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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Safely Remove Drill Chuck; Receive Motor, Gearbox, and Clutch

There’s a treasure trove of usefulness inside of an electric drill. [Steven Dufresne], Hackaday writer and the mad scientist behind Rimstar.org, kindly documented how to safely and reliably remove the chuck from a drill motor. You may think this is easy, but once in a while you’ll come across a drill determined to hold onto all its bits. We certainly were entertained by the lengths [Steven] went to in the video below to get a Black and Decker to give up its chuck.

An understanding of how the chuck and gearbox are connected, combined with the right tools and a bit of force, gets you a motor, gears and gearbox, and a clutch. There’s not much left in the drill after that, and you can put some or all of those components to new use — like using them for the drive system of a BB-8 Droid.

Many projects (like this walking scooter) make use of cordless drills as motor sources. Being able to skip the chuck in order to interface directly to the shaft is useful for those projects where the drill is at least a semi-permanent part of the build. Ask your friends, neighbors, and at work. Cheap cordless drills and screw guns have been around for a long time. It’s usually the batteries that go and many people have the drills lying around and will be happy to part with them knowing you’re going to do something awesome with them.

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Gearshift Display for a Rally Car

[Andrea] was helping out a local rally racing team with their car and was asked to create a device that would display the current gear on a big, bright display. Of course, a device like this already exists, but the team didn’t want to invest the significant resources into a ready-made product. Instead, [Andrea] was tasked with creating one.

The device is basically a pot attached to the gear shifter, but in testing, [Andrea] ran into a problem; between reverse and 5th gear, the shifter would turn 360 degrees, meaning these gears were indistinguishable.

The solution to this problem was a calibration procedure for when the driver starts the car. By setting a jumper, the driver puts the car into all gears, sorting out the reading and storing the analog values in the microcontroller’s EEPROM.

LEGO gearbox – seven speed plus reverse

We know LEGO is a very versatile medium to build with but this is beyond what we considered possible. Seven speeds and a reverse gear were built into the gearbox for this LEGO vehicle. It’s not completely an original design, but adds to the five-speed design found in a ten-year-old LEGO set. See it demonstrated in the video after the break. The design uses a sequential gearbox; shifting is accomplished by clicking the stick up or down depending on how you want to shift. If you’ve got enough parts on hand you can build this using the assembly photos that [Sheepo] posted.

Can’t get enough of the gears? Check out this model of a double clutch transmission.

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Double clutch transmission model

[Alan] did an extraordinary job building a computer controlled model gearbox. His project from several years back is based on a dual-clutch Direct Shift Gearbox that was developed for VW and Audi vehicles. His design uses a gear head motor to provide the locomotion to this transmission. Shifting is computer controlled through serial cable, with servo motors providing the physical motion to change gears. Seeing all these moving parts in the clip after the break might make you a bit dizzy.

This is some extreme model building. It reminds us of the guy who built that aluminum aircraft model that was all over the Internets in December.

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