Geared Reversible CVT

Finished tolerancing the holes, and I added the pulley to the input gear. I also changed the large bearing mount for the gear shifter and also redid the lead screw mount because stuff was hitting. Here’s what I did:

• I went through like 70 holes, compared it to the toleranced version that was assembled. Lots of problems happened when I had to oversize the holes. For example, the linear bearing holes on the gear shifter mount had to be oversized, which made the thickness of the wall like 0.8mm thick. I then had to go into my mastersketch and change up the dimensions which took a stupidly long time. Regeneration times are hitting near 2 minutes (300 features isn’t good, plus tons of dependencies, and so many dimensions that it takes up the entire sketch).
• I added the pulley to the input gear. I had to switch to a different featurescript because the one I was using didn’t have GT2. After that it was pretty easy, just had to cad the walls, chamfer a bit and boolean and bore it.
• The most annoying part was that the copper lead screw nut (on the mount) was hitting the 1:1 gears completely ruining the whole thing. I basically had to redo the shaping of the lead screw mount. I moved the copper part further up the part, keeping the standoffs at basically the same level. As a result, I had more space at the bottom for two screws instead of 1. Also, now all the constraints are fully dependent on the external parts, so there’s no random dimensions I did just to make stuff look good, which is good because it means if I change the gearing or something in the mastersketch, the mount should update accordingly. This also took a pretty long time and 2 min regeneration doesn’t help.

Cleaned up a lot of the stuff hitting and a lot of the tolerances too. I also had to do some cooked surface modeling with onshape (I have never surface modeled before). Here’s what I did:

• The blue pieces were also hitting at the bottom, so I had to make the material even thinner than it was (really cooked, near 1.5mm thickness and barely clearing eachother). The standoff placements really cook everything so I’ll probably just extend the plate and move the standoffs further from the gears. However it will be uglier, and I would rather have a good looking cvt that doesn’t work than a ugly cvt that works.
• I had to do some really cooked stuff with surface modeling. Basically, the wrap feature wasn’t working. I spent like an hour or two trying to learn surface modeling, but nothing was working because the shape was weird, so I ended up just doing 8 separate revolutes, boolean, and then some move faces. Also, the bumps can’t be radial because the bearing isn’t radial (it faces horizontal, so the edge closer to the center moves up first which causes the whole thing to jam). To fix that I had to do even more cooked remove revolutes, then bridge curving and then knitting (I had never used these before) and fileting. I need to figure out a clearer way to do it because it’s getting on my nerves.
• I went through the latest V3 and compared around half of the holes to the V2 (it turns out there’s like 3 holes per part and theres like 100 holes to go through, not including clearances). The clearances also cooked some of the spacing so I went and fixed that.

I’ve been spending some time thinking about the 1way bearing solution, and I completely switched up and now think it’s impossible.

Finished most of the cad, just need to clean up tolerances and split a few parts. Here’s what I did:

• I made the rings for the gearshifter bigger because the gear shifter mount on the lead screw was hitting the center 1:1 gears. This caused lots of issues with sketches breaking so I had to redo those.
• I had to change the gearing for the last stage. The 1:1 gears were hitting the bearings so the only solution is to move the bearings further from the center, hence change the gear ratio. This also caused tons of problems and I had to redo a lot of the parts again, especially the gear shifter mount that mounts onto the lead screw.
• I added cutouts onto the blue part (it’s gray now, but the one that houses the bearing that the dog clutch goes on. The blue parts used to be hitting the 1:1 gears but now it clears by like 0.5 mm.

I’m still deciding whether I want to assemble this or not. I can’t figure out the 1way bearing based thing, and I’m starting to feel like it’s fundamentally impossible.

I mirrored the whole thing, and the V3 looks complete but there’s some fundamental flaws. I also thopught a lot about the 1way bearing based solution. Here’s what I did:

• Mirrored the whole thing onto the other side. I didn’t run into any spacing issues which means I’m good at mastersketching.

• Currently, the 1:1 gears are hitting the big bearing that the dog clutch is in. I dont’ know how to fix this because it means I’ll have to change the gear ratios.

• I spent a lot of time thinking about the 1way cvt that doesn’t use clutching. I realized that I could put the input gear on a 1way bearing and somehow run different sets of gears based on the direction. However, everything is inevitably linked to the same output which jams everything. Also, the arm system is inherently not backdrivable which is makes the input on a 1way bearing solution not work. I’m gonna have to think more about a better solution.

I need to do some finishing touches to the V3, but I’ll spend more of my time thinking about the 1way bearing cvt.

Made the 1:1 gears to power the cam and made a new rail system for the ring. Today was really productive, here’s what I did:

• initially, I messed with a lot of the dimensioning and spacing with the rails on the outside. I realized there’s no way it was gonna work, and even if it could, it would take up tons of space. I needed a better solution.
• Having the rails on the outside makes everything really big which doesn’t fit. I figured out a way to add a rail inside the tube. Instead of the ring being constrained to a rail, the inside thick square piece is constrained to a rail. This leaves tons of space on the outside for gears (almost 6mm of space on each side).
• I finally added the gears. I had 6mm of space which is more than enough. However, the gears hit the bearings that track the ring, so I’ll probably end up making the ring bigger either way. Another terrible thing is that the gears hit the blue piece. It actually goes far enough to cut into the bearing. Either I shift into smaller bearings, or I change the spacing between the gears. I still have to decide which on to do.

I don’t think I’ll be building this version in hopes of coming up with a way to use one-way bearings.

More cad. I assembled the lead screw and gear shifter. Here’s some stuff I did:

• After building my v2, I realized the ring is super unstable and can easily tilt, causing the whole thing to jam. This is especially true because its only being pushed at one point (the contact of the bearing). Therefore, I added some holes for rails so it can slide along the holes. However the rails need mounts which take up space, taking away space for the gear, so I might switch the rails to something else.
• The rails made the ring bigger so it started hitting the blue piece again, so i changed the position of the standoff to create more distance.
• I assembled the center shaft, which includes the output gears and the perpendicular cam. I had to change up some of the dimensions because it wasn’t fitting. I also removed the from the part because it would make it hard to print, and instead used a separate spacer.

I’m starting to become pretty unproductive at cad because almost 40-50% of the time spent is just thinking about how I can design it rather than actually designing it. I also spent some time thinking about the one-way bearing solution. I finally got my hands on them so I’ll be trying stuff out instead of just trying to visualize them.

Did tons of cad, semi finished the parts (still need to fix some stuff) and started an assembly. Here’s some stuff I did/problems I ran into:

• I cadded the new lead screw mounts for the gearshifter. I lowk dont have any clue what I’ll do about it hitting the 1:1 gears. Hopefully there’s some geometry fixes I can make.
• The bottom moving piece (that moves back and forth following the cam) is oversized and will hit the ring for the ramp. I will change it tmmrw.
• I realized a lot of my new parts are gonna be really hard to print so I split them.
• I started the assembly. I finished the basic side (most of the rest should just be mirorred).
• I have to figure out a better way to transfer torque while also spinning (remember the linear bearings spinning smooth). The current method just has something sliding on a shaft which is high friction. There are actual linear bearings that prevent rotation, but they are crazy expensive and barely produced anymore.

I’ve also been thinking more about the one-way bearing based solution. I realize that maybe the key is just to mirror the whole gearbox and change the direction that it’s clutched in.

Did more cad, especially working on the gear shifter mechanism. I was having lapse and hackatime issues so I couldn’t really record much or post a devlog. Here’s what I worked on and some problems I ran into:

• chromebooks are slow as hell and are literally impossible to cad on (hence i need the macbook). This means the only time I can cad really productivley is at home which is annoying because I don’t do anything at school.
• For the gearshifter to work, it needs to be geared 1:1 with the tubes. This is a huge problem geometrically because it hits the blue piece. In fact, it goes into the bearing hole for the blue piece which means I can’t just cope and be lazy by making the piece thin. The closer I move the output gears to the dog clutch gears, the closer the blue piece moves to the center gear which cancels out making the 1:1 gears smaller. I have to figure out a solution soon.
• I swtched from the cam being sandwiched between bearings to the bearings being sandwiched between the cam because it gives space for the gears to be on the outisde. I’m pretty sure this is also better force wise because instead of pulling out each bearings individually when it moves side to side, the bearings are in contact so you effectively have to pull out both bearings at the same time. Also the lever arm for the center version looks smaller than the version with the separate gear just for the shifting which means less friction.
• I had to tweak the ratios and spacing a bit because the blue piece barely has space. Even now, it’s way too thin (1mm) which I don’t like.

No, I haven’t forgotten the mythical one-way-bearing based concept, I’m still thinking about it. I have a vague idea of what it should kind of look like (somehow have two sets, both of them mirrored, each of them ratcheting the other way). I’m pretty sure there’s a solution but I’m not smart enough to figure it out.

Finalized the sketching and starting making some parts. Here’s some stuff I did:

• I realized mod 1mm is way too small and I want the macbook more than a smaller cvt, so I’ll be sticking with mod 1.25mm.
• I basically went through like 35 features and redo them because of the new dimensions. I have yet to go through 210 more and add more features on top of that.
• Since I’m keeping the gears as mod 1.25mm, I increased the radius of the gear shifting from 9mm to 11mm (like it was originally).
• Based on how the built model performed, I redid a lot of the tolerances. I also needed to cad a new base plate because of the new shape.
• the gears were hitting so I changed the output and dog-clutch gear sizes.

Now that I’m devlogging, I realize that I seriously need to lock in on the constant-speed gears. I’ll be spending lots of time tomorrow working on that.

Look who’s back. Back again.

I was banned from using my personal computer because my parents saw that I was cadding instead of studying for sat, but I just took it and I can finally cad now.

I feel like I’m close to finding a way to eliminate the clutch but I can’t figure out how to yet. Therefore I decided to save it for a v4 and focus on other stuff for a v3. Here’s some stuff I did today:

• I sketched out what the v3 will look like. Instead of a pentagon it’ll look more like a trapezoid because I don’t need the 3rd gear anymore. I’m still not sure if it’s possible to gear the gear selector 1:1 with the outside gears because it has to be bigger than the tube.
• After building my v2, I realized my gearshifting mechanism was completely cooked. It jammed a ton because there was nothing stopping the ring from angling and binding with the tube. Adding fuel to the fire was the fact that the worm gear mech only pushed it from one side making it impossible to stop the ring from angling. I wanted to add support rods for my v2 but it was impossible because the gears were way too close, but now it’s possible because of the new spacing. Also, the worm gear is effectively moved downward, more in line with the centers of the rings, which lets me wrap it around the ring and make bending less easy. I still haven’t decided if I want to stick with ramps or switch to something else.
• I switched everything to 1mm mod gears, but I realized spacing was way too cooked because there’s PROBABLY no space for the cutout for the ramps (or whatever I choose to use, it’s just that I have no space for 2 linear bearings in a row). I still haven’t figured out the cutout dimension fully, but there’s a good chance that I’ll end up switching back to 1.25mm mod. Also, 1mm mod means I need to buy new bearings and stuff which are expensive and cut away money from my stardust payout (which I wanna maximize because I NEED THAT MACBOOK so I can cad during school).

Did tons of math and tons of brainstorming. The math is absolute hell and annoying but desmos is carrying. I got a shape for the non-circular gears for now (they can’t be called elliptical), see the first image. The sharp angles might be a problem with the gears depending on how many teeth are on them, so I may have to change a fully flat output to something very slightly oscillating.

I spent a good amount of time thinking about how to eliminate the clutch. I am no longer as confident about there being a solution as right after opensauce, but I may be onto something. I came up with a mechanical “absolute value” system which takes an input and basically gives the absolute value of it. The input will be both geared and belted to an output shaft, and the recieving gear and pulley will have a one way bearing on them. Since the direction of each recieving thing is opposite to eachother (the gear changes direction while pulley keeps it the same), one bearing will always be ratcheting while the other is transmitting torque. Therefore, regardless of how you spin the input, the output always spins in the same direction.

Also, after doing the math, it turns out that the output osciallting speeds isn’t symettric in both directions: it’s actually faster when spinning one way than the other. This is really good because it gives me a way to differentiate between the two directions. I sitll haven’t figured this out yet but I think I’m in the right direction.

Overall, the math is complete hell and I’m not too sure whether it’s even possible to eliminate the clutch entirely and shift to a system of one-way bearings. However, I do feel like I’m somewhat onto something.

I haven’t devlogged in a while cuz I was busy with outpost/opensauce, but I almost finished the build. I had terrible printing problems (my parts were warping all over the place) and I basically had to print/build the entire thing in 2 nights. As a result i have rlly bad friction on the gear shifting mechanism. After talking to some people at outpost and opensauce, I believe it is possible replace the clutch with a system of one way bearings, so I will spend most of my time brainstorming solutions for a v3 or v4.

I finished printing all the parts and tuned all of the tolerances. I ran into far too many printing issues (I probably wasted as much filament as will be used in the project), especially with bed adhesion. It was to the point where even a 10mm brim with 0 brim-object gap and increasing the bed temp by 5 degrees and washing the bed couldn’t stop warping. But at the end of the day I thugged through and got all my parts. I also ran into some cooked tolerancing with the bearings and even the screw holes for some reason. But all of that is behind me now cuz I can finally start building.

I ordered all the parts and set stuff to print to test the tolerances and I ran into some pretty annoying issues. Here’s some of the issues I ran into:

• There was only 4 packs of 2 3x6 linear bearings in stock so I had to redesign the lead screw gear shifter to use 6x12 ones.
• 32x39 bearings are literally 12 bucks per and there’s only one singular vendor for it so I switched to 30x37 bearings which are way cheaper. In doing so I ran into really sketchy wall thicknesses.
• The slots for the 28mm dowel pins were way too close to the walls of the gear, so I had to change up some of the geometry so it doesn’t just print as a half circle.
• I spent a good amount of time tuning the tolerances so that the bearings would actually pressfit and not slide off easily. Same thing with the dowel pins.
• The biggest problem I ran into was that apparently you CAN rotate linear bearings around a shaft very smoothly. Every google search made it seems like I would break my wrist and explode trying to rotate a linear bearing, and it was pretty shocking to see it spinning smoother than a fidget spinner. This completely cooks my entire design and I still can’t figure out a good solution
• the second biggest problems was that, when switching from 32 to 30mm bearings, I forgot to change the dowel pin size so now they don’t fit in the bearings. I might just end up 3d printing pins if they’re too expensive/take too long to ship.
• a lot of the parts were really hard to 3d print so I split them into multiple to screw in.

Apparently the maximum devlog time limit is 10 hrs. I had 22 hrs logged because I wanted to have some aura post with 40 hrs where the entire thing was built, but I ended up losing 12 hrs instead.

another great lock in, the cad is done (finally). V2 seems like it could work IRL so I’m gonna actually order parts and build it. Today, I split the gray gears (with the tube) into two parts so I can actually assembly it, added countersinks to parts that need it, and fixed up some tolerances.

I don’t have too many new ideas for the V3, but hopefully after I build/test V2 I can notice some key problems. Here’s the general gist of I’m aiming to accomplish:

• Obviously, I need to actually lock in with elliptical gears for the V3. This is the biggest problem with the V2. Because of the sinusoidal motion, the output gear isn’t constant speed (it oscillates slightly too).
• The whole extra gear for the CAM is super annoying, so I’m gonna keep it coaxial to the input/output shaft (running three things coaxial) and gear it from the tubes instead of a separate thing. I need a huge geometry change for this which is why I’m saving it for a V3.
• I want to figure out a better way to do the dog clutch system. I’m hoping there’s a smarter way which doesn’t rely on meshing/unmeshing but so far I couldn’t think of anything.

I’m really happy with where this has come, and I can’t wait to start assembling this.

For those who want to take a closer look, here is the link to the cad: https://cad.onshape.com/documents/c369754a085e1b437744081a/w/8784f23027b47ba880d55ef1/e/7f96dc46c879863ea30c1be9?renderMode=0&uiState=6a3f9f14c9069ebe4a356101

insane lock in, I finished the whole linear motion, and made tons of small changes. Here’s some of the bigger stuff I did:

• I was originally planning to use thrust bearings, but they were way too big. Instead, I just decided to use 3x6 bearings sideways (ball bearings are designed to handle radial load anyway). The packaging was cleaner than thrust bearings anyway.
• for the linear motion, I had to add more dowel pins - linear bearings to stop the thing from rotating with the lead screw.
• I ran into some really stupid onshape problems where everything was off by 0.088 degrees for some reason. I was messing with random parts and doing random mates for like 30 minutes until suddenly it worked. I have no clue how, but that doesn’t matter.
• The linear cams were hitting the 3mm dowel pins inside the gear so I cut out part of it.
• The linear cam seemed really weak, so I connected the bottom of the ramp to the main assembly. This was a huge pain because there’s barely any space, so tolerances had to be tight.

Just one more day of cad and I will be done with it.

Huge lock in, finished up the linear CAM so it should work now, and started the worm gear for the gear shifter. I realized I was doing the linear CAM wrong, and it has to be mirrored instead of just a 180 degree turn, so I fixed that and made a new part for the other side. I also added the lead screw and bearing for the gear shifting. Turns out everything packages nicely (i love uxcell) so I don’t have to do cooked stuff. Just another day or two of CAD and I should be ready to build.

Did tons of changes to the design and continued procrastinating my devlogs. I realized the whole dog clutch thing was too cooked with that little space because it means less space between the bearings for the perpendicular cam. It was also better to change the angle of the linear cam to 45 degrees, and doing so gave me more space. I finished up the dog clutch stuff. I also spent some time cadding the perpendicular cam, and I ended up spending a couple of hours learning surface modeling in Onshape (it was super hard to get it to work). I also put tons of time into thinking about a better way to power the cam: having a whole separate gear is messy, so I wanted to keep it coaxial on the output shaft, but it turns out there isn’t enough space. Hopefully I can switch to this in a V3. I’m also saving elliptical gears for a V3 cuz I have to get this done by outpost. I just need to do some final touches and a full assembly check before I can start building.

I added the dog clutches and realized there’s some big spacing issues. I mated the dog clutches and switched from a 19mm to 18mm length linear bearing. There’s some really bad spacing issues with the linear bearings: not only is it super long, but there also needs to be space between the two separate shafts so that the linear bearings don’t contact two at the same time. However, this distance can’t be too much or else the distance between the clutch and the gear in disengaged state will be too small. I spent some time searching for that balance only to realize that my linear bearing was contacting the flanged bearing, so I changed the lengths up but still no luck. I’m probably going to just make the whole thing a bit wider (because the angle for the linear motion is too steep right now anyway) which should make everything a lot easier.

Finished around half of the assembly. I assembled some of the parts in onshape and realized there’s a few intersections and some of the spacings were off so I changed those. I didn’t run into much problems, but I had a few better ideas that I’ll try implementing in the future:

• It turns out I was being stupid and you need two separate dog clutches for each side. This might actually be better because since they just have to rotate differently but the spacing between them is constant, I can make that outer ring much thicker. This gives me space to bearing sandwich the cam instead of doing some other cooked stuff. However this also means you need two separate shafts which are cantilevered. I need to figure out a way to support the shafts from the inner end.
• While I was assembling, I realized I had done the linear cam (for the gear shifting) wrong because everything can be one part. This will make the entire thing thinner.
• I had a stroke of genius and realized that instead of using that fifth bottom gear which makes everything bigger and ugly, I can gear the perpendicular cam (for the dog clutches) to the gear shifting mechanism, making the entire gearbox so much cleaner. This is kinda cooked because it means the gears will be sliding on each other and because it relies on the tolerancing of 3d printed parts which I don’t trust too much. But if it means making the gearbox look much better, it may be worth it (aesthetics are the most important consideration when designing functional parts).
• I realized I could switch everything from mod 1.25mm to mod 1 or even mod 0.8 because there’s no more cooked gear meshing/unmeshing. However, it may be too late to do this for the V2, so I’ll probably save it for a V3.

The gearbox is not only thinner than the V1, but is also much less cooked. And (probably best of all) the packaging will be really really clean. It does take up more space radially, but that can easily be fixed by switching from mod 1.25 to mod 0.8.

I’ve been procrastinating my devlogs, but I finished up basically all the parts and fixed a ton of problems. Now I can get started with the assembly. I’ve been procrastinating way too much with devlogging because every time I finish recording its late at night and I’m too lazy to devlog but here’s a summary:

• I tried implementing the linear cam (which is just a fancy name for a sliding ramp) but I quit halfway through because there was barely any space and I was too lazy to make it work. I then implemented my old idea (the linkage) but when you mirror it, it takes up 50mm which is huge. I then decided to go back to the linear cam. I added two ramps and two slots instead of just one so its more stable. I plan to add a screwed in 3d print plate underneath so it doesn’t bend. Now it only takes up like 35mm which is slightly better.
• I mirrored the gear and realized the plate that switches the gear ratio will be hitting the outer bearing of the dog clutch, so I spaced out the gears a bit more. I’ll probably be switching away from the outer gear on the dog clutch because it takes up tons of space.

The parts are basically done, I just have to see how everything works in an assembly.

Figured out perpendicular cam geometry. I was running into quite a few issues and managed to find a solution that fixed most of them. I pivoted from 6mm ID bearings to 32mm for the second stage of gears (the oscillating ones). I also realized that instead of moving the dog clutch directly, I have to mount another bearing around it with a 3d print mount. This not only allowed me to save tons of space, but now I only have to use one perpendicular cam because I can make the 3d prints 90 degrees offset, preserving phase. Here are some problems I ran into and how I tried fixing them:

• The 32mm bearings were hitting, so I changed up the main geometry and will be alternately adding flange space on each side of the main plate. There isn’t enough space for 2 flanges to be next to each other, but there’s enough space for 1 flange and a normal bearing to be next to each other (0.1mm of space).
• With my old design (screwing a sidways bearing directly on the dog clutch), I had to use two separate cams because the phase was not 90 degrees offset. However, with another bearing around the whole thing, I can change the angle to not be radial, making it exactly 90 degrees.

Looks like V2 will take the shape of a pentagon, and will soon look like a hexagon once I add the linear motion for the gear shifting mechanism.

I did tons of brainstorming and came up with a better replacement for the meshing/unmeshing gears (I actually had 2.5 hours more recorded the night before but lapse ran into a problem so they aren’t counted for here). I realized I could keep the gears in contact the entire time, and instead use a perpendicular CAM (idk what it’s called, it’s basically a CAM that has its offsets parallel to its axis of rotation) to engage a dog clutch onto the gears. The dog clutch basically has 0 chance of bad alignment because the clutch will self align. This hopefully makes everything much more reliable and efficient. To power this, I need a third gear directly connected to the input gear that takes the linear CAM below the input shaft (you can’t run it coaxially). To make it fit, I changed up some of the gear ratios. I soon plan to switch from 1.25 mm to 1mm modulus.

Continued sketching my V2. I spent most of my time visualizing the whole thing (I spent almost two hours sketching the thing out and doing the math). Here are some of the problems I ran into (and how I fixed them):

• I need the inputs on both sides to be powered, but I also want the output to be a pulley on the side (not in the center). This is impossible with a normal coaxial setup. Instead, I linked the first stage of gears (the one that has the ration changing mechanism) and will be changing up the linear motion mechanism.
• When connecting the first stage, it hit the output gear, so I had to change some of the geometry.
• As mentioned before, the radial force by the gear changing mechanism of V1 will probably cause the linear bearings to bind, so I’ll be changing this to a static linear-CAM type of motion for a constant force throughout the motion. Because I’m linking the first stage, everything will basically be inside a tube.

Did some math for the V2. I want the output to be at a constant speed, which means the gears have to be noncircular. The output right now actually isn’t even sinusoidal, and Claude and I had to do tons of weird trig to find the angle as a function of time. After graphing everything on Desmos, I figured out the ideal shape of the gears. Next, I’ll do more mastersketching, and export the shapes from Desmos into Onshape. In the image, the black curve is the position as a function of time, and the blue and red curves are the ideal gear shapes. Actually, now that I think about it, this is wrong and I need to change the whole thing.

I made some minor changes and I’m almost ready for a v2. I fixed up some of the spacers, changed the direction of the linkage that changes the ratio, changed some of the bearings. I also changed the coloring, and it looks much cleaner (I chose pink because I have pink filament loaded in, if you guys have any recommendations please tell me). Here are some fundamental problems with the current version and how I’ll fix them in the v2:

• The biggest problem is probably gears meshing. The entire thing has to be perfectly synchronized for the gears to mesh perfectly every time, which is obviously impossible. The only thing preventing jams right now is my prayers. However, backlash does give it some room for error. I’ll probably find a better gear tooth profile for my V2, but this is sort of a fundamental problems that will exist.
• The second biggest problem is that the gears oscillate from max speed to 0 speed every half-cycle, which means the speed will be constantly oscillating. This is easily fixable: in my V2, I’ll use more driving gears (probably 4) each active for a smaller fraction of their period. This combined with elliptical gears to counter the sine waves should make the output basically constant speed.
• The linkage for the gear changing has basically zero torque, and backlash will completely fry it. Also, this adds weird thrust forces on the linear bearings which will probably cause them to bind. In my V2, I’ll probably shift from a linkage to a linear CAM type of thing (I still have to figure it out).
• This is really big and wastes some space. My V2 will (hopefully) have better packaging and be smaller. This is achieved by putting the second layer of gears on the inside of the plate and praying there is enough space.

The uniform coloring makes it look way better. Once again, if you have any colors you think would look better, please tell me.

I basically finished up the linear motion for the CAM. All that remains is some minute adjustments.

Here’s some problems I ran into:

• The geometry was incredibly hard due to the lack of space, and I ended up just trying a bunch of possibilities and landing on one that worked decently. While I was planning to use belts, I switched to gears after I saw how little space there was.
• Screws were hitting the servo for the gear changing mechanism, so I rearranged it so the lip is on the outside of the plate, giving me a precious 4mm to work with.
• It was hard to come up with a way to ensure the full range of motion always happens. There’s nothing pushing the gears up after the CAM pushes it down. Initially, I was planning to do some complex linkage relying on the definition of an ellipse (the sum of distances from the foci is constant). I tried sketching it out but there was literally no space. At the end, I thought of tying a string to both gears and wrap it around an idler to keep the constant sum of distances.

This thing’s gonna look clean once everything is colored. All that remains is some minute adjustments and I can move on to a V2.

Started the linear motion for the CAM. I was initially thinking about using MGN3 linear rails until a realized that each rail is over 100 bucks. Instead, I decided on linear bearing based motion with 3mm rods similar to how the ratio changes. Here’s some problems I ran into:

• Cheap MGN rails were way too big so I decided on the linear bearings (I spent way too long searching for cheap MGN3 linear rails)
• I initially wanted to put the rods between the yellow and blue plate, but after sketching it I realized the tolerances were too sketchy.
• Initially I was going to do one main CAM in the center, but I realized when the CAM is pushing the shaft to the outside, the angle is weird so the force is basically transmitted perpendicular to the direction of the motion, which really cooks efficiency. So instead I decided on 2 smaller CAMS that are belted to the main gear.

some future/long term problems I need to fix:

• I don’t think there’s enough space for the belts and cams, so this whole design might be fried
• The 3mm rods aren’t constrained on their ends, so I have to figure out a way to do that (right now its only held by friction).
• The motion of the driven gear will oscillate a ton because of the CAM. One potential solution is to use elliptical gears and have the gears engage only in a certain phase where its speed is high (so its not stopping)
• There’s something similar to the coaxial effect from swerve drives in this gearbox too: I’m gonna call it the CVT effect. When the gear ratio changes, the linear motion makes the gear change phases. Something similar happens because of the CAM, but this isn’t that big of a problem. But when in doubt, assume software can account for it.

Mounted the CAM gear, added a front plate, and added screws. I ran into a problem where one of the hubs hits the belt to the lead screw so I changed up some of the geometry. The gearbox is starting to look pretty complicated and dense without the second most complicated part (the CAM). I am holding off coloring everything and pocketing till the very end because it’ll be very satisfying.

Finish up Linear Motion for CVT. Mounted the linear bearing, added the servo, and finalized the linkage so the actual CVT part now works. Now, I have to work on the CAM mechanism.