# Get the Newton force of a brushless motor

• 02-01-2021, 06:00 PM
Schokolino
Get the Newton force of a brushless motor
Hi,

i want to ask if its possible to get the force in newton, when a brushless motor is spinning?
• 02-01-2021, 06:10 PM
luni
You probably mean the torque in newton-meter?

Here some information about dynamometers https://en.wikipedia.org/wiki/Dynamometer, commercial: https://www.eth-messtechnik.de/en/me...g_sensors.html
• 02-01-2021, 06:40 PM
Schokolino
idk i mean can i calculate the force that generates the motor to move an object?
• 02-01-2021, 06:51 PM
luni
A motor doesn't generate a force but a torque (the rotational equivalent of force). If you have an object with a weight of say F=10N on a lever arm of say L=0.5m length the motor needs to generate a torque of M = F x L = 10N x 0.5m = 5 Nm to lift the weight. If you have the same weight on a lever arm of L=1m the motor needs M= F x L = 10N x 1m = 10 Nm to lift the weight.

• 02-01-2021, 06:53 PM
Schokolino
ok Dankeschön :)
• 02-02-2021, 11:35 PM
MarkT
For DC motors the torque is linked to the current. Measure the current and you can estimate the torque in real time.
There are very simple equations for DC motors given below.

[ This connection between torque and current does _not_ apply to stepper motors, note. ]

DC motor:

torque = motor_constant x current - friction_torque [ units being newton-metres and amps ]
voltage = motor_constant x no_load_speed [ units being volts and radians/second ]

The motor constant can be given in Nm/A or in Vs/rad, these are completely equivalent, believe it or not.
Sometimes the reciprocal of the motor constant is given - units being rad/s/V, or A/(Nm). Sometimes