Torsional stiffness converter
Convert torsional stiffness between N·m per radian and per degree, and the imperial equivalents.
That's 57× as stiff as a self-closing hinge, while a car anti-roll bar is 8.7× stiffer. Twisting it a quarter turn would take about 90 N·m.
What it means
How stiff is that twist?
This is the rate of a torsion spring or shaft, valid while it stays elastic. Past the yield point the relationship stops being a straight line.
Every unit
Your stiffness in every unit
Learn
Three things worth knowing
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1 N·m/rad = 0.01745 N·m/deg
Because a radian is 57.3 degrees. Catalog figures are nearly always per degree; textbook formulas are always per radian.
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The radian keeps the formulas clean
Torque equals stiffness times angle only if the angle is in radians. Every degree-based figure has the 57.3 hidden somewhere.
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Not the same as bending stiffness
A thin-walled tube is excellent in torsion and poor in bending if it is slit lengthwise. The two stiffnesses come from different properties of the section.
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Background
About torsional stiffness
Torsional stiffness is the twisting version of a spring rate: how much torque it takes per unit of angle. Engineers quote it per radian in theory and per degree in catalogs.
The factor between them is 57.3, which is a large enough difference to destroy a design if it is missed.