3D printers are celebrated for their capacity to replace missing or broken parts. How about an entire T-62 tank?
Now hold on a second — this is only a model replica. It is, however another expression of the myriad uses for 3D printers. Designed in Maya and requiring almost three weeks to print all 62 parts from about 70 meters of PLA filament. The assembly is not terribly involved, made easier by printing a few large sections such as the crew section and hull while the parts don’t get much smaller than the turret hatches. Nonetheless, he final product is about as true to life as you can get when designing the parts from scratch.
Every now and then someone gets seriously inspired, and that urge just doesn’t go away until something gets created. For [Paulius Liekis], it led to creating a roughly 1:20 scale version of the T08A2 Hexapod “Spider” Tank from the movie Ghost in the Shell. As the he puts it, “[T]his was something that I wanted to build for a long time and I just had to get it out of my system.” It uses two Raspberry Pi computers, 28 servo motors, and required over 250 hours of 3D printing for all the meticulously modeled pieces – and even more than that for polishing, filing, painting, and other finishing work on the pieces after they were printed. The paint job is spectacular, with great-looking wear and tear. It’s even better seeing it in motion — see the video embedded below.
It’s great to see different kinds of hardware and software tossed into a project together, allowing someone to mix things that don’t normally go together into something new. [Freddy Kilo] did just that with a project he calls his VR Robot Tank. It’s a telepresence device that uses a wireless Xbox controller to drive a tracked platform, which is itself headed by a Raspberry Pi.
The Pi has two cameras on a pan-tilt mount, and those cameras are both aimed and viewed via a Google Cardboard-like setup. A healthy dose of free software glues it together, allowing things like video streaming (with U4VL) and steering via the wireless controller (with xboxdrv). A bit of fiddling was required for some parts – viewing the stereoscopic cameras for example is done by opening and positioning two video windows just right so as to see them through the headset lenses. It doesn’t warp the image to account for the lens distortion in the headset, and the wireless range might be limited, but the end result seems to work well enough.
The tank is driven with the wireless controller while a mobile phone mounted in a headset lets the user see through the cameras; motion sensing in the phone moves those cameras whenever you move your head to look around. Remote Control hobbyists will recognize the project as doing essentially the same job as FPV setups for model aircraft (for example, Drone Racing or even Snow Sleds) but this project uses a completely different hardware and software toolchain. It demonstrates the benefits of having access to open tools to use as virtual “duct tape”, letting people stick different things together to test a concept. It proves almost anything can be made to work if you have a willingness to fiddle!
For most of us, hacking is a hobby, a pleasant diversion from reality. Yes, a lot of us work on projects which have the potential to change the world – witness the 2015 Hackaday Prize semifinalist list. But in general, almost any of us could walk away from the shop at any time without dire consequences. Indeed, that’s the reason a lot of our work benches are littered with projects started with the best of intentions but left unfinished for lack of funds, lack of interest, or lack of time. We’re free to more or less willingly shelve a project and come back to it whenever we please, or not at all.
But not everyone has that luxury. For some people, hacking is much more than a hobby – it’s a means of survival. Sometimes people are thrown into situations where they have to cobble together a solution to an immediate problem with whatever is at hand, when the penalty for failure is much higher than a cluttered bench and a bruised ego. I’ve already covered one such case, where biohacked insulin saved hundreds of lives in occupied Shanghai in WWII.
In this occasional series I’ll explore historical cases where hacking really counted; cases where lives were saved or improved by a hack performed under desperate conditions.
A Bustle in the Hedgerow
Unsurprisingly, war offers a lot of opportunities for field expedient solutions under dire circumstances, and battlefield conditions might be the most extreme example of hacking when it counts.
In the early days of the Invasion of Normandy during WWII, Allied forces were having a difficult time dealing with the bocage terrain of northern France. A mixture of pasture and woodland, the Normandy bocage was a natural killing field for Allied tanks because the woodlands took the form of hedgerows – earthen dikes topped with thick tangles of brush. Hedgerows separated pastures and kept livestock controlled, but also made things tough on infantry and mechanized cavalry alike. Climbing the steep hedgerows exposed the vulnerable bottom hull of the tanks to enemy fire, and waiting for engineers to demolish the hedgerows with explosive made them sitting ducks for German artillery. The Allied advance was seriously hampered by the hedgerows, and both men and materiel were being winnowed down from fixed German positions chosen specifically to take advantage of the bocage terrain.
Enter Sgt. Curtis Grubb Culin III. Sgt. Culin, a tanker himself, was acutely aware of how vulnerable he was in his Sherman M4. The hedgerows were the problem, one apparently known to Allied command prior to the invasion for which no provision had been made. In the tradition of soldiers at the front of every battle throughout history, Sgt. Culin and his fellow tankers had to improvise a solution.
While kicking around ideas, one of the men suggested setting saw teeth on the front of a tank to cut through the hedgerows. He later attributed the comment to “A Tennessee hillbilly named Roberts”, and it was met with general laughter from the group as a crackpot scheme. But Sgt. Culin saw the potential in the idea, and began to develop it into a prototype.
Raw materials for his prototype were not hard to come by. Czech hedgehogs, giant anti-tank barriers made of crossed steel beams, still littered the Normandy beaches. The failed German defenses were harvested with a cutting torch and welded to the underside of a tank to form a series of “tusks” across the hull between the tracks. Equipped with these tusks, the tank could now blast through the tangled roots of the brush-covered earth of the hedgerow dykes.
When demonstrated for General Omar Bradley, he was impressed enough to order them built in quantity for the tanks. Eventually the prototype became an engineered product (dubbed the “Culin Rhino Device”) that was fitted to many tanks before being shipped over from England. Rhino-equipped tanks ripped across Normandy and shredded the German battle plan, which assumed the hedgerows would funnel Allied forces through heavily defended chokepoints.
Without Sgt. Culin’s battlefield hack, and his inspiration by a hillbilly named Roberts whom history otherwise forgets, the invasion of Europe might have taken a very different course. The fact that he did the hack while under fire makes it all the more impressive, and is a perfect example of hacking when it counts.
Know of any more examples of hacking when it counts? Send us a tip for use in a future Hacking When it Counts article.
There are a lot of robotics platforms out there, and whether for educational use or for robot fightin’ time, two things remain constant: tracks are often the best solution, and there aren’t very many modular track systems that can be used with a variety of designs. There are even fewer that can be built at home. [jupdyke]’s project fixes that. It’s a modular and easy to replicate system for tracked vehicles.
The design for this system of track uses roller chain, chosen because the components of roller chain are mass-produced in incredible quantities, sprockets are available in every imaginable size, and all the parts are available in different materials.
Rolling two chains around a few sprockets isn’t a problem; the hard part of this build is figuring out how to make the actual treads, and then making a lot of them. [jupdyke] is making them by 3D printing a few mold masters and doing a few test prints with silicone and polyurethane rubber. For a one-off project, it’s a lot of work, but if you’re making thousands of tracks, molds are the way to do it.
If you’re building a robot for off-road or rough terrain, chances are you’ve thought about using a tank-tread style drive. There are a ton of kits available with plastic tread and wheels, but they are typically really expensive or pretty flimsy. Instead of going with an off-the-shelf solution, [Paul B] designed a heavy-duty tank tread made with common bike chain and conduit.
Some DIY tread designs we’ve featured just use a single bike chain on either side of the tread pieces. This gets the job done, but each section of tread is usually bolted through the chain. This means that you can’t use a sprocket to drive the chain since all the bolt heads block where the teeth engage. Instead, these designs typically use drive wheels inside the tread, which are prone to slip under a heavy load. [Paul B]’s design is a bit different: it uses a DIY double-wide chain so he can bolt tread segments to the chain and still use a drive sprocket.
Constructing the double-wide chain took quite a bit of work. [Paul B] completely disassembled a couple of bike chains with a delinker tool and then reassembled the chain in a double-wide configuration with M3 bolts instead of the original chain pins. Each section of tread (made out of cut pieces of plastic conduit) bolts on the outside section of chain, and a sprocket runs on the inside. His DIY chain approach saves him money too, since double-wide chains are pretty expensive. Since his sprockets directly engage the drive train, his design should be able to handle as much torque as his drivetrain can put out.
There are just somethings you don’t see often when it comes to motorcycles, 2 wheel drive and tank tracks. Well, [jeep2003] has combined both those oddities into one project he calls the Track-Powered 2×2 MiniBike.
As his descriptive project name suggests, this minibike has tracks instead of wheels. The track assemblies originally came off a snow blower. As if just having tracks wasn’t difficult enough, both sets are powered. The back has a straight forward chain and sprocket setup while the front ads in a clever jack-shaft and universal joint contraption which is shown in the video after the break around the 3:08 mark.
[jeep2003] doesn’t say where the tubing for his custom made frame came from, but from the photos available it appears they were once old bicycle frames. The powerplant is a 6.75hp vertical shaft Briggs & Stratton engine. The output shaft connects to a Peerless 5 speed transmission that also has reverse. This transmission usually outputs to two rear drive wheels of a riding lawnmower. [jeep2003] dedicates each axle output from the transmission to power one of the two track systems.
Although this minibike won’t be breaking any land speed records anytime soon, we here at HaD still think it’s a pretty rad build.