Schmidt dynohub drag

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neilob
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Schmidt dynohub drag

Postby neilob » 17 Sep 2008, 12:38pm

I just treated myself to a Schmidt hub with Lumotec LED light. Great combination. I read all the stuff about the low drag when the light is off but I'm pretty sure I notice it anyway....it's added about 5 mins to my 1 hour (daytime) commute. Is this everyone else's experience or are my legs shutting down for winter?? It's not a problem, and I'm sure when the darkness comes it will get worse because of the laws of physics but I just wanted to know what you all think.
N
Using a car to take an adult on a three mile journey is the same as using an atomic bomb to kill a canary.

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CJ
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Postby CJ » 17 Sep 2008, 1:20pm

I think those five minutes are the result of psyclelology: you think that hub must have some drag so you don't feel like working as hard, so you don't. It's a feeling that can afflict us all. A noisy bike won't go as fast as a silent one, even if the noise is not an actual source of drag and even if the silence comes from softer but slightly less efficient tyres.

Schmidt hubs with the lights switched off have about the same drag as a hill that rises one foot in a mile. All you can feel is a slight buzz from the "cogging", an alternating pull and push between magnetic poles as they turn past each other. It feels bad when you turn the axle with your fingers, but since the push is almost as big as the pull, barely one watt of energy is needed to turn the wheel at typical riding speed.

Drag will increase when you switch the lights on: to something like 5 foot in a mile. Still pretty insignificant, but just discernible by a sensitive rider. It might even delay you by one or two minutes on a one hour commute, not more.
Chris Juden
One lady owner, never raced or jumped.

neilob
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Joined: 31 Jan 2008, 3:58pm
Location: Notts/Lincs borders

Postby neilob » 17 Sep 2008, 1:36pm

So it's my legs then....thanks for the reply CJ, I had read that 'one foot per mile' estimate so I guess the big question is whether other Schmidt owners leave the hub on all year or just fit during winter months.
Using a car to take an adult on a three mile journey is the same as using an atomic bomb to kill a canary.

Tom Richardson
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Postby Tom Richardson » 17 Sep 2008, 2:11pm

I got a schmidt dynohub last month but only fitted it at the beginning of last week. I did think that there was some drag to begin with but stopped noticing it now. Either its worn in a bit or the psycleology mentioned by CJ has worn off.

I plan to put the old wheel back on next spring so save wear, a bit of weight and the small risk of having it nicked but its nice having it lights available all the time. I'll leave it on while ever I think i might use them.

james01
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Postby james01 » 17 Sep 2008, 2:28pm

Tom Richardson wrote:I plan to put the old wheel back on next spring so save wear, a bit of weight and the small risk of having it nicked but its nice having it lights available all the time. .


Quote : neilob : so I guess the big question is whether other Schmidt owners leave the hub on all year or just fit during winter months.


Don't you people cycle after dark in the Summer? :)

Tom Richardson
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Postby Tom Richardson » 17 Sep 2008, 2:38pm

james01 wrote:
Don't you people cycle after dark in the Summer? :)


I don't remember it getting dark in the summer but i have some battery lights just in case. The batteries last for ever (nearly) because I never use them

Tallis the Tortoise

Postby Tallis the Tortoise » 17 Sep 2008, 2:57pm

I've never been able to notice the drag from Schmidt whilst riding. Nor can I notice any difference between lights on and lights off. And as there is no noise, I've frequently kept riding with lights on in broad daylight without noticing. Then again, I'm on a heavy galaxy so the proportional extra effort must be very small.

AndyB
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Postby AndyB » 17 Sep 2008, 3:11pm

I suspect the extra weight compared to a normal hub will make a bigger difference than the drag, if your route is hilly. Still minimal though.

neilob
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Location: Notts/Lincs borders

Postby neilob » 17 Sep 2008, 3:44pm

Don't you people cycle after dark in the Summer? :)[/quote]

Not on my commuting bike......but I have been known to venture out in the dark sometimes!! :lol:
Using a car to take an adult on a three mile journey is the same as using an atomic bomb to kill a canary.

rogerzilla
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Postby rogerzilla » 17 Sep 2008, 6:48pm

I can feel the lights-on drag and also measure it - 0.5mph off my normal average commuting speed of about 17mph. However, this shouldn't be 5 minutes in an hour.

The new Shimano DH-3N80 is lighter in weight than a SON28 and apparently has lower drag with the lights off. Madison don't import it, but you can get it from the EU.

Tallis the Tortoise

Postby Tallis the Tortoise » 18 Sep 2008, 12:35pm

rogerzilla wrote:I can feel the lights-on drag and also measure it - 0.5mph off my normal average commuting speed of about 17mph. However, this shouldn't be 5 minutes in an hour.


If I could average that speed I wouldn't be worrying about the drage from a dynamohub :wink:

tb
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Postby tb » 19 Sep 2008, 10:26pm

you have to look at it from a different perspective.

I still use a bottom bracket dynamo ( 32 miles commuting in the dark during the winter ) and it's like riding with the brakes on, but when I get on the bike and it's daylight I go twice as fast for longer :D