Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 1 Drive Train Calculations Week 3 Day 1

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 2 Drive Train Calculations Draw pictures Make estimates Draw force diagrams Do calculations in terms of algebraic symbols - include ‘safety’ factors Substitute numbers Refine calculations as robot takes shape

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 3 Drive Train Calculations Speed Required - Example –Distance to be traveled - 20 feet –Time allotted – 1.5 minutes / 90 sec Torque Required –Static analysis of robot on ramp –Constant velocity on ramp allows static analysis

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 4 Calculating the Velocity Required Distance to be traveled - measure your path on the course - example 20 feet Time allotted – 1.5 minutes - use 90 sec V = Distance / time = 20 feet / 90 sec = 0.22 ft/sec Assume the robot must go faster, example 0.25 fps or 3 inches / sec (allow for pick and deposit time) Robot wheel is 1.75 in diameter, radius is in Motor speed required = velocity / (2*Pi*r) which is rev/sec or 32.7 rpm

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 5 Calculating the Torque Required Estimate weight of Robot - ~ 5 lb (use scale to weigh parts) –Handy Board and Motors –Drive Train - gears / axles / wheels / shaft encoders –Chassis - includes hot glue –Sensors - micro switches, CdS cell Estimate internal Friction - FI ~ 0.5 lb. Try pulling or pushing robot on level ground using the spring scale. Estimates of velocity and weight include some ‘safety’ factors

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 6 W WNWN W II P FIFI Sum of Forces parallel to plane = 0 P - W II - F I = Check the length and height of the ramp Static (Const. Velocity) Analysis

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 7 P - W II - F I = 0 W II = W sin (slope angle) slope angle = atan(3/7) = ~23 degrees W II = 5 lbs (sin(23)) = 1.97 lb P = 1.97 lb lb = 2.47 lb Torque = P x Radius of Wheel = 2.47 x = 2.16 lb-in = 34.6 oz - in Torque Speed Stall No Load Speed Usable performance Static (Const. Velocity) Analysis

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 8 Torque Speed Stall No Load Speed Usable performance Different Power Settings Motor Performance Curves

Engineering H193 - Team Project Gateway Engineering Education Coalition Spring Quarter P. 9 Drive Train Calculations Is the required Torque divided between two motors? If Torque and speed required don’t match characteristics, then gearing or motor change is required What are critical factors? –Weight –Internal Friction –Time –Slope of ramp

Engineering H193 - Team Project Gateway Engineering Education Coalition P. 10Spring Quarter ItemPoints Cover Page2 Sketch – Paths on Course6 Average Speed Calculation6 Sketch – Free Body Diagram6 Show Computation for Weight Calculation of Torque Required6 On level and on ramp Plot Required Torque and Speed4 On Your Motor Curve TOTAL30 Grading for Power Train Calculations