While wheels might seem like a foundational technology, they do have one major flaw: they typically need maintained roads in order to work. Anyone who has experience driving a Jeep or truck off-road likely knows this first-hand. For those with extreme off-road needs the track is often employed. [Let’s Print] is working on perfecting his RC tracked vehicle to take advantage of these perks using little more than 3D printed parts and aluminum stock.
This vehicle doesn’t just include the 3D printed tracks, but an entire 3D printed gearbox and drivetrain to drive them. Each track is driven by its own DC motor coupled to a planetary gearbox to give each plenty of torque to operate in snow or mud. The gearbox is mated to a differential which currently shares a shaft, which means that steering is currently not possible. The original plan was to have each motor drive the tracks independently but a small mistake in the build meant that the shaft needed to be tied together. [Let’s Print] has several options to eventually include steering, including an articulating body or redesigning the drivetrain to be able to separate the shaft.
While this vehicle currently has no wheels in order to improve traction, [Let’s Print] does point out that a pair of wheels could complement this vehicle when he finished the back half of it since wheels have a major advantage over tracks when it comes to steering. A vehicle with both could have the advantages of both, so we’re interested to see where this build eventually goes.
The design is by no means fast; it’s intended more for crawling around “at a slow deliberate pace” as [Alex] puts it. Off-the-shelf 12 V gear motors are used to provide plenty of torque to get around. The modular design means that it can be built with just wheels, or set up with tracks fitted for additional performance in softer terrain. Skid steering is used to turn the platform.
Fitted with a Raspberry Pi Zero 2W, the rover can be controlled remotely over WiFi. A separate FPV camera and transmitter is then used to stream video remotely to pilot the bot. However, if you’re so inclined, you can probably use the Raspberry Pi to stream the video, too.
When we think of tracked vehicles, we normally think of tanks, or perhaps heavy construction machinery. Meanwhile the average member of the public is left out of the fun. [Bob] of [Making Stuff] won’t be one of them, however, having put together a ride-on tracked vehicle for his own enjoyment.
The machine is welded together from plenty of steel, making it more than tough enough to soak up the punishment of off-road duty. The design features four suspended buggy wheels on either side running inside rubber tracks, with a cogged drive wheel at the front. Propulsion is thanks to a 440 cc DuroMax engine good for a full 18 horsepower and 26 ft-lbs of torque, driving the tracks through a differential mounted up front.
The design has one major issue at the moment. The heavy engine is mounted ahead of the front wheel inside the tracks, which means the vehicle wants to nosedive at the slightest provocation. Such an event would be highly uncomfortable for the rider, so mods are needed, either by scooching the engine back a little or pushing the wheels forward.
We look forward to seeing [Bob] fix the issues and get the machine driving soon. We’ve seen other tracked builds before, too – often on the smaller scale. Video after the break.
When it comes to dominating offroad performance, many people’s first thought is of tracked vehicles. Bulldozers, tanks and excavators all use treads, and manage to get around in difficult terrain without breaking a sweat. Today, we’re exploring just what makes tracked vehicles so capable, as well as their weaknesses.
It’s All About Ground Pressure
Let’s first look at how tank tracks work. There are a huge variety of designs, with differences depending on application. Different trends have been followed over time, and designs for military use in combat differ from those used for low-speed construction machines, for example. But by looking at a basic tank track design, we can understand the basic theory. On tanks, the track or tread itself is usually made up of individual steel links that are connected together with hinges, though other machines may use rubber tracks instead. The tracks are wrapped around one or more drive wheels, often cogged, which directly pull on the track. On the bottom of the vehicle are the road wheels, which ride on top of the track where it lies on the ground. The weight of the vehicle is carried through the road wheels and passed on to the tread, spreading out the load across a broader area. Outside of this, the track system may also have one or more idler wheels used to keep the track taught, as well as return rollers to guide the track back around without touching the road wheels.
Scope creep is a real pain in the real world, but for projects of passion it can have some interesting consequences. [rctestflight] was playing around with 3D printed rover gearboxes, which morphed into a 3D printed tank build.
[rctestflight]’s previous autonomous rover project had problems with the cheap geared motors, and he started experimenting with his own gearbox designs to use with lower RPM / Kv brushless drone motors. The tank came about because he wanted a simple vehicle to test his design. “Simple” went out the window pretty quickly and the final product was completely 3D printed except for the fasteners, axles, bearings, and electronics.
The tracks and gears are noisy, but it works quite well. On outdoor tests [rctestflight] did find that the tracks were prone to hooking on vines and branches, which in one case caused it to throw a track after the aluminium shaft bent. An Ardurover navigation system was added and with a 32 Ah battery was able to run autonomously for an entire day and there was surprisingly little wear on 3D printed gearbox and tracks afterward. All the STL files are up on Thingiverse, but [rctestflight] recommends waiting for an upcoming update because he discovered flaws in the design after filming the video after the break.
Anyone who has used an FDM 3D printer knows just how long the process can take, especially when you really start filling up the available print volume. Apparently [Ivan Miranda] has absolutely zero fear of insanely long print times, and is in the process of building a massive ridable tank (YouTube playlist of the whole build) that is almost completely 3D printed.
[Ivan] is no stranger to large prints, but this tank is on a different level altogether. The chassis, which is reinforced with aluminium and steel square tubing, took around 1200 hours to print and each of the wheels took 6 days! The rolling chassis with wheels and track weighs close to a 100 kg. Having built a few smaller 3D printed tracked vehicles before, [Ivan] used a lot of that knowledge to design the latest monster.
Connecting the tracked section together has always proven challenging for [Ivan]. This time he used plastic fish tape (wire puller) for the pins, and blocked off the end holes with screws. The bogies (wheel sets) are also interesting, with 3D printed springs that sit parallel to the ground. Almost all the parts are printed in PLA, which can be quite brittle, so it would be interesting to see how it holds up.
When we want to build something to go where wheels could not, the typical solution is to use tracks. But the greater mobility comes with trade-offs: one example being tracked vehicles can’t go as fast as a wheeled counterpart. Information released by DARPA’s ground experimental vehicle technology (GXV-T) program showed what might come out of asking “why can’t we switch to tracks just when we need them?”
This ambitious goal to literally reinvent the wheel was tackled by Carnegie Mellon’s National Robotics Engineering Center. They delivered the “Reconfigurable Wheel-Track” (RWT) that can either roll like a wheel or travel on its tracks. A HMMWV serves as an appropriate demonstration chassis, where two or all four of its wheels were replaced by RWTs. In the video (embedded below) it is seen quickly transforming from one mode to another while moving. An obviously desirable feature that looks challenging to implement. This might not be as dramatic of a transformation as a walking robot that can roll up into a wheel but it has the advantage of being more immediately feasible for human-scale vehicles.
The RWT is not the only terrain mobility project in this DARPA announcement but this specific idea is one we would love to see scaled downed to become a 3D-printable robot module. And though our Hackaday Prize Robotics Module Challenge has already concluded, there are more challenges still to come. The other umbrella of GXV-T is “crew augmentation” giving operators better idea of what’s going around them. The projects there might inspire something you can submit to our upcoming Human-Computer Interface Challenge, check them out!