BME162 - 2022 - Participation Activity #3

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Mechanical Engineering

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Apr 3, 2024

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BME162 Winter 2022. Participation Activity #3 – Individual Activity. Due to LEARN Dropbox by Sunday, April 3 by 11:59 pm E.T. Important : This participation activity contains a mandatory activity (NIOSH Lifting Equation Problem) and an optional activity (Biomechanics Problem). You only need to complete the NIOSH Lifting Equation problem to receive full marks. The biomechanics problem can be completed at your own discretion. Feedback will be provided, if the problem is completed. Mandatory: NIOSH Lifting Equation Problem A student working at POETS must lift and stack cases of beverages. Each case currently holds 24 beverages and weighs 13 kg. The student works for no more than 2 hours. The handles on the cases are fair. The student must hold the cases at 30 cm from the body (measured from the midpoint between the ankles). The vertical distance at the start of the lift is 78 cm. The vertical distance of the student’s hands from the floor at the destination is 165 cm. The student rotates 45 degrees during the lift. The student is expected to move 100 cases during the work shift. PART A : Use the NIOSH Lifting Equation to calculate whether or not this is a safe lift for the student. Use the template below to complete your calculations. PART B : If you were to redesign this lifting task, pick one feature that would be the easiest to change? PART A: Calculate load constant (LC): Hint: See Table 13.1. Available on the last page of this assignment or in the Lee textbook. LC = 23 kg Calculate Horizontal Multiplier (HM): HM=25/H H is horizontal distance between hands lifting load and midpoint between ankles (cm) HM = 25 30 = 0.833 cm Calculate Vertical Multiplier (VM): Hint: Consider the beginning and the end of the lift! VM=1-0.003|V-75| V is the vertical distance of the hands from the floor (cm) V start = 78 cmV end = 165 cm V M start = 1 0.003 | 78 75 | = 0.991
V M end = 1 0.003 | 165 75 | = 0.73 Calculate the Distance Multiplier (DM): DM=0.82 + 4.5/D D is the vertical travel distance between the origin and the destination of the lift (cm) D = V end V start = 165 78 = 87 cm D = 0.82 + 4.5 87 = 0.872 Calculate the Asymmetry Multiplier (AM): AM = 1-0.0032A A is the angle of torso twisting involved in the lift (in degrees) A = 45 ° AM = 1 0.0032 45 = 0.856 Calculate the Frequency Multiplier (FM): Hint: See Table 13.2, Round up. Available on the last page of this assignment or in the Lee textbook. FM = 0.88 Calculate the Coupling Multiplier (CM): Hint: See Table 13.3. Available on the last page of this assignment or in the Lee textbook. CM = 1.00 Calculate the overall RWL: Hint: Consider the beginning and the end of the lift! RW L start = 23 0.833 0.991 0.872 0.856 0.88 1.00 = 14.57 kg RW L end = 23 0.833 0.73 0.872 0.856 0.88 1.00 = 9.19 kg Calculate Lift Index (LI): Hint: Consider the beginning and the end of the lift! LI start = 13 14.57 = 0.892 LI end = 13 9.19 = 1.41 Interpret Lift Index (LI): (This is the answer to Part A) LI ≤ 1.0: Lift is safe LI > 1.0: Will pose an increased risk to some workers LI > 3.0: Will pose a high risk of low-back pain and injury to most workers
At the start of the task, the lift is safe since the Lift Index is less or equal to 1.0 ( 0.892 1.00 ) However, at the end of the task the lift will pose an increased risk to some workers since the Lift Index is greater than 1.00 ( 1.41 > 1.0 ). PART B: For this lifting task, what would be the easiest element to change? Th easiest element to change would be an element at the end, which could be the vertical multiplier, perhaps trying to lower the height requirement for where the student needs to place the boxes. Improving the Vertical Multiplier would also help improve the Distance Multiplier. ------- Optional: Biomechanics A person is carrying their recycling to the curb. They are carrying it with both hands such that their arms are fully extended and rotated 45 degrees down from horizontal. The recycling bin weighs 10 kg. The entire arm weighs 4.4 kg and is 65 cm long (from shoulder to hands). The entire arm can be considered to be one rigid body/segment. The center of mass of the arm is 44% of the total arm distance measured from the shoulder joint to the hand. Calculate the reaction force and moment at the shoulder to maintain a static position.
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Table 13.1. NIOSH Lifting Equation Components and Related Equations (Lee et al., p. 433) Component Metric System US System Load Constant (LC) 23 kg 51 lb Horizontal Multiplier (HM) 25/H 10/H Vertical Multiplier (VM) 1 - 0.003|V-75| 1 - 0.0075|V-30| Distance Multiplier (DM) 0.82 + 4.5/D 0.82 + 1.8/D Asymmetric Multiplier (AM) 1 - 0.0032A 1 - 0.0032A Frequency Multiplier (FM) See Table 2 See Table 2 Coupling Multiplier (CM) See Table 3 See Table 3 Table 13.2. Frequency Multiplier (FM) Values (75 cm = 30 in) (Lee et al., p. 433) Work Duration ≤ 1 hr ≤ 2 hr ≤ 8 hr Frequency (lifts/min) V < 75 cm V ≥ 75 cm V < 75 cm V ≥ 75 cm V < 75 cm V ≥ 75 cm 0.2 1.00 1.00 0.95 0.95 0.85 0.85 0.5 0.97 0.97 0.92 0.92 0.81 0.81 1 0.94 0.94 0.88 0.88 0.75 0.75 2 0.91 0.91 0.84 0.84 0.65 0.65 3 0.88 0.88 0.79 0.79 0.55 0.55 4 0.84 0.84 0.72 0.72 0.45 0.45 5 0.80 0.80 0.60 0.60 0.35 0.35 6 0.75 0.75 0.50 0.50 0.27 0.27 7 0.70 0.70 0.42 0.42 0.22 0.22 8 0.60 0.60 0.35 0.35 0.18 0.18 9 0.52 0.52 0.30 0.30 0 0.15 10 0.45 0.45 0.26 0.26 0 0.13 11 0.41 0.41 0 0.23 0 0 12 0.37 0.37 0 0.21 0 0 13 0 0.34 0 0 0 0 14 0 0.31 0 0 0 0 15 0 0.28 0 0 0 0 >15 0 0 0 0 0 0 Table 13.3. Coupling Multiplier (CM) Values (75 cm = 30 in) (Lee et al., p. 434) Coupling Multipliers (CM) Coupling V < 75 cm V ≥ 75 cm Good 1.00 1.00 Fair 0.95 1.00 Poor 0.90 0.90