, not as a simple
metal box, but as a collection of complex interconnected parts.
To do real damage to any system this is how you must look at the
target of the hit - a collection of vulnerable parts.
An earth mover, for example, is not a simple machine. It is a
complex system comprising...
- Mechanical systems with moving parts, hinges, cables and bearings;
- Engines, using petrol or diesel as a fuel, which provide power
to the whole system;
- Electric motors which convert electrical energy into mechanical
motion, or turn compressors or pumps to move fluids;
- Hydraulic and pneumatic systems which develop the large forces
necessary to drive the machines excavators;
- Electric systems which run lights, valves and the control
- 'Static' devices, not directly involved in the main system,
such as locks, radios/communications equipment, and security systems.
All these elements come together to 'create' that which we call
an 'earth mover'. Therefore, to effectively disable, or preferable
write-off the subject of the hit, you need to have a working knowledge
of each of the individual systems. The alternative would be to
learn about the system itself - a standard JCB for example, But
learning about the principles of how these machines work in general
is preferable because the knowledge is more easily applied to
any situation you may encounter.
In terms on machines in general, when you conduct your scoping
exercise while planning the hit, or while you assess the 'problem'
when you are first presented with the system you wish to disable,
you should ask yourself a simple series of questions...
- Where does the power come from [the source]? (e.g., electrical,
engines, electric motors, etc.);
- How is the power moved around [the conduit]? (e.g., electrical
cables, mechanical rods/shafts, hydraulic or pneumatic systems);
- Where is power expended [the sink]? (e.g., hydraulic rams,
electric motors, mechanical arms or electrical components);
- How is the movement or conversion of power regulated [control
systems]? (e.g., valves, control panels, switches or automated
- Does the operation of these parts involve lubricating or cooling
of devices? (e.g., engine oil sump, pipes delivering lubricating
fluid, chillers/refrigerators, air cooling or water cooling)
By systematically taking these five criteria, and applying them
to your system (with practice it will become second nature) you
will be able to identify the key parts of the system, and hence
the key weaknesses. You can then plan the appropriate steps and
requisition the appropriate tools with which to carry out the
For example, in an earth mover, the major mechanical parts are
built of extremely tough materials because they must survive in
a harsh environment, under extreme load conditions. For this reason
taking on the arms of the machine, or cutting its hydraulic system,
causes little real damage. On the other hand, the fact that the
entire system relies on the provision of power from one diesel
engine means that by taking out that engine, using grinding powder
in the sump or ball bearings in the cylinders, you deny power
to the system. On the other hand a complex manufacturing plan
may rely on computerised control systems, in which case damaging
these is more effective than removing the power supply, or damaging
individual parts of the machines.
2.2 Power sources
All mechanisms need energy to function. This energy can be derived
from a number of sources...
- Electrical energy: Electricity supplied in cables, or in more
complex systems, which may be generated from other energy sources
within the system;
- Electrical potential energy: This is really a category used
to differentiate supplied electrical energy from electrical
energy stored electrical energy. There are many systems,
from computers to industrial plants and road vehicles, that rely
on the storage of energy within some form of battery to help them
operate. Batteries contain 'potential' energy because it does
not actually exist as electrical current, but rather as charges
on the atoms of chemical compound which are release as part of
- Chemical energy: Fuels which contain energy, such as petrol,
diesel, and methane or propane gas, can be utilised within machines
as a heat source, or within engines as a source of kinetic energy;
- Kinetic energy: Kinetic basically means movement - that is
the turning of drive shafts or the push/pull of connecting roads.
Many pulled units, farm machinery is the main example, are powered
by kinetic energy supplied by a drive shaft which plugs into the
tractor's engine (this is called a Power Take-Off [PTO]).
Denying the source of energy to any system is the most effective
way of shutting it down - but sometimes this is only a temporary
setback for the operator...
- Destroying or removing the battery from a system is only temporary
because batteries are easily replaced;
- Removing the electrical supply by cutting cables is very temporary
as cables can be replaced in a day. Even a mains trunk cable can
be repaired in just one or two days;
- Removing fuel from the system is very temporary - you only
have to fill up the machine again, or new supplied can be ordered
or bought the same day.
It is therefore obvious that cutting energy sources is only effective
when it includes other forms of damage. For example, rather then
just spiking or removing the fuel from a generator, it is always
advisable to do serious damage to the generator itself.
However, removing power supplies really comes into its own when
speed of action is necessary. For example, all petrol stations
have a little box on the wall marked, "petrol pumps switch
off here". This enables the fire brigade to turn off
power to the pumps in the event of a fire or spillage. It also
means that smashing this box, or cutting the cables, disables
all equipment on the station forecourt - this is much faster and
easier than trying to damage each pump or cut every pipe.
Safety when cutting power cables (figure 2)
The only precaution must be to ensure your safety. Any source
of energy is capable of imparting energy to you when you damage
it - that can be fatal. To solve this problem there are simple
steps you can take.
Electrical cables should be isolated at the fuse box before cutting.
If this is not possible, use tools with a long insulated handle
- such as an
axe. If in doubt you need to connect a thick copper wire - preferable
coated in plastic - to the tool you are using, and then connect
the other end to a large metal object embedded in the ground (such
as a fence post) or the 'earth' plug of a wall socket (see diagram
above). This will make the electricity earth to ground via the
wire rather than you. As a precaution, you should also wear thick
rubber gloves - for example the type you use for washing up.
Where voltages higher than 415 volts are involved, no amount of
earthing will ensure your safety - splashes of molten metal from
the arc generated when the cables are cut can also injure you.
For this reason you should consider other measure such as burning
through the cable with an incendiary compound (see 'combustion'
The batteries on conventional cars or lorries are relatively safe.
The main danger comes from the acid they contain. The risk with
these batteries is when they are on charge because they give off
highly explosive hydrogen gas. Cutting one cable at a time, and
then removing the battery is quite a straightforward process,
but a spark near an open cell could initiate a fire.
Large battery arrays, such as those found on electric milk-floats
and other electric vehicles, present a danger because of the sheer
amount of electrical current they are able to generate. If you
short the cables you will get a small explosion as the current
melts and fuses the metal in the cables. In extreme circumstances,
it may also cause other parts of the electrical installation to
short out - perhaps explosively if electrical 'capacitors' are
involved - and catch fire. Again, the basic instruction is disconnect
one terminal or cut only one stand of the cable at a time. If
the cable is 'multi-core' - that is there is more than one stand
of wire within it, strip off some of the electrical insulation
with a Stanley knife and cut one strand of wire at a time.
Again, where large battery arrays are involved with voltages greater
than 24 volts, it is a good idea to earth the tool you are using
if the only option is to cut rather than disconnect cables.
Most fuels are volatile - that is they burn readily with only
minor ignition sources such as bright lights, heat or sparks.
Petrol, gases and some solvents (such as acetone) fall in this
category. Other fuels such as paraffin or diesel are more difficult
There are three tactics with fuels - spiking, disconnection or
- Spiking involves the addition of substances to make the fuel
burn under extreme conditions. Adding sugar or syrup to fuel produced
large amounts of carbon which block the cylinders and valves of
engines. On the other hand adding a litre or two of acetone to
the fuel tank of a car, if it doesn't dissolve the pipes or the
carburettor float first, causes the cylinder temperatures to rise
to the point where pistons or cylinder vales melt and fuse;
- Disconnection - basically means that you cut the fuel line.
This in itself can cause great problems because by cutting the
line the fuel escapes to cause pollution, or it covers you. There
are a number of alternatives. You could close off valves in the
fuel lines and then superglue them shut (it's generally not a
good idea to solder or weld a fuel line!). The other option, which
applies to metal fuel lines, is to crimp them shut using pliers.
It is possible to use a hammer (sometimes the blunt end of a chisel
or screwdriver proves an effective tool to use) to flatten the
fuel line at two points, but this may cause the contents to ignite.
If you crimp the fuel line in two places, and then cut the line
in between the two, the fuel should not escape.
- Removal - quite simply, just take the stuff away.
By the very fact that they carry large amounts of energy (the
technical term is 'torque'), drive shafts and PTOs are constructed
of very hard and tough materials. This makes them very difficult
things to cut, bend, or generally damage. However, almost all
drive shafts rely on bearings and rotating joints to keep them
turning efficiently. You should therefore attack the joints and
bearings rather than the shaft itself.
The simplest way to damage a baring is to inject grinding powder,
suspended in lubricating oil or grease, into the bearing. Over
the course of a few hours this reworks the running surfaces and
makes everything a little more 'loose'. With universal joints,
if you can bang out one of the spindles on which the joint pivots
then you can disconnect the drive shaft.
The other option is to unbalance the drive shaft. As the shaft
rotates very quickly, and the shaft is very heavy, it must be
in perfect balance along the axis of rotation. Any deviation causes
the drive shaft to vibrate. If you add weight to just one side
of the drive shaft - by strapping a weight around one side of
it - the vibration could damage the bearings and joints before
the operator notices. On larger shafts there are actually small
weights which screw in and out of the shaft to vary the balance.
Screwing the weights fully in on one side, and fully out on the
other, will perform the same function as strapping a weight to
the shaft. It also helps if you superglue the bolts too.
Alternatively - and this works very well with the propeller shafts
of boats - just connect a length of steel cable to the shaft,
and wrap it around the shaft. With luck, especially in enclosed
spaces, the cable will snarl up and unbalance the shaft. However,
you should always make sure that the rotating cable will not injure
someone - a cable rotating at speed can be lethal.
Finally, with the PTOs of tractors or construction plant, if the
drive shaft is not connected, just try and jam up the connection
socket. The best way to do this is to melt solder onto the surfaces
of the socket using a blowtorch - but don't forget to clean the
metal surfaces of grease and rust using petrol or solvent, and
then burning the residue off with the blowtorch, before you start,
or the solder won't stick.
2.3 Power conduits
After power has been produced from the source, it must be moved
around to where the work needs doing. There are a number of ways
this can happen...
- Electrical power is moved along cables, through a series of
switches, fuses and control instrumentation;
- Where pressurised fluids or gases are used, pipes and vales
regulate the flow of fluid to its destination;
- Where kinetic energy is involved, gear, shafts and tension
cables (steel cables, rubber/canvas drive belts or rope) transmit
- Especially where telecommunications equipment is concerned,
the 'information' can be carries as light within fibre optic cables,
or as a radio wave within coaxial cables.
Essentially, what we are trying to do here is severe the flow
of energy along the conduit. With electrical, communications or
fluid cables this is simple - just cut it. But you should beware
when cutting fluid cables in case the fluid or gas in the pipe
is still under pressure. Again with electrical cables, as outlined
above in relation to electrical sources, you should make sure
that the cable is not live before you cut it, or take appropriate
steps to protect yourself when cutting.
Thew problem here is that cables and pipe are relatively easy
things to replace, relatively quickly. They are also relatively
cheap. What we must do, in order to create the greatest expense
and delay, is to damage or remove those parts of the system which
control the flow of energy through the conduit:
- With electrical cables, switches, fuses, instrumentation and
electromechanical relays all act to channel the flow of energy.
By damaging these items you can disable a piece of equipment while
repairs are made. With very specialised equipment, spares will
not be readily available either. The key items to hit are relays,
switches, and most importantly gauges, computers or programmable
logic controllers (PLCs) and instrument panels;
- With hydraulic systems, the pipes are nearly always reinforced
with hardened steel, making them very difficult to cut without
very large and expensive bolt-cutters. The simple method is to
drill the pipe, or even better, smash the valves which control
the flow of the fluid. On basic mechanically controlled systems
the valves are controlled by levers, so you should just rip off
the levers, and perhaps smash the valve housing. On electromechanical
systems electrically powered relays operate the vales. These are
quite easy to disable because you can rip out the electrical cables,
but more importantly, you should try and remove the 'solenoid'
(the electrical coil and magnet) mounted on the top of the valve
(easily identified as the electrical cable is plugged/connected
- With pneumatic systems, the pipes are not normally reinforced,
but the system is controlled by the same type of valves as hydraulic
systems, so the same rules apply;
- With telecommunications systems, just cut the coaxial or fibre-optic
cables, but you should try to access the transmitter units and
smash them, or rip off any visible transmitter antennae. Alternatively,
with coaxial cables, just fire a few dozen staples into the cable.
The short circuit may damage the output transistors of the transmitter;
- Kinetic/mechanical systems are more difficult. Drive shafts,
as explained above, are difficult to damage, but they are susceptible
if they have exposed bearings or rotating joints. The best place
to damage any mechanical system is at the gearbox - just fill
it with sand, or better still, grinding powder. If the gearbox
does not contain an kind of lubricating fluid, fill it with epoxy
'potting compound', effectively sealing the moving the parts in
a block of hard plastic. Drive belts can be a problem. Smaller
ones are easily cut as they are generally rubber with a canvas
reinforcement. Larger ones, and things like conveyor belts, have
steel reinforcement and so tin snips, side cutters or bolt-cutters
will be required. Hacksaws will work, but it can be slow going.
With drive cables, such as those on cranes, the cable is normally
made of tensile steel which is difficult to cut without heavy
duty side cutters or bolt cutters. Hacksawing can take a long
It must be stressed that the simplest and most direct method is
to damage the control systems. Even on hydraulic systems, where
the system relies on a pump, it is still more effective to take
out the control systems because the pumps are so solidly made.
2.4 Power sinks
When the power has been moved to where the work takes place, it
can be used. Energy can be expended in many ways - from the hook
at the end of the winch cable that lifts the load, to the computer
at the end of the mains cable. For this reason, there is no general
approach to damaging the appliance to which power is supplied.
In general it is possible to say this...
- All electrical equipment should be damaged by hammering chisels/
screwdrivers into it, or if this is difficult pour acid or salted
water inside it;
- All mechanical equipment should be 'fouled up' using wire,
dismantled using tools, filled with sand or grinding powder, or
just filled up with quick setting epoxy 'potting compound';
- All hydraulic/pneumatic appliances should have holes drilled
in the cylinders.
But when considering the above options, you should consider the
time factors involved. Sometimes effectively taking out the power
conduit or source will be as effective, but more importantly quicker,
than trying to damage every part of the system that utilises the
energy supplied to the system.
The regulation of energy was noted above in relation to energy
conduits. Without control systems, machines will not function.
For example, why spend half an hour trying to get into the locked
engine compartment of a earth mover when you can just smash through
or remove the window of the cab, and smash, damage or remove all
of the controls levers, switches and instrumentation?
When taking on control and instrumentation panels there are a
few general tips:
- Any accessible electrical cables should be cut or ripped out.
If you have a number of cables bound together or fixed in a 'loom',
the simplest thing is to loop the mass of cables around a screwdriver
or crowbar, and then twist around and around. As the cables twist
and tighten on the bar, the tension will snap or rip them from
- Any gauges, displays or meters should be smashed. The best
way to do this is to take a long, thin (about 3-4mm diameter),
blunt screwdriver, and hammer it through the face of the dial.
If it goes through easily, try again - unless you encounter resistance
as you hammer it through you are not doing any damage;
- Computers and PLCs should, if possible, be removed and disposed
of in the nearest canal or ditch. If this is not possible you
should take the same approach as that outlined for gauges and
meters. If the construction does not allow you to hammer in the
screwdriver, then use the wedge end of a crowbar and hammer it
through using a lump hammer (if available);
- Any key locks or key switches should be superglued;
- Conventional switches or levers should have the arms broken
off. You can do this with a hammer. Sometimes the levers and knobs
are fixed in place by small screws in the handle - if this is
the case just loosen the screw, pull of the handle, and get rid
of it off the site. This then leaves the spindle which the knob
or lever was fixed too - this is best broken off using a hammer
and chisel. For push buttons there is only one simple solution
- either hammer then button through the face of the control panel,
or superglue it in place.
However, sometimes there is just not time to do all of the above.
In these cases the only (and ultimate) solution is to douse the
control panel in petrol or diesel and torch it. This unfortunately
attracts a lot of attention, and so you may with to use some sort
of time-delay incendiary device to do this.
Finally, many mechanical systems require careful lubrication to
keep friction and wear to a minimum. Many gearboxes, engines and
drive shafts contain spindles, cogs and bearings which must be
lubricated to keep friction to a minimum, and remove excess heat.
There are two basic methods for working on lubricating systems:
- Drain it: Drain the lubricating oil into a container (unless
you are certain the oil will not cause pollution). Of course the
operator will notice this, or the machine will indicate a low
oil pressure, so this can only really work on a machine which
is already running (in which case beware because the oil will
be hot and under pressure), or a machine which you are sure you
will be able to start up. If you cannot find or are unable to
remove the plug in the oil sump, the simplest alternative is to
drill a small hole through the sump using a hand or power drill.
- Spike it: If you have access to the sump filler on the engine,
gearbox, or the lubricating nipple on the baring, you can inject
a mixture of oil and grinding powder into the machine. Grinding
powder expensive, but especially on bearings, it is the only option
because only a very fine power can be injected into the necessary
space. However, on engines and gearboxes a cheaper option is sand.