Continually Variable Transmission with Clutch & Reverse

i recently made a ball shaped omni wheel and then made three of them and attached them to an omnidirectional robot which can move in three axes and mix the axes together so that it can move in both translation and rotation at the same time this worked out pretty well even driving over some obstacles and i'll be revisiting this type of wheel for another build in the future each ball shaped wheel has a main driven axle and also a perpendicular axle with two hemispheres and an idler wheel mounted the two hemispheres and wheel are currently passive they're just mounted on bearings so they spin freely this is very similar to standard omni-directional wheels and provided there are at least three wheels on the robot we can still just power the main axle and move in any direction there were some suggestions in the comments that we could power these hemispheres as well to make a one or two wheel balancing robot this would be possible although we'd have to vary the speed of each of the hemispheres as the main axle rotates this is because the effective circumference of each wheel touching the ground changes as the contact point with the ground changes as the wheel rotates about its main axis however we can use this to our advantage by using this mechanism in reverse and using it to make a continuously variable reduction there are various examples of continuously variable transmissions and some are used in real vehicles often these consist of belts on pulleys that can change diameter and some even have arrangements of balls between two plates so today i'm going to make a really simple example of a ball-based continuously variable transmission that we can use for something practical my plan is to use one hemisphere on a pivot running between two wheels one wheel will be powered and the other is the output as the hemisphere pivots the circumference of the hemisphere that runs on each wheel will change to give us a variable reduction i'm going to use my version 2 cycloidal drive reducer to drive the input since that has plenty of power and i'm going to drive two outputs each with their own variable reducer [Music] [Music] thanks to 3d fuel for the filament for this project and lots of other projects so check out my channel for more 3d printing projects and check out 3dfuel.com the hemispheres are made of tpu and those have a rigid core which has some bearings mounted so we have the flexible part on the outside and something rigid for it to run on on the inside with two eight millimeter internal diameter bearings mounted there are two of those one is yellow and one is blue and both of those spin freely on the two skate bearings which are mounted on there and those are mounted on eight millimeter steel shaft i've got two pivot blocks which those are mounted on and that allows the whole assembly to pivot and the hemisphere to still rotate freely each hemisphere is actually slightly less than half a sphere but the pivot point that the whole thing pivots on is in the middle of where it would be if it were a ball i found my cyclodal drive version too which is exactly how it was since i tested it with the skateboard and you can check that video out in my channel that's mounted onto a plate that we can mount the whole mechanism on and we've got a wheel on there with another tpu tyre which is the white part around the outside of the yellow the black plate holds two other orange mounts and those hold the two pivots holding the hemispheres on each side we've got just enough friction there that we can disengage them and engage them and run those hemispheres at different speeds as we adjust the angle i've slowed down the motor so we can see what happens but you can see as i tilt the hemisphere onto the smaller circumference rubbing on the wheel then the screws go round faster and if we tilt it back then it goes much slower even though the cycloidal drive and its output wheel are both spinning at exactly the same speed so all we need now is the output that's actually going to end up being the wheels of a robot and again i've got a tpu tyre on a wheel with some skate bearings fixed in the middle and these fit on either side we'll come back to how they freewheel in a moment but let's just put a mark on the wheel so we can see how fast they go with the motor running we can see that we now have a continuously variable reduction as i tilt the hemisphere if i tilt it so the larger circumference is rubbing against the output wheel that means the smaller circumference is running against the cycloidal drive wheel and that's gearing us up to give us a faster wheel on the output and of course if i move it back the other way then the smaller circumference is running on the output wheel and the bigger circumference running on the cycloidal drive output so that gears us down so that we can run the wheel slower and of course we've got a dead spot in the middle where it's de-clutched even though the motor is still running and that's there because we've got a hole in the bottom of the wheel which essentially gives us a dead spot as you can probably tell by now i'm planning to make this into a two-wheel robot that i can drive with servos pulling the clutches and continuously variable transmissions however there's one slight flaw in the plan which is that the wheels will only ever go in opposite directions and that means that the robot will always spin on the spot and will never be able to drive in a straight line the fix is pretty easy though and that's to complete the sphere by adding another hemisphere so we have a complete ball which runs between the two wheels and that means wherever we tilt it it's always getting driven by the wheel which is on the output from the cycloidal drive but before we see how well that works it's time for a quick hand from the video sponsor which is keeps i've got lots of hair but did you know that two out of three guys will experience some form of male pattern baldness by the time 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that's k-e-e-p-s dot com slash brewton so now if i tilt the lever in one direction we can vary the speed of the output wheel in one direction it's d-clutched in the middle and if i push it the other way then the wheel goes in the other direction the sphere is always spinning in the same direction but a different side of it is running on the output wheel and that means it can change direction so that seems to be working pretty well so to save me having to operate those manually i'm using two servos which are high-tech hs 805 bb pluses and those fit in each side on a plate mounted on the top of the robot like so with two levers which are going to operate the main levers i've been operating manually so far now this is just a test to see how well these clutches work so the whole thing looks pretty hacky like most of the other projects i've built recently on the front we've got one 24 volt battery and we've got a vesc which is powering that cycloidal drive which is going to run pretty continuously while the robot's in use on the other side we've got an arduino mega with the nrf24l01 radio receiver and a boost pack to power it as well as a 5 volt regulator that's going to power those fairly hefty servos i'm using my universal remote which came from open dog 2 as usual which has the other arduino mega and the other half of the nrf24l01 link which is going to read those knobs and send us the data i thought varying the motor speed would be pretty handy so i've coded it up so i can jog it up and down by twisting one of my remote sticks and change direction by twisting it in the other direction and it goes up and down in quite good increments so now i've just connected those servos to each stick so it'll steer like a tank remember they both move in the same direction to move forward on the opposite direction for it to turn the servos seem substantial enough to move those clutches and continuously variable transmission balls they are actually pretty stiff to move by hand so i wasn't sure how well it would work but it seems to give us a good graduation of speed we've got the dead spot and we can move in either direction pretty well so now it's time to power it up on the floor and see how maneuverability is and how well we can drive it especially in a straight line [Music] [Applause] [Music] so [Music] it [Music] [Applause] [Music] foreign [Music] that's actually pretty easy to drive and it's quite maneuverable as you can see the only disadvantage is driving with two sticks i really should have just driven it with one stick by pushing forward and backwards and left and right and make some code that mixes to put the servos in the right positions because it's quite hard to push them forward exactly at the same time in a straight line to drive in a perfectly straight line but the clutches work and that's the main thing we wanted to test with this demo the only slight issue is of course when we de-clutch the wheel can freewheel so if i was moving an id clutch it still rolls so to fix that we really need a worm gear after the continuously variable transmission and clutch so that it can't back drive and it just locks but that means we could have multiple clutches like this on one big drive shaft perhaps with lots of wheels running and we could control a robot arm a bit like the 80s toy armatron and we could have lots of servo clutches all the way along and lots of gears or cable drive for something more elaborate but i'm pretty happy with how that's gone and i'm going to publish all the cad and code so you can find that link in the description to github where you can find all my other open source projects so if you'd like to support me through patreon or youtube channel membership those links are in the description as well and patrons and youtube channel members can get access to all the videos up to a week early and sneak peeks and pictures of what's coming up so you can be part of that discussion alright that's all for now [Music] you

Channel: James Bruton

Views: 233,253

Rating: 4.9567494 out of 5

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Id: KXb1gDpeq-Y

Length: 12min 58sec (778 seconds)

Published: Mon Jun 21 2021