Fall 2020 Design I Final Competition

Section C: The Last Airbenders

Solution Summary: How can we decrease the transmission of viruses indoors by updating existing systems to decrease the aerosol spread of Covid-19?

Team Members: Blake Kneebone, Ryan McDermott, Ryan McDermott, Abraham Sitanggang, Austin Spaulding and Nathan Taylor

Instructor: Bridget Wetzel


  1. Dear team The Last Airbenders, thank you for an engaging presentation. The last part was a bit unexpected. But I suppose it is a good demonstration of how your product works. Have you looked very closely on the pricing and do you think that your product can be installed with under $100 per unit? I am curious about maintenance and . Also, who did you speak to regarding your product? What type of feedback did you get from your stakeholders? Finally, your product serves well for people that are able-bodied. What type of modifications are needed for people with disability/accessibility issues?

    • In our pricing report shown in the video, we determined that our product could be produced for under $100 per unit. Because we had included an engineering overhead fixed cost, this price would actually go down proportionally with a higher quantity of products sold. Colorado School of Mines contains roughly 300 toilets scattered throughout all of its buildings. However, half of the publicly accessible restroom stalls are closed off due to capacity restrictions. According to our cost analysis, it would cost $72 per toilet and $14,400 for 200 toilets; an important acknowledgment is that this also includes the $8,000 engineering overhead fixed cost. Finally, it would take less than 24 man-hours to install all of the lids.

      • This is question 1 and refers to the installation cost.

    • 2) Maintenance
      An average toilet seat and lid have a minimum life-span of 5 years. Because the lid closes softly and won’t require human interaction, it will likely be extended. In addition, the product is extremely modular so it will be easy to replace our product-specific-components and even easier to replace the standard parts.

      To address the cleaning side of maintenance, we determined that the addition of a lid wouldn’t affect a custodial worker. The cleaning process associated with the lid would consist of spraying disinfectant and subsequently wiping it down. Since our design is enclosed in a housing that sits above the flush aerosolization zone, there is no risk of electronic water damage.

      An interesting note is that there is a lot of janitor-induced cross contamination in public restrooms. Because the infected flushing aerosols are constrained within the toilet bowl, custodial workers will be able to clean with a reduced danger of contracting an illness.

    • 3) Stakeholders and Feedback

      We spoke to the following stakeholders:
      The Associate Director of Environmental Health and Safety at Mines, Timothy Sweitzer
      Assistant Director of Environment Health and Safety at Mines, Lee Ann Underwood
      Custodial Service Manager at Mines, Jesse M. Vigil
      Chemical Safety Officer at Mines, Cory Smith

      Stakeholder Concerns:
      How will the product be powered?
      How durable is it?
      Is Covid-19 transmission via toilet plumes a problem?
      Will it be effective?
      How costly is the design?
      How will it not require additional cleaning?

      These concerns were addressed in the video and in responses to other questions.

      Positive Feedback:
      While there is not yet much research on the number of viral particles produced when using the restroom for Covid-19, for other viruses, like the norovirus, the restroom is a significant mode of transmission. According to Cory, “Preventing aerosolization of these particles from flushing could be huge.”

      Concerning the surface contact transmission of COVID-19 and other viruses, Lee Ann Underwood agreed that the lid needs to be automatic. Otherwise, “people would have to be touching them coming in contact with potentially contaminated surfaces and you are reliant on peoples diligence to close the lid.”

      Timothy Sweitzer noted: “To prevent hand to hand transmission, you are definitely looking at a winning idea.”

    • 4) Handicapped Application

      To preface, the Americans with Disabilities Act of 1990 gives specific regulations for properly compliant handicapped restrooms. This includes things such as handicapped bars, toilet seat dimensions, and stall dimensions. Our product is completely within these regulations and is ADA compliant.

      Concerning the operation of our system, the sensor can be calibrated to a very specific distance; we used a distance that was 2-10cm directly in front of it. When it is pointed at the handle to flush the toilet, the only way to trigger the sensor is to place your hand on the handle in an action to flush. In addition, the retrofitting of the toilet lid and the housing will be securely attached to the base of the toilet and the pipes. These attachments and systems will be able to withstand all non-standard movements. The idea is that our design should not have a significant impact on how the toilets are used regardless of ability.

      Thank you very much for all of your time and questions; we really appreciate it.

  2. Great video, and really interesting and novel final product. I could see this product being used beyond the pandemic, to reduce the transmission of viruses and microbes. My questions are:

    1. Did you reach out to the custodial staff to see what they think about cleaning the bathrooms with this product installed. Would it make their jobs easier or more difficult?
    2. With your cost estimates, did you take into consideration that most bathrooms have stalled closed off due to capacities, so not all the toilets would need this device installed?
    3. Did you have any major pivots when you designed this product? If so, what did you change and why?

    • 1)
      We reached out to the manager of the custodial department at Mines, Jesse Vigil. Jesse’s main concerns were about how the product would be powered and the durability of the design; he didn’t address cleaning.

      In response to his questions, the product will be powered by an extension cord from an outlet in the bathroom. All bathrooms are required to have a ground-fault circuit interrupter outlet that monitors the current flow to ensure safety. The extension cord will simply have a rubber cord cover so it is not a tripping hazard. Additionally, the average toilet seat and lid have a minimum life span of at least five years and since the lid will be closing softly and doesn’t require human interaction, this lifespan will likely be extended. Such a lifespan will ensure that maintenance costs for hardware replacements stay low.

      According to our research though, toilet cleaning mainly consists of spraying disinfectant on contact surfaces and using a toilet bowl cleaner and then wiping down the inside of the bowl. Since our final design will be completely enclosed in the housing unit, there is no risk of it getting damaged by the cleaning process.

      Overall, the product should not have a significant impact on their jobs because it is a touchless product and is open by default. The only potential impact is that it might be advisable for the custodian to also disinfect the inside of the toilet lid. This is not necessary, though, since it won’t actively be touched by anyone. In the event that they did decide to, it would add very little time to their process.

      • I’m happy to hear you reached out to Jesse. He gave you some good feedback. Thanks for taking the time to answer my question.

    • Thank you for your questions and time.

      2) We did not consider that many stalls are closed off due to capacity limits. This would drastically reduce the overall cost of implementation because about half of the stalls are closed off in publicly accessible restrooms, at least on campus. However, due to the design’s benefit to overall hygiene, our product will be beneficial for use in bathrooms even after the pandemic is over.

      • Agree! This would have benefits beyond this current pandemic. Thanks for the answer!

    • 3)
      The first iteration for the design included a retractable toilet lid. The original plan was to have a cover that would extend horizontally from the back of the toilet to cover the bowl of the toilet. We decided to use a traditional hinged lid instead because it was much easier to implement with existing materials.

      Initially, we wanted to open the lid using a motor at the hinge. We immediately ran into the issue of torque and retrofitting. If the motor is at the axis of rotation, it will apply very little torque to the lid; we would need a much stronger motor. It would also have been difficult to connect a motor to the hinge of a pre-existing lid, so we would likely have needed to design our own. Instead, we decided to use a winch. This allowed us a lot more freedom with the placement of the motor and also meant we could apply more force to the rotation with the same motor.

      Since the motor was no longer going to be installed at the toilet lid hinge, we decided that it would be helpful if all of the electronics could be contained in a single housing unit. This would make it easier and faster to install our design and also make it safer and more reliable. There would not be dangling wires running along the toilet or exposed electronics that could be damaged. The most important part of the housing unit was the integrated winch system.

      Our initial plan for the winch was to use a string connected to an eye-hook on the top of the toilet lid. Eventually we realized that there would be a significant problem if the toilet lid ever opened past 90°: it would not be able to close again. Since a winch is tension based, if it opened past vertical, unwinding the winch would only cause the line to get longer and sag. It wouldn’t apply any outwards force to the toilet lid. Our solution for this was to use a tape measure instead of string. Tape measures are specifically designed to maintain a rigid shape when they are extended while still being able to roll up upon retraction. For our design, we cut off a 4ft section of a tape measure and designed and 3D printed our own spindle that was the correct radius for the project and could fit onto the shaft of the motor. The cylinder fits into a specially designed section of the housing

      • Excellent rework! Now I understand how you iterated to your final design. Lots of good changes. Thanks for the answer!

  3. Great video team, and interesting concept. I have a couple of questions for the team based on your presentation:

    How large of a problem do you have? How many toilets in US?

    Great demo, what risks are associated with using a tape winch vs. other modes of raising and lowering the toilet seat?

    You have a great cost estimate for CSM, what would be the price (including margin) you would sell this product for?

    Are there any competing technologies on the market?

    How does this solution integrate with auto-flush systems?

    • 1) How large of a problem do you have? How many toilets in US?

      One of the most important things that we considered is that everyone uses the restroom; in the western world, almost every public place and household has a toilet. This means that our product is applicable to almost every resident in the US. In the US alone, the Plumbing Manufacturer’s Institute claims that there are approximately 225 million toilets in the US. In addition, between 2020 and 2024, business wire says that the smart toilet seat market will grow by $700 million.

    • 2) Great demo, what risks are associated with using a tape winch vs. other modes of raising and lowering the toilet seat?


      -Easy and retrofittable implementation; not reliant on toilet seat type
      -Requires less power and torque compared to a hinged motor
      -Requires less power than a hinged based motor due to torque
      -Does not tangle due to the rigidity and shape

      Risks and Comparisons:

      -It is external, so it may be vulnerable to damage by users
      -The best other option would be having a motor installed at the hinge of the toilet lid. Because a hinged motor isn’t retrofittable and is dependent on the toilet dimensions, this would work better in a permanent, luxury installation.
      -Another option could be a retractable, horizontally extending, toilet lid. This design would also have to be custom made but would effectively create a sleeker design. However, maintenance and installation would potentially be more difficult depending on the design of the lid.

    • Unfortunately, the format of our answers got messed up; Please refer to my new post below.

      Thank you again for your time and questions.

  4. 3) You have a great cost estimate for CSM, what would be the price (including margin) you would sell this product for?

    There are a few important costs associated with our analysis. The first is our $8,000 engineering overhead and the second is our variable labor costs. In our video, we presented that it would cost Colorado School of Mines $72 per toilet. This cost assumed that we had not sold enough product to consolidate our engineering overhead and it also assumed that labor costs would equate to $900.

    Stripping all of the associated costs for a company, each toilet would cost $39.60 for us to produce. Assuming that we would sell our product for $70, the selling marin would be 43%. Not only is $70 significantly cheaper than the alternatives, but a 43% margin is generally considered to be very profitable.

    • 4) Are there any competing technologies on the market?

      The solutions that currently exist on the market are not designed to specifically prevent the spread of viruses. Current toilet sanitization, automatic lid, and boudet systems are specifically applied for domestic use and their high cost, which would not be feasible for commercial businesses. For instance, one of the cheapest automatic toilets was the iTouchless Round Touchless Toilet Seat that cost $183. Finally, the installation of these products are often more difficult and less versatile.
      Ultimately, the goal of the team’s design was to incorporate the positive aspects of each design, easily retrofittable, auto closing with a sensor, and at a low price point. Our design is also extremely versatile as companies can install it for temporary, extended, or permanent use.

    • 5) How does this solution integrate with auto-flush systems?

      This is a good question. Our original design was primarily meant for toilets with manual-flush, but we are aware of the prevalence of auto-flush systems. What would need to happen is that the sensor is pointed towards the user, instead of the handle, like the integrated sensor on the toilet. The only other change is that the program for the arduino would have to close the toilet when the person leaves. The program would keep track of when the distance measured by the sensor increases past the sitting range. Currently, it triggers when the sensor detects an object less than 10cm away, your hand.

      Thank you for your time and questions.