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Project 2: Modified Desk

Abstract

The goal of our project is to create a custom desk that can accommodate a child that has a tracheostomy and is on a ventilator. The desk must have the ability to change its height to accommodate when the child is standing or sitting on a chair or couch.

Michael Khalil, Joshua West, Hugo Morales, Michael Lumsdaine, Michel Habib

Problem Statement

Our child has a tracheostomy, a ventilator, and is overall quite weak. She is homeschooled and gets anxious, distracted, and uncomfortable while working on schoolwork. She needs something that can make her comfortable and allow her to change position (standing, sitting on a couch, and sitting in a chair). We are considering any other features that will make the desk convenient and help her focus.

Design Specifications

  • The desk must raise and lower (24” up to standing height) 
  • Must be able to be pulled up to a couch 
  • Portable 
  • Ability to Disassemble 
  • Ease of Use 

Background Research

This project, because of its one degree of motion, gives a lot of different ideas to consider. Items like linear actuators and hydraulic pistons are used every day to raise and lower items. We have also investigated mechanical systems like gas lift cylinders and trailer jacks are notable examples of entirely mechanical systems that raise and lower objects. Aside from the methods by which our desk will raise and lower, we have researched methods that keep it portable and easy to move, such as hard or soft floor casters.

Concept Design 1

Table base using linear Actuator:  

This table will raise and lower through a mechanical system using a twelve-volt power source. This idea uses a free-flouted tabletop that will use gravity to decrease in height. This design also has the ability to be stored easily because of the construction.  

  

Pros: 

  • Fairly easy to assembly 
  • Lot of information about linear actuators  
  • Easy to raise and lower 

 

Cons: 

  • There could be noise 
  • Electrical components could be challenging 

  

Materials: 

  • Wood  $30
  • Metal  $190-230
  • Linear actuators  
  • Power converter   (All three) $180
  • Two direction switch 

Total Cost  $370-410

Concept Design 2

By utilizing a prefabricated frame with fully integrated electrical components, this design not only simplifies the setup process but also ensures a safer and more user-friendly experience. This approach frees up valuable time, enabling us to concentrate on enhancing the desk with additional features that will benefit our child. 

Pros: 

  • Cheap 
  • Safe 
  • Easier to use  
  • Minimal noise  
  • Gives us time to add a number of extra features. 

Cons: 

  • We may have to do modifications to the frame (cutting and welding) 

Materials: 

  • Frame  
  • Desktop 
  • Wheels 
  • Wood for extra features 

Cost:

  • Frame: $170
  • Wooden Top: $90
  • Casters: $17

Total Cost: $277

Concept Design 3

Crank

The crank design would require two legs that could telescope via a crank connected to a worm gear in the legs. 

Pros: 

  • Cheap 
  • No electrical worries 

Cons: 

  • Annoying to use 
  • The most mechanically complex (no reliance on electronics) 

Materials: 

  • Crank 
  • Gears and connecting beams 
  • Telescoping legs 
  • Desktop 
  • Wheels 

Selected Concept Design

We decided to go with the prebuilt desk frame.  The major benefit of building our own frame is that it would allow us to tailor it to Kiera’s exact needs.  We couldn’t find a prebuild desk frame without issues (such as being too tall).  But, after much thinking and discussion, we decided the issues with the prebuilt desk frame were navigable and that choosing it would likely save time and money.

Decision Matrix

Overview of Selected Design

Our final design consists of a few changes from the preliminary design. First, the parents agreed that the desk being slightly oversized is better than cutting and risking damage to the frame. So, our desks will use a quality frame to expand on. We tried to keep the height as low as possible while keeping it mobile and sturdy. By using side-mounted casters we can keep the desk at a minimal height, and we have picked a chair that will raise her high enough to use the desk. Second, the keyboard desk pull-out will allow her to sit on the couch and still use the desk. Finally, attachments for storage will be added to further improve the function of the desk.

Describe Design Details

A major want of the family is easy disassembly, so we have made decisions on pieces to make this easier. To note, some of the pieces will remain attached permanently because of cost.

 

The pieces are as follows:

  • Adjustable Desk Frame
  • Side-mount Casters and mounting Brackets
  • Butcher Block Desk Top
  • Epoxy-coated MDF Extension Tops
  • Book Cabinet Brackets
  • Keyboard Desk Slides
  • Chair

 

Working from the ground up. The casters will be attached to a custom bracket mounted to the side of the leg assembly. By using these side-mounted casters we will cut the height down by approximately 2”. 

 

Then, we decided on a quality frame that has dual motors that will hold plenty of weight with a nice butcher block desk top for a clean modern finish. This will be attached to the frame with threaded inserts to make disassembly easier. 

 

Finally, storage will be made through the addition of under-mounted shelving and 3D-printed products that will give a sense of customization to the end product. The project will be finished with some artistic details that will make the desk hers. 

 

Engineering Analysis 1

We measured the stress on the top of the table (0.195 lbf/in^2) and the stress on both legs of the desk (17.5 lbf/in^2) for each leg.

Engineering Analysis 3

For our third analysis, a simulation was ran on SOLIDWORKS over how well our intended final design would withstand forces acting on the desk surface.

To run this simulation we determined and approximated what materials our desk parts would be made out of:

  • Desk Top Surface: Hevea Wood
  • Pull-Out Desk Top: Medium Fiberboard
  • Desk Frame: Annealed Stainless Steel
  • Book Brackets: Steel Alloy
  • Caster Fasteners: Cast Iron
  • Casters: Steel Alloy

Once we picked out the representative materials of our parts, we then ran the static simulations we intended.

First we ran a simulation with a 225 lb load distributed across the desk surface. This was to evaluate our desk’s displacement when subjected close to the maximum load that the frame was presented to withstand.

The second simulation we ran used a more commonly thought load of 30 lb across the desk surface. This was so the desk’s displacement could be evaluated when under the load of school books and a laptop.

CAD Drawings

Bill of Materials

Semester

2023 Spring