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Design Workshop October 27, 2012 Mechanical Systems

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October 27, 2012 Introduction Parthiv Shah Graduate of University of Waterloo Bachelor of Applied Science in Mech. Eng. Joined 1241 in 2011 Lead Design Mentor

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October 27, 2012 Objectives Types of Common Mechanisms Used in FRC Types of Motors Used in FRC Gears and Sprockets Example Problems

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October 27, 2012 Types of Mechanisms Four Bar Linkages Crank / Slider Pulley Systems Rack and Pinion

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October 29, 2011Parthiv and Malavya Shah Four Bar Linkages

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October 29, 2011Parthiv and Malavya Shah Crank Slider

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October 29, 2011Parthiv and Malavya ShahPulleys

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October 29, 2011Parthiv and Malavya Shah Rack and Pinion

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October 29, 2011Parthiv and Malavya ShahMotors 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)

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October 29, 2011Parthiv and Malavya ShahMotors MotorStall Torque (N m) Free Speed (RPM) Picture CIM Fisher Price Denso Window

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October 29, 2011Parthiv and Malavya ShahMotors MotorOutput Torque (kN m) Free Speed (RPM) Picture BaneBots Servo Motor

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October 29, 2011Parthiv and Malavya Shah Stall Condition Maximum Power No Load Condition Maximum Efficiency

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October 27, 2012 Gears Pinion Gear –or Driving Gear Driven Gear Pitch – Number of Teeth Per Inch Pitch Diameter – Circle at which the two gears meet Pinion Driven Gear

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October 29, 2011Parthiv and Malavya Shah P=N/d Where: P= diametral pitch (teeth per inch) d = pitch diameter (in) N = number of teeth

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October 29, 2011Parthiv and Malavya Shah Types of Gears Spur Gears Planetary Gears Helical Gears Bevel Gears Worm Gears

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October 29, 2011Parthiv and Malavya Shah Gear Ratios GR = N2/N1 = T2/T1 = ω1/ω2 If N2>N1 Torque is increased, speed is decreased If N2

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October 29, 2011Parthiv and Malavya Shah 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

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October 29, 2011Parthiv and Malavya Shah ANSI B29.1 roller chain standard sizes SizePitchRoller diameterTensile strengthWorking load in (6.35 mm )inmm in (3.30 mm) 781 lb (354 kg)lbkg140 lb (64 kg) in (9.53 mm) in (5.08 mm) 1,758 lb (797 kg)480 lb (220 kg) Calculating Center to Center Distances Between Sprockets: OR Where: C=center to center distance L=length of chain N1=# of teeth on driving sprocket N2=#of teeth on driven sprocket p=pitch

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October 27, 2012 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. Torque Example Given: Tm = 2 N-m Larm = 1.5m M=1.5kg Solution: Force = Mass x Gravity = 1.5kg*(9.81N/kg) = N Torque = Force x Length of Arm = N x 1.5m = N-m ~ 22 N-m Gear Ratio: GR = Load Torque / Torque Motor = 22N-m / 2N-m = 10

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October 27, 2012 Determine Gear Ratio for a motor that Rotates at 5000 rev/min to drive a 4 in wheel 16 ft/s 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) = rps x 60= rpm Gear Ratio: GR = Motor Speed/ Wheel Speed = 5000rpm / = 5.45

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