Steven JorgensenChani Martin

Motor Characteristics

Stall torque – Maximum Torque output with 0 rotational speed.

Stall Current – Current drawn at stall torque

Free Speed – Fastest Free spin of the motor with 0 load.

Motor Power- Mechanical power motor has.

Motor Curve Demonstration Look and explain F-P Motor Curve

here Show Graphical Representation

Stall Torque Stall Current Free Speed Maximum Power

Designing Around Motor Specifications Calculate Power Requirement Select Appropriate Motor Find the Working Torque and Apply

Gear Ratio Calculate Effective(Actual) Gear

Ratio Calculate Effective (Actual) Power

Output

FRC Problem

Lift a 5lb Ball 7ft in the Air within 6 seconds

Step 1: Power Requirement

Power = Torque * Angular Velocity• P = Τω = (69N-m)(0.393rad/s) = 27.117

Watts Arm Parallel to Ground requires most

torque

Step 2: Select Appropriate Motor Maximum Available Power for 2010

Motors CIM (337 Watts at 2655rpm, 172oz-in) Fisher Price (185 Watts) Denso (22 Watts) Mabuchi Motor (30 Watts)

Step 3: Working Torque w/ Gear Ratio Gear Ratios – Transmit Loads at the

Gear’s Teeth F-P Stall Torque = 63.4 oz-in Design around 20%-50% of stall torque

so that gear ratio reflects a torque load on the motor that is near max power.

45% Stall Torque = 28.98oz-in 630 oz-in / 28.98 oz-in =

21.74:1 Gear Ratio With this Gear Ratio F-P motoronly experiences 28.98oz-in of load

Step 4: Effective Gear Ratio Effective Gear Ratio = Motor Power *

Total Component Efficiency Each Gearing Stage Loses 10%

Efficiency Two Stages (7:1 to 4:1)

7*90% * 4 * 90% = 22.68:1 Effective Gear Ratio

Step 5: Effective Power

F-P Motor Experiences 28.98 oz-in Refer to Motor Curve to find Power

Output of F-P motor at this torque input. Power @ 28.98 oz-in Torque = 180

Watts Effective Power = Motor Power * Efficiency E.P = Motor Power * (Gear Ratio Efficiency)

* (Motor Efficiency) E.P. = 180 * (0.9*0.9) * (0.5) = 72.9 Watts

Lifting Ball only requires 27.11 Watts

Conclusion Power Requirement

27.11 Watts Select Appropriate Motor

F-P motor (190 Watts Available) Working Torque

28.98 oz-in Working Torque. Needs 21.74 GR Calculate Effective(Actual) Gear Ratio

22.68 G.R. After Efficiency Loss Calculate Effective (Actual) Power

Output 71.9 Watts Available after Efficiency Loss