Check out some similar questions!

Sumeer09 · May 17, 2013, 05:00 AM

Hi, I am a 4th year mechanical engineering student, I am currently designing a satellite tracking system. I require asisstance on with the selection of a motor. Im using a fly wheel pinion set to rotate my system and my system weighs approx. 100 kg. how do I go about calculating the torque of the system and power and selecting an apporpiate motor?

Any asisstance will be much appreciated

ebaines · May 17, 2013, 05:53 AM

You'll need an estimate of the static and kinetic friction of the bearings in the track system. Then the torque required comes from the equations you know and love regarding the torque required to overcome friction ( $\vec T = \vec F \times \vec r$ ) and to accelerate or decelerate the system in rotation ( $\vec T = I \vec {\alpha}$ ).

Sumeer09 · May 17, 2013, 06:18 AM

How I estimate the kinetic and static friction on the bearings and how do I obtain the angular accelaration? Also what force is that in the torque equation?

ebaines · May 17, 2013, 07:23 AM

The angular acceleration is something you need to decide on, based on how quickly do you want the antenna array to rotate. It takes more torque to get it to accelerate quickly than to accelerate slowly.

The force in the equation is friction force times the moment arm of the friction force from the axis of rotation. You may be able to estimate the static and dynamic coefficients of friction from a mock-up or by measuring friction of similar large rotating mechanisms.

Sumeer09 · May 17, 2013, 11:16 AM

Thank you so much ebaine you've been a big help, so I guessing that after I calculate the torque required by system, I use the gear ratio between the flywheel and starter gear and calculate the torque need from the motor?

ebaines · May 20, 2013, 05:44 AM

Originally Posted by Sumeer09

Thank you so much ebaine youve been a big help, so i guessing that after i calculate the torque required by system, i use the gear ratio between the flywheel and starter gear and calculate the torque need from the motor?

The gear set matches the speed of the motor (probably in the range of several hunderd RPM) to the desired speed of the antenna (perhaps 5 RPM or so). Once you have the values for the torque needed for the antenna as described previously and the gear ratio, the torque needed from the motor can be found from:

$<br /> T_{motor} = T_{antenna} ( \frac {\omega _{antenna}}{\omega _{motor}})$