Open Ventilator Design and Production

One of the very interesting things about our response to covid19 has been to watch who responded, who felt both the need and the capability to help. Now, I don’t want to discount the admirable efforts of the formal healthcare system and its many practitioners, but I want to focus here on people that changed what they were doing and attempted to expand the capability of our society to respond to this pandemic. Seeing Dave Franchino’s post on open hardware design this past week, I’d like to express a few observations, to enumerate some of the breakdowns I saw and preview how my company Mechanomy is working to fix these issues for the next supply chain emergency.

Mid-March, I gave some thought to the improvised/open ventilator efforts and covid, looking to see if I and Mechanomy could help in a way that wasn’t nakedly marketing. I was quickly dissuaded by the disparity between the predictions of impending tragedy in mass media, necessitating significant action, and the lack of any formal engagement from healthcare providers and manufacturers. Locally, I saw a job posting as GE Healthcare stood up 2nd and 3rd shifts, but they were not seeking engineers or really attempting to change their product or design around supply chain shortfalls. Likewise there were no anesthesiologists or other practitioners explaining to the broader world what a ventilator needed to do, what features they can do without, and how they would vet or come to trust non-name-brand solutions. Continue reading “Open Ventilator Design and Production”


Two liter soda bottles are made of clear plastic to show off the product.  They’re pretty robust, surviving shipping while internally pressurized to ~30psi with very few scratches, and are readily available in convenience and grocery stores.

Given reports of ongoing shortages of face-shields for personal protection, we realized that a clear 2L bottle could be adapted into a face shield in ~10 minutes; see our design at GitHub and below.  Now, we have no particular competency at designing face shields but if anyone is facing a need for a face shield, this design is highly accessible.

Instructions for assembling a face shield from a 2L soda bottle.
Instructions for assembling a face shield from a 2L soda bottle.

The key feature is the use of the bottle’s curvature to grip the forehead and to close the mask below the chin, as below.  It lies close to the face, with room for a close-fitting mask, but larger respirators are unlikely to fit.  As I’ve worn it air is limited to flow only around the chin, the close-pressing sides and complete forehead contact prevent flow through the top or sides of the shield.  Visual distortion is noticeable below the waist-level, anything held chest-level and above will be clear.

Ben wearing the SodaShield.
Ben wearing the SodaShield.

We would appreciate feedback or commentary from practitioners and would love Pepsi, Coke, or independent bottlers to join in meeting this need.  If you know people in the medical community that may not have sufficient protection, send them a link.  Stay safe everyone.

Rethinking Disposables

One of the core motivations for our work at Mechanomy is the belief that many of today’s systems are too complex.  While complexity is inherent in every system, a significant portion is incidental to the core problem, added to the system by inefficient business, development, and production processes.
And it is this incidental complexity that the ongoing COVID2019 pandemic is particularly revealing: anecdotes abound of situations that, while defensible in normal times, appear unwise under today’s more trying circumstances.

Take, for instance, CDC’s notice that some ‘expired’ N95 masks remain usable.  While only the manufacturer and the CDC know what actually limits the usability of a mask, it is likely not the critical element of the filter, but rather that the rubber gasket becomes less soft with age and seals less effectively.  Sealing is a critical aspect of a mask, but it is one that might be remedied by tightening the face straps, etc.

When we look at the requirement to wear masks, then, we see that the requirement’s sensitivity is not expressed, modeled, or known (publicly). We don’t appear to know how the masks’ effectiveness degrades with time: I would expect that, when new, a N95 mask (95% of particles are filtered out) actually filters, say, 98.5% of particles and that the 95% is only reached at the designated expiration date (the design life of the mask).  That’s a slow degradation curve, 3.5% reduction over, say, 3 years; if the alternative is no mask at all, that expired mask is still useful. Continue reading “Rethinking Disposables”

Telling the Future: Frank

I appreciated Oleg Shilovitsky’s vignettes on the future of system development and use; at Mechanomy we are also trying to enable this future of mass personalization and programmatic manufacturing.  In turn, I’d like to tell you the story of Frank.

Frank has a problem. As he was leaving the worksite last Friday he noticed an old, battered satellite core.  Frank’s predecessors had long since harvested its solar arrays and antenna for their readily accessible constituents, but they left the core to be buried behind other assets.   Now that the backlog has been cleared it’s his job to ensure that the core has been safed and to classify it for materials recapture.

Continue reading “Telling the Future: Frank”

A Tour of Modelica

This is the first of a recurring series touring the capabilities and features of Modelica, a systems modeling language that we have great hopes for.

Where to begin?

At its core, Modelica is a programming language that allows users to write down equations that describe the behavior of some system.  In this usage, system refers to some group of things that interact according to identifiable rules.  A robot arm is a ready example as it is composed of multiple motors, transmissions, sensors, and rigid structures.  The interactions of these elements are described by equations that convert the user’s digital command signals into electrical currents that spin motors whose torques are modified by transmissions and applied to the arm’s rigid structures.  Taken together, the Modelica model of the robot arm allows the user to predict how the arm will move for given commands, allowing the arm’s suitability for the user’s application to be evaluated digitally. Continue reading “A Tour of Modelica”