A Spanner (called a wrench in the US and Canada) is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning.
In Commonwealth English (excluding Canada), spanner is the standard term. The most common shapes are called open-ended spanner and ring spanner. The term wrench is generally used for tools that turn non-fastening devices (e.g. tap wrench and pipe wrench), or may be used for a monkey wrench - an adjustable spanner.
In North American English, wrench is the standard term. The most common shapes are called open-end wrench and box-end wrench. In American English, spanner refers to a specialised wrench with a series of pins or tabs around the circumference. (These pins or tabs fit into the holes or notches cut into the object to be turned.) In American commerce, such a wrench may be called a spanner wrench to distinguish it from the British sense of spanner.
Higher quality spanners are typically made from chromium-vanadium alloy tool steels and are often drop-forged. They are frequently chrome-plated to resist corrosion and for ease of cleaning.
Screw theory is the algebra and calculus of pairs of vectors, such as forces and moments and angular and linear velocity, that arise in the kinematics and dynamics of rigid bodies. The mathematical framework was developed by Sir Robert Stawell Ball in 1876 for application in kinematics and statics of mechanisms (rigid body mechanics).
Screw theory provides a mathematical formulation for the geometry of lines which is central to rigid body dynamics, where lines form the screw axes of spatial movement and the lines of action of forces. The pair of vectors that form the Plücker coordinates of a line define a unit screw, and general screws are obtained by multiplication by a pair of real numbers and addition of vectors.
An important result of screw theory is that geometric calculations for points using vectors have parallel geometric calculations for lines obtained by replacing vectors with screws. This is termed the transfer principle.
Screw theory has become an important tool in robot mechanics, mechanical design, computational geometry and multibody dynamics. This is in part because of the relationship between screws and dual quaternions which have been used to interpolate rigid-body motions. Based on screw theory, an efficient approach has also been developed for the type synthesis of parallel mechanisms (parallel manipulators or parallel robots).
Wrench may refer to:
We look past the obvious
We blind ourselves to the truth
No escape, resistance is futile
The old roads lead back home
A place where I belong
I lay my head where I lay my head
(Affection, redemption)
A clenched fist screaming
There's pain and then there's living
Both makes sense to those who're willing
And there's nothing left to say
We carry on, we carry
(Sacrifice, every single day)
To make amends for the debt we pay
(This way)
An instrument of constant struggle
There's nothing left to regret
(A promise is a promise kept)
Whether history will forget
(To open up with friendly arms)
This wrench screaming
There's pain and then there's living
Both makes sense to those who're willing
And there's nothing left to say
We carry on, we carry on
We carry on, we carry
We struggle every single day
Never giving up or giving in
No single sense of self-respect
We turn around and walk away
No sense of community
We fear each and everyday
Behind closed doors and closed minds
We shelter away from our lives
There's pain and then there's living
Both makes sense to those who're willing
And there's nothing left to say
We carry on, we carry on