The Ratcheting CVT

by Gear_Down_For_What, published

The Ratcheting CVT by Gear_Down_For_What Mar 11, 2018
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Description: https://youtu.be/G9-N-nIqc4g

Torque Capabilities

Please know that i designed this CVT for a demonstration model, it's not intended to be used as an actual transmission

How This Works

  • Watch the video!

Look out!

  • Somehow I lost all of my last changes to this project after I printed it, and I had to go back into the cad model and remake them, I do not have time to reprint the whole thing again, so there is a possibility of clearance issues (or other issues) for the first few people that print this, if you have ANY problems with this model, please leave a comment and I will try to fix them ASAP.
  • Is their anything missing? Let me know!
Hardware Required!
Print settings
  • You need to calibrate your printer to +/- .02 mm on a 20mm calibration cube before you print this or it will not fit and/or work properly, use horizontal expansion to accomplish this if necessary, but often oversized parts are caused by printing speed or worn out nozzle.
  • It is also necessary to level your bed - especially if you have an auto leveling sensor. This one cause me to have to reprint due to compensation that is done after auto leveling.
  • 1.2mm wall thickness and 10% - 30% infill at .2mm layer height.
  • Print everything in the orientation that it's already in (yes print the cam adjustment shaft horizontally)
  • Use supports where necessary, I think I marked everything that needs it but use your own judgement.
  • PRINT ALL THE GEARS SEPARATELY (including the ratchet gear) and slow your printing speed down substantially, otherwise they will come out too rough and will not fit together.
Part Preparation
  • Use a screwdriver (or the cam control shaft) to break the custom support material out of the inside hole of the crankshaft, this is there to help bridging and is only one layer thick.
  • Separate the eccentric components from each other, they should not be attached.
  • The two halves of the eccentric mount have a bearing race around them, its likely that the bearing race might have a small "bump" where the two halves meet due to printing jerk, use an exacto knife to make this bearing race nice and even.
  • I plan to make an assembly video sometime soon, but until then, follow these instructions.
  • Assembly order
    1. Assemble all three ratchets onto the output shaft, making sure that the ratchet pawl's are facing the clicker thingy, and the ratchet body's are facing the same way.
    2. Install the crankshaft into the frame. The hex side of the crankshaft should be on the frame left side, then loosely place the three large pushrods (the giant circles) around the crankshaft.
    3. Slide the output shaft with the ratchets into the frame.
    4. Place the other side of the frame onto the machine, and use sheetrock screws to attach it.
    5. Assemble the ratio adjuster gearbox, it's really hard to put together, and if it doesn't spin super freely you will need to reprint with a negative horizontal expansion setting. Ring gears need to be installed so that they are in the order of 1,2
    6. Install the ratio adjuster with large carrier facing towards the frame, align the index marks on the crankshaft and the ring gear, and make sure the small carrier is facing out.
    7. Install the cam control shaft through the entire apparatus, placing the cam gears into each pocket of the crankshaft in order of the marks on them with the marks facing the same direction, rotate the cam control shaft or the cam gears until the shaft slides through them( align the index position marks)
    8. Install the ratio adjustment cover, aligning the notches on the cover to the notches on the ring gear.
    9. At this point, the crank shaft should spin somewhat freely, and the cam gears should rotate at the same speed as the crankshaft assembly, if It does not, the gears are binding somewhere.
    10. Install the two half's of the eccentric mount on the crankshaft in whichever spot you like, making sure to mate the rack of gears up with the cam gear.
    11. Slide the pushrod over the top of the two halves of the eccentric mount and fill the grove up with 4.5mm BB's.
    12. Once the raceway is filled with BB's, remove one or two BB's and then install the small wedge shaped piece into the bearing fill hole, the side with two faces should face out. I used a dab of hot glue to hold this piece in.
    13. Repeat steps 8,9 and 10 for the other two eccentric's making sure not to flip them around (I.E. The build plate side should be on the same side for all three)
    14. Place the wrist pins through the ratchets one at a time, use the eccentric offset adjustment to make the middle ratchet accessible

Other Important Info:

CAD Files??
  • I Included the Fusion 360 Project with this, But the most recent version of this project can be downloaded in lots of different formats from this link: http://a360.co/2IhRLLa
  • Feel free to create your own modifications and parts for this project, and if you do, make sure you create a remix and upload them, I'll link to them and possible create a collection for all of them!
Show Your Work!
  • Make a "make" and show everyone what you made! Everyone will thank you for it!

For More Cool Gearbox Projects, Don't forget Subscribe to Gear Down For What?! https://www.youtube.com/c/GearDownForWhat


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Really nice and interesting project. One small recommendation for the next Fusion project. Use different files and make an assembly. It was really difficult to figure out where is what. I wanted to change the small balls diameter and it took me awhile to find the place where you have defined it. Otherwise, create work!

You are 100% correct, this is the first situation where I have really wished that I would of done that, not doing that caused me a lot of trouble actually.

You should consider uploading your design!

You used 4.5mm BBs, I have 3mm balls that I could use for this project. Next week or so I hope I can start printing the components out.

the pins for the ratchet mechanisms are missing

Your right, I’ll get them added tonight if I have time

what layer height did you design the crankshaft for? at 0.2mm the custom support material is 2 layers thick in my preview.

Hmm maybe it is just that thick then. Should work anyways.

I’ll check when I get home

Wow. Awesome thing. Awesome vid too.

Just watched the video on this what a great video