Compact CVT manual gear shift 6×6.5×3 studs, from gearing ratio 1:2 to 2:1
About this creation
My compact CVT manual gear shift model was inspired by Sheepo's linear actuator controlled CVT gear shift. I wanted to simplify and downscale it for smaller scale, non-RC models. Also, important issue was relatively good torque tolerance. I tried to achieve it replacing rubber bands of Sheepo's model with tension of ABS frame itself, to generate sufficient friction between the 2 cone wheels and the rubberized friction wheel. The disadvantage of this solution that the lenght of the unit is not integer number of studs. It dimensions are 6 studs height × 6.5 studs lenght × 3 studs width. It can shift continuosly from gearing ratio 1:2 to 2:1, pushing the yellow lever forward/backward, which slides friction wheel with the help of a fork. Friction wheel can run and slide freely on the oblique axis. Of course, this CVT has no reverse gear, but using reversable electric motor drive, it is not an issue.
Quoting Jeremy McCreary
Gabor, A LEGO buddy with a CVT in his car recently decided to build one. A search for examples brought me to yours -- the cleverest I've seen yet. Great design, as always. Jeremy
Thanks. In the meantime, I recognized that intead of using small diameter rubber tyre with separate hub and sloped axis, professional double-cone based CVTs use a large diameter rubber tyre WITHOUT hub and separate axis: one of the cones is inside the tyre, the other presses from the outside. It gives way better friction than small tyre. Hovewer its correct positioning at gear shift is difficult: it requires at least 2 driving rollers instead of the current simple sliding fork. So it wont be so compact.
Quoting Joost Cumps
Genius!!! Can't wait to see an application
Thanks. I will try to put togeteher this CVT, 3 compact Torsen differentials (my earlier design), and portal axis + king pin suspension in a really compact 4WD vehicle. But that will be a long and painful development story.
Quoting XY EZ
Really great! But wouldn't you loose torque with this, because the cones are very slippery? Anyway, really good idea and job, nice alternative to cogwheels! 5/5 8-)
Thanks. The basic idea is Sheepo's, I just tried downscale it. In my experience (originated from Mindstorms tracks) you can reduce slip adding some honey. However, this solution is very sensitive to humidity level: there is a medium level, when it reduces slip maximally.
Quoting Matt Bace
Very impressive! Do you have an application in mind for this CVT?
Thanks. Yes, I just thinking about a very compact 4WD electric driven Jeep, which can be loaded into the cargo/bomb bay of my SkyTank heavy battlefield helicopter curently under construction. It has cargo bay 17 studs wide, 16 studs tall, and 44 studs long. That means a big challenge.