Drill through the top of the seatpost and loop the wire down to the light.
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I seemed to have killed my hub and/or light. Wouldn’t turn on after being parked in a drizzle all day. Maybe I should stop doing that? But it’s a touring bike, it’s gonna be out in the rain all day sometimes!?
SP PD-8X powering a Luxos U. Curiously the light does turn on, but only the standlight. The hub rotation feels normal. When I hook things up to my other (working) dyno bike, the hub doesn’t power the other light, nor does the other hub (1.5w, but still) power this light! Did I somehow kill both at once? Is it possible to kill a light s.t. the standlight still works?
I guess I will look into a UR705 if I don’t want to continue the SP lottery…
luxos U is a complicated beast, mine died a while ago similarly
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We had one act up after 2 years and tons of use. Sent it to PWC for service. They put a new battery in it and sent it back for <$30.
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Luxos u is such a fussy lamp
I’ve had the switch body water logged and doing the blinking light thing, let it dry out and it’s fine.
On another I did the same thing and it was fried.
I’d say never again but it kind of is the only ame in town for those kinds of details
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Someone here correct me, drag on a dyno hub remains pretty low when not in use (light on, charging etc), and increases (albeit slightly) once a load is placed on it?
Use case; considering building a new wheelset I have dreams of using for some longer bikepacking / night rides, but also sees a lot of normal mtb use. I don’t really want to kill the ride by overkilling utilitarian side.
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Outside of spinning the dyno wheel in the stand I don’t notice any drag at all fwiw but yeah there’s supposedly a small but measureable difference with the light on vs off.
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Should be about 5w of drag. SON 28 shows 6v, 3w printed on the hub body. Claimed 60% efficiency, IIRC. 3w is 60% of 5w, so there you go. Less drag with light off.
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I’m a huge very inefficient watt machine and I honestly don’t notice. I have one bike that’s designed to be fast and has a dyno, I could roll it down a hill a few times for science
Sounds like I’m good to beat up my wallet and take my mtb to 11
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The thing I’ve been morbidly curious about with regard to dyno drag is whether it’s significantly more efficient to run dyno lights or wired lights on an e-bike. I’m too lazy to do the math, I am guessing the drag from a dynamo consumes slightly more power than lights wired to the battery, but also if you are coasting then maybe the dynamo technically wins?? I’m sure it’s a mouse fart of a difference at the end of the day
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If we’re talking cruising around town then I bet the weight of a Shimano dynamo hub has a bigger impact than the slight drag the hub causes. I think Peter White said the drag amounted to something like 3 minutes extra time on a century, all things being equal.
charging my ebike with my dynamo hub
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I’ve measured the current draw of the IQ-X E front light on my ebike at 6.3W, not sure what the rear light adds to that. That matches up pretty closely with the SON28 with the light on at 30 kph in the chart above. Say you’re only tootin’ around at 20 kph on that ebike, that’s only about 1.2-1.3W more than the same hub.
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A front hub motor is just a dynamo with different geometry.
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Think about it this way: do you think it’s more efficient to plug a lamp straight into the wall outlet, or plug a motor into the wall, that spins a generator, that powers the lamp?
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the e-bike versions of the lights are much brighter
and despite that, they draw less input power at speed because they’re running at close to perfect efficiency
(plus you get full brightness from zero and handlebar controls)
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In practice, and imho, the drag on a dynamo hub is about 3 tenths of fuck all. Many times on long descents I’ve rolled past dudes on aero bikes on my steel, fendered, dynamo-lit bicycle. There are so many factors at play that it just doesn’t seem worth worrying about.
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