Mechanisms: Gears

Even before the Industrial Revolution, gears of one kind or another have been put to work both for and against us. From ancient water wheels and windmills that ground grain and pounded flax, to the drive trains that power machines of war from siege engines to main battle tanks, gears have been essential parts of almost every mechanical device ever built. The next installment of our series on Mechanisms will take a brief look at gears and their applications.

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Keeping Magnetized Marbles from Stopping the Music

Take a couple of thousand steel balls, add a large wooden gear with neodymium magnets embedded in it, and what do you get? Either the beginnings of a wonderful kinetic music machine, or a mess of balls all stuck together and clogging up the works.

The latter was the case for [Martin], and he needed to find a way to demagnetize steel balls in a continuous process if his “Marble Machine X” were to see the light of day. You may recall [Martin] as a member of the band Wintergatan and the inventor of the original Marble Machine, a remarkable one-man band that makes music by dropping steel balls on various instruments. As fabulous a contraption as the original Marble Machine was, it was strictly a studio instrument, too fragile for touring.

Marble Machine X is a complete reimagining of the original, intended to be robust enough to go on a world tour. [Martin] completely redesigned the lift mechanism, using magnets to grip the balls from the return bin and feed them up to a complicated divider. But during the lift, the balls became magnetized enough to stick together and no longer roll into the divider. The video below shows [Martin]’s solution: a degausser using magnets of alternating polarity spinning slowly under the sticky marbles. As a side note, it’s interesting and entertaining to watch a musician procrastinate while debugging a mechanical problem.

We can’t wait to see Marble Machine X in action, but until it’s done we’ll just settle for [Martin]’s other musical hacks, like his paper-tape programmed music box or this mashup of a synthesizer and a violin.

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Gorgeous Engineering Inside Wheels of a Robotic Trail Buddy

Robots are great in general, and [taylor] is currently working on something a bit unusual: a 3D printed explorer robot to autonomously follow outdoor trails, named Rover. Rover is still under development, and [taylor] recently completed the drive system and body designs, all shared via OnShape.

Rover has 3D printed 4.3:1 reduction planetary gearboxes embedded into each wheel, with off the shelf bearings and brushless motors. A Raspberry Pi sits in the driver’s seat, and the goal is to use a version of NVIDA’s TrailNet framework for GPS-free navigation of paths. As a result, [taylor] hopes to end up with a robotic “trail buddy” that can be made with off-the-shelf components and 3D printed parts.

Moving the motors and gearboxes into the wheels themselves makes for a very small main body to the robot, and it’s more than a bit strange to see the wheel spinning opposite to the wheel’s hub. Check out the video showcasing the latest development of the wheels, embedded below.

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Automated Parts Counter Helps Build a Small Business

We love to see projects undertaken for the pure joy of building something new, but to be honest those builds are a dime a dozen around here. So when we see a great build that also aims to enhance productivity and push an entrepreneurial effort along, like this automated small parts counter, we sit up and take notice.

The necessity that birthed this invention is [Ryan Bates’] business of building DIY arcade game kits. The mini consoles seen in the video below are pretty slick, but kitting the nuts, bolts, spacers, and other bits together to ship out orders was an exercise in tedium. Sure, parts counting scales are a thing, but that’s hardly a walk-away solution. So with the help of some laser-cut gears and a couple of steppers, [Ryan] built a pretty capable little parts counter.

The interchangeable feed gears have holes sized to move specific parts up from a hopper to a chute. A photointerrupter counts the parts as they fall into plastic cups on an 8-position carousel, ready for bagging. [Ryan] also has a manual counter for wire crimp connectors that’s just begging to be automated, and we can see plenty of ways to leverage both solutions as he builds out his kitting system.

While we’ve seen more than a few candy sorting machines lately, it’s great to see someone building hardware to streamline the move from hobby to business like this. We’re looking forward to seeing where [Ryan] takes this from here.

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Customize Your Ratios with a 3D-Printed Gearbox

Small DC motors are easy to find — you can harvest dozens from old printers and copiers. You might even get a few with decent gearboxes too. But will you get exactly the motor with exactly the gearing your project needs? Unlikely, but you can always just print a gearbox to get exactly what you need.

There’s nothing fancy about [fortzero]’s gearboxes. The motors are junk bin specials, and the gears are all simple spur gears 3D-printed from PLA. There are four gears in the train, each with a 2:1 reduction, giving a 16:1 overall ratio. The gears ride on brass shafts that are press-fit into the housing, and there’s not a bearing in sight — just a few washers to keep the gears spaced apart and plenty of grease. Despite the simplicity, the gearboxes turned out to be pretty capable, lifting a 3.5 kg load. The design files are available and should make it easy for you to get just the ratio you want for the motor you have.

Of course more complicated gearboxes are possible with a 3D printer, including a split-harmonic planetary gear, or a strain wave gear using a timing belt. No 3D printer? No problem! Just build a LEGO gearbox.

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Unique Planetary Gearbox can be Custom Printed for Steppers

Stepper motors are a staple in all sorts of projects, but it’s often the case that a gearbox is needed, especially for applications like the linear drives in CNC machines and 3D printers. In those mechanisms, a high-torque, low backlash gearbox might be just the thing, and a 3D printable split planetary harmonic drive for the popular NEMA 17 motors would be even better.

Right up front, we’ll say that we’re skeptical that any plastic gearbox can stay as backlash free as [SirekSBurom] claims his creation is. But we can see the benefits of the design, and it has some nice features. First off, of course, is that it’s entirely 3D printed, except for a few screws. That it mates perfectly with a NEMA 17 motor is a really nice feature, too, and with the design up on Thingiverse it shouldn’t be too tough to scale it up and down accordingly. The videos below show you the theory: the stepper drives a sun gear with two planet gears orbiting, each of which engages a fixed ring of 56 teeth, and an output ring of 58 teeth. Each revolution of the planets around the fixed ring rotates the output ring by one tooth, leading to almost 100:1 reduction.

We think the ‘harmonic’ designation on this gearbox is a little of a misnomer, since the defining feature of a harmonic drive seems to be the periodic deformation of a flex spline, as we saw in this 3D-printed strain wave gear. But we see the resemblance to a harmonic drive, and we’ll admit this beastie is a little hard to hang a name tag on. Whatever you call it, it’s pretty cool and could be a handy tool for all kinds of builds.

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Baby’s First Hands-Free Stroller

So you’ve had your first child. Congratulations; your life will never be the same again. [Dusan] was noticing how the introduction of his children into his life altered it by giving him less time for his hobbies in his home laboratory, and decided to incorporate his children into his hacks. The first one to roll out of his lab is a remote-controlled baby stroller.

After some engineering-style measurements (lots of rounding and estimating), [Dusan] found two motors to drive each of the back wheels on a custom stroller frame. He created a set of wooden gears to transfer power from the specialized motors to the wheels. After some batteries and an Arduino were installed, the stroller was ready to get on the road. At this point, though, [Dusan] had a problem. He had failed to consider the fact that children grow, and the added weight of the child was now too much for his stroller. After some adjustments were made (using a lighter stroller frame), the stroller was eventually able to push his kid around without any problems.

This is an interesting hack that we’re not sure has much utility other than the enjoyment that came from creating it. Although [Dusan]’s kid certainly seems to enjoy cruising around in it within a close distance to its operator. Be sure to check out the video of it in operation below, and don’t forget that babies are a great way to persuade your significant other that you need more tools in your work bench, like a CNC machine for example.

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