Bicycle Mechanics - sturmey archer hub "renovation"
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04-14-11, 05:55 PM
iv been very interested in the benefits of running an internal gear hub(in my case a sturmey aw 3-speed), but the only thing that keeps me on single speed instead of that is the efficiency. with 1st and 3rd gear giving noticeable friction loss, i thought there has to be a better way.. i know its a bomb-proof system but its far from perfect.. so heres my idea. i think most of the friction comes from the planet pinions spinning on the pinion pins, and the large diameter bearing between the driver and the hub body. lets say we replace the bearing between the driver and hub body with a sealed cartridge bearing(like an integrated headset bearing) and we made the holes in the planet pinions much larger to accept small cartridge bearings. what do you think? i really want some feedback on this one
04-14-11, 06:03 PM
Rohloff... the planetary gears roll on needle bearings, in a light oiled casing..
... part of the reason they sell for $1K+,
But when You raise the capital to compete on the world market,
with a needle bearing AW3, with oil seals and such, do write back.
04-14-11, 07:42 PM
Spend $1000 save a couple watts of human power. Who cares?
04-14-11, 08:07 PM
"Reinvent the wheel"
"Reinvent the wheel"
-nah, just the hub...
04-14-11, 11:09 PM
i HIGHLY doubt it would cost 1000$ to do this. bearings aren't that expensive and i can do all the machining myself. its not an idea im trying to profit from, so im not worried about the world market. i just want to do it for my own sake, as a project. in my mind, its worth the "couple watts"
04-15-11, 05:14 AM
I believe he was referring to the Rohloff hub at 1K+
04-15-11, 05:35 AM
Noticeable friction loss? Seriously? A lubricated and adjusted AW hub is one of the most efficient drivetrains after singlespeed and/or fixed gear. We are talking couple of percent anyway and if you are riding such a hub you are not aiming at hour record/TdF prologue where everything is important.
However, if you are so inclined to tinker go ahead I am curious to see what happens. I think that a sealed bearing will give you tad more friction due to the seals.
P.S. I think Sturmey did experiment with bearings on the planets but the difference was not at all significant. Also a chromed pin+planet is as simple and trouble-free as it gets. After all there are hubs that are 50+ years old and still going strong. =P
IMO the friction of the planetary pivots is as nothing to the friction inherent in transmitting power via meshed gears.
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