P14032: Skipper's Chair
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Detailed Design

Table of Contents

Prototyping

Due to time and budget constraints, a simple prototype was built using components from the previous team (P13032). The rig was setup with the primary goal of testing the steering system feasibility. Building a mock-up of the Tractor Arm design, it was mounted to one side of the chair base-plate. Lines were later attached to visually inspect line crossover potential.

The picture on the left shows the mock prototype, which was assembled with parts that were acquired from Piers Park and other miscellaneous parts. Alongside it is the previous iteration installed inside one of the Sonar boats at Piers Park.

Prototype Assembly
Figure 19: Test Rig for Tractor Arm

Figure 19: Test Rig for Tractor Arm

Figure 20: Chair System placed in Sonar Boat

Figure 20: Chair System placed in Sonar Boat

The prototype was built to match the image in the Sonar as closely as possible. The chairs serve as the sides of the boat, holding the assembly in place on top. Since the chair had already been placed in the Sonar before, it was known that the rail fixture that we had acquired worked and fit into the boat. To reiterate, the main concern was feasibility of the steering system.

A physical model for the chair had to have been assembled in order to reinforce the idea that the system will work. With the mock tractor arm near the front of the chair, back and forth motion is not a problem and the user should have enough room when seated to swing freely.

Prototype
Figure 21: Pull Position

Figure 21: Pull Position

Figure 22: Push Position

Figure 22: Push Position

The seat concept was a combination of the tractor seat with the last Senior Design iteration concept. This is the tractor seat that is used at Piers Park Sailing Center.

Figure 10: Tractor Chair

Figure 10: Tractor Chair

Finalized Design

Figure 23: Full Assembly with Tiller

Figure 23: Full Assembly with Tiller

System Components


In order to stay within budget and reduce additional custom parts, some components from the previous design (P14032) were kept. The following images present these various parts:

Current Components
Figure 24: Base Plate

Figure 24: Base Plate

Figure 25: Chair Base Plate

Figure 25: Chair Base Plate

Figure 26: Old and New Handholds

Figure 26: Old and New Handholds

Figure 27: Pedestal

Figure 27: Pedestal

Figure 28: Short Tiller

Figure 28: Short Tiller

Figure 29: Tiller Strut

Figure 29: Tiller Strut

Figure 30: Track and Platform

Figure 30: Track and Platform

Figure 31: Track Platform Pulley

Figure 31: Track Platform Pulley

CAD Images & Animations


These are new components that were analyzed for use in the system.

CAD Components
Figure 32: 4 Inch CAD Chair Model

Figure 32: 4 Inch CAD Chair Model

Figure 33: Jack system

Figure 33: Jack system

Figure 34: Steering System Attachment

Figure 34: Steering System Attachment

Steering CAD Videos
Figure 35: Steering Test

Figure 35: Steering Test

Figure 36: Track and Steering Test

Figure 36: Track and Steering Test

Figure 37: Track Test

Figure 37: Track Test

Steering System Iterations
Figure 38: Crank System of previous iteration

Figure 38: Crank System of previous iteration

Figure 39: V1 of Lever

Figure 39: V1 of Lever

Figure 40: V2 of Lever

Figure 40: V2 of Lever

Figure 41: V3 of Lever

Figure 41: V3 of Lever

The primary goal of the steering system is to allow the user to "feel" the forces of the water acting on the Sonar rudder. A major concern, is possible line entanglement due to lines leading from the tractor arm toward the tiller. The following images show the line arrangement along the system:

Rope Systems
Figure 42: Chair Rope System

Figure 42: Chair Rope System

Figure 43: Chair Rope System Push

Figure 43: Chair Rope System Push

Figure 44: Chair Rope System Pull

Figure 44: Chair Rope System Pull

Figure 45: Chair Rope System front path

Figure 45: Chair Rope System front path

Figure 46: Chair Rope System side path with strut

Figure 46: Chair Rope System side path with strut

Adjustments were made from the previous design to eliminate line crossover.

Simulations

Steering ANSYS


The steering system was tested using Ansys Workbench. The materials for the model were chosen based on average values found. Young’s modulus was estimated at 420,000 psi and poison’s ratio was estimated at .3. An ultimate strength was found to be 7500 psi. The specimen was fixed at the pivot pipe in the center of the lever. A force of 40 lbs was applied to the very top of the lever and the bottom to induce the greatest moment at the pivot point. The highest stress that was caused in the pipe was 2630 psi. This value is well under the ultimate strength so the pipe will be able to endure what we have considered worse case condition.

Stress and Deformation Analysis
Key Steering Lever
Figure 47: Stress (psi)

Figure 47: Stress (psi)

Figure 48: Stress in the Steering Lever

Figure 48: Stress in the Steering Lever

Figure 49: Deformation (inches)

Figure 49: Deformation (inches)

Figure 50: Deformation of the Steering Lever

Figure 50: Deformation of the Steering Lever

Chair ANSYS


While visiting Piers Park Sailing Center, we were able to better understand their needs by seeing their most used devices. The one below follows the same concept design and is one of the most used items.

Figure 35: Chair With Sailing Material

Figure 35: Chair With Sailing Material

An ANSYS simulation was done in order to see how the PVC pipe that was chosen for the chair would handle itself under worst-case loading scenarios. For this test, there is a 50 lb force acting in the y-direction and a 300 lb force in the z-direction on the top joint of the chair. This results in a 300 lb force at a 10 degree angle relative to the normal plane. This force was used because it simulates the worse case scenario with a 300 lb male exerting all of his weight on the back of the chair. In addition, the chair was already tilted at 10 degrees.

Stress and Deformation Analysis
Key Chair
Figure 51: Sress Key (psi)

Figure 51: Sress Key (psi)

Figure 52: 4 Inch Crossbeam PVC Chair Stress with 300lbs applied force, 10 degrees from the Horizontal

Figure 52: 4 Inch Crossbeam PVC Chair Stress with 300lbs applied force, 10 degrees from the Horizontal

Figure 53: Deformation Key (inches)

Figure 53: Deformation Key (inches)

Figure 54: 4 Inch Crossbeam PVC Chair Deformation with 300lbs applied force, 10 degrees from the Horizontal

Figure 54: 4 Inch Crossbeam PVC Chair Deformation with 300lbs applied force, 10 degrees from the Horizontal

The results show that the most stress on the chair is ~4920 lbs around the joints at the mid-section of the chair. The yield stress of the PVC is 7500 lbs. This gives us a factor of safety (FOS) of about 1.5. In addition, the most deformation experienced by the chair was 0.01 inches around the area where the force was applied.

Sonar ANSYS


Note: Previous calculations and analysis' were completed to determine which device to incorporate. This analysis is within the system design page.

An ANSYS software analysis was done to test if the jack compressive forces would fracture or deform the Sonar sides. The following assumptions were made:

Stress and Deformation Analysis
Key Inward View Outward View
Figure 55: Stress (psi)

Figure 55: Stress (psi)

Figure 56: Inward View of Sonar Stresses due to Jack Compressive Loads

Figure 56: Inward View of Sonar Stresses due to Jack Compressive Loads

Figure 57: Outward View of Sonar Stresses due to Jack Compressive Loads

Figure 57: Outward View of Sonar Stresses due to Jack Compressive Loads

Figure 58: Deformation (in)

Figure 58: Deformation (in)

Figure 59: Inward View of Sonar Deformation due to Jack Compressive Loads

Figure 59: Inward View of Sonar Deformation due to Jack Compressive Loads

Figure 60: Outward View of Sonar Deformation due to Jack Compressive Loads

Figure 60: Outward View of Sonar Deformation due to Jack Compressive Loads

The result shows that the maximum force exerted by the Jacks to the Sonar is 402.12 psi. The yield strength of Balsa wood is between 15-25 MPa. The average (2901 psi) of the range was used and converted to psi in order to compare it to the simulation. The result was well under the yield strength, giving a factor of safety of ~7.2.

Because of budget constraints, the jack system was not implemented into the final system, but software testing was done to see if handholds could be replaced with the jack system. The following document contains the simulation and results: Handhold Analysis

Bill of Material (BOM)

Figure 61: Bill of Materials/P14032 Buy Parts

Figure 61: Bill of Materials/P14032 Buy Parts

Bill of Materials

The bill of materials contains components that we have already acquired from Piers Park. The list pictured above shows only the parts that will need to be purchase, while the link has the entire list of materials.

Test Plans

Test Plans

Risk Assessment

Figure 62: Risk Management

Figure 62: Risk Management

Figure 63: Risk Management Severity and Likelihood Key

Figure 63: Risk Management Severity and Likelihood Key

Updated Risk Management

Objectives that will be completed in beginning stages of MSD II:

Improvements

Note: Specific to user

Design Reviews

Final Feasibility Review

Final Feasibility Review (pdf)


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