Classified Drivetrain Efficiency Measurements

Classified’s four design principles leading to improved drivetrain efficiency:

1. The Classified hub is used with an 11 tooth as the smallest sprocket on the cassette and the biggest chainring in front, so the highest ratio of the geared hub is 1:1. The gears in the hub are then locked and rotate as one piece, resulting in a rear hub that works just like any other rear hub, with >99.7% efficiency in the 1:1 ratio. The small loss is due to the bearings and seals in the hub and driver, as in any other hub.

2. By using a planetary gear set only to decrease the ratio, we were able to choose the most power dense and efficient gear layout possible. With our selected planetary gear set topology, a >99% gear efficiency is measured in the 0.7 ratio. Classified has developed an advanced hub tester with measurement accuracy of 0.1W.    

3. More often a straighter chain line compared to a 1x can be used, as the 0.7 ratio creates virtually larger sprocket sizes. This also contributes to a higher drivetrain system efficiency in the 0.7 ratio and compensates the low gear loss. Below the measurement results with on the bicycle test rig of Classified. By comparing the required input power with the same output speed and similar overall ratio between crank and wheel the loss difference can be accurately measured.    

The test-result above shows that there is 0.3W less input power needed to ride at the same cadence and speed using the 0.7 ratio compared to using the 1:1 ratio. This is due to the additional chain losses in the 1:1 ratio having an angled chain-line.  

4. Compared to a 2x set up, the chain forces will be reduced significantly. The fact that the 0.7 ratio of the hub still uses the large chainring in front, we do not have to increase the chain tension with 45% by using a small chainring. This also results in lower chain, crank and hub bearing losses, and also lead to a stiffer drivetrain and less flexing of the frame.

Together with professional athletes, Classified has done real-life tests, comparing a traditional 2x set-up with a Classified set-up in lowest gear on a 14% hill with around 320W input power. We measured the average power from the power meter and the time to cover a fixed distance on the hill in order to define the energy which was needed to climb the hill.

The test-result above shows that there is at least 1% less input energy needed to climb a 14% hill using the Classified setup compared to using a traditional 2x setup having the same overall ratio. This is due to the 45% higher chain forces with the small chainring in a traditional 2x setup.  

Conclusions:

Classified measures the efficiency of every hub produced, with each one showing an efficiency of above 99% in the 0.7 ratio and 99.7% in 1:1 ratio.

Compared to a traditional 2x drivetrain setup the efficiency of the Classified 1x setup is measured to be:

• Equal in the 1:1 ratio and riding on the small sprockets of the cassette as there is no change
• >0.5% better in the 0.7 ratio riding on the middle sprockets of the cassette due to a straighter chain line
• >1% better in the 0.7 ratio riding on the larger sprockets of the cassette due to the significant lower chain forces

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