Anyone who has ever snapped a chain or a crank knows how much torque a bicycle’s power train has to absorb on a daily basis; it’s really more than one might naively expect. For that reason, [Well Done Tips]’s idea of 3D printing a gear chain from PLA did not seem like the most promising of hacks to us.
Contrary to expectations, though, it actually worked; at the end of the video (at about 13:25), he’s on camera going 20 km/h, which while not speedy, is faster than we thought the fixed gearing would hold up. The gears themselves, as you can see, are simple spurs, and were modeled in Fusion360 using a handy auto-magical gear tool. The idler gears are held in place by a steel bar he welded to the frame, and are rolling on good old-fashioned skateboard bearings–two each. (Steel ones, not 3D printed bearings.) The healthy width of the spur gears probably goes a long way to explaining how this contraption is able to survive the test ride.
The drive gear at the wheel is steel-reinforced by part of the donor bike’s cassette, as [Well Done Tips] recognized that the shallow splines on the freewheel hub were not exactly an ideal fit for PLA. He does complain of a squeaking noise during the test ride, and we can’t help but wonder if switching to helical gears might help with that. That or perhaps a bit of lubricant, as he’s currently riding the gears dry. (Given that he, too, expected them to break the moment his foot hit the pedal, we can’t hardly blame him not wanting to bother with grease.)
We’ve seen studies suggesting PLA might not be the best choice of plastic for this application; if this wasn’t just a fun hack for a YouTube video, we’d expect nylon would be his best bet. Even then, it’d still be a hack, not a reliable form of transportation. Good thing this isn’t reliable-transportation-a-day!
Neat, and even if it won’t last a long time this would be cool on an art bike.
Next step: 5 speed transmission.
Nice project. Be sure to check comments on yt as there is a lot of interesting stuff about gear types and configurations.
No reason you couldn’t use a fancy hub transmission. Dirt and grit is the worst concern use a light synthetic oil that wont be sticky. Avoid mudslinging puddles.
I’d think any grit will make short work of plastic gears?
Synthetic oils will leak and harm the environment. Ordinary cooking oil will also lubricate and it’s natural.
Yes, but it oxidizes and gets gummy much more quickly.
In my experience it’s really not that big of an issue. Plus nowadays there are additives for vegetable oils that prevent oxidation pretty effectively at low temperatures. A lot of chainsaw oils are just canola oil with a few % of additives. Works well, and I’ve never had my saw gum up from it.
At this point, just spit on it and get it over with
Another option is using a self-lubricating material. PC-PTFE, or PETG-PTFE, are commercially available filaments. Then there are the Iglidur-brand ones.
A trick to save cost could be printing just the gear ring, and attach it onto a hub via some sort of splines match. No sliding wear there, just static force transfer. And once the wheels are worn, the ring can be replaced with ease. Experimenting with various tooth profiles also gets easier. Or even milling the tooth ring from metal, as a low-weight alternative to full-metal gear.
Thought… could the low-wear surface be electroformed in-situ from nickel or some copper alloy?
Get a body part into a bike chain, and you get hurt.
Get a body part into that, and you lose it.
Shoes, feet and whole legs will be crushed to bits I am sure… Maybe even whole bodies?
PLA gears killed my father, and enslaved my mother
So, like spokes?
Nerf the world!
The injury potential is the best part of this project.
Nah, it would just get mangled, assuming the gears didn’t break instead. At high speeds, the human body is mostly bubblegum. Easy to squish, hard to tear.
You’re going to be shocked and appalled by these things called chains.
If he pedals with constant speed, adding few more gears will transform the bike into a watch.
Why do people do this stuff with PLA /eyeroll
Obviously this is just for the clicks, otherwise they would have used a plastic that can survive outdoor environments.
Because it’s a prototype? I’m not gonna use expensive plastic until I’m sure the design works.
i hope it’s not a prototype :)
i think the impressive part of this project is the implausibility of it. i believe pla is pretty strong when it’s fresh, and when it’s thick. So the small gears don’t stretch my imagination too much. But even so, that big ‘chainring’ gear in the front is surprising to me. It’s just surprising that it works at all.
That is a seriously funky frame, but neat that you can remove the chain without cutting it.
Probably for Belt drive, most belts aren’t split.
Neat. Herringbone gears should work nicely here; they self-center and are much smoother. You can make them by extruding and twisting standard gears, then doing the same thing in the other direction.
Herringbone gears typically operate in a unidirectional manner, designed for efficient power transmission in one direction. To make them work in reverse, modifications to the system are necessary.
One effective approach is to incorporate a reversible gearbox that allows the motor to rotate in the opposite direction, thereby changing the output direction of the gears. This ensures functionality without altering the herringbone design significantly.
Another method involves changing the direction of the input shaft. By using a motor that can switch rotation, you can drive the input shaft in reverse, causing the output to follow suit. Incorporating clutch mechanisms can also be beneficial; these disengage the primary drive and engage a system that facilitates reverse motion.
Additionally, combining herringbone gears with other types, such as bevel or worm gears, can allow for reverse operation while still capitalizing on the advantages of the herringbone design. Implementing a gear selector mechanism can enable seamless switching between forward and reverse functionalities as needed.
When making these changes, it’s important to consider load ratings and potential wear on the gears due to the different stresses encountered in reverse operation. Careful design and alignment adjustments may be required to ensure the system maintains operational reliability.
Why would you use ChatGPT to make your posts for you? Don’t you want to have a conversation yourself? I’m not going to respond to a machine.
Maybe some kind of social experiment… I’ve noticed that bot also doppelgangers the usernames of various people
‘Simple’ spur gears? Last I knew there was a lot of math in making them work properly.
I mean maybe, maybe not. If you mess up the profile, you’ll get an involute anyways if you run them together long enough. Life finds a way.
Touché
I had a belt driven bike (Priority Continuum Onyx) that used a glass-filled nylon drive/crank pulley. It worked fine and was never an issue. I rode that bike for a few years before I sold it and bought another belt driven bike. I can’t foresee ever going back to chain drive.
With this other one we are starting to have some contestants for a “PLA gears” race :)
https://www.youtube.com/watch?v=RATcc7wJd8c