Progress Of Group 21 in Capstone
Blog #1
Rotating Barber Chair:
Barbers all over the world spend 40 hours a week on their feet cutting their customers hair. Oftentimes this can lead to fatigue, foot pain, and a host of other issues. If a barber suffers any sort of physical injury that inhibits their ability to move/stand, this makes their lives much harder and hinders their hair cutting performance. We aim to create a barber chair that resolves any of these potential issues so barbers no longer have to worry about standing and moving around their client when they cut their hair. This would also address the physical back and ankle pain barbers endure from years of standing. Our modified barber chair will include a regular chair for the client to sit just like a regular chair would work. This chair that the client is in will always remain statically planted on the ground unable to move. We will then include our main modification where we have a second chair that is connected to the base of the static client chair. This second chair will be able to rotate around the clients chair with a range of motion of 360 degrees. This is where the barber will sit.
Our team is addressing the specific problem of physical discomfort and pain that comes from standing for long periods of time. The system needs to compact but also grant the barber enough room to cut hair and do his thing.We are unsure of what the space constraint will be as we are still doing research on this. However the chair must be able to rotate 360° degrees so that the barber can cut the clients hair from any angle needed. Both chairs need to maintain vertical adjustment so it may be used for barbers and clients of different heights.. The chair's distance from the client to the barber also needs to be adjustable to maximize the comfort of the barber when cutting hair. The chair attachment must be stable and rigid to hold the weight of different barber weights. We aim to hold a barber with the maximum weight of 220 lb (100 Kg). In order for the chair to stay upright the chair must be able to resist large moments.
However creating some sort of mechanism that allows the barber to sit and relieve pressure off their back and ankles has a few challenging obstacles we aim to overcome. One obstacle we will have to overcome is allowing the barber to easily adapt to the change of sitting but also being comfortable while cutting hair. The mechanism also has to be safe for both the client and barber. Creating a stable and safe system will be critical to the success of the project. This system also needs to be adjustable so different barbers and different clients are able to comfortably and safely sit in the chair. We look forward to overcome all those challenges and create an mitigated risk of injury for the certain industry.
Visualizing our concept:
Blog #2
Physical Constraints & Challenges:
Technical Problem Statement:
- We aim to build a chair that enables any reasonably sized barber to effectively cut hair as if they were standing. This poses several technical challenges. Building mechanisms that allow the barber to easily change his distance, angle, and height above/below his client mid cut is quite the challenge. All while being confined to a booth size of 8x8 feet which is only slightly larger than the average booth size standing barbers typically cut in.
Technical Analysis:
1. Statics analysis – analysis of the stress expectations on the static components that meet our weight safety goals. Using Finite element analysis the weight of the barber and the weight of the attached linkage system will be considered as forces on the chair frame.
2. Dynamics analysis – analysis of the forces required to rotate the attachment chair with max weight, also keeping in consideration friction forces that may come from the ground.
3. Materials analysis – analysis of material properties on candidate materials to create linkage systems. Analysis based on material strength, durability, availability, and budget constraints, analyzing the ideal material that meets these goals.
4. Fatigue analysis – Fatigue life of variable load bearing components (DME). Static failure analysis for components that bear static loads during operation (DME). Beam deflection (DME) for our component that connects the Clients chair to the Rotating Barber Chair. Bearing Life calculation (DME) for our rotating components that require bearing.
Soft Challenges:
- One soft challenge that needs to be addressed is the connection points of the various components. We have established some connection points such as the shaft/cantilever beam connecting the clients chair and barber chair to be welded together but this will not work for all connecting points. We will need to consider other connections such as bolts and nuts for connection points that do not provide welding as an option.
- Another challenge that may arise is lubrication between all the swivel points. We will need to make sure they are properly lubricated to make sure they offer smooth rotation. If not properly lubricated this may play a role in how usable the system is.
Barber Assessment:
Blog #3:
Current Progress
The team consulted with the UH machinist, Jamar Murray, who informed them that the original bearing planned for use would not work with the client chair shaft they had purchased. This was due to the fact that bearing the team originally envisioned fitting onto the shaft was almost 6 mm less than the shaft (shaft diameter: 50.8 mm original bearing diameter: 45mm) which is far too large of a margin for thermal expansion to account for, according to the machinist. Instead the machinist advised the group to purchase a bearing that is at least 5-6 mm larger than the shaft so that he could machine a sleeve that served as a buffer between the shaft and the bearing. The sleeve would have roughly the same ID as the shaft, 50.8 mm, and would be screwed onto the shaft to secure it on. The OD would roughly match the ID of the bearing the group decided to purchase so that the bearing could be press fitted onto the shaft. Additionally, Jamar cautioned against the intended method of using an induction heater to attach the bearing to the shaft, as it could potentially affect the functionality of the bearing.
The team went to Intech Bearings, a local bearing shop right off of I-45 on the north side across from campus, to purchase a new bearing. The team walked away with a new 60mm ID bearing, they were unable to find a 56 to 57 mm ID bearing that was the machinists first recommendation but 60mm was that second option so the team settled for that.
This means that the thickness of the sleeve would need to account for the 9.2mm difference between the bearing the team purchased (ID: 60 mm) and the shaft the team wants to fit the bearing onto (ID: 50.8mm). The exact dimensions for the sleeve need to be confirmed by the machinist, so the group will need to set up another meeting to iron out those details. The team knows from the meeting that the maximum difference between the OD of the collar and ID of the bearing should be less than 0.008 inches or 0.2032 mm and they figure that they would want the bearing to be slightly smaller, meaning the collar should have an OD slightly larger than the shaft ( 60 mm< Collar OD < 60.2032 mm) so that it squeezes onto the shaft and remains secure there, but they are still unsure of that detail as it is a question they didn’t think of the question until after the meeting was over. Below is the CAD of the sleeve.
The machinist recommended that the sleeve should be made out of Aluminum 6061 and that the team should try to buy an aluminum 6061 collar as close to the designed dimensions as possible and if they could find an exact match that was great, less work for him, but he highly doubted that the team would, so he said they should just get a sleeve/collar whose ID 50.8 mm or lower (shaft OD: 50.8 mm) and whose OD is 60 mm or higher (bearing ID 60mm) and that he could machine the difference to make it fit. The machinist recommended going to either Morris Metals or Metal Supermarket to find a viable sleeve/collar so the team will need to take care of that in the next week. With the bearing bought, the team was able to finalize the dimensions for the clamp that was designed to fit onto the outside of the bearing so that it could be connected to the shaft. They were also able to print a prototype of the clamp to see if it would successfully clamp onto the bearing without falling off, which was a success. Pictures of the prototype and the clamp with dimensions can be seen below.
The team was also able to draw a CAD of the client chair design which has now been finalized now that the bearing has been purchased. The only dimension that is not exactly known is that of the collar, mentioned earlier, but the range of uncertainty is so small the design is all but finalized and since that decision is in the machinists hands the work on the teams end is done all they need to do is meet with the machinist again to confirm the last dimension. Creating a CAD of the system gave the team a concrete idea of the maximum and minimum height of the client chair and the base radius so that the team can design the barber chair around it to meet all of the system's physical constraints, especially the movement specifications. The CAD drawing of the system can be seen below, dimensionless, and with dimensions, at max and min heights.
With this set in stone the group looked up some anthropometric data to see how effective the adjustment ability of the client chair would eliminate the variation in client sitting height. The group found a study from Stanford for the average US adult sitting in a chair and used this data as their basis in the range for tallest possible client, from the top of the seat to the top of the person’s head, and shortest client, also from the top of the seat to the top of the person’s head. The aforementioned dimensions came from row 8 of table below and are pictured in the image below that. The calculations are also included with the accompanied data, results will be discussed below the image. The team wanted to find the lowest and highest client heights with the distance being measured from the ground the client chair rests on to the top of the clients head. For the lowest height the team adjusted the client chair so that it would be as tall as possible and then added the distance for a female in .15th percentile for category 8. For the highest height the team used a 99.85th percentile male and the lowest possible client chair setting.
After crunching through the numbers the team found that when using the 8 inches of adjust ability designed into the client chair height they could shorten the range between maximum and minimum client top of the head to the ground heights to only a three inch difference which the group was quite pleased with. Of course this is not the only variation that the team needed to account for as they were curious about what would happen at the extremes: when a really short barber is cutting a very tall person's hair and when a very tall barber is cutting a short person's hair. After studying repetitive behaviors of barber, and asking our personal barbers the group determined that the optimal cutting height for barbers is for their sternum (chest) to be about even with the top of the clients head. The team then wondered how high the barber chair would need to go for the shortest barber to be able to cut the tallest client's hair in this configuration. The group also wondered how low the barber chair would need to adjust so that the tallest barber could cut the shortest client's hair at this position as well. The team figured that if the systems worked at these extremes then it would work for any other client barber combo in between. The team could not find data for sitting height from the top of the chair to the mid chest but they found data in the same study that measures from the top of the chair to the top of the shoulder (see 10 below) so they used this and just subtracted three inches from the heights, which they figured put the measured height at about mid chest.
The calculations below show the results:
After running through the numbers the group found that the height of the barber chair, from the ground to the top of the chair, would need to be 42.17 inches for the shortest female barber to cut the tallest male client's hair where her chest was at the top of his head. On the flip side of things the team found that the lowest the chair would need to go so that the tallest male barber could cut the shortest female’s hair where the top of her head was at his mid chest was 31.26 inches. This means that the team would need to design a barber chair with roughly 11 inches of vertical height adjustment with a minimum height, ground to chair top, of 31.2 inches and a max of 42.17 inches. The group now has to decide to what extent they want to meet these extremes. 42.17 inches is quite far off the ground and might be a bit unnecessary for most use cases. It also might be hard for someone with a lower body injury to get up that high to sit down which is an important use case of the project. For those just looking to get off of their feet it would not be an issue. The team could just include a stepping stool to help shorter or less mobile barbers get up that high. Now that the team knows the exact numbers they know that it will be necessary for the barber chair to have an adjustable height range which changes the design a bit as the group had gotten rid of the height adjustment in the barber chair about a month ago in an attempt to simplify the design but after going through the numbers it is clear that this is no longer possible if the team wants to meet their initial constraints/specs set at the beginning of the semester. This should not be too big of an issue. The group can likely purchase a chair base with around 10 inches of adjustability and then add on their own designed components like the designed rail system to customize the chair to their liking.
Future work the team needs to complete in the next two weeks
By 4/19 the team plans to have milestone 1 completely accomplished. All design components of the system will be finalized. This includes the proper dimensions for the adjustable rails on the barber chair, shaft dimensions, bearing-shaft-clamp dimensions,& the wheels that will be used.
The tasks that have been completed are: Design mechanism for barber adjustment ability, procure client chair, select bearing fitting needs, and how components will connect together, and designing the bearing-shaft connection bracket.
The tasks left to accomplish milestone 1: Suitable base for client chair, procure a barber chair, and finalize shaft length and diameter for connecting both chairs.
Other miscellaneous tasks the group needs to take care of that have come up due to unexpected problems/changes or development in the project. Meet again with the machinist, preferably next week, to update him on the team's progress and set a date to give him all of the materials so he can set the collar on the shaft and the bearing on the collar for the team. The team also needs to determine the shaft length that will connect the two chairs and they need to finalize their design for the barber chair. At this point the team understands exactly what they need their barber chair to do and they have designs for specific components to meet these functions they just need to blend all of these together into a single chair that can be attached to the shaft. The team also needs to find an aluminum sleeve for the machinist to use to press fit the bearing onto the shaft. Once all of this is finalized the group needs to order the parts that fit their design. Once this is done the team needs to perform more force analysis on the components they have designed and do some slipping and tipping calculations for the system. Specifically they need to calculate, factor of safety for base bolts, bending of the rail system at extremes, and factor of safety for the bearing (fatigue life).
Obstacles and Challenges the Team will face in the next 2 weeks
A big challenge the team faces is finding parts that blend with their designed components while also ensuring that when they are blended together that the final system fits all physical specifications and constraints. This has been a tough issue for the group the entire project because of how unique their product is. The group has been trying to find parts online from chairs that come unassembled that can fit their vision and work around other unique parts they have had to design. The group has found that sometimes it is better to commit to buying some parts and then simply figuring out a design that works around it using 3-D printed and machined components. For the barber chair the team is considering buying another unassembled chair so they can use the wheels, the shaft, and its built in vertical adjustability. On top of this the team still needs to add a platform for the rails to mount onto that is compatible with the purchased shaft and another platform that can attach to the top of the rails, so the chair seat can slide forwards and backwards, and figure out a way to mount the seat on this platform. These are the immediate challenges the team faces when designing the rest of the barber chair once this system has been finalized that will complete the initial design. Then the group will need to analyze the system to ensure that there are no holes in the design before they start really accelerating the fabrication phase of the project. Some smaller issues that will not make or break the design are also listed in the next paragraph.
As we proceed with the project and move out of the designing phase and into the assembling phase, our team anticipates encountering a couple of important challenges related to our designed product. The first issue is with the mobility of the barber’s chairs wheels, which may not roll as smoothly as planned on certain rough surfaces or surfaces with ridges. To address this, we are opting for chairs with wheels of an exceptional grip and a larger diameter, which will enhance mobility on various surfaces and overcome the possible ridges in the floor. Another concern is maintaining the optimal working distance for the barber compared to the client's chair, to ensure the barber works comfortably. Our solution involves adjusting the height of the client chair, which would be simpler due to it being stationary, also since the barber's chair will remain adjustable. This approach allows us to accommodate different heights and maintain comfort without significant alterations to the chair designs. As a backup plan we would possibly purchase a client chair with a shorter shaft, or use a high top stool with wheels as the barber chair. However these issues might appear later on while assembling the product, as of now in the designing stage there seems to be no issue with the height adjustment ability.
Our biggest concern was connecting the bearing onto the shaft. This seems to be resolved after consulting the machinist.
Blog #4:
Work Progress:
In the past 10 days, group 21 has been actively engaged in various tasks aimed at furthering the objectives of our capstone design project. In this time period the key activities we have completed are Analyzing all forces on our barber chair design components, analyzing material for the components of the device, and conducting push forces for our device’s movement. Work we still have in progress includes analyzing slipping and tipping forces, bearing fatigue life, and finalizing our budgeting.
Key Components of our Design:
Our main goal with this barber chair design was to solve issues that barber chairs face standing 30-40 hours a week. This issue comes with a substantial amount of aspects that make their work less sufficient such as injuries mainly in their lower backs, legs, and ankles. Our design tackles that issue with reducing standing time significantly making it an option to stand up while working rather than a requirement. The bearing connects an additional chair for the barber that is adjustable in all three dimensions (x,y, & z) all while being able to retain the ability to have the barber work efficiently.
Important Analytics:
Important analysis we have made which shows the effectiveness of our device are the forces it takes for the barber assuming even at the highest force required (when the barber is 300 lbs) the force to rotate the barber chair would approximately be under 137 N when it is static and under 63 N when it is kinetic. Another key component of our analysis would be the Factor of Safety of our barber chair rail system which allows the barber to move closer and further away from the client. The FOS resulted in a value of 41.2 which is significantly higher than our aim of FOS=1.5.
Kinetic Force Validation: Static Force Validation:
Upcoming Work plan:
Our group plans to utilize our time in the summer to get a head start before our Capstone II. As we are in progress of procuring all of our device’s materials at the moment, we plan to have all our machined device components to be completed prior to our Capstone II during the summer, and all of our 3D printed components to be printed allowing for any adjustments to be made prior to our assembly. After hopefully completing those tasks we have in mind, if time is available we aim on beginning the assembly process to gain familiarity with our device and possible issues that may appear during the assembly process to conduct a fair amount of problem solving.
Finalized Design components:
These components shown in the figures below are some components of our finalized device to show our progress before our group starts manufacturing components that have not been manufactured or machined yet and assembling the components afterwards. (To see more figures of our components, see previous Blogs)
Rail System Prototype:
Connecting Shaft: (Dimensioned)
Top Plate for Rail (dimensioned)
Bottom Plate for Rail (Dimensioned)
Blog #5
For the work period of August 19 - September 6, what work toward your team's project has been completed? Please provide a description of tasks that are completed, as well as tasks currently in progress.
During this work period we have 3D printed our prototype for the base-shaft adapter that connects the base and the shaft of the chair together. From printing the prototype we encountered a slight gap in the shaft connection. We revised the diameter to fit the shaft more snuggly. The final adapter is currently in the process of being printed. The team has also worked on sourcing the appropriate drill bits that are capable of drilling through the steel to create holes for the adapter to bolt to the base.
For the work period of September 7 - September 20 what is your team's plan for near term work? What major milestones does the team hope to achieve in your work?
For the next work period the team plans on assembling the base and the shaft of the chair together. The team also will source the connecting shaft and print the final 3D printed bearing-shaft adapter. The connecting shaft and adapter can then be tested for fitment.
What obstacles does the team foresee in your project work over the next two weeks? What solutions does the team have in mind and what back-up plans does the team have?
Some obstacles the team foresees are issues with assembling our manufactured parts while finalizing our device. These issues could be where our custom manufactured parts would need remodeling due to fitment issues or functionality issues.
Provide at least 3 figures to show the concrete progress and current status of the team's work. Please refrain from presenting your team's Gantt charts and from providing only photos of acquired materials with no further work.
Blog 6
For the work period of September 6th - September 20th the team was able to fully assemble their first model of the client chair. The team first had to connect the shaft of the client chair to the base via the adapter, which needed to be bolted down to the base. The team drilled four holes in the steel base on the evening of the 19th, but the tap and die kit broke and they had to wait until this morning to buy a new kit and thread the four holes.
Once the team got this done it was smooth sailing in terms of installing the rest of the chair on top of this. The team ran into only one issue, albeit a major one, when testing the integrity of the newly assembled client chair. This issue is the stability of the client chair. The adapter was only printed at 20 percent infill due to the excessive amount of material needed to print at denser infills and the increased likelihood that the print will fail. This backfired on the team as the adapter's upper walls that secure and stabilize the client chair shaft in place are too weak and they bend fairly easily when the person sitting in the chair leans back or side to side. This can be seen in the video below.
The team will be spending the work period from September 20th to October 13th trying to figure out how to fix the issue right now the main two solutions being considered are adding external supports or reprinting a new adapter with a higher infill density and hoping it will be much stronger. Aside from this the team would like to start ordering the rest of the parts they need to build the barber chair as well so it can stay on schedule there too
BLOG 7:
For the work period of October 13 - October 25, our team has been assembling and testing our 3D printed parts, with the majority of the focus on the rail system. While drilling and threading the holes required. We have currently completed almost half of the holes required for the rail system to be drilled and threaded; however we are currently waiting for the remaining parts to be 3D printed, they should all be ready by this weekend/early next week so that the team can assemble the prototype. (Assembly includes drilling and threading a steel plate). Figure 1 shows our end product. And Figure 2 shows our progress as of today. The team also 3-D printed and tested their clamps on the bearing and the shaft of the barber chair, both were successful fits
Figure 1:Final Rail Design
Figure 2: Current Rail Progress
For the work period of October 25 - November 9, We plan to have the demo device complete by the 29th of October and are hopeful for a successful demo test. October 29th through to November 9th our group hopes to analyze our completed demo device, finding design improvements/changes we can implement on the device and validating the core functions of the system outlined in the validation plan. The team has already drilled and threaded 26 holes and the team still needs to drill and thread 26 more holes. If all these holes are successfully drilled and threaded into the top and bottom plates at the correct locations the team should be able to fully assemble a fully functional prototype by this wednesday. The main challenge here is going to be making sure all of the holes are aligned correctly relative to each other. The team is confident they can execute on this.
Challenges we faced recently are screws obstructing the placement of our sliding blockers in our rail design on the steel plate. To fix this we plan to readjust the design of our sliding blocks to face our unexpected challenge. The width of blocks, seen in Figure 3 below, was 2.75” which turned out to be too wide, as the gap on the top plate for the blocks to fit in is on 2.25”. The blocks were also too long so the team shortened their length from 9” to 7” as seen in Figure 3 and Figure 4 below. Another challenge the team faced was drilling and threading the holes. Initially the team was using a very efficient technique when trying to drill and thread properly aligned holes in their steel plates. Long story short they were not pressing hard enough and they were spinning the drill too fast which was causing excessive heating at the drill bit tip contact point which was stripping the drill bits very quickly ruining them. The team, using this poor technique, drilled only 8 threaded holes in 5 hours. The team then adopted a new technique where they drill pilot holes, holes of a smaller diameter, by pressing very hard and spinning the drill slowly, the team then did the same with the larger drill bit to increase the size of pilot holes. This new process was much quicker and allowed the team to drill and thread 20 holes in about 1.5 hours.
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