You’d be hard pressed to find an aircraft that wasn’t designed and tested without extensive use of simulation. Whether it’s the classic approach of using a scale model in a wind tunnel or more modern techniques such as computational fluid dynamics, a lot of testing happens before any actual hardware gets bolted together. But at some point the real deal needs to get a shakedown flight, and historically a favorite testing ground has been the massive dry lake beds in the Western United States. The weather is always clear, the ground is smooth, and there’s nobody for miles around.
Thanks to [James] and [Tyler] at Propwashed, that same classic lake bed approach to real-world testing has now been brought to the world of high performance quadcopter gear. By mounting a computer controlled thrust stand to the back of their pickup truck and driving through the El Mirage dry lake bed in the Mojave Desert, they were able to conduct realistic tests on how different propellers operate during flight. The data collected provides an interesting illustration of the inverse relationship airspeed has with generated thrust, but also shows that not all props are created equal.
The first post in the series goes over their testing set-up and overall procedure. On a tower in the truck’s bed a EFAW 2407 2500kV motor was mounted on a Series 1520 thrust stand by RCBenchmark. This stand connects to the computer and offers a scripted environment which can be used to not only control the motor but monitor variables like power consumption, RPM, and of course thrust. While there was some thought given to powering the rig from the truck’s electrical system, in the end they used Turnigy 6000mAh 4S battery packs to keep things simple.
A script was written for the thrust stand which would ramp the throttle from 0% up to 70% over 30 seconds, and then hold it at that level for 5 seconds. This script was run when the truck was at a standstill, and then repeated with the truck travelling at increasingly faster speeds up to 90 MPH. This procedure was repeated for each of the 15 props tested, and the resulting data graphed to compare how they performed.
The end result was that lower pitch props with fewer blades seemed to be the best overall performers. This isn’t a huge surprise given what the community has found through trial and error, but it’s always good to have hard data to back up anecdotal findings. There were however a few standout props which performed better at high speeds than others, which might be worth looking into if you’re really trying to push the envelope in terms of airspeed.
As quadcopters (or “drones”, if you must) have exploded in popularity, we’re starting to see more and more research and experimentation done with RC hardware. From a detailed electrical analysis of hobby motors to quantifying the latency of different transmitters.
From the windtraps and stillsuits of Dune’s Arrakis, to the moisture vaporators of Tatooine, science fiction has invented fantastic ways to collect the water necessary for life on desert worlds. On Earth we generally have an easier go of it, but water supply in arid climates is still an important issue. Addressing this obstacle, a team of researchers from MIT and the University of California at Berkeley have developed a method to tease moisture out of thin air.
A year after the team first published their idea, they have successfully field-tested their method on an Arizona State University rooftop in Tempe, proving the concept and the potential for scaling up the technology. The device takes advantage of metal-organic framework(MOF) materials with high surface area that are able to trap moisture in air with as little as 10% humidity — even at sub-zero dewpoints. Dispensing with the need for power-hungry refrigeration techniques to condense moisture, this technique instead relies on the heat of the sun — although low-grade heat sources are also a possibility.
Continue reading “Coaxing Water From Desert Air”
An oasis in the desert is the quintessential image of salvation for the wearied wayfarer. At Burning Man 2016, Grove — ten biofeedback tree sculptures — provided a similar, interactive respite from the festival. Each tree has over two thousand LEDs, dozens of feet of steel tube, two Teensy boards used by the custom breath sensors to create festival magic.
Grove works like this: at your approach — detected by dual IR sensors — a mechanical flower blooms, meant to prompt investigation. As you lean close, the breath sensors in the daffodil-like flower detect whether you’re inhaling or exhaling, translating the input into a dazzling pulse of LED light that snakes its way down the tree’s trunk and up to the bright, 3W LEDs on the tips of the branches.
Debugging and last minute soldering in the desert fixed a few issues, before setup — no project is without its hiccups. The entire grove was powered by solar-charged, deep-cycle batteries meant to least from sunset to sunrise — or close enough if somebody forgot to hook the batteries up to charge.
Continue reading “An Interactive Oasis At Burning Man”
The original story is in French, and the Google translate is very rough. Please forgive us if we don’t get this completely accurate.
While traveling through the desert somewhere in north west Africa in his Citroen 2CV , [Emile] is stopped, and told not to go any further due to some military conflicts in the area. Not wanting to actually listen to this advice, he decides to loop around, through the desert, to circumvent this roadblock.
After a while of treading off the beaten path, [Emile] manages to snap a swing arm on his vehicle, leaving him stranded. He decided that the best course of action was to disassemble his vehicle and construct a motorcycle from the parts. This feat would be impressive on its own, but remember, he’s still in the desert and un-prepared. If we’re reading this correctly, he managed to drill holes by bending metal and sawing at it, then un-bending it to be flat again.
It takes him twelve days to construct this thing. There are more pictures on the site, you simply have to go look at it. Feel free to translate the labels and post them in the comments.
Update: From [Semicolo] in the comments
You got the translation right, but there’s not just a swing arm that’s broken, there’s a frame beam broken too (not sure about the exact term, one of the 2 girder of the chassis).
He’s not far away but he has a lot of tools and other hardware that could be stolen if he leaves them unattended.
When you are in the middle of the desert, pretty much every solution to a mechanical or electrical problem is a hack. [Sgt.M] who was deployed in Iraq sought out the help of radio guru [H.P. Friedrichs] about a static problem he was having. When dust storms would blow in strange things would happen in camp. Humming and crackling could be heard and [Sgt. M] actually had an electrical arc from a lamp to his hand at a distance of about 2 feet.
[Friedrichs] helped him find the problem. Their antennae were acting as static electricity collectors in the dust. All that dust friction in the dry air constantly built up a charge. The solution was simple, discharge the electricity at the antenna when it isn’t in use. Several solutions are outlined on the page, so check them out.