He incorrectly claims that a cyclist can get more torque by having a crank arm that’s “longer” but bends back towards the center, keeping the pedals the same distance away from the axis as a traditional straight crank. Levers don’t work like that. It doesn’t matter what shape the lever arm is, it only matters how far away the pedal is from the center of rotation.
Good to note that the Kickstarter attempt failed miserably, not so good that there’s a smaller-scale attempt elsewhere.
One of the finest achievements of European furniture making, this cabinet is the most important product from Abraham (1711–1793) and David Roentgen’s (1743–1807) workshop. A writing cabinet crowned with a chiming clock, it features finely designed marquetry panels and elaborate mechanisms that allow for doors and drawers to be opened automatically at the touch of a button. Owned by King Frederick William II, the Berlin cabinet is uniquely remarkable for its ornate decoration, mechanical complexity, and sheer size.
Insert your own joke about x-rays here.
An Innovative and Cheap ‘Solar Bottle Bulb’ Solution Lights Homes in Manila
This is a really neat solution to the problem of dwellings that could really use passive light; it’s not truly an alternative to something like the gravitylight , which is not passive, but for closely-spaced dwellings that don’t have much in the way of window real estate relative to the interior area, and lack (affordable) electricity, it’s just the ticket to light them up during the day.
This is a kind of light pipe (one version of which is a deck prism seen on some boats). I have to think something like this would have been useful for a playhouse when I was a kid. Some more detailed instructions exist, if you are inclined to employ on of these.
How To Make the Best Snowfort Ever
Pedantic note: if you go with the pykrete option, it’s no longer a snow fort.
I ran across a bit touting some new lamp, called GravityLight, which would give you “free” lighting — all you have to do is lift a weight. My first reaction was a flashback to the Gravia lamp, which I critiqued in the first few months of this blog. Turns out the Gravia was a concept piece that had over-reached the light output and duration that was possible — it was only capable of putting out a few tens of milliWatts to generate the light, well short of what was promised.
But the GravityLight appears to be the real deal, and it’s being funded on indiegogo as a replacement for kerosene lamps in areas without a power grid. The difference? It promises less light over a shorter time, plus a slight increase in efficiency of LEDs, and that’s all the difference you need. Instead of 800 lumens of light, sent in all directions, you get a beam from the LEDs. If you drop the output from 4*pi steradians (i.e. all directions) to, say, 1/8 of that, it’s the equivalent of just 100 lumens, and super-bright LEDs have a luminous efficacy of about 100 lumens per Watt, meaning you only need ~1 Watt output for such a light.
The previous system could only supply ~17 milliWatts of power, but that was because the energy was promised over a 4-hour period. If you release the same energy over a shorter time, the power is greater. A 20kg mass raised a little over a meter is 200 Joules, so that’s a Watt for 200 seconds. If you lower the light output, via dimming or making a narrower beam, or you use a greater mass and/or raise it higher, it will last longer.
What Porcupines Can Teach Engineers
It doesn’t seem to make sense that a barbed quill would go in more easily than a smooth one. But Karp and his colleagues discovered that the barbs work just like the bumps on a serrated knife. The knife’s wavy blade concentrates force at the tips of the teeth, requiring less power overall to cut soft foods like tomatoes or bread.
Knife makers have known that for a long time. Now it turns out that North American porcupines know it, too.
The Ups and Downs of Making Elevators Go
Here is a typical problem: A passenger on the sixth floor wants to descend. The closest car is on the seventh floor, but it already has three riders and has made two stops. Is it the right choice to make that car stop again? That would be the best result for the sixth-floor passenger, but it would make the other people’s rides longer.
For Ms. Christy, these are mathematical problems with no one optimum solution. In the real world, there are so many parameters and combinations that everything changes as soon as the next rider presses a button. In a building with six elevators and 10 people trying to move between floors, there are over 60 million possible combinations—too many, she says, for the elevator’s computer to process in split seconds.
“We are constantly seeking the magic balance,” says the Wellesley math major. “Sometimes what is good for the individual person isn’t good for the rest.”