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I've made a new gearbox for my next car. This gearbox can either be set to a gear ratio (driving the wheels) or to a function, allowing the drive motors to power something else. In total, there are 4 forward gears, 2 reverse gears and 6 function "ports". The reverse gears weren't intentional - they happened to exist when I added the gearing for the forward gears. The gearbox consists of a turntable with an off-center gear positioned on it. This design uses two off-center gears on the same axle - an 8t and a 12t. This allows more meshing combinations. The off-center gears are driven by a 24t gear in the middle of the turntable, which is powered by the drive motors. Around the turnable, there are many axles with gears on them (12 in this design). When the turntable is rotated correctly, one of the off-center gears meshes with one of the gears on the outside, turning that axle. Some of the axles are connected with extra gears to form a transmission with different speeds; the unconnected ones will be used for functions. Here you can see the internal workings of the gearbox. These are the gear ratios (including the 3:5 gearing before the transmission): Gear 1: 1:2.5 Gear 2: 1:3 Gear 3: 1:4.167 Gear 4: 1:5 Reverse 1: 1:3 Reverse 2: 1:5 Functions 1, 3, 4 and 6: 1:7.5 Functions 2 and 5: 1:5 The gear ratios are rather close, and the reverse ratios are too high, but there is little choice in choosing gears since all of them have to mesh properly with the off-center gears on the turntable. I made all the gear ratios quite high since I'm planning to drive the vehicle with 2 EV3 Large motors, which have tons of torque. There are two inputs - this is purely because I plan to use 2 EV3 Large motors - one on each side of the gearbox. The shifting input drives the turntable with a 28:8 gear reduction - this could be increased, possibly with a worm gear. Note that it is ESSENTIAL to use a MINDSTORMS motor for shifting, since the shift positions are in strange places and not in order. This gearbox can handle plenty of torque - the gearing up before it does help. However, when under high load, the turntable can move out of place and make gears grind. This gearbox works best with minimal backlash on the shifting input. Also, some clever programming can make the turntable adjust its position a little bit depending on the amount and direction of the load, countering the forces pushing the gears apart. The gearbox is very compact for its functionality - comparable in size to a 4-speed sequential gearbox. However, it can only be used with a MINDSTORMS motor for shifting, which will make it useless for most of you guys (unless of course someone develops a version that can be controlled by a PF servo...) -
Hello all, I want to present you all my newest MOC: Switch Engine UW [front/right] by UrbanErwin(EPJL), on Flickr It is an switcher for railyards. The build is 7 studs wide. Switch Engine UW [front/left] by UrbanErwin(EPJL), on Flickr Switch Engine UW [back] by UrbanErwin(EPJL), on Flickr Switch Engine UW by UrbanErwin(EPJL), on Flickr Switch Engine UW It is used by the fictional company UW. As you can see my sticker skills are far from perfect. Thanks for reading, Comments, constructive criticism and likes are always appreciated. Erwin by UrbanErwin(EPJL), on Flickr
