Team Vision for System-Level Design Phase
During the systems design phase of MSD I, team MUSIC set out complete a variety of tasks related to the design of our product in regards to it's functions.
- Create a complete functional decomposition of the product
- Generate concepts through brainstorming and benchmarking
- Generate alternatives and select concepts
- Phase appropriate feasibility and risk assessment
A functional decomposition was generated as a method of determining the subsystems within the design.
Concept Development and Morphological Chart
Functional Decomposition led to an understanding of the different aspects that required design focus. Through independent consideration and group brainstorming, we were able to establish a list of concepts for each function. This was complied in a morphological chart. Feasible combinations were then compared to one another in a series of Pugh charts.
To assist with the Pugh charting process, team MUSIC narrowed considerations, based on discussion, to a limited number of concepts from two of the function categories.
In discussion, the team concluded that creating a Pugh chart with just two of the main categories would be more valuable to analyze to start.
For transformation method, the team chose to analyze:
- Rotate 90
- "Revolving Stage"
- "Garage Door"
- "Gym Risers"
- "Transformer II".
For TV/Exhibit Mounting Solution, the team chose to analyze:
- Removable TV
- Anti-vibration Mounting
- Removable Stage Section
- Lowering it from the ceiling
In order to create concepts, the reasonable ideas from each category of the morphological chart were combined to create system level concepts. These concepts were compared to isolate the best options.
To narrow the amount of concepts generated for a more efficient comparison, concepts were generated from only the 'transition method' and 'TV mounting style' categories. Reasonable concepts were compared against the others using a Pugh chart and the a set of predetermined metrics. This Pugh comparison was performed twice, with a different datum each time. Metrics:
- Ease of use
- Setup/takedown time
- Reliability (number of moving parts)
- Design difficulty
- Cool factor
After discussion, the concepts highlighted in green were selected as the best options to move on and should be considered and compared again with the lift assist system taken into account. The options determined to be the most desirable are listed below.
- Rotate 90 with anti-vibration TV mounts.
- Rotate 90 with a removable stage section the TV will mount to.
- Two small outside sections rotate 90 and expand inward, TV mounts to center wall section.
- Garage door style, TV mounts to fake wall.
The rotate 90 with expanding sides was not in the original Pugh comparison. The team concluded this concept was more feasible than originally discussed following discussion from the first Pugh analysis. The team decided this concept should be added for further comparison.
Pugh Analysis with Lift Assist The lift assist options selected for being the most reasonable options to implement include: helical springs/gas springs translating linearly, torsional springs, and counter weights.
Following this comparison, the concepts listed below were determined to be the best options for this design problem.
- Rotate 90 with anti-vibration TV mounts using springs/shocks.
- Rotate 90 with side stages expanding and using springs/shocks.
- A garage door style using counter weights.
Feasibility: Prototyping, Analysis, Simulation
Feasibility Analysis for Rotate 90° with anti-vibration TV mounts:
- Are anti-vibe mounts within budget?
- Yes. A rubber mount cost ~$10.
- What force does the lift assist need to exert to
maintain the maximum lift spec? Assume 437lbs distributed
evenly over entire 8’x10’ section.
- The sum of the force exerted from the shocks/springs must be 1658lbs (see calculations below) not to exceed 31 lbs of lift force when the stage is creating the greatest moment arm (parallel to floor).
- Using the same assumptions, how much shear force will
the hinges have to resist?
- The sum of the hinges must resist a shear force of at least 2064 lbs (see calculations below).
- Is the cost of gas springs within budget?
- Should consult, but looking through Grainger and McMaster-Carr, we can get gas springs that exert ~200 lbs of force for under $50.
- Is the cost of hinges within budget?
- Need to consult, Grainger and McMaster-Carr show huge range of hinge costs.
- Are gas springs or conventional springs more
feasible? – Should consult.
- To maintain a constant lift of 31lbs, the force the lift assist needs to provide follows a sinusoidal trend, (force applied) = 663*sin(θ) [lbs].
- Gas springs:
- Constant force.
- Can use cams to produce non-linear force applied to stage.
- Idea is to lengthen moment arm as stage drops.
- Use of cams can also help keep the stage in the upright position by maintaining a resistive force.
- Constant force.
- Helical springs.
- Linear force rate.
- Is a linear rate close enough to approximate a sine wave from 0 to 90?
- Linear force rate.
- Should consult over the decision between gas springs and helical springs.
Loading condition feasibility:
- Studs are pressure treated 2x4s
- Vertical studs are spaced 24” on center (standard for stages)
- Two runs of horizontal studs
- Aluminum conduit truss on either side for rigidity
- 7/8” plywood on top surface (for floors)
- Stage extends 100” past pivot point, into the room
- Stage extends 10” behind the pivot point
- This is also where the lift assist force is applied to the stage
Assuming the stage weight calculated above, and the lift assist force is applied 10 inches behind the pivot point, the following loading scenario is represented:
The following calculations determine the force experienced by both the hinge(s) and lift assist.
Conclusion Under this loading condition…
- The total force exerted on the stage by the lift assist system must meet or exceed 1658 lbs. to meet the MIL spec lift requirement of ≤ 31 lbs.
- The hinge mechanism(s) must operate adequately while under 2064 lbs of vertical force.
Feasibility Analysis for Rotate 90° with Expanding Side Sections
- The lift assist should be as feasible as or more feasible than the basic 90 degree concept
- The hinges should cost the same as or less than the ones in the basic 90 degree concept.
- The same lift assist potential energy storage should be feasible as in the basic 90 degree concept.
- The two primary issues unique to the expanding side
section concept are:
- Can the expanding section feasibly hold all the
- The expansion sections would likely be 3’-4’ in width, making 3 total support struts 18” or 24” apart, with 4 legs, which is well within reason.
- Can we make the expanded sections the same height
as the side sections?
- One basic concept has the expansions fold out instead of slide out. This is the easiest way to make the platforms the same height.
- Another concept involves expanding outward and then inserting leaves into the center, similar to the way that variable size dining tables work.
- Can the expanding section feasibly hold all the desired weight?
Feasibility Considerations for Garage Door Designs
- If Pushed from a deployed to a stowed position, would
the stage be sufficiently rigid to move?
- A pulling lift assist would prevent this from being an issue, even if stage wasn’t sufficiently rigid.
- Can lateral motion be prevented, so that the opening
mechanism doesn’t jam?
- Guiding rails could be used, as one solution.
- How tall would the removable section of wall have to
- Variable depending on size of separate stage sections, and geometry of design. If one portion of the garage door stage was 2 feet front to hinge, removable portion would not need to be taller than 2 feet.
- How much space would counterweights require?
- Depends on density of material. Metal counterweights are very expensive, but space saving. Concrete is ludicrously cheap, but weighs 100-150 lb/ft3. 3 to 4 times greater a volume of space would be required when using concrete weights and metal counterweights.
- Could a shelf-available torsion spring be used?
- Some sort of force multiplying pulley system would likely need to be used. Weight for a section could be 300-400 lbs, and torsion springs are typically rated for ~100 lbs.
Murphy Bed Lift Assist Systems
- Murphy beds traditionally fold out of a wall cabinet 90 degrees to be placed in the bed position. This is very similar to the "Rotate 90 Degree" option that can be seen on this page. Murphy beds utilize lift assist systems to aid the operator in raising and lowering the bed. These systems will be benchmarked here to analyze their feasibility for Team MUSIC's Murphy Stage.
Helical Spring Lift Assist
- This usually consist of series of springs that are pulled into tension as the bed is lowered into the bed position. This tension relieves some of the weight of the bed from user while both lowering and raising the bed.
- Can be adjusted by adding or removing springs
- Spring tension can hold bed in upright position without locking mechanism
- Springs are relatively cheap and can be replaced easily
- Noisy during operation
- No safeguard if springs fail
- Springs fatigue over time
Gas Spring Lift Assist
- This lift assist system consists of a single gas spring on each side of the bed that is in a constant state of compression. The compression of the pistons relieves some of the weight of the bed from the user during raising and lowering.
- Quieter than springs during operation
- Total failure is less likely than springs
- Less pinch point hazards
- Use of pneumatic/hydraulic pistons risks leaks of hazardous material
- Usually requires a separate locking system
- Generally more expensive than springs
Click here to view the source of this information.
Quik Stage and similar concepts
The Quik Stage, and other temporary stage solutions like it, is an alternative space-saving stage concept that is simply a stage to pull out of a closet and set up, rather than fold out of a wall.
- Proven, off-the-shelf option, making replacement parts and maintenance easy
- Large amount of customization possible
- Completely out of the way when not in use
- Difficult for one person to set up alone
- Lacks the “cool factor” that the Rochester Music Hall of Fame is looking for in a stage
- Requires closet space to hold
- Setup/takedown takes significantly more time than murphy solution is likely to
- Inspiration and takeaways
- “Bag chair” style support structure is very light and easy to set up
- Separate top platforms are cumbersome to carry and need precision to attach to stage
- Solution needs to exceed this concept in most metrics (baseline)
Garage Door Transformation Method
The garage door transformation method was inspired by the common house-hold item. A few obvious differences are in the orientation, the structure of the item being raised/lowered, and the presence of a motorized lifting apparatus.
- System behaves predictably
- Can easily integrate different lift assist systems
- Torsion springs require specialized maintenance
- System requires rails to guide movement
Table Leaf Expansion Method
- Efficient use of space
- Useable surface is expandable
- Storage keeps leaves safe from damage
- Depending on table size, leaves may be heavy
- Requires additional moving parts to separate table
- Inspiration and takeaways
- Expandable stage sections
- Use existing stage section as storage for added sections
Designs and Flowcharts
Animations of the concepts the selection process converged to are shown below. Click on the individual pictures to view the animation.
Systems ArchitectureSchematic diagrams of the desired concepts were developed in order to solidify understanding of the concept.
After coming to a consensus on a design concept, Team MUSIC revisited the Risk Analysis developed during the Preliminary Design Phase. A few items were added, and some risks were determined to be less relevant through research, or changes in concept. Some of the more noteworthy changes Include:
- Risk of the hinge mechanism degrading, causing the different portions of the stage to separate or overlap. It was decided that this was more likely to be an issue, because the team may have to implement a customized solution, that would bear a lot of weight. It was also decided that this would be less severe than initially thought.
- A concern that emerged more fully was the possibility of the wall mount failing. This is a now a greater consideration, as the team has become aware the supporting wall is constructed with metal studs, so stable attachment requires specific hardware, or methods.
- One risk that has been diminished is the lack of outside meeting times. While this has required extra effort, there hasn’t yet been a time when the team has been unable to arrange meeting with at least some members when the need has arisen.
- Something that has been considered that was unthought of previous to feasibility research is the consistency of lift-assisting force. The risk here is that, if force is properly calibrated for stowing, it might be too great, or too little for deploying.
Link to live document: here
Design Review Materials
Plans for next phaseGantt Chart for Systems Design phase
Links to individual 3 week plan: