Specifications

FCS1362 Page 20 of 74 © Nov 2010
Consideration should also be given where the equipment is to be fitted into an area of the vehicle that
may be occupied by passengers. Some specialist vehicles will require the equipment to withstand
specified g-force to avoid equipment breaking loose and causing injury to passengers in the event the
vehicle is involved in an accident.
2.6.1.1. Fixing types
The type of fixing to be used will depend on the size and weight of the equipment to be secured, the
material being fixed to and any loading likely to be put on the equipment and fixings when the vehicle is in
use.
In many cases simple self tapping screws will suffice but are not recommended as prime options when
fitting items of relatively high mass, for example transceiver main units. In addition the use of self tapping
screws will need to be reviewed if the fixings are subject to an additional load, i.e. equipment fitted to the
underside of a shelf or to a vertical wall or bulkhead. With the use of self-tapping screws care must be
taken because they can work loose.
Bolts, washers and nuts should be used in preference. Wherever possible bolts with locking nuts, plain
nuts with shake-proof washers or hank bushes should be used, particularly where the fixing is for a heavy
item or where it may be subject to rough handling.
Plastic fixings should meet the flammability requirements imposed by the type of vehicle the equipment is
being fitted to.
2.6.1.2. Methods of fixing equipment
Methods of fixing equipment can include:
• Screw/ bolts with locking nuts or plain nuts with shake-proof washers are the preferred method to be
used, particularly where the fixing is for a heavy item and/or where it may be subject to rough
handling
o This method may not always be practicable unless both sides of the holding surface are
accessible
• Rivet nuts offer a stronger solution than self tapping screws. Rivet nuts come in various types and
provide a blind nut or a threaded stud
o These fixings often require special tools for fitting
• Self tapping screws are acceptable where a strong and secure surface is available to screw into, and
the back of the screw does not protrude into an accessible area leaving a sharp point that may cause
injury or damage.
o Be aware that self-tapping screws can work loose
• Self tapping screws combined with flat nuts, or spring nuts may be used where fixing to softer or
thinner materials and where the screw alone would not offer sufficient grip.
• Rivets provide a more permanent fixing and so consideration needs to be given with regards to the
servicing needs of the equipment being installed.
o Not generally suitable for use because of this reason
Precautions should be taken on all of the above to avoid the fixings working loose with vibration. The use
of shake proof washers, locking nuts or flat nuts is recommended.
Corrosion resistant fastenings should always be used in areas exposed to the elements, for example:
stainless steel nuts & bolts.
2.6.1.3. Cable retention & tidying
Consideration should always be given to ongoing maintenance of equipment, so methods of retaining or
tidying cables should be chosen with this in mind.
• Where cables are in a protected environment then simple ‘P clip’ type cable clamp fixings can be
used to hold the cables in place. Cable ties can be used to secure cables together between the cable
fixings. This allows for maximum access to the cable loom.
o Cable ties should be cut off flush to avoid sharp edges.