Go Down

### Topic: RE: Servo Torque (Read 121 times)previous topic - next topic

#### ilovetoflyfpv

##### Apr 19, 2018, 11:45 pmLast Edit: Apr 19, 2018, 11:47 pm by ilovetoflyfpv
Hi Guys

I want to use a servo to rotate a solid disk that is 0.1m in diameter and 0.1kg in weight. If I use the following formula (mass moment of inertia);

I=1/2 mr^2

I=1/2(0.1kg)(0.1m)^2

I=0.0005kg∙m^2

Does this mean that I would need to apply a minimum of 0.0005kg of torque at 0.1m in order to make it rotate? If this is the case then a servo that can produce 1.6kg.cm (0.16kg at 0.1m) of torque would be more than adequate?

Am I on the right track?

Cheers

Jase

#### MarkT

#1
##### Apr 20, 2018, 02:23 am
Not really.

The moment of inertia is relevant to angular acceleration.  Assuming no friction or other losses,
angular acceleration = torque / MoI

You have the correct MoI value.

In practice the imbalance forces of the disc may dominate.  If the mass isn't evenly distributed rotation
will move the centre of mass against gravity.

So is the disc nicely balanced with no other masses attached?  Is there any appreciable friction to overcome?

Do you have a requirement for the angular acceleration needed.

Nm (newton-metres)
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### ilovetoflyfpv

#2
##### Apr 20, 2018, 07:31 am
Hi MarkT

Thanks for getting back to me. The mass will be evenly distributed with little friction. I'm not sure what my angular requirements are at this stage except to say that I'm not looking for a rocket ship.

I'm curious to know how the torque given by servo manufacturers eg 1.6kg.cm relates to my project? In addition, I'm curious about what other factors/formulas I need to be aware of.

Cheers

Jase

Go Up