William Ligon-Bruno/Senior Design Project
Calculations
These are the different analysis conducted to make sure the string adheres to the design requirements specified earlier. More calculations were conducted, but these are the finalized relevant calculations to determine material and design.
Given an 11lb mass, the beam deflection was calculated for solid and hollow 6061-T6 aluminum to ensure the requirement of 1in or less deflection is to be met.
Given the 11lb mass and a max tension of 90lbs being pulled, the distance the drop-mass has to be from the axis of rotation is calculated for both a hollow and solid shaft of aluminum 6061-T6.
At the maximum tension of 90 lbs, the stress was calculated to ensure the ratchet does not fail at the maximum operating conditions.
Given an 11lb mass, the beam deflection was calculated for solid and hollow 6061-T6 aluminum to ensure the requirement of 1in or less deflection is to be met.
Beam Deflection
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As shown in the analysis above, the design was chosen to have a beam deflection less than 1.00in. With a deflection greater than this there starts to be noticeable change in the tension drawn.
Moment
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This calculation was done to choose the design that give the distance the mass has to be for a specific variance in tension. The system then has to be built so that it can withstand this max force.
Clamping Force
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The angle from which this force acts is given in this calculation. This angle will vary depending on the tension desired, but there is no limit on the degree of rotation save the length of string being tensioned.
Force on Strut
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This calculation was done assuming a ridged pin connection into the base from the swivel arm. The angle was designed to reduce the force applied.
String Angle
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This analysis was done to see what angle starts to have a large effect on the tension of the string being drawn. The devices ability to adjust laterally was to mitigate this loss of tension.
Ratcheting Gear
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This analysis was the most extensive as it required many design decisions that affected one another.