So I thought I would continue with removing planets to see if I can learn anything about the efficiency. The only other number of planets that has any chance of working is 3. This will double the load and torque transferred by each planet. If my theory is correct that increasing the torque reduces the efficiency then a noticeable drop should be experienced.
I decided to risk a major failure and use the 3 planet hub for commuting to work. The performance is a bit of a surprise. It's far from the very inefficient hub I was expecting. The 5 planet hub was a different thing being unbalanced and it didn't perform very well with the traction rings getting pulled off center. Amazingly there really isn't any noticeable difference in the efficiency of the 3 planet hub. If anything I'm convinced that it's actually more efficient under some conditions. As if the efficiency of these hub could get any more complicated.
In full underdrive and a low sprocket ratio the "squishiness" is very noticeable and on a really steep hills it's quite extreme making pedaling a bit difficult. Under high torque, low speed situations the efficiency is possibly slightly lower. But considering the amount of "squishiness" it doesn't feel like the hub is eating up as much torque as it could be.
My only explanation for the increase in efficiency or at least no drop is simply the same reason that a 3 wheeled vehicle will have less rolling resistance than a 6 wheeled one. With half the number of contact patches to drag it makes up for the loss due the increased torque. When torque is lower there may actually be a gain from not having so many contact patches.
I'm beginning to think a 3 planet hub has serious potential. The 6 planets are obviously to reduce loads and ensure a long life. I'm wondering if I would probably get more life from a hub if I wear out half the guide slots because I could then switch to the other three. Maybe they'd wear out twice as fast so I don't know. I do know I would probably be risking a major traction ring failure. It would therefore not be a good idea to use the hub for trailer towing, mountain biking or on steep hills. However I think that if I lived in a flat place and installed the hub on a light weight road bike geared for road use the 3 planet hub could be a possibility.
I've done over 40 miles so far with no issues.
I decided to risk a major failure and use the 3 planet hub for commuting to work. The performance is a bit of a surprise. It's far from the very inefficient hub I was expecting. The 5 planet hub was a different thing being unbalanced and it didn't perform very well with the traction rings getting pulled off center. Amazingly there really isn't any noticeable difference in the efficiency of the 3 planet hub. If anything I'm convinced that it's actually more efficient under some conditions. As if the efficiency of these hub could get any more complicated.
In full underdrive and a low sprocket ratio the "squishiness" is very noticeable and on a really steep hills it's quite extreme making pedaling a bit difficult. Under high torque, low speed situations the efficiency is possibly slightly lower. But considering the amount of "squishiness" it doesn't feel like the hub is eating up as much torque as it could be.
My only explanation for the increase in efficiency or at least no drop is simply the same reason that a 3 wheeled vehicle will have less rolling resistance than a 6 wheeled one. With half the number of contact patches to drag it makes up for the loss due the increased torque. When torque is lower there may actually be a gain from not having so many contact patches.
I'm beginning to think a 3 planet hub has serious potential. The 6 planets are obviously to reduce loads and ensure a long life. I'm wondering if I would probably get more life from a hub if I wear out half the guide slots because I could then switch to the other three. Maybe they'd wear out twice as fast so I don't know. I do know I would probably be risking a major traction ring failure. It would therefore not be a good idea to use the hub for trailer towing, mountain biking or on steep hills. However I think that if I lived in a flat place and installed the hub on a light weight road bike geared for road use the 3 planet hub could be a possibility.
I've done over 40 miles so far with no issues.
- Oran