Pulleys within Pulleys form a Unique Transmission for Robots

After a couple of millennia of fiddling with gears, you’d think there wouldn’t be much new ground to explore in the field of power transmission. And then you see something like an infinitely variable transmission built from nested pulleys, and you realize there’s always room for improvement.

The electric motors generally used in robotics can be extremely efficient, often topping 90% efficiency at high speed and low torque. Slap on a traditional fixed-ratio gearbox, or change the input speed, and efficiency is lost. An infinitely variable transmission, like [Alexander Kernbaum]’s cleverly named Inception Drive, allows the motor to stay at peak efficiency while smoothly changing the gear ratio through a wide range.

The mechanism takes a bit of thought to fully grok, but it basically uses a pair of split pulleys with variable spacing. The input shaft rotates the inner pulley eccentrically, which effectively “walks” a wide V-belt around a fixed outer pulley. This drives the inner pulley at a ratio depending on the spacing of the pulley halves; the transmission can shift smoothly from forward to reverse and even keep itself in neutral. The video below will help you get your head around it.

We’ve seen a couple of innovative transmissions around here lately; some, like this strain-wave gear and this planetary gearbox, are amenable to 3D printing. Looks like the Inception Drive could be printed too. Hackers, start your printers and see what this drive can do.

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Robot Graffiti

There’s talk of robots and AIs taking on jobs in many different industries. Depending on how much stock you place in that, it might still be fair to say the more creative fields will remain firmly in the hands of humans, right?

Well, we may have some bad news for you. Robots are now painting our murals.

Estonian inventor [Mihkel Joala] — also working at SprayPainter — successfully tested his prototype by painting a 30m tall mural on a smokestack in Tartu, Estonia. The creative procedure for this mural is a little odd if you are used to the ordinary painting process: [Joala] first takes an image from his computer, and converts it into a coordinate grid — in this case, about 1.5 million ‘pixels’. These pixels are painted on by a little cart loaded with five colours of spray paint that are able to portray the mural’s full palette once combined and viewed at a distance. Positioning is handled by a motor at the base of the mural controlling the vertical motion in conjunction with tracks at the top and bottom which handle the horizontal motion.

For this mural, the robot spent the fourteen hours trundling up and down a set of cables, dutifully spraying the appropriate colour at such-and-such a point resulting in the image of a maiden cradling a tree and using thirty cans of spray paint in the process.

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[Homo Faciens] Builds a Winchbot

The trademark hacker style of Hessian YouTuber [Homo Faciens] is doing a lot with a little. Given a package of parts from a sponsor, he could have made something “normal” like a fancy robot arm. Instead, he decided to make a winchbot. (Video embedded below.)

What’s a winchbot? It’s a big frame that supports three relatively heavy motors that pull steerable gripping arms around. It’s a little bit like the hanging Hektor / wallbot / plotterbot and a little bit like a delta-style 3D printer. Although [Homo Faciens]’s build doesn’t showcase it, a winchbot is also a great way to lift heavy things because the parts that need to be beefy — the frame and the lifting motors — don’t have to move. We love the gimballed square rod that works in concert with the winches!

With five extra servos on hand, and the computing power of a Raspberry Pi, [Homo Faciens] couldn’t just stop with lifting a claw. Instead, the gripping-arms part of the bot is mounted with four degrees of freedom and is powered with software that makes it stay parallel with the table and rotate around the gripper to make programming easier. Watch it in action in the video to see what we mean.

The biggest unsolved problem that we can see is the jerkiness that it displays in moving things around. That doesn’t stop it from building up a tower and a domino knock-down. We suspect that there’s some combination of firmware and hardware tweaking that can solve this problem, or it could just be run slowly so that the wobbles damp themselves out. We’re also quite confident that [Homo Faciens] will come up with an elegant and cheap solution. Have you seen his CNC machine?

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Pulley Lamp Stands Up With You

Standing desks are either the best thing since sliced bread, or the fastest way to make your legs tired and get you ridiculed by your coworkers in the bargain. This leads some folks to compromise and make standing desks that can be re-lowered to sitting height when you need to take a break. But now the distance from your desktop to the light source that illuminates it has changed. We can’t have that!

fo6i703itw44bt1-medium[John Culbertson] came up with a very elegant solution to the “problem”. He made lights that are suspended on pulleys that raise and lower with the desk itself. We’re not sure that you’re in the same situation he is, but we’re sure that you’ll agree that he did a nice job.

Besides the pulley mechanism, the light shades are a work of art. [John] clearly wanted a retro feel, so he used low-voltage lightbulbs, but augmented them with LED strips to pump out the lumens. All in all, there’s a tremendous attention to detail in the project, and it shows.

Disclaimer: your humble author is writing you this missive from a standing desk. Ours is just a regular desk put up on bricks — a temporary solution that’s become permanent. We’re always keeping our eyes out for mechanisms to make the desk convertible, but everything that we’ve seen is either overkill or ridiculously overpriced or both. It’s hard to beat 24 bricks at $0.35 apiece. Anyone have any suggestions?

Of course, with an adjustable desk come the problems of moving your lighting along with it, but [John] has solved that one for us.

Pep up your house cat’s boring wintertime life

With winter upon us, and all the windows shut, [Garfield] and [Socks] can get a little restless. But [Dino] is determined to keep his furry friends entertained through the cold dark months. He hit the junk box, and used some interesting fabrication techniques to build the Chase-a-Mouse motorized cat toy.

The toy is popular with the cats because it incorporates two traditionally satisfying features; something to chase, and an obstacle to chase it around. The base of the unit is a long plank which is held up from the floor by a couple of inches. The loop of rope which spans the board’s length has a mouse attached to it with about six inches of string. When the motor is flipped on it bounces and jerks its way around the circuit, darting in and out of the space below the base.

As you can see in the video after the break the motor is a bit loud. [Dino] used the sweeper motor from a Roomba for this. It might freak the kitties out at first, but curiosity will get the better of them eventually. It’s a quick build, and we love the drill-turned-lathe that is used make the wooden pulley for the system.

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Mechanical engineering primer

So you’re master of electrons; able to program multiple chip architectures without batting an eye. Good for you. The only problem is that blinking LEDs gets boring after a while and you’re going to want to do something else. Here’s a chance to expand on your physical construction skills. Make: Skill Set is sharing the first chapter from the book Making Things Move by [Dustyn Roberts].

This chapter, which comes in PDF form, covers simple machines. It’ll guide you through the three different types of levers, including examples of how you use these in your everyday life. Next it’s on to pulley systems, wheels and axles, inclined planes and wedges, screws, and gears. [Dustyn] rounds out the chapter by talking about how these concepts are combined into machines like the Rube-Goldberg device seen above. Take some time to look this chapter over and then put it on the holds list from your public library if you’re interested in reading more.

Automated car cover

[Mike] covers his car whenever he puts it into the garage because the top is always open. After years of this ritual he decided to upgrade his garage to automatically cover the vehicle. The car cover, made from a few bed sheets, attaches to the bottom of the garage door. At the front of the stall the cover has two half-pound weights sewn in with plenty of padding to protect the car’s finish. Ropes attach to these weights, travel through a pulley system, and connect to the garage door opener carriage. This $65 dollar solution makes sure [Mike’s] car is always taken care of.

[Thanks 02TA]