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First and foremost this is not my MOC. As promised in his thread, I finally found the time to build @PTNYC’s Rocket Crawler. Now, I don’t call it the Rocket Crawler, and made some modifications (discussed below), but other than these this is his build. Also, I am creating a new thread for this and other builds as I am also building his Chili Crawler. I did this years ago, and I loved it. One of the more fun Lego models to drive out there. HOwever, I took it apart; so I had to rebuild it with minimal changes. Original video can be seen on my YT video. I plan on doing more videos with these two beasts and some comparisons. At this point, I do not know which, the Rocket or the Chili crawler will be superior. The Rocket has 2x the power, but also tons more weight as well (need to get an official weight). It will be interesting to pit them against eachother. My money is on the Rocket, with a longer wheelbase and likely (unconfirmed) better power-to-weight ratio. But as for now, here is my version of PunkNYC’s Rocket Crawler. I call it the Bully Crawler. This thing really is a beast. Really the only differences I made were to the body/appearance, the tires and hubs, and added planetary gear system inside the tire hubs. Final gear ratio is 3:1 x 4:1 = .0833. If we take information from philohome then the final RPM output for each axle would be approximately 31 (unloaded). ANother reason for this new post is that I wanted to share a few principles of rock crawling for Lego. I know these principles from personal experience with the sport. Not with Lego or RC Crawlers, but with rock crawling in side-by-side vehicles. One is the advantage of having good, strong steering. In crawling, it is often necessary to begin at one angle, only to turn against that angle while locking your brakes so that your tires bend into the rock as you turn. This can cause immense pressure and an exceptional power steering system is needed. In the video I am posting this can be demonstrating when at the top of the “hill” (minute 2:26) I am steering one direction that is about to steer me off the hill, but then I stop, (vehicle is locked so it doesn’t roll backwards) and then turn the other direction. Because the vehicle is locked in place and I am bending the tire against the obstacle I am creating something like a “pinch” technique. Not only am I increasing traction as I increase the tire’s surface area over the rock but I actually am pinching the obstacle against the front and back tires (because they are staying in place). I tried to climb the obstacle in question multiple times without this method and I could not make it. Using this method however the crawler was able to overcome it handily. Another principle, at least in Lego crawlers with no brakes, is to have the drivetrain so heavily down-geared that it is near impossible to turn motors from the tires. This serves as brakes for going down hairy slopes. If one is not cautious about going down, with a good crawler the greater impediment may very well be going down a mountain rather than going up! In minute 3:58 of this video one can see how well this is demonstrated. If the gearing did not stop the vehicle, even though I was giving no power, it would have easily tumbled down my little “hill”. In another video I did years ago with my modified Chili Crawler I had an incident where this was even better represented. My Crawler was going down a slope (minute 2:36), and one tire even became airborne, but because of the intense resistance in the drivetrain when power was cut off it stopped dead in its tracks, stopping what would have easily been a failed attempt at de-escalating that obstacle. Here are the two videos. Enjoy!