piece that the limbs attach to.
function is very basic as it should keep the
limbs in position. Should be as light as
possible as it mounted at the front of the
crossbow and must allow free pass of the arrow
including fletching. In order to be light and
strong the riser is made of aluminum or
magnesium, often machined with holes or pockets
in order to reduce weight. The crossbow riser
must be very rigid in order to keep the limbs
perfectly aligned at full draw and during
release. Every manufacturer has developed its
own design that has become distinctive for its
flight rail/barrel is the component that
supports the arrow and separates the riser/bow
assembly from the trigger mechanism. This
component, often made of extruded aluminum must
be very rigid in order not to flex at full draw.
Every manufactured developed its own solution:
most use custom designed aluminum extruded
beams, some use molded synthetic (special
plastic loaded with filler such as glass fibers
to add strength) component that integrates the
stock. Some crossbow design named trackless do
not have a flight rail (the arrow is not
completely supported) but there still is a
component that separates the riser from the
stroke is the distance from the rest position of
the string to the fully cocked position into the
trigger mechanism. As the string is released by
the trigger the limb exert a force on the string
that propels the arrow.
stroke is a fundamental parameter for a
physics the amount of work that a machine
(crossbow) generates is equal to the product of
a force by the distance:
W= F x
explains clearly that all parameters being equal
a crossbow with a longer power stroke generates
more work. The work is used to accelerate the
arrow thus longer power stroke = faster arrow.
mechanism, housed into the stock
at the end of the flight rail/barrel that
keeps the arrow into the cocked position and
releases it upon pressure on the trigger. The
mechanism is fairly simple, being made of some
levers but crossbow trigger face conflicting
requirements: must be very strong to hold full
force generated by the bow (sometimes over 200
lbs), should require low activation force
(trigger pull is generally 3-5 lbs) should move
enough to clear the arrow with a short
activation distance. The trigger mechanism is
complicated by the addition of a safety that
prevents the trigger from being pulled (and the
arrow released) without disengaging the safety
is a shaped component that allows the shooter to
shoulder the crossbow. Stocks are often made by
molded synthetic plastic , a few manufacturer
offer laminated wood stocks. The stock should
allow the shooter to easily hold the crossbow
and take aim, in order to do this a stock should
allow the correct spacing from shoulder, allow
the shooter to rest the cheek aligning the eye
with the scope (or other aiming device). Some
manufacturer offer adjustable stocks. As the
stock integrates the rear grip so it must
provide a comfortable grip and correct spacing
from the thumb-index to the trigger.
stock designs integrate also the front grip:
also in this instance the grip should be
ergonomically correct both in positioning (for
good balance) and dimensioning (for a good,
grip design should provide some means to prevent
the fingers from touching the string/cables
the flexible part of the bow. Limbs are made
(very often) of laminated fiberglass. Fillers or
exotic materials such as carbon fibers are
sometimes used to tweak the characteristics of
responsible for storing energy as they are
flexed and releasing it as the crossbow is shot.
very stressed components.
composed of glass laminations glued together,
for this reason should never be left in very hot
places (in your car under the sun for example).
Limbs may be damaged by dry firing.
action ( either deliberate or accidental) of
shooting a crossbow without an arrow.
never be done. Limbs may be permanently damaged
as well as other components of the crossbow. The
action is dangerous and may injury the shooter
as well as other people standing close by. Some
manufacturers equipped their crossbows with an
anti dry firing mechanism that prevents the
string to be released (or the trigger pulled) if
an arrow is not present.
event in which the string runs over the arrow
causing a situation similar to dry fire
connection of the cables to the cam axles. It is
made by a loop connecting the cable end to the
two tips of the cam axles (seen from behind
seems a Y lying on the side). The two ends of
the loops are (often but depends on crossbow
design) twisted several times (usually the lower
loop many times more than the upper) in order to
create more tension on the lower limb , this
helps the string remain in contact with the
crossbow design where the limbs instead of
flexing toward the shooter flex toward the front
of the crossbow. This design, originally
conceived by Leonardo DaVinci offers advantages
such as compactness and low vibration. Examples
of commercial crossbow using this design are:
Armcross, Scopryd, and some Horton models.
rope that connects the limbs (in a recurve
corossbow) , the often backmost rope in a
the string does not touch either arrow
nock or flight rail directly as a serving is
interposed. Strings are made of high strength
(more than steel) synthetic fibers such as
dyneema fast flight. Strings should have low
spirally wounded filament that covers the center
portion of the string. Serving prevents the
string from being worn by friction onto the
flight rail. Serving material is different from
string material as main requirement is wear
resistance. Should be replaced as needed.
Lubricants are often applied to flight rail in
order to reduce friction.
tutorial on how to apply serving see our
technical corner here.
that connects the cams in a compound crossbow.
It used to keep the cams sincronized. High
strength synthetic fibers are used. The part of
the cable that contacts the cam is often covered
with serving material.
specially profiled (non circular) wheel used in
the compound crossbow.
profile is designed in order to maximize work
that crossbow generates to launch the arrow. All
parameters being equal crossbow with cam (vs
wheel) is able to generate more work resulting
in faster arrow.
used to reduce friction between the cables and
the flight rail/barrel and the cable themselves.
Sometime a specially designed piece of low
friction material, can be as simple as a strip
military standard dovetail attachment used to
attach optics and accessories (laser,
flashlights, grips etc) to small arms. Weaver
rail is a worldwide accepted standard therefore
well suitable to allow interchangeability. The
Weaver rail consist of a rail with locking
slots, whose dimensions are defined in the
that prevents the optics from moving.
Sometimes confused with the Picatinny rail, that
share same external dimensions, but differs in
the slot dimensioning.
used to cock the crossbow while reducing the
Can be as
simple as a pulley /rope mechanism that reduces
the effort by 50% or a crank device (either
removable or permanently integrated) that
reduces the effort down to a few pounds. Cocking
devices allow perfect cocking as the string is
kept centered resulting in superior shooting
consistency and precision. Each manufacturer
offer its own solution sometimes customers are
offered both choices, some manufacturers
integrate the cocking device into the stock