Torque calculation

[brettball]

I am struggling to understand how the units equate to NM in the formula below when calculating torque requirement for a motor.
torque = moment of inertia * angular acceleration
Given that:-
units for Torque=Nm
units for Moment of inertia=kg/m2
units for angular acceleration=radians/sec2

Therefore
Nm=(kg/m2)*(radians/sec2)

 

[desertfox]

Hi brettball

The units of rotational moment of inertia as units of kgm^2
and not as you have written them kg/m^2

regards

desertfox

 

[Twoballcane]

I’m not familiar with this equation is this Kinetics?

Tobalcane
"If you avoid failure, you also avoid success."

 

[Twoballcane]

Ok I see it N= Kg(m/s^2) so what is left over is m so you have N-m = (Kg(m/s^2) x m)

Tobalcane
"If you avoid failure, you also avoid success."

 

[aharcourt44]

F=MA
F - Force
M - Mass
A - Acceleration

Basic physics and if it gets real crazy it would be statics. Kinetics is force in motion. The previous equation will not help you calculate torque as it relates to tightening a bolt. (when tightening a bolt, the clamp load is what your trying to achieve. 90% of the tq put into the bolt is lost between various forms of friction.)

Try
T = KDF
D - nominal diameter
F - force
K - nut factor (usually ranges from .03 to .35)

For calculating horsepower and torque use
HP = (2pi(Tq)(RPM)))/33000
this works for english measurements

Hope this helps some.

 

[FeX32]

1kg is equivalent to N/m/s^2........
btw, this is a basic 1st or 2nd year dynamic relation.



Fe

 

[desertfox]

Hi aharcourt44

The formula brettball is using is correct the relationship that :-

Torque= I * [α]

where I = moment of inertia in kgm^2

[α]= angular acceleration in rads/s^2

units :- kgm^2/S^2 radians are unitless

therefore we have (kgm/s^2)*m but kgm/s^2 = N

therefore we end by substituting N for kgm/s^2

torque = N*m

His problem I believe stemmed from writing the units for moment of inertia incorrectly in the first place.

desertfox

 

[FeX32]

Fe