Fight Disease With A Raspberry Pi

Despite the best efforts of scientists around the world, the current global pandemic continues onward. But even if you aren’t working on a new vaccine or trying to curb the virus with some other seemingly miraculous technology, there are a few other ways to help prevent the spread of the virus. By now we all know of ways to do that physically, but now thanks to [James Devine] and a team at CERN we can also model virus exposure directly on our own self-hosted Raspberry Pis.

The program, called the Covid-19 Airborne Risk Assessment (CARA), is able to take in a number of metrics about the size and shape of an area, the number of countermeasures already in place, and plenty of other information in order to provide a computer-generated model of the number of virus particles predicted as a function of time. It can run on a number of different Pi hardware although [James] recommends using the Pi 4 as the model does take up a significant amount of computer resources. Of course, this only generates statistical likelihoods of virus transmission but it does help get a more accurate understanding of specific situations.

For more information on how all of this works, the group at CERN also released a paper about their model. One of the goals of this project is that it is freely available and runs on relatively inexpensive hardware, so hopefully plenty of people around the world are able to easily run it to further develop understanding of how the virus spreads. For other ways of using your own computing power to help fight Covid, don’t forget about Folding@Home for using up all those extra CPU and GPU cycles.

A Simple LEGO Automatic Transmission

The automatic transmission in your average automobile can be a complicated, hydraulic-y thing full of spooky fluids and many spinning parts. However, simpler designs for “automatic” gearboxes exist, like this Lego design from [FUNTastyX].

The build is based around a simple open differential but configured in a unique way. A motor drives what would typically be one of the output shafts as an input. The same motor is also geared what would normally be the main differential input shaft as well. In these conditions, this double-drive arrangement would sum the speed input and lead to a faster rotational speed at the other shaft, which becomes the output.

However, the trick in this build is that the drive going to what would be the usual differential input is done through a Lego slipper clutch. This part, as explained by [TechnicBricks], allows the outer teeth of the gear to slip relative to the shaft once torque demand is exceeded. What this functionally does is that when the output of the “automatic gearbox” is loaded down, the extra torque demand causes the clutch to slip. This then leads to only one input to the differential doing any work, changing the gear ratio automatically.

It’s likely not a particularly efficient gearbox, as there are significant losses through the very simple clutch, we suspect. However, it does technically work, and we’d love to see its performance rated directly against other simple Lego gearbox designs.

It’s a little confusing to explain in text, but the video from [FUNTastyX] does a great job at explaining the principle in just a few minutes. We’ve seen plenty of crazy Lego gearboxes over the years, and we doubt this will be the last. Video after the break.

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Harmonic Drive Uses Compliant Mechanism To Slim Down

[Levi Janssen] has a secret: he doesn’t like harmonic drives. But rather than abandon the torque-amplifying transmission completely, he decided to see about improving them using 3D-printed compliant mechanisms.

For the uninitiated, harmonic drives, also known as strain-wave gears, are a compact, high-torque gearbox that has become popular with “robotic dog” makers and other roboticists. The idea is to have a rigid, internally-toothed outer ring nested around an externally-toothed, flexible cup. A wave generator rotates within the inside cup, stretching it so that it meshes with the outer ring. The two gears differ by only a couple of teeth, meaning that very high gear ratios can be achieved, which makes them great for the joints of robot legs.

[Levi]’s problem with the harmonic drive is that due to the depth of the flexible spline cup, compactness is not among its virtues. His idea is to couple the flex spline to the output of the drive through a flat spring, one that allows flexion as the wave generator rotates but transmits torque efficiently. The entire prototype is 3D-printed, except for the wave generator bearings and stepper motor, and put to the test.

As the video below shows after the excellent introduction to harmonic drives, the concept works, but it’s not without its limitations. Even lightly loaded, the drive made some unpleasant crunching sounds as the PLA springs gave out. We could easily see that being replaced with, say, a steel spring, either machined or cut on a water-jet machine. That might solve the most obvious problem and make [Levi]’s dream of a compact harmonic drive a reality. Of course, we have seen pretty compact strain-wave gears before.

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Peeking Inside A VW Gearbox Reveals Die Casting Truths

Recently, I was offered a 1997 Volkswagen Golf for the low, low price of free — assuming I could haul it away, as it suffered from a thoroughly borked automatic transmission. Being incapable of saying no to such an opportunity, I set about trailering the poor convertible home and immediately tore into the mechanicals to see what was wrong.

Alas, I have thus far failed to resurrect the beast from Wolfsburg, but while I was wrist deep in transmission fluid, I spotted something that caught my eye. Come along for a look at the nitty-gritty of transmission manufacturing!

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LEGO Delivers Corvette Experience On A Budget

Many dream of tooling around in a high performance sports car, but the cost of owning, maintaining, and insuring one of them make it a difficult proposition. While this LEGO version of the Corvette ZR1 might not beĀ exactly like the real thing, it’s 4-speed manual and electronic gauge cluster can give you a taste of the supercar lifestyle without having to taken out a second mortgage.

Working through the gears.

Built by [HyperBlue], this desktop speedster has more going on under the hood (or more accurately, the roof) than you might expect. While it looks pretty unassuming from the outside, once the top is lifted, you can see all the additional components that have been packed in to motorize it. The functional gearbox takes up almost the entire interior of the car, but it’s not like you were going to be able to fit in there anyway.

But the motorized car is really only half of the project. [HyperBlue] has built a chassis dynamometer for his plastic ride that not only allows you to “start” the engine with realistic sights and sounds (recorded from an actual GM LT1 V8 engine), but put the mini ‘Vette through its paces. With a virtual dashboard powered by the Raspberry Pi, you can see various stats about the vehicle such as throttle position, RPM, and calculated scale speed; providing a real-world demonstration of how the transmission operates.

While a LEGO sports car might not be quite as exciting as getting yourself a real project car, there’s something to be said for being able to rebuild your transmission without getting your hands dirty.

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Ford’s Powershift Debacle

In the automotive world, change is a constant, and if you’re not keeping up, you’re falling behind. New technologies and methodologies are key to gaining an edge in the market, and companies invest billions each year trying to find the next big thing, or even the next minor incremental improvement.

In just such a quest, Ford Motor Company decided to explore an alternative to the traditional automatic gearbox, aiming for greater fuel efficiency in their small cars. On paper, there were gains to be had. Unfortunately, not everything went according to plan. Continue reading “Ford’s Powershift Debacle”

3D Printed Dogbox Transmission Kicks Your Desk Into High Gear

It’s often been our experience that some of the most impressive projects are the passion builds, the ones where the builder really put in their all and obsessed over every detail. Even if they don’t always have a practical application, it’s impossible to look at the final product and not respect the accomplishment.

Case in point, this absolutely incredible 3D printed model of a sequential “dogbox” transmission created by [Indeterminate Design]. All of the STL files and a complete bill of materials are available for anyone brave enough to take on the challenge. It might never be mounted to a vehicle and driven around the track, but you can still flick through the gears and watch the complex gearing do its thing.

Even if you don’t want to necessarily build the model itself, [Indeterminate Design] takes you through the concepts behind this unique transmission and how it differs from the sort of gearboxes us lowly commuter drivers are familiar with. He’s even nice enough to explain what a dogbox is.

Put simply, this type of transmission allows the driver to simply move the gear change forward and backwards to step through the gears like in a video game. This prevents you from having to navigate an H-pattern gear shift while dealing with all the other stresses of competition driving. Watching it in action, you can certainly see the appeal.

If you prefer your printed gearboxes to be of the practical variety, we’ve certainly seen plenty of those as well. They’re perfect for next time you need to move an anvil around the shop.

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