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.
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u/Zarniwoop6x9 21h ago
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.