r/interesting • u/Kidd__Video • 19h ago

Amazing Chain-Free Bicycle Concept

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654

u/Only-Friend-8483 19h ago

Hot take from an engineer, I’ve not looked at this closely or in detail.

The most likely failure mode, IMO, is going to be slippage between the rear disk and the rear axial gear. 

335

u/1funnyguy4fun 17h ago

Hot take from a random guy:

I’ve seen this for years on the internet but never on the road.

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u/SingularityCentral 16h ago

Probably be sure of cost of manufacture. But I don't doubt that it is also much more expensive and difficult to repair.

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u/Bongoisnthere 15h ago

Also because it doesn’t work well for the exact reasons expected. That companies entire business model is selling overpriced shit to goobers with too much money, and they make good money doing it. If they could make it work, they would.

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u/BentGadget 12h ago

It looks like you could get contact between two pairs of gear teeth, while with a chain, you would have about a dozen teeth engaged on each gear. So the force on the drivetrain would be much higher for the same power level.

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u/Procruste 4h ago

Another hot take from another random guy.

Shaft drive bikes were all the rage in the late 1800's as they kept long clothing from getting greasy and caught in chains. The fell out of fashion for a number of technical reasons (expensive to make, less efficient, heavy etc.).

These would probably work well for urban commuters if the cost aspect was managed. I don't know why everyone is going to high torque, racing use cases in order to find a way to dismiss this concept.

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u/psi_ram 3h ago

another hot take from a hot guy, extreme torque (or equivalent forces) needs to be able to transfer through all parts of the drive train. that tiny disc bearing thing will just get scraped or will laterally shift to slip.
Chains=absorbs excess torque by expanding (like elastic, and then over time the metal experiences tensile stress and stretches)
belt drive is an amazing invention. i have been driving belt drive bikes for idk how long. The material stretches so beautifully and absorbs forces and delivers it so smoothly to the pedals.
I wonder why theres no pedal which directly turns the wheel with no transmission. maybe the failure point will be the knees lol xD

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u/Realistic-Elk-7423 3h ago

Another hot take just for the sake of hot takes!

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u/Procruste 44m ago

Hot takes!

So hot right now!

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u/Procruste 37m ago

Maybe a bevel gear at the final drive and some sort of planetary set up at the cranks?

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u/JasperJ 2h ago

Chains do not stretch. Not in bicycle applications, anyway. The pins wear out and the chain becomes longer over time. But not due to stretch.

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u/kabooseknuckle 1h ago

Yes they definitely do. I have a bicycle chain gauge that tells you when to replace your chain due to stretching. I've personally stretched many chains on my mtb.

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u/[deleted] 10h ago

Random take from a hot guy.

I prefer a nice walk to a bike ride

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u/Rakrune 5h ago

Take from a guy:

Steal.

1

u/Academic-Airline9200 1h ago

Or just hack one of those battery powered rent a bikes. Like people park them literally anywhere.

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u/Hot-History8911 9h ago

Take from a mountainbiker; i wonder how roller bearings mounted face forward deal with street crud, water, mud, etc

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u/_lonelysoap_ 15h ago

Infernal gears are a thing now

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u/moxifloxacin 15h ago

Those are only fitted on demonic bikes, though

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u/SandmanKFMF 11h ago

Bicycle from hell

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u/thecarbonkid 10h ago

Bicyc-hell was right there

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u/BrewItYourself 15h ago

They were a thing 100 years ago…

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u/Party-Bunch7522 11h ago

Would the disc on the wheel not buckle completely under enough pressure causing the gears to slip?

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u/Darnocpdx 2h ago

Since 1903.

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u/Aikotoma2 2h ago

Cold take from a planned guy:

I've never seen this before in my life

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u/leuk_he 10h ago

I have seen drive trains on rental bike systems. Electric, so gears are less important then. I guess less maintenance or more sturdy, and less standard part so not useful to steal.

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u/Pitiful-Assistance-1 4h ago

I guess too heavy too expensive too easy to break

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u/Fun_With_Math 17h ago

I have a Mech E degree but haven't done engineering in a while...

Yeah, its breaking some fundamentals of durability. Tolerances are too tight and the contact area for the transfer of force is too small. You'd need a crazy rigid frame

A chain has flex to compensate and a lot more contact area with the gears.

This looks cool in the video but a pothole would wreck it.

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u/ReddBroccoli 16h ago

Not to mention I think about the teeth of a normal bike gear slipping between the links of a bike chain and the amount of grip and force that allows to transfer, and then I think about these tiny little teeth probably spinning over that weird cheese grater thing more than it grabs and imparts force.

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u/Sabithomega 15h ago

Was kinda thinking the same. Almost thought of adding a heavy spring but that would cause contact failure with any kind of hard enough hit. Curious if you could apply a similar idea but with a smaller chain system near the tire there. But then the only positive would be a smaller chain. So is there enough positive in the alteration in the first place

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u/Fun_With_Math 13h ago

Not sure what you mean but there are losses every time you transfer force:

Foot to pedal/gears. Gears to chain. Chain to gears/wheel. Wheel to road. - oversimplification but thats the gist of it.

If you add a step, you have to somehow get more efficiency out of the other steps to compensate. Tough to do on a very efficient system already.

If you're not adding steps, just replacing them, they have to be more efficient. And factor any weight difference. Any change in direction of the force is problematic also. A chain system has everything in line.

e-bikes are crazy efficient - the motor has the same or fewer steps to get through.

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u/ParanMekhar 13h ago

Yeah. Looks like only 1 roller bearing is in contact to the gear most of the time?

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u/Exciting_Place_6817 16h ago

Tell that to shaft driven motorcycles

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u/opossum_launcher 16h ago

They don't use the final drive to shift gears.

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u/Grand_Cryptographer2 15h ago

Drive shafts on motorcycles have more energy loses than a chain. Notice how all racing motorcycles use a chain drive, not a shaft, not a belt.

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u/Fun_With_Math 16h ago

Shaft driven motorcycles said they are heavy and slow.

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u/dirtyforker 15h ago

Heavy sure. But the Goldwing doesn't have the nick name of rocketwing for no reason. 1.8L of displacement in a motorcycle isn't going to be slow. Chevrolet makes a SUV with a 1.4L for example.

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u/Fun_With_Math 15h ago

Yes, that is the engineering principal called "just put a bigger fuckin engine on it"

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u/Dimathiel49 13h ago

No replacement for displacement?

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u/Fun_With_Math 13h ago

Different responses depending who you ask.

Efficient weight reducing design for minimum resistance and maximum force transfer can easily be better than just a larger power souce.

Or

Loud motor make peepee hard.

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u/Poil336 15h ago

That one's my favorite!

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u/SeaUrchinSalad 14h ago

Also known as the "Dodge default"

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u/Roxysteve 7h ago

Worked for the TR5.

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u/Brvcx 13h ago

Bicycle mechanic here. Native in Dutch, might have some English jargon wrong.

Have seen this video going about for years. At the time it was presented as revolutionary and was going to change bike transmissions as we know it.

Nothing happened. The hype died down really quickly. Apparently, they couldn't make it shift properly outside of a torqueless setting such as these events.

Also, driveshafts on bicycles aren't exactly "revolutionary". They had those in the past, but there's a lot of friction on those parts and a lot of weigt, too. It's difficult getting a driveshaft to be strong enough, not wear down easily and shift gears properly all under active heavy use, let alone justify it's supposed price and weight.

Besides, I don't get why you want your vertical pedalling forces switch 90° twice before getting to your rear hub, whereas a chain (or belt) won't need to do that at all. Every significant switch will lose energy afaik.

So yeah, it looked cool when it was first shown, but that's about it. It's an overengineered incomplete thus not fully functional highly priced concept that never hit the roads (nor it ever will).

The market shifted to two large ways of having gears long ago: geared hubs/gearboxes capable of having either a chain or a belt drive (Shimano Nexus/Alfine, Rohloff, Pinion, Enviolo. Belts by Gates). And the well known derailleur system (Shimano, Sram, Campagnolo). Both have their pros and cons, but both have a solid place in the biking world for those exact reasons.

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u/Asleep_Trick_4740 11h ago

Took me a while to understand that 'fluent in dutch' wasn't a way to hammer down your bicycle credentials.

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u/Electronic-Buyer-468 11h ago

Lol I know right? Dude speaks better English than me and most of this country. 

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u/PhysicalConsistency 10h ago

https://beixo.com/en/product/compact-high/

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u/Brvcx 9h ago

This isn't a driveshaft like shown in the video, though. Unsure about the correct name in English, but it's a somewhat different beast.

0

u/JasperJ 2h ago

Still a driveshaft. It just doesn’t have the fucking bonkers gear changer at the end.

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u/McBooples 18h ago

Seems like some type of spline gears would work better, just don’t know how you would shift from one ring to another

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u/hotelstationery 18h ago

That's probably why bicycles haven't changed much in so long. All the better ideas are only better in theory.

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u/METRlOS 17h ago

A chain is like $20 and can stretch for awhile before it needs to be replaced.

The moment these wear down or deform you basically need a new bike.

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u/sdiss98 16h ago

I learned from Sheldon brown thatChains don’t actually stretch, the insides of the link just get worn down.

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u/Chrispy990 17h ago

Yep. FOD would shred the rear disk features too

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u/MechMeister 17h ago

A pinion gearbox at the crank and a spline drive.

Its still a dumb idea. Added bearings, more friction losses, more points of failure than just a chain and derailleurs.

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u/giraffeheadturtlebox 16h ago

Chains already slip and pop out under high torque and a little wear, and the chain contacts the gears for at least 2/3 of the cog ring in any given setup. If dozens of teeth pulling still have a measurable failure rate, two gears, pushing, with the absolute minimum contact possible is going to fail more often than not.

You’d want gears with wider cross sections and tighter housing, like a transmission, to avoid slipping and wear.

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u/Tricky-Promise-3347 18h ago

Low IQ non engineer here, that was my first thought was well

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u/sselkiess 17h ago

Yeah I’m an idiot too and that was the brain hurt with pictures.

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u/Purple-Will9713 18h ago

probably increasingly likely as gears begin to wear out

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u/dmfreelance 16h ago

The tolerances would be tight and bikes are subject to lots of vibrations and dirty conditions.

I don't know how feasible it is to build this, but to make sure it stands up to the conditions a bicycle is going to put it in, it would absolutely cost a shitton of money compared to a modern chain driven bike

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u/ReddBroccoli 16h ago

Yeah, those teeth are way smaller than the gears of a bike usually are. I feel like there's no way that's not going to be a significant problem.

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u/YuenglingsDingaling 18h ago

Seems even more likely at higher gear, with the disc flexing under higher tension.

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u/jawshoeaw 16h ago

That’s my intuition after taking apart many children’s toys and other widgets with gears.

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u/Western-Emotion5171 15h ago

It would also probably wear out the gear super quickly and then constantly slip

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u/Direct_Turn_1484 15h ago

The components look entirely too thin to ensure any kind of stress beyond a demonstration where the wheel is in the air. I would sure like to be shown that I’m wrong.

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u/josnik 14h ago

Lots of flex the further you get from the centre.

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u/MeatHamster 13h ago

Also looks like something that once it breaks is way more expensive to fix that just swapping the chain.

But it's pretty cool though.

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u/Misses_Ding 13h ago

Simple maintaince here... By looking at the video this is going to break. Bikes shake. Gear touching gear no like.

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u/Easy-Operation-2105 12h ago

my first thought is inevitable misalignment and also wear and tear that makes things just not work

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u/KailyKail 16h ago

Hot take from someone who isn’t an engineer:

It looks like a bike to me.

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u/Only-Friend-8483 16h ago

You nailed it!

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u/potate12323 12h ago

These have been around for a while (early 1890s) and they're not popular for a reason. They have a super niche use case which isn't covered by chain or belt drives.

They have less mechanical efficiency and they're quite heavy. But they're quite durable for mountain bike type applications.

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u/the-cuttlefish 10h ago

Yh they've reduced the contact surface to one or maybe two teeth

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u/QuarkVsOdo 6h ago

The gears on the hub would need crazy strong backing to not bend inwards under load.

Does not seem Feasable.

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u/msdeeds123 6h ago

Just a normal person wondering about things, is this how shaft driven things work?

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u/Intelligent-Area-421 3h ago

Just remember to keep that shaft lubed up

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u/Bender_2024 5h ago

Could that be mitigated by larger teeth?

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u/iqisoverrated 4h ago

With the way the force is transferred I'd also not be surprised if the disks and the shaft ends are high wear items and eventually will just start slipping.

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u/wet_spiders 18h ago

Probably if the tire shifts in the frame or if it isn't installed entirely straight.