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Motor Specking for Rotating Mass System

Motor Specking for Rotating Mass System. Jordan Hodge – Team Ground Control. Problem. How would you go about specking a motor in order to move a certain rotating mass a distance in a specific amount of time? Our Case: 3 Meter Mesh Dish and Assembly: Aprx . 45 N (100lbs). Background.

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Motor Specking for Rotating Mass System

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  1. Motor Specking for Rotating Mass System Jordan Hodge – Team Ground Control

  2. Problem • How would you go about specking a motor in order to move a certain rotating mass a distance in a specific amount of time? • Our Case: 3 Meter Mesh Dish and Assembly: Aprx. 45 N (100lbs)

  3. Background • Dynamic Torque- The torque encountered by a system that is not only in motion, but accelerating. • Static Torque- The torque produced at constant velocity (rest or running). • Center of Mass- The mean location of all system masses. • Moment of Inertia- A measure of an object's resistance to changes to its rotation. It is the intetia of a rotating body with respect to its rotation.

  4. Physical Equations • Torque=Fd F= Magnitude of Force (N)|d= Length or Magnitude of Lever arm (m) • F=ma m= mass (kg) | a= acceleration due to gravity (m/s2) • Moment of Inertia (J)=mr2 m=mass (kg) | r= axis of rotation • Center of Mass (Semicircle)=4r/3pi m=mass (kg) | r= axis of rotation

  5. Calculation/Prediction Equations • TStarting=KrunningTrunningKrunning = Running Torque Multiplier • To= [ 5250 x HP ] / N To = Operating or running Torque ( ft-lbs ) | HP = Horsepower delivered by electric motor **Note: Values switch from N = Rotational velocity ( rpm)| metric to English Units 5250 = Constant converting horsepower to ft-lbs/minute and work/revolution to torque • T = [ N x WR2 ] / [ Ta x 308 ] T  = Time ( seconds )|N = Velocity at load (rpm ) Ta = Average Torque During start ( ft-lbs ) WR2 =  Rotating Inertia (lbs-ft3)|W =Weight (lbs) R = Radius of Gyration (ft2)| 308 = Constant derived converting minutes to seconds, mass from weight, and radius to circumference

  6. Torque Produced By Dish • TorquedishTorquerunning=FdF=ma • F=(45kg)(9.81m/s2)=441.45 N • Torque= (441.45 N)(0.889m)=392.45 N-m

  7. FBD- Free Body Diagram FN FReacting FDx FDy

  8. Example DC Motor Datasheet

  9. Ways to Reduce Torque/ Lighten the Load • Counterweight • Counter torque • Better Bearings

  10. Other Ways to Predict • Solid Works- Flow Works • Scaling Down, measure, scale back up • Buy torque measuring device

  11. Questions…

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