How To Get Into Cars: Endurance Racing Builds

Many an automotive enthusiast finds themselves at a track day eventually. Typically, this involves competing against the clock to better one’s laptimes in short sessions throughout the day. Such events are fun, but it often creates a perishing thirst for a greater level of competition.

Regularity and endurance events are often the next step up for a lot of people. These events involve long runs at race pace that stress a car to (or beyond!) the breaking point. Careful preparation is required if one is to see out the race to the chequered flag. Let’s break down what you’ll need to consider.

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The Longest Ever Flight Was Over 64 Days In A Cessna 172

Often, when we think of long-endurance flights, our first thoughts jump to military operations. Big planes with highly-trained crew will fly for long periods, using air-to-air refuelling to stay aloft for extended periods.

However, many of the longest duration flights have been undertaken as entirely civilian operations. The longest of all happened to be undertaken by that most humble of aircraft, the Cessna 172. From December 1958 to February 1959, Bob Timm and John Cook set out to make history. The duo remained aloft for a full 64 days, 22 hours and 19 minutes, setting a record that stands to this day.

A Test of Endurance

One might expect that such an effort was undertaken to push the envelope or to strike new ground in the world of aerospace engineering. However, the real truth is that Bob Timm was a slot machine mechanic and former bomber pilot who worked at the Hacienda casino in Las Vegas. Proprietor Doc Bailey was always on the hunt for promotional ideas, and Timm pitched his boss that a record attempt in a plane bearing the casino’s branding would be a good way to go. Bailey agreed, and committed $100,000 to the effort. 

Modifications to prepare the aircraft for the stunt took the best part of a year. The pint-sized Cessna was fitted with a 95-gallon belly tank, paired with a electric pump that could transfer fuel to the main wing tanks as needed. Special plumbing was also added that would allow the engine oil and filters to be changed while the engine was still running.

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Electric RC Plane Flies For Almost 11 Hours

Electric RC aircraft are not known for long flight times, with multirotors usually doing 20-45 minutes, while most fixed wings will struggle to get past two hours. [Matthew Heiskell] blew these numbers out of the water with a 10 hour 45 minute flight with an RC plane on battery power. Condensed video after the break.

Flight stats right before touchdown. Flight time in minutes on the left, and miles travelled second from the top on the right.

The secret? An efficient aircraft, a well tuned autopilot and a massive battery. [Matthew] built a custom 4S 50 Ah li-ion battery pack from LG 21700 cells, with a weight of 2.85 kg (6.3 lbs). The airframe is a Phoenix 2400 motor glider, with a 2.4 m wingspan, powered by a 600 Kv brushless motor turning a 12 x 12 propeller. The 30 A ESC’s low voltage cutoff was disabled to ensure every bit of juice from the battery was available.

To improve efficiency and eliminate the need to maintain manual control for the marathon flight, a GPS and Matek 405 Wing flight controller running ArduPilot was added. ArduPilot is far from plug and play, so [Matthew] would have had to spend a lot of timing tuning and testing parameters for maximum flight efficiency. We are really curious to see if it’s possible to push the flight time even further by improving aerodynamics around the protruding battery, adding a pitot tube sensor to hold the perfect airspeed speed on the lift-drag curve, and possibly making use of thermals with ArduPilot’s new soaring feature.

A few of you are probably thinking, “Solar panels!”, and so did Matthew. He has another set of wings covered in them that he used to do a seven-hour flight. While it should theoretically increase flight time, he found that there were a number of significant disadvantages. Besides the added weight, electrical complexity and weather dependence, the solar cells are difficult to integrate into the wings without reducing aerodynamic efficiency. Taking into account what we’ve already seen of [rcflightest]’s various experiments/struggles with solar planes, we are starting to wonder if it’s really worth the trouble. Continue reading “Electric RC Plane Flies For Almost 11 Hours”

Row Your Bike To China

If you’re a fan of endurance racing motor vehicles, there’s one that puts the 24 Hours of Le Mans, the Dakar Rally, and the Baja 1000 to shame, and the race doesn’t even involve cars. Indeed, the vehicles used for this massive trek from France to China are electric bicycles, powered only by solar panels. This is the epic Sun Trip endurance race, and one of its competitors built a unique tandem bike that is powered both by pedaling, rowing, and the solar panels.

The tandem bike is interesting on its own since the atypical design uses a back-to-back layout which means one person is facing backward, but the storage space is dramatically increased over the normal forward-facing layout. The person in the rear doesn’t pedal, though. [Justin_le] built an upper-body-powered rowing station for that spot so that the person riding back there can rest their legs but still help propel the vehicle. Of course, there’s also a solar panel roof so the two riders can pedal and row in the shade, which includes MPPT and solar tracking which drives a small electric motor on board as well.

This race started in June but is still going on. There’s a live GPS feed so you can keep up with the teams, and if you get really inspired you can go ahead and sign up for the 2019 race as well. This particular bike was also featured on Radio Canada as well if you’d like to learn more about it.

Thanks to [Arthur] for the tip!

Endurance Test Machine Is Not Quite Useless

It seems [Pete Prodoehl] was working on a project that involved counting baseballs as they fell out of a chute, with the counting part being sensed by a long lever microswitch. Now we all know there are a number of different ways in which one can do this using all kinds of fancy sensors. But for [Pete], we guess the microswitch was what floated his boat — likely because it was cheap, easily available and replaceable, and reliable. Well, the reliable part he wasn’t very sure about, so he built a (not quite) Useless Machine that would conduct an endurance test on the specific switch brand and type he was using. But mostly, it seemed like an excuse to do some CAD design, 3D printing, wood work and other hacker stuff.

The switches he’s testing appear to be cheap knock-off’s of a well known brand. Running them through the torture test on his Useless Machine, he found that the lever got deformed after a while, and would stop missing the actuator arms of his endurance tester completely. In some other samples, he found that the switches would die, electrically, after just a few thousand operations. The test results appear to have justified building the Useless Machine. In any case, even when using original switches, quite often it does help to perform tests to verify their suitability to your specific application.

Ideally, these microswitches ought to have been compliant to the IEC 61058 series of standards. When switches encounter real world loads running off utility supply, their electrical endurance is de-rated depending on many factors. The standard defines many different kinds electro-mechanical test parameters such as the speed of actuation, the number of operations per minute and on-off timing. Actual operating conditions are simulated using various types of electrical loads such as purely resistive, filament lamp loads (non-linear resistance), capacitive loads or inductive loads. There’s also a test involving a locked rotor condition. Under some of the most severe kinds of electrical loads, a switch may be expected to last just a few hundred operations. But if the switch is used for low power applications (contact current below 20 mA), then it is expected to last up to its mechanical endurance limit. For most microswitches, this is usually in the range to 100,000 to 300,000 operations.

Coming back to his project, his first version was cobbled together as a quick hack. A 3D-printed lever was attached to a motor fixed on a 3D-printed mount. The switch was wired to an Arduino input, and a four-digit display showed the number of counts. On his next attempt, he replaced the single lever with a set of three, and in yet another version, he changed the lever design by adding small ball bearings at the end of the actuator arms so they rolled smoothly over the microswitch lever. The final version isn’t anywhere close to a machine that would be used to test these kind of switches in a Compliance Test Laboratory, but for his purpose, we guess it meets the bar.

For those interested, here is a great resource on everything you need to know about Switch Basics. And check out the Useless Machine in action in the video below.

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Another Electric Longboard Goes The Distance

Looks like electric longboards are becoming a thing, with increasingly complex electronics going into them to squeeze as much performance as possible out of them. When an electric longboard lasts for 35 miles, can longboard hypermiling be far behind?

If endurance longboarding sounds familiar, it’s because we just covered a 25-mile electric that outlasted its rider. To get the extra 10 miles, [Andrew] cheated a little, with a backpack full of extra batteries powering his modified Boosted Board, a commercially available electric longboard. But the backpack battery was only a prototype, and now [Andrew] is well on his way to moving those batteries to a custom underslung enclosure on his new “Voyager” board. Eschewing balancing and monitoring circuitry in favor of getting as many batteries on board as possible, [Andrew] managed sixty 18650s in a 10S6P configuration for 37 volts at 21 Ah. He didn’t scrimp on tools, though – a commercial terminal welder connects all the battery contacts. We really like the overall fit and finish and the attention to detail; an O-ring seal on the 3D-printed enclosure is a smart choice.

Voyager isn’t quite roadworthy yet, so we hope we’ll get an update and perhaps a video when [Andrew] goes for another record.

Flash Memory Endurance Testing

[Gene] has a project that writes a lot of settings to a PIC microcontroller’s Flash memory. Flash has limited read/erase cycles, and although the obvious problem can be mitigated with error correction codes, it’s a good idea to figure out how Flash fails before picking a certain ECC. This now became a problem of banging on PICs until they puked, and mapping out the failure pattern of the Flash memory in these chips.

The chip on the chopping block for this experiment was a PIC32MX150, with 128K of NOR Flash and 3K of extra Flash for a bootloader. There’s hardware support for erasing all the Flash, erasing one page, programming one row, and programming one word. Because [Gene] expected one bit to work after it had failed and vice versa, the testing protocol used RAM buffers to compare the last state and new state for each bit tested in the Flash. 2K of RAM was tested at a time, with a total of 16K of Flash testable. The code basically cycles through a loop that erases all the pages (should set all bits to ‘1’), read the pages to check if all bits were ‘1’, writes ‘0’ to all pages, and reads pages to check if all bits were ‘0’. The output of the test was a 4.6 GB text file that looked something like this:
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