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  1. #51
    Senior Member Homeyba's Avatar
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    Quote Originally Posted by RChung View Post
    Perhaps so, but since this was Steamer's estimate would you address his assumptions and calculations?
    Actually I think I did. I don't see a problem with the actual calculations. What I was disagreeing with (and this is a minor point really) is that he's saying that you're running the light 24hrs a day and most of us don't do that (unless you forget to turn them off). Most of us are only running the light between dusk and dawn. That would be a more realistic calculation. If he is running them 24hrs then it's more valid for what he's doing. That's all.
    It doesn't get harder, you just go slower.

  2. #52
    Senior Member Homeyba's Avatar
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    Quote Originally Posted by Weatherby View Post
    To do a 600K in under 23 hours, your power/speed relationship was well outside the linear range. You probably ride the flats at 35kph+ where aerodynamics trump frictional losses rather quickly. The dynohub impact was probably more like 20 minutes on your time. For a slower rider using all of the allowed time, the impact would be over one hour.
    If the slower rider was running his lights during the whole ride, possibly. If not, I doubt it. BTW, I don't usually ride brevets that fast. I usually ride with the slower riders in the back. I've finished 600k's 15 minutes before the cut off too.
    It doesn't get harder, you just go slower.

  3. #53
    Senior Member Steamer's Avatar
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    Quote Originally Posted by Homeyba View Post
    Actually I think I did. I don't see a problem with the actual calculations. What I was disagreeing with (and this is a minor point really) is that he's saying that you're running the light 24hrs a day and most of us don't do that (unless you forget to turn them off). Most of us are only running the light between dusk and dawn. That would be a more realistic calculation. If he is running them 24hrs then it's more valid for what he's doing. That's all.
    Agreed that most probably don't. But I noticed Unterhausen rides with his light on all the time. And I started doing that too last year*. I figure it represents a small bit of life insurance.

    *because I like to emulate the kool kids.

    BTW, "Good at coasting" might make a good tag line...

  4. #54
    Senior Member Steamer's Avatar
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    Quote Originally Posted by unterhausen View Post
    well, the assumption that a rider will ride at exactly the same power level regardless of light choice probably isn't true. But that assumption is a really good starting point. And if the watts that are wasted cause one not to ride with a faster group of riders, then the time penalty could be huge. This is why Steamer contacted you to for your opinion about testing, it's certainly an interesting question to me.
    The next step up in more detailed integration is to model the ride in three parts. Uphills, downhills, and flat. So if you have a 200K with 6600 feet of climbing, how about breaking the calc into three parts - 66.6K at 3% grade, 66.6K at -3% grade, and 66.6K of flat. Use 85% of FTP for the uphills, 55% of FTP for the flats, and 25% of FTP for the downhills. Look at the impact of the dynohub at each condition, using a wattage loss that matches the approximate speed of each portion.

    This is still not reality, but gotta be more accurate than doing it all as 200K of steady state.

    Edited to add: I just realized that I don't totally understand the point you were making in your first sentence.

    Quote Originally Posted by unterhausen View Post
    well, the assumption that a rider will ride at exactly the same power level regardless of light choice probably isn't true.
    I thought you were commenting on the error introduced by doing the simple calc holding slope and power constant (cause that is obviously not real...). But I realize now you were saying something I bit different (I think).
    Last edited by Steamer; 03-05-14 at 07:38 PM.

  5. #55
    Senior Member Steamer's Avatar
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    Quote Originally Posted by unterhausen View Post
    I'm sure he has occasion to regret the day that he invited me along on that first ride
    Interesting. I always figured it was the other way around... (that you regretted accepting the invite...). The only ride I ever regretted was hours 21 through 23.9 of last years Fleche.

  6. #56
    Senior Member Homeyba's Avatar
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    Quote Originally Posted by Steamer View Post
    Agreed that most probably don't. But I noticed Unterhausen rides with his light on all the time. And I started doing that too last year*. I figure it represents a small bit of life insurance.

    *because I like to emulate the kool kids.

    BTW, "Good at coasting" might make a good tag line...
    I figured you did, and it really isn't a bad idea I suppose.

    I don't call it good at coasting, I call it having well developed descending muscles.
    It doesn't get harder, you just go slower.

  7. #57
    Senior Member downtube42's Avatar
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    The battery/dyno part of this thread captures the debate I had with myself when selecting lighting for my new rando bike. Some of my more heated discussions occurred on brevets this past fall, when finishing up my R-12. Eventually the dyno side won; I purchased a Shutter Precision dynohub and mated it with my old CYO.

    The battery side is still not speaking, which makes for quieter if less entertaining rides.
    What is bicycle touring?
    "So I kept looking and eventually found that a spark plug had same threads. So I cycled next two days until I got to Jackson, MS with a spark plug instead of right pedal." - mev

  8. #58
    Randomhead
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    Quote Originally Posted by Homeyba View Post
    I don't call it good at coasting, I call it having well developed descending muscles.
    I learned decades ago that as a climber, I'm a really good descender

  9. #59
    Senior Member Homeyba's Avatar
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    Quote Originally Posted by unterhausen View Post
    I learned decades ago that as a climber, I'm a really good descender
    Isn't that the truth, me too!
    It doesn't get harder, you just go slower.

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