transmission

32 Articles

Homebrew Optical Sensor Helps Your Diesel Pass The Smoke Test

June 27, 2022 by 50 Comments

We’ve all heard of the smoke test, and we know that it’s the lowest possible bar for performance of an electronic device. If it doesn’t burst into flames when power is applied, you’re good to go for more functional testing. But the smoke test means something else for cars, especially those powered by diesel fuel. And passing diesel exhaust tests can become something of a chore.

To make passing these tests a little easier, [Janis Alnis] came up with this diesel exhaust monitor that measures the opacity of his car’s emissions. The sensor itself is quite simple, and mimics what commercial exhaust analyzers use: a LED and a photodiode at opposite ends of a tube of a specified length. Soot particles in exhaust passing through the tube will scatter light in a predictable way, and the numbers work out that a passing grade is anything greater than 53% transmission.

The sensor body is cobbled together from brass pipe fittings with glass windows epoxied into each end. Exhaust enters via a tee fitting attached to a hose and sampling tube, and exits through another tee. One window of the sensor has a cheap battery-powered flashlight as a light source, while the other end has a Texas Instruments OPT101 photodiode sensor. The sensor is connected to one of the analog inputs of an Arduino, which also runs a 128×64 pixel LCD display — inspired by this air quality meter — to show the current smokiness both graphically and as a percentage. The video below shows the sensor at work.

While there were some issues with soot buildup and water vapor condensation, using the sensor [Janis] discovered that a little bit of a warm-up drive got things hot enough to clear up his ride’s tendency to smoke a bit, allowing him to pass his inspection. Continue reading “Homebrew Optical Sensor Helps Your Diesel Pass The Smoke Test” →

Fight Disease With A Raspberry Pi

September 20, 2021 by 4 Comments

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

July 22, 2021 by 9 Comments

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.

Continue reading “A Simple LEGO Automatic Transmission” →

Harmonic Drive Uses Compliant Mechanism To Slim Down

April 7, 2021 by 15 Comments

[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.

Continue reading “Harmonic Drive Uses Compliant Mechanism To Slim Down” →

Peeking Inside A VW Gearbox Reveals Die Casting Truths

December 14, 2020 by 70 Comments

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!

Continue reading “Peeking Inside A VW Gearbox Reveals Die Casting Truths” →

LEGO Delivers Corvette Experience On A Budget

September 8, 2020 by 5 Comments

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 be 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.

Continue reading “LEGO Delivers Corvette Experience On A Budget” →

Ford’s Powershift Debacle

June 3, 2020 by 203 Comments

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” →