Lauwenmark

The Hound: a Wolf redrawn Although the RbtKpfW III/A (and B) made a quite satisfying exploration unit and firing platform, it wasn't without flaws: poor turning radius, underpowered offensive tactical subsystems and limited telemetry limited its use to one of a command unit. The OKL - Lego's military high command - still wanted a heavy armoured vehicle suited for offensive strikes deeply into enemy territory. Given that Heimser Waffenfabriek AG, designer of the A and B revisions, was unable to improve it further, the OKL called for help another industrial weapon manufacturer, Société des Gladiateurs, to work on the problem. The engineers at SI rebuilt most of the chassis from scratch, only keeping the general shape. The main improvement was a much better power distribution system, finally allowing it to support a heavy artillery piece. The resulting robot, registered as Robotkampfwagen III Ausf. C "Snow Hound" was equiped with the rather powerful 10-studs Heimser's Howitzer, making it a formidable long-range artillery platform feared by many. Despite the limitations of its cannon (the 10-Heimser being long to reload and difficult to properly direct) as well as the reduced walking speed against previous versions, the RbtKpfW III/C was one of the most powerful heavy war machine of its time and played a key role in many battles. Design notes As said above, the chassis has been entirely redesigned from scratch. Only the head and the legs survived from the previous version. Both pairs of legs are not fed by a single axle running from front to tail. The motor in the tail is connected to it through a pair of clutch gears. Transmission to the legs is performed by worm gears. The result is that although the robot is a little slower, it can now move with only a single motor, instead of two. This frees one for supplementary functions. Turning is still performed as before - a pair of linear actuators control the turntable binding the front and the back parts of the robot. Since the machine is a little shorter, the maximum angle of turning is slightly bigger. The top front engine is now not connected directly to the actuators anymore - instead, the third motor under the robot is used as a selector between the "cannon" and "turning" functions. The selection between functions is performed by a "piano" selector system. The first picture shows a single "piano" function selector in engaged state. The "selector" clutch pushes a 2x4 L beam on which two gears are fixed: the driver gear (connected to the driver motor) and the transmission gear. The transmission gear is pushed against the output gear, hence when the driver turns, the output turns. The single picture shows the same "piano" selector in disengaged state. The selector clutch doesn't push the L beam anymore; the transmission and output gears are not connected, so when the driver turns, the output doesn't move. By grouping several of such L-beams with selector clutches at a given angle with each other, you can easily select between many different functions. "Snow Hound" uses a pair of 3x5 L-beams with 16-teeth gears; the spring mechanism is made of rubber bands attached to sliding axles hidden under the front of the robot. The cannon is crude, ugly, but very effective - with a proper rubber band, it can throw a 10-length beam several meters away. The orange 2x4 L-beam visible on the picture holds the missile (a 10-length beam with a black pin) in place and is attached to the 16-teeth gear. That gear is blocked by a rack. When the "cannon" function is selected, the driver motor makes the rack move away from the gear, freeing it. The stretched rubber band is then strong enough to push the orange L-beam away, letting the missile free. The control system is basically similar to the one used for the previous version of the model: an NXJ program running on the NXT exchanging data through bluetooth with a remote computer running a client java application. Not a wonderful model by far - but at least, unlike the first I built, this one works! :) I'll probably try to improve the design of the cannon - the current one looks awful - and, of course, the software side, which is currently little more than a remote control. Advices and opinions welcome!

*cough* - my camera was non-functional, so the video was delayed somewhat - apologizes for the lateness :)

Not yet - it was too dark already to take one. I'll try to make one Tomorrow morning :).

Edit (September 10th): I finally got a video of the beast walking :) History The High-pressure Turtle After the failure of the Robotkampfwagen II project, the OKL - OberKommando des Lego was left with virtually no heavy tank to replace the obsolete T1-Cs, designed more than 30 years before. Professor Edband Heimser would get them out of that dead-end. Heimser had previously studied the past campaigns of the empire in the central territories. He got to the conclusion that mud always was one of the biggest issues, severely hampering the advance of the armies for several months each year. He thus worked on legged vehicles that would be better suited for such difficult conditions. The first prototypes built by the Heimser Waffenfabriek AG made attempts to reuse the new HPV-6 (Hochdruck Pump V-6) compressor designed for the RbtKpfW II project. Heimser wanted to use pneumatics to operate the knee joints of the legs, controlling the upper leg joints with more conventional NXT engines. While theoretically correct, that design choice was actually a mistake. The HPV-6 had been designed to power slow-motion devices with no more than two pistons working at a given time; for Heimser's planned use, the compressor was vastly underpowered, unable to maintain the pressure needed for more than a couple knee movements. Attempts to increase the threshold pressure in the pneumatic circuit weren't successful; when five workers were injured by the explosion of a high-pressure conduit during a test, Heimser decided to scrap the idea and went back to the drawing board. The failed prototype - nicknamed Hochdruckschildkröte (The high-pressure turtle) was dismantled at the Imperial Scrapeyards shortly thereafter. The following pictures were taken after the electronics were removed, shortly before the turtle was scrapped. The Snow Wolf The new prototype used a more conventional "pantograph-like" leg design, giving less degrees of freedom than the HPV-6-based robot, but ensuring better stability and strength. Each pair of legs was powered by its own NXT engine. The front and the back were designed as separate entities, joined together by a turntable part to allow the model to turn. Turning was controlled by a third NXT engine powering coupled linear actuators. A tail gave the machine some supplementary stability. The now traditional Ultrasonic detector was used as the primary long-range scanning device; audio capture was added at the front while a contact sensor was appended to the tail to complement the sensor array. The first test prototype was presented to the OKL and immediately received strong support. The project was classified as R3X-1 under the name of "Project Snow Wolf" (Schneewolf). Minor design changes were made to the steering system, while a more complex rear gear train was implemented to allow the future connection of an electrically-powered 12std cannon. The initial series got into production shortly thereafter under the designation of Robotkampfwagen III Ausf. A. The RbtKpfW III displayed here is such a "A" revision. The "B" revision was externally identical, upgrades being entirely in the controlling, featuring a brand new control panel designed by Lejos Industria. Although performing as expected, the RbtKpfW III/A and /B revisions weren't without faults; rushed in production before all mechanical issues could be resolved, they lacked several planned features. In the initial design specs, the head could rotate to allow a 135° sonar scan in front of the machine; the /A and /B revisions had a fixed head, forcing the driver to stop and flex the robot body left and right to get a rough equivalent. Moreover, it lacked a complete gear train to power the planned 12std cannon, forcing the OKL to equip it with much smaller artillery pieces. Finally, its rotation radius was quite big, often forcing the driver to perform several back-and-forth maneuvers to make a 90° turn when space was limited. Despite those shortcomings, the RbtKpfW III performed well on the battlefield. **** Design notes Nice points: It can move by itself, which is a huge improvement over my previous model ;). It also does what I wanted to get: a remote-controlled walker. Not so nice points: I wanted to implement a system to derive a new function from the motors - the idea was to use a differential as a "substractor" between the front and back leg motors - the derivation would turn only when both motors were running in opposite direction. I didn't manage that - I was not able to find a way to fit that on the chassis. It would have been fun to use it as a rocket launcher platform, though :). The gear train visible at the rear is part of that - it currently serves no other purpose than moving air around :). Short-term plansFinish writing the controlling software - I wrote a small Java control panel to command it from my laptop, but it is quite ugly and doesn't really do anything with sensors yet. And who knows, maybe I'll find a way to finally fit that damn 12std cannon on its back? :) **** Thoughts? Ideas? Opinions for improvement welcome!

No offense taken - that's quite a likely possibility; I just wanted to try a few things with what I got before going the easy way. Even if the result is a dead-end, it was fun trying :). Aah, that's indeed interesting info for sure! I've also found the philohome's motor comparaison page, which is definitely an invaluable piece of data. That taught me a lesson: check good ol' Internet *before* designing a model :D. Oh, sure, but where would I have spent all those headaches? :D Just like its glorious(err?) ancestor the Panzer VIII Maus, the RbtKpfW II Ausf. B is an error of nature that deserves the Pit of Oblivion. But for sure I've learned a few things all the way. I'll now whip the design braincells so they quickly come up with a better prototype! ;) Thanks for the comments!

Well, I didn't try to make it as complex as possible intentionally :). I started by developing the base chassis with the four wheel suspension. I only owned a single differential part, so I built two out of multiple gears instead. But those differentials have the drawback of being larger than the pre-made ones... And so the chassis was set as a rather large one. The second issue I had to face was the motorization of the whole. I had planned to use one NXT motor for direction, a second for propulsion, and the last one I own to control extra function (a top arm). Given the weight of the chassis, I couldn't use the NXT motor for propulsion directly - it obviously lacked torque. I then changed plans, and thus decided to use the much more powerful XL, with the NXT controlling its course. The last problem was powering the pneumatic compressor. The first design of the motorization control circuit used one NXT motor to flip the XL switch. The problem with that approach is that since the compressor could be needed at any time, I had to find a way to 'shut down' the wheel power while maintaining the compressor circuit alive - and thus, I needed a gearbox. The weird rotating design I made for it came from that I needed a synchronized gearbox. Its main flaw is exactly what Zblj underlined: it is too sloopy to drive high-torque functions. I'm not sure I understand the remark about the alignment of the wheels - I made tests, and the chassis seem to turn well, without breaking down or imposing hard constraints on the parts. I understand your remark about the compressor - I just checked your site after having read the link to your gears tutorial, and found a model of compressor that uses the same basic structure as mine. The lever part of your design is not the same as mine, so I'll try your variant and see if it isn't sturdier than what I had done myself. You obviously are way more expert in brickology than me! :) As for the shock absorbers, well, I have no real choice - those are the only ones I own! :) Sure enough, I could try to find more/harder ones. On the short-term, I have made tests to increase the hardness of the suspension by binding the left and right suspension elements with a large rubber band underside the car (I removed those to make pictures). This makes the suspension hard enough for the weight, although of course it would have been better with using only real lego parts. Now indeed, the result is definitely a clockworker's nightmare, I'm very aware of it :). That's why I'm trying to design a better, sturdier way of powering the wheels and control the direction of the rotation. But I admit that I don't really know how to solve the issue without buying specific parts, like pre-made differentials or 16-clutched gears - but that would be cheating, in a way :P. Replacing the suspension train by a dual pendular system would of course help making the chassis somewhat smaller and lighter, but that would be giving up the 4-wheel independent suspension. Maybe I expected too much from the brave old Lego? I was probably overly ambitious... :) Probably the best would be to scrap this model and rethink it entierly, *snif*! Thanks for the comments! Edit: Added a view of the wheels turned at the maximum acceptable range here. Not exceptional, but good enough for my needs.

Note: After extensive testing, the OKL - OberKommando des Lego - concluded that the RbtKpfW II Ausf. B prototype was "unsuitable for the battlefield" and withdrew the project. The following is thus kept there only for historical purposes. Hello! The Robotkampfwagen II is my first attempt at a 'major' homebrew Lego design since more than 15 years. And, well, it seems that I'm not skilled enough to successfully complete it... The original design goal of that model was to create a sort of "explorer bot", a remotely-controlled robot with a rotating "sonar" sending the trace of obstacles around to the computer performing the control. Some pictures of the model in its current stage can be found here. In particular: - Full side-view; - Full top-view (Wheels turned); - Detail view: read gearing train; - Detail view: front gearing train; - Underside view: 'gearbox' assembly; - Underside view: compressor and front differential; - Rear view: rear direction transmission; Current design notes: - Suspension: Spring-based. Each wheel got an independent suspension. - Motorization: I have used a single Power Function XL motor as the main movement engine. Each pair of wheels is connected with a hand-made differential. The main design idea regarding the engine is that the XL Motor is never stopped - instead, I use a 'gearbox' to select between the two possible directions and the 'zero move' position. This is because I wanted the same motor to be connected to the pneumatic compressor, hence it was important to allow it to turn even when the robot was not moving. - Movement selector: the 'gearbox' to select the direction of the current movement ('advance', 'rear move', 'stop') is controlled by a single NXT motor. This is a rotating wheel on which transmission gears are fixed. By rotating the control wheel by 180°, the movement is reversed. Any intermediate position of the control wheel disengages the gears, so the car stops moving. - Direction: An NXT motor controls the direction. It is rack-and-pinion-based. The pairs of wheels are connected by bars, and gears transmit the movement from the motor to the bars. - Compressor: The initial plan was to connect the compressor to the XL motor and use it to drive an arm that could be used to grasp and carry small objects around. Currently the compressor is mounted, but not connected to anything. The main issue with this model is that it is way too heavy! The power transmitted to turn the wheel is not sufficient, and the gears of the movement selector tend to slip, because the resistance is too high. I'm unsure on what I should do now: should I scrap the model completely and restart from scratch? Maybe somebody here has a better idea on how I could make the model functional? I'd like to get advices about this from more experienced people than me. Anyway, thanks in advance for any help!

Hello, people! Long ago, there was an Empire whose greatest asset was its Lego mines. Extracting the finest quality parts from its huge supplies, minifigs of the Empire erected cities, built machines of all kinds and waged wars against their arch-nemesis Kingdom of Bigger Sister. The orders of the Emperor were dutifully executed, from the Bedroom Capital to the faraway countries of Living Room. Then came an era of scientific discoveries. The discovery of the pneumatic technology led to dramatical improvements in the daily lives of the citizens of the Empire. Machineries of peace and war led to a Golden Era of technology. Wired telegraph allowed instant communication across distant provinces. The mastering of the rubberband accumulator technology became a key point in the imperial military weaponry. Boats and submarines were experimented with some success. Computing machines were built for the greater good of science. Then things changed. New populations came from the mountain borders of Televisia. They called themselves "The People of Mario", and came known to the Empire as "Nintendists". Although ultimately winning exhausting wars against them, the Empire left the conflict weakened. When the Computian tribes invaded its borders a few years later, the Lego civilization had to concede most of its former territories to the newcomers. Yet the Empire survived, somehow. Although greatly diminished, its science was not forgotten. Remains of its glorious past were kept as sacred relics by the Order of Librarians, carefully ensuring that all necessary material was kept safe for better days. Then came a rumor from across the oceans. Travellers and traders from overseas spoke about strange living machines born from a new science that puzzled even the wisest Technifig giants. The emperor sent an expedition in an attempt to learn more about those legends. The tale of their odyssey is now so famous that I won't retell it again here; suffice to say that they bring back one of those strange pieces of technology, studied it with careful attention, and quickly put it into use. And so started the Era of the New Empire - technology rose to unprecedented levels, and the old knowledge of the Librarians went out of their dusty books, coming back to life. The New Empire is now stronger than ever, and ambitious projects are being laid down, offering to its citizens a bright future. At least, that's how they tell the story of my Lego bricks. And who am I to contest what my very own minifigs are telling? :P