NAEPIS
North American Engineering Parts Inquiry System
NARROW GAGE (track)
When the distance between the heads of the rails is
less than 4' 8". See Board gage,
Standard gage, and gage of track.
NATURAL FREQUENCY
Natural frequency of a body of system is a
frequency of free vibration.
NATURALLY ASPIRATED
Refers to a diesel engine in which the charge air
enters the cylinders by atmospheric pressure, I.e., 101.2kPa (14.7 psi), which
is known as 1 atmosphere.
NEGATIVE PROOF
Proof that an event or sequence of events could
not have occurred.
NESTED
Packed one within another net ton 2,000 pounds.
Also called a short ton.
NET CONTACT AREA
The area enclosing the pattern of the tire tread in
contact with a flat surface, excluding the area of grooves or other
depressions.
NET HOLE DOOR CONCEPT
A process using precision pierced holes in the door
hinge which align to precisely located topping plates on the body for a
non-adjustable door installation. Process can be applied to other modular
assembly installations.
NET TON
2,000 pounds.
NET TON MILE
The movement of a ton of freight one mile.
NET WEIGHT
(a) The weight of an article clear of packing and
container (b) as applied to a
truckload, the weight of the entire contents of the truck.
NEUTRAL SAFETY SWITCH
A switch which completes the starter circuit and
the backup lamp circuit and provides power to the belt warning system,
depending on which gear the driver selects.
NEUTRAL STABILITY
Neutral stability exists at a prescribed trim if,
for any small temporary change in disturbance or control input, the resulting
motion of the vehicle remains close to, but does not return to, the motion
defined by the trim.
NEUTRAL STEER
A vehicle is neutral steer at a given trim if the
ratio of the steering wheel angle gradient to the overall steering ratio equals
the Ackerman steer angle gradient.
NEUTRAL STEER LINE
The set of points in the x-z plane at which
external lateral forces applied to the sprung mass produce no steady-state yaw
velocity.
NEUTRAL STEER POINT
The neutral steer point is the hypothetical point
about which the tire lateral forces are balanced
NEWTON'S FIRST LAW
An un-accelerated body remains un-accelerated
unless it is caused to change that
state by forces exerted on it by the environment.
NEWTON'S SECOND LAW
The acceleration of a particle is equal to the
ratio of the net force acting on the particle to the internal mass of the
particle. A =f/m
NEWTON'S THIRD LAW
To every action there is always an opposed equal
reaction. The action forces and reaction forces are on different bodies.
NHTSA
National Highway Traffic Safety Administration
95 PERCENTILE MANIKIN
Two or three dimensional manikin of the human body
with dimensions as large as 95 percent of the population.
NOMOGRAPH
A chart on which three or more scales are arranged
so that a straight line drawn through values on any two will cross the third at
a corresponding value; nomograph; a graphic calculator.
NON-CENTRAL COLLISION
A non-central collision is a collision between two
vehicles, or a vehicle and a fixed object, in which the principle force is not
directed through the centers of mass of the involved vehicles
NON-COLLISION
Includes, but not limited to; overturn,
jack-knifing, fire / explosion, gas inhalation, a fall from a vehicle, an
injury inside a vehicle not associated with a collision.
NON-FIXED OBJECT
Objects that are moveable or moving but are not
motor vehicles, pedestrians, pedal-cyclist, animals, or trains.
NON-SEQUENTIAL WARNING
A type of belt warning system which only senses
whether or not the belt is fastened, not in which sequence the belt is fastened
and the seat is occupied.
NORMAL
Perpendicular
At right angle to a given line or plane
NORMAL ACCELERATION
The component of the vector acceleration of a point
in the vehicle in the z-direction.
NORMAL FORCE
(y): The
perpendicular component of the force
exerted by a supporting surface on a surface resting or sliding on the
supporting surface.
NORMAL FORCE COEFFICIENT
(C z) is
based on the aerodynamic force acting in the z direction.
NORMAL SPEED
The maximum authorized speed shown in the time
table.
NORMAL SURFACE
General contour of a part excluding local
deformations.
NORMAL VELOCITY
Normal velocity (w) of a point in the vehicle is the component of the vector velocity
in the z-direction.
NOTCHBACK
Body styling where the backlight is in a noticeably
different plane than both the roof and the deck.
NOZZLE
Injector tip with venturi to atomize fuel.
NTSB
NTSB is an abbreviation for the National
Transportation Safety Board
NVH
Noise, Vibration, Harshness
NVH TERMINOLOGY
Terms describing NVH problems as developed and used
by Ford Customer Service (See Below)
NVH TERMINOLOGY
BOOM - Low pitched sound like a drum roll or
distant thunder. May cause pressure on the ear drum.
NVH TERMINOLOGY
BUZZ - Low pitched sound, something like a bee.
Usually associated with vibrations.
NVH TERMINOLOGY
CHATTER - Rapidly repeating metallic sound.
NVH TERMINOLOGY
CHIRP - High-pitched rapidly repeating sound, like
chirping birds.
NVH TERMINOLOGY
CHUCKLE - Rapid noise that sounds like a stick
against the spokes of a spinning bicycle wheel.
NVH TERMINOLOGY
CLICK - Light sound, like a ball point pen being
clicked.
NVH TERMINOLOGY
CLUNK/THUMP - Heavy metal-to-metal sound, like a
hammer striking steel.
NVH TERMINOLOGY
GRIND - Abrasive sound, like a grinding wheel or
sandpaper rubbing against wood.
NVH TERMINOLOGY
GROAN/MOAN - Continuous, low-pitched humming sound.
NVH TERMINOLOGY
GROWL/HOWL - Low,
guttural sound, like an angry dog.
NVH TERMINOLOGY
HISS - Continuous sound like air escaping from a
balloon.
NVH TERMINOLOGY
HUM - Continuous sound of varying frequencies, like
a wire humming in the wind.
NVH TERMINOLOGY
KNOCK - Heavy, loud, repeating sound like a knock
on a door.
NVH TERMINOLOGY
PING - Similar
to knock, except at higher frequency.
NVH TERMINOLOGY
RATTLE - A sound suggesting looseness, such as
marbles rolling around in a can.
NVH TERMINOLOGY
ROAR - Deep, long, prolonged sound like an animal,
or winds and ocean waves.
NVH TERMINOLOGY
RUMBLE - Low, heavy, continuous sound like that
made by wagons or thunder.
NVH TERMINOLOGY
SQUEAK - High-pitched sound, like rubbing a clean
window.
NVH TERMINOLOGY
SQUEAL - Continuous, high pitched sound, like
running finger nails across a chalkboard.
NVH TERMINOLOGY
TAP - Light, hammering sound like tapping a pencil
on the edge of a table. May be rhythmic or intermittent.
NVH TERMINOLOGY
WHIR/WHINE - High-pitched buzzing sound, like an
electric motor or drill.
NVH TERMINOLOGY
WHISTLE - Sharp, shrill sound, like wind passing a
small opening.