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Design Workshop

Design Workshop . Mechanical Systems. Introduction. Parthiv Shah Graduate of University of Waterloo Bachelor of Applied Science in Mech. Eng. Joined 1241 in 2011 Lead Design Mentor. Objectives. Types of Common Mechanisms Used in FRC Types of Motors Used in FRC Gears and Sprockets

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Design Workshop

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  1. Design Workshop Mechanical Systems

  2. Introduction • Parthiv Shah • Graduate of University of Waterloo • Bachelor of Applied Science in Mech. Eng. • Joined 1241 in 2011 • Lead Design Mentor

  3. Objectives Types of Common Mechanisms Used in FRC Types of Motors Used in FRC Gears and Sprockets Example Problems

  4. Types of Mechanisms • Four Bar Linkages • Crank / Slider • Pulley Systems • Rack and Pinion

  5. Four Bar Linkages Parthiv and Malavya Shah

  6. Crank Slider Parthiv and Malavya Shah

  7. Pulleys Parthiv and Malavya Shah

  8. Rack and Pinion Parthiv and Malavya Shah

  9. Motors • Electrical Motors used in FRC • Properties of a Motor: • Stall Torque [N*m or oz*in] • Torque at which motor speed is 0 • Free Speed [rad/s or rpm] • Speed at which motor torque is 0 • Terminal voltage [V] • Voltage required by motor • Efficiency • Power Out / Power In = (T*ω) /(V*I) Parthiv and Malavya Shah

  10. Motors Parthiv and Malavya Shah

  11. Motors Parthiv and Malavya Shah

  12. No Load Condition Maximum Power Maximum Efficiency Stall Condition Parthiv and Malavya Shah

  13. Gears Driven Gear Pinion Pinion Gear –or “Driving Gear” Driven Gear Pitch – Number of Teeth Per Inch Pitch Diameter – Circle at which the two gears meet

  14. P=N/d • Where: • P= diametral pitch (teeth per inch) • d = pitch diameter (in) • N = number of teeth Parthiv and Malavya Shah

  15. Types of Gears Spur Gears Helical Gears Planetary Gears Bevel Gears Worm Gears Parthiv and Malavya Shah

  16. Gear Ratios • GR = N2/N1 = T2/T1 = ω1/ω2 • If N2>N1 Torque is increased, speed is decreased • If N2<N1 Torque is decreased, speed is increased • Gear Train: • GR = (N3/N2)(N4/N3)(N6/N5) Parthiv and Malavya Shah

  17. Roller Chain Sprockets • Pitch – Distance between rollers • Pitch Diameter – Circle at which the roller chain sits on the sprocket D=p/(sin(180°/N) where: D=diameter, p=pitch, N = teeth Parthiv and Malavya Shah

  18. Calculating Center to Center Distances Between Sprockets: Where: C=center to center distance L=length of chain N1=# of teeth on driving sprocket N2=#of teeth on driven sprocket p=pitch OR Parthiv and Malavya Shah

  19. Torque Example Given: Tm = 2 N-m Larm = 1.5m M=1.5kg Solution: Force = Mass x Gravity = 1.5kg*(9.81N/kg) = 14.715N Torque = Force x Length of Arm = 14.715N x 1.5m = 22.0725 N-m ~ 22 N-m Gear Ratio: GR = Load Torque / Torque Motor = 22N-m / 2N-m = 10 • Determine Gear Ratio for a motor that has output torque of 2 N-m and is used to rotate an arm 1.5m long with a mass of 2kg at the end of it.

  20. Speed Example Given: n = 5000rpm Dwheel = 4in V=16ft/s Solution: V=n*π*D so Wheel Speed n = v/(D*π) = 16/((4/12)*3.14) = 15.27 rps x 60= 916.2 rpm Gear Ratio: GR = Motor Speed/ Wheel Speed = 5000rpm / 916.2 = 5.45 • Determine Gear Ratio for a motor that Rotates at 5000 rev/min to drive a 4 in wheel 16 ft/s

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