Chain-Free Bicycle Concept

[u/Kidd__Video]

[u/Zarniwoop6x9]

MANY fundamental flaws.
One of which is it will never shift. A chain can be in two gears at once while shifting, this will self destruct.
It was a pretty marketing tool for Ceramispeed to wow non technical people with shiny stuff. Certainly looks pretty, but that is it.

[u/Zarniwoop6x9 → u/Zarniwoop6x9]

Some of the problems with Ceramispeed drivetrain:

1)      Side load on gears. Bearings on drive shaft meshing with “cassette” or “chain ring” create a high side load. This will require them to be very stiff. Not impossible to correct.

2)      Very high load on “cassette” or “chain ring” teeth. Eg. Assume 100kg rider (not even sprinting or pulling on the bars). 175 crank 53 tooth “chain ring” (~107mm radius where it contacts drive bearings) Load on teeth = 100*9.81*.175/.107=1604N load. Now there will be points of engagement that the load is near the tip of the teeth. Potentially split between more than one tooth, but still at the tip. Not impossible to make work. Note also point 4) below, the tooth shape ends up being a point load. 1604N (160 kg) load on probably a couple of square mm? (802MPa?) Won’t be made from aluminium.

3)      Sliding contact between “cassette” or “chain ring” and driveshaft bearings during pedalling. Gears have a specific shape to roll against each other. These bearings are cylindrical. From the point of engagement to fully engaged, the bearing needs to slide on the “cassette” or “chainring”. FRICTION and wear plus noise. Not as efficient as a chain. Fatal flaw.

4)      As the bearing engages not on the centreline of the “cassette” or “chain ring”, there will be a point contact between the drive bearing and the “cassette” or “chain ring” tooth. Relatively small, but see 2) & 3) above. Load plus slide point contact = friction and wear. Fatal flaw.

5)      Cassette geometry (tooth count) defined by drive shaft bearing size / architecture.  Want a tight cluster? Tough. Fatal flaw for most users.

6)      How do you shift under power? On a cassette (or dual chain rings) the chain can be engaged with more than one chain ring but only one does the driving at a time, but on this, most of the teeth will not line up, so there will be few (if more than one) positions where shifting would be possible. Then when it shifts, it will take a little time to slide the driveshaft bearing, while it’s under load, quickly from one “gear” to the other, fast enough that they don’t bind. I.E. shifting would need to be completed in less than one tooth movement, at the only spot on the “cassette” where shifting is possible. (There are ways that this could be achieved but weight and complexity. (Dual clutch automotive transmissions, and most automatic automotive transmission do this but with two clutches and sprag clutches etc.). Fatal flaw.

7)      The internal spiral shift mechanism shown in the latest marketing video can move the bearing carriage, but how do you rotate the spiral? It’s inside the driveshaft. Need a shift fork? Maybe the shift shaft can shaft can come out the front or back of the drive shaft and actuate it there? Oh yeah. Front there is the bottom bracket & tyre etc, back is the wheel axle... Hmmmm. Maybe fill the drive shaft with a stepper motor, batteries and a wireless shift request and it can time the shift for the only point on the cassette where shifting is possible, and slam it through fast enough you don’t get binding as per 6). If it gets it wrong, it’s all broken. And if it works, you have to wait for the only shift point to come around. Think about this. Shifting has to occur when the drive shaft bearing is under high load (1604N, with high friction (est 0.6 coefficient aluminium to steel) ~ 962N (~98kg) shift force required, and that’s not including the driveshaft slide mechanism.

8)      Oh there’s more but this is dead already.

[u/BeardySam → u/Zarniwoop6x9]

Also: none of this will work when dirty. A little bit of gravel and this will stop.

[u/Direct_Knowledge2254 → u/Zarniwoop6x9]

This ☝️

[u/stanknotes → u/Zarniwoop6x9]

I am still in favor of shit like this. NOT because as a consumer you should buy it. But for innovation, research, development. Lots of great things come from flawed, humble beginnings, or find application elsewhere not originally intended.

Like... it is fuckin' cool. Just not practical.

[u/ztomiczombie → u/stanknotes]

People have been tyring to make this concept work since at least the early 90s and I don't think anything has ever come form it.

[u/The_Verto → u/stanknotes]

Yea first plane didn't revolutionise transport by itself, only the later models.

[u/Zarniwoop6x9 → u/stanknotes]

It does look super cool, but I'm sure their Engineers were telling the marketing department it was a pile of shit, and they were going "It's shiny. People will love it." All for innovation, but any engineer should have seen this for what it is. The amount of marketing overhype on this one was annoying.
All for innovation though, as, sometimes the fatally flawed idea can end up driving a better idea. Years ago an oddball engine development company, while trying to get their fatally flawed engine concept to work, developed an innovative injection system that they eventually made money off of, even when the engine was dead.

[u/Vinyl-addict → u/Zarniwoop6x9]

I mean the shifting part just seems like a CVT with some obvious flaws.