P15741: Air Table Mover
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Systems Design

Table of Contents

Agenda

  1. Update and Changes since Last Review
  2. Functional Decomposition
  3. Concept Generation and Selection
  4. Discussion of Chosen System Idea
  5. Feasibility
  6. Risk Analysis

Update Information

End State Deliverables for Week 9

  1. Finalized Concept with Engineering Analysis and CAD Documents
  2. Resolution to Budget Concerns
  3. Continued Updates of Engineering Requirements as Needed.

Action Items

  1. 2/17/15 Concept functions list and function decomposition constructed
  2. 2/19/15 Selection criteria finalized and initial candidate concepts are formed using morphological chart and function decomposition
  3. 2/24/15 Team evaluates concepts based on selection criteria and initial feasibility analysis
  4. 2/26/15 Feasibility Analyses performed (tipping, stability, weight capacity)
  5. 2/28/15 Team developed final concept for proposal from pugh chart
  6. 3/3/15 Team implemented System Proposal to EDGE

Areas of Concern

  1. Through benchmarking theoretical proposed budget of $500 from MSD is insufficient. According to OSHA standards we need a factor of safety of 5 for all components. Approximated steel cost for frames/structures of considered designs approaches or exceeds $500.
  2. Initial concept generation phase did not create sufficient braking system. This will be addressed in weeks 6-9. Therefore this function is not in morphological chart.

Functional Decomposition

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Engineering Requirements Mapped to Functional Decompoisition

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Morphological Chart

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Selection Criteria

Selection Criteria

Selection Criteria Working Document

Pugh Chart

Pugh Chart

This chart shows our generated concepts for the completion of various needed functions for our system. System concepts were generated by combining various subsystem functions from the morphological chart. The Pugh chart compares the various system designs to a set datum. Our first datum was the current method by which these tables are moved. This method involves large amounts of manual labor and engine lifts. Since virtually all of our proposed methods were better than the default the datum had to be moved. When the datum was moved to the rotating jaw system a set of clear "winning" designs became obvious. The systems we contemplated further were the rotating jaw system and the rail gear system.

Working Pugh Chart File

Concept Development and Selection

Concept Development

Concepts were developed evaluating the morphological chart and selecting components that would achieve objectives based on our functional decomposition. Each team member proposed a potential candidate concept and then gave an analysis to the remaining team members of said concept. Using our pugh chart evaluation, our team was able to preserve the best functions of each concept in order to create our final candidate design.

The "Jaws" concept essentially consists of a large pair of clamps that will be centered on the wide end of the isolation table. The lifting height will be adjusted using a hydraulic lift or automated lift assist device. In order to rotate tables to fit through doorways, the clamps will be attached to an axle rod that will be turned using the wheel as seen on the back of the device. It should be noted that two sets of "Jaws" will be built and placed at each end of the table in order to accomplish these tasks.

public/Systems Level Design Documents/jaw concept.JPG

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1.) The clamping system involves two separate plates to generate force on the object. The plate on top will move be moved using a threaded rod behind the plate to create a screw clamp, while the bottom plate will be stationary.

2.) The unit's clamps and "head" will be able to rotate around the axle that is connected to a manually operated wheel. This will fulfill our rotational requirement in positioning the table vertically.

3.) To generate lift, a hydraulic pump or piston will be centered at the base of the support structure. This lift assistance device will be connected to the "head" of the unit.

4.) The clamping head will be raised and lowered by a method similar to that of car lifts. The central rotational axis will be a shaft that passes through the head and attaches to the clamping unit. This shaft will pass through a bearing inside a hollow central supporting column. Inside this column will be a locking system which prevents the bearing from sliding down at any unwanted time. The head system itself will be lifted by the hydraulic cylinder.

5.) The clamps will contain machine compartments to fit steel dowels. These dowels allow vertical stability when the clamps are rotated as well as versatile option in supporting multiple loading shapes that would not survive the clamping force.

We have also considered alternative methods to lift the clamping jaws in this system design. Instead of hydraulic cylinders cable and pulley systems with attached to either a motor or manual ratchet such as a come along hoist.

Alternative Designs

public/Systems Level Design Documents/rail gear concept.JPG

Systems Architecture

Our proposed system follows the rotational clamping jaws concept. We will have a heavy metal base with caster wheels to provide stability to the system. The tables will be lifted and manipulated via a set of clamping jaws which are raised and lowered by hydraulic cylinders. A support column with internal locking mechanisms will provide additional support to the jaws. The jaws will be attached to an axle/shaft which will be rotated by a manually operated wheel.

Feasibility and Benchmarking

1.) Hydraulic Piston Feasibility

Hydraulic pistons generate pushing force by increasing fluid pressure inside of piston. Using the equation F=P*A you can calculate the required fluid pressure necessary in a piston to lift out table. Our largest table weighs approximately 1150 lbs. To be safe the analysis was completed at an assumed weight of 1300lbs. A small 2" bore hydraulic cylinder was assumed (This size piston is in our price range). This cylinder has an effective area of Pi*radius^2. If one cylinder is used (our cylinder would use two) the needed pressure would be 413 Psi. These cylinders can take in excess of 2500psi before failing. Hydraulic cylinders are therefore a viable lifting system.

2.) Calculating Required Rotational Force. i.e. can a human rotate tables.

A rotational analysis of our largest potential table was performed. Given the size of the table (5'x8'x8", and 1150 lbs), Z axis moment of inertia was found. Rotational torque was assumed to be rotational acceleration multiplied by IZ.

T=Iz*(alpha)

Alpha was calculated per its rotation with displacement and original rotational velocity.

Rotational torque was assumed to be applied by a tangential force on a rotational wheel of radius r. Calculated values and formula were put into an excel spreadsheet. Required human input forces were calculated based on total time of rotation and varying wheel sizes (see spreadsheet). This analysis showed that a person can reasonably rotate the table in a system given a large enough wheel (40lb input with 1' wheel.)

public/Systems Level Design Documents/Rotating.jpg

public/Systems Level Design Documents/Analysis Documents/table schematic.JPG

public/Systems Level Design Documents/Analysis Documents/iz calculation.JPG

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Rotational Calculation Spreadsheet

3.) Tipping Analysis

A tipping analysis was completed for the proposed design. This tipping analysis assumes forces being applied along the axis of the thickness of the table, while the table is in the moving device. The table is most stable along its long axis and least stable while moving in the direction of its thickness. The analysis which shows it moving down our maximum slope value of ten degrees shows that the table should never be moved down a slope in this orientation as an applied force of approximately 900lbs is needed to keep it from tipping. On a flat surface the table is stable and needs an applied force of approximately 300 lbs to tip. The analysis was performed for applied forces 4 feet from the ground (my arm height). The center of gravity of the table was assumed to be 3 feet off of the ground (1/2 foot clearance with ground).

public/Systems Level Design Documents/Tipping2 modified with assumptions added.jpg

public/Systems Level Design Documents/Analysis Documents/slope tipping page 2.JPG

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public/Systems Level Design Documents/Analysis Documents/flat surface tipping.JPG

4. Clamp Feasibility

public/Systems Level Design Documents/Clamping_Analysis.jpg

Benchmarking

Optical Breadboard Manufacturer Vere manufactures a hoist for optical breadboards. This can be found at

http://www.vere.com/html/table_hoist.html

Their table mover design is similar to our proposed system design. This system instead of using clamping jaws uses a frame which is placed on the table. The frame is secured in place with threaded rods which are inserted at at predetermined holes. The holes are drilled in place for various widths of tables. The rods act as stoppers for table motion. The framing system is separate of the lifting system. After the framing is attached to the table the other components are moved into place and the table framing is secured to them. This system addresses various safety concerns with locking pins, rubber stoppers, and a beam which attaches the two segments of the lifter to each other during transport. The system is not rated for overhead lifting, so users must keep their body parts out of under the table during movement.

Risk Assessment

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Working Risk Analysis Document

Systems Design Review

Citations

1 Enerpac Basic Hydraulics Information at http://www.enerpac.com/en-us/basic-hydraulics

2 http://www.northerntool.com/shop/tools/category_hydraulics+hydraulic-cylinders

3 table information taken from https://www.newport.com/, and http://www.thorlabs.com/navigation.cfm

4. Car lift example for internals of vertical column :http://www.eagleequip.com/product/MTP-9F.html?gclid=Cj0KEQiA1NWnBRDchObfnYrbo78BEiQA-2jqBdzLaFFaitNgOveI1WhQlUSA6KsHiuyIZo_gKYt6wagaAlbH8P8HAQ


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