Wow, getting kicked by the pedals does not sound fun. Sorry to hear about the folks who have had problems with this. However, I am very encouraged to hear that should I ever run into this problem, it can potentially be solved with a shoe! Luckily I carry 2 on every ride. The thought of sending a wheel to Germany from the states has always sounded like a real headache.
Fortunately for me, my hub has been nothing but stellar. And as others have mentioned, it certainly does have personality. My freewheel noise changes pitch and speed with the seasons, with the level of oil and with whatever neutral routing my hub chooses at the moment (from what I understand, this can be a few different paths, depending on what gear you are in). Sometimes while maintaining a coasting speed, my freewheel noise will audibly shift as the hub decides on an easier neutral output.
Besides that, just the standard whirring noise while pedaling in gears 6 and especially 7. I love the noise because it reminds me of the mechanics happening inside.
By the way, I'll take a stab at the 6th and 7th gear noise:
-First, let’s set the stage. Imagine standing behind the bike, looking at the hub. Drive sprocket on the right.
-I theorize that it is a misalignment of the spur gear teeth where the twin planet carrier meshes/ouputs to ring gear 2.
-I think the twin planet carrier has a touch of slop (not the assembly itself, but how much space is allowed between its planets, and the ring/sun gears that they mesh with), which is good for manufacturability, and also raising efficiency. If you think about it, it MUST have slop, since it interfaces with so many other gears. When I think of the twin planet carrier, I think of it “floating” in between the 4 sun gears inside and the 2 ring gears outside. I have seen a picture of this assembly and the planet-to-sun gear mesh does look a bit loose.
-So, while in gear 6 or 7, ring gear 1 is locked to the right side of the twin planet carrier and also to the first two sun gears.
-Now the left side planets walk within ring gear 2, but perhaps it is being leveraged by the firmly-held right side of the twin planet carrier, ring gear 1 and the first 2 sun gears?
-Basically all the tolerance or slop is being forced to the left side and it causes the left side of the twin planet carrier to misalign or torque (slightly) with the interior of ring gear 2.
-Spur gears are noisy by nature with their large contact faces, but a touch of misalignment during the meshing really turns up the noise.
-So now imagine all three planet gears on the left side of the twin planet carrier, being slightly tilted as they walk around the inside of ring gear 2.
-Does this also explain why most efficiency tests rate 6 and 7 as the least efficient gears?
-Gear 6 rates slightly better, and I imagine this is because only 2 gears are mating (planet and sun gear). Gear 7 is worse, because now 3 gears are mating (planet, sun and ring)
-So why only 6 and 7?
-In gears 1 and 2, the left side of the twin planet carrier is locked, and the right side (ring gear 1) is walking the planets. Seems like it would perform just as noisily as gears 6 and 7, however ring gear 1 is very close to three sets of supporting bearings and closest to the input drive (sprocket), so I envision less flex or tilting happening on this end.
-In gear 4, the twin planet carrier is locked on both sides, so there is no gear meshing happening anyway.
-In gears 3 and 5, the planets are being walked in both ring gears 1 and 2, which seems like a balanced distribution of force on the twin planet carrier.
-So, since gears 6-7 and 13-14 are essentially the same, why are only 6 and 7 noisy?
-I don’t know. Maybe 13 and 14 are as noisy, but at those speeds and the difference in typical cadence, it just isn’t as easy to hear.
-Or, maybe the locking of planet set 3 in gears 13-14 helps balance the load of the twin planet carrier between ring gear 1 and ring gear 3?
-Lastly, I wonder if the interface (possible slop) between ring gear 3, planet carrier 2 and sun gear 3 are behind all of this. No, that cant be, because in theory all gears 1-7 would be noisy if that were the case.
-And last but not least, maybe I am totally off point, and the whole thing is just an acoustic phenomenon.
Looking forward to hearing others thoughts,
Beave
