Solar Panel vs dyno hub for TD

[Veetack]

I'm trying to weigh the benefits of a solar panel over a dyno hub while racing the TD. The two products I'm comparing specifically are the Shimano Dynamo hub and the Guide 10 Goal 0 solar panel. I'll be powering 2 headlights, a Garmin Edge 800, and an iphone. My biggest concerns are the rolling resistance on the hub, and the availability of sun for the panel. Guide 10 does make battery packs that will recharge and subsequently charge my devices when they're not in use. Does anyone have experience with either or both that could maybe give me some guidance?

[sthig]

Veetak,

I owe you an email - you emailed me while I was on a training run so it got buried.

I have both, the dyno hub >>> than the solar panel.  The Guide 10 gave me a lot of grief...ESPECIALLY SINCE YOU CAN'T USE ANYTHING BUT RECHARGABLE BATTERIES! (boy what a bait and switch there)

I had 0 rolling resistance with my hub, loved it and climbed 13k with it this weekend and didn't think anything about it. 

[Veetack]

Thanks for the reply. I'm curious what I have to add to the hub to get the charging ability for all my devices. I also really like the idea of the battery pack so I can charge those devices while I sleep. I'm also really concerned about water resistance on the hub when you have to cross water that is greater than hub deep.

[sthig]

I almost have a blog post ready about all that for Friday

[Veetack]

Perfect. I've been waiting for that one.

[DeanHill]

Some where i saw someone claimed the drag of the shimano dyno equals about 1foot lost per mile.   If you have the wheel off the ground the can feel the drag, but with the momentum of the bike it is pretty small.   

I think you would want to pair it with something like this.

http://www.thinkbiologic.com/products/reecharge-power-pack

[fotooutdoors]

I just did the calculations base on data from several sites (http://www.peterwhitecycles.com/shimano3n70.asp) and it looks like it is nearer to 10 ft/mile for the shimano hubs (8.5 to be exact for a 200lb load of bike+rider+gear with a 3 watt light or charging load).  Of course, if you need to brake anyways, that drag doesn't matter; it only matters when going flat or up.

[DeanHill]

Nice,  Thanks for the correction.    Would that make it a 4.42 miles for the great divide race (2745 miles)?   That's an interesting way to think of it. 

I calculated the  record is around a 7.3 mph average.   So for most people you will lose at least 1/2 hour in drag.   Then there is the weight.   And the time you spend fiddling with charging stuff. 

 Can anyone do a calculation on how much faster you ride with music?


Randy

[ascar_larkinyar]

i like the solar over the hub.  the drag on the hub made it a "no go" for me, even though it's a more simple idea. 

setting up the solar with the rechargeable(AA) as the buffer made it work.  i charge my 18650 batteries, then my phone, then the AAA's,then the mp3, then leave my phone plugged in as it uses the most power.  it's a bit much, but after you get in the habit it's easy.  when i stop at a food stop i pull it off and charge it at the table.  i have it all set up in a compact unit.
having the usb helps to make it versatile as well.

[bmike-vt]

get a SON and forget about it. 1.5 watts when lights are off on the SON, probably a bit less on the new SON.
i have one on my rando bike. the convenience and the ease of use over anything else is how i was planning for the TD.
plug and play, and forget. i'd get an eWerk or something similar for charging. haven't followed the state of the art on that end.

no solar panels to worry about (what do you do when there is no sun?). you run your lights whenever you want, no worries on batteries, etc.

the weight is negligible, unless you are a featherweight on a featherweight bike, with all ultralight cuben fiber clothes and kit and gear.
how much does the solar kit weigh?

[fotooutdoors]

Nice,  Thanks for the correction.    Would that make it a 4.42 miles for the great divide race (2745 miles)?   That's an interesting way to think of it. 

I calculated the  record is around a 7.3 mph average.   So for most people you will lose at least 1/2 hour in drag.   Then there is the weight.   And the time you spend fiddling with charging stuff. 

It is 4.4 miles "climbing" in drag, except it really isn't.  If you are descending fast enough that you aren't pedaling, then you lose a tiny bit of speed and get that portion of the "climbing" for free (ie for every mile you coast, you get the energy that you would have expended to climb 10 feet).

As far as the half hour, unfortunately, 4.4 miles of climbing doesn't work out that way.  Assuming you output about 150 watts (which may be a bit high), that translates into an extra 11.6 hours of riding.  The 4.4 miles of climbing is not 4.4 miles of riding, it is pulling yourself vertically (using your bike, of course) upward that distance. 

However, as I explain above, you get some of that climbing for free in descents.  Additionally, as bmike's graph shows, you don't use nearly as much energy if you aren't charging anything off the hub (lights, cell phone, etc), so the actual amount of drag is much lower.  Plus, I did not subtract out the drag of a normal front hub; my calculations are comparing a dynohub to a frictionless hub.

In short (I will try to wrap up the geeking), I would roll a good quality dynohub on the Divide if I had rechargeable batteries that couldn't last at least a few days (cell phone, depending on usage is a prime example).

[pickupel]

I'm going to be using a SON28 (new version) dynamo hub for the TD this year. I've used SON hubs in the past for touring on the road and have never noticed any drag — I'm sure it's there I just haven't found it affected my riding (same daily distance in the same time). As the graph that bmike-vt posted shows, the drag of a SON hub vs. a good quality front hub is negligible (0.1 - 0.2W) between 5 and 15 km/h — provided the hub is not powering anything. As most people will climb between 5 and 15 km/h, this means that there will be almost no difference in the time it takes two equally strong riders, one with dynamo the other without, to climb the same pass.

True, the hub does suck a greater number of watts when it is charging a device, or powering a light, but it is still a small number. At 20km an hour the SON28 will pull about 6W from your legs — this is a similar number to the benefits provided by wearing an aero helmet. Obviously, there is a reason time-trialists worry about the watt-saving advantages of aero gear. It does help, but the gains are marginal — in the world of pro bike racing such gains can be the difference between 1st and 3rd, but the TD is a different beast all together. My impression, as I haven't ridden it yet, is that a good mental state is key to the TD — I think having a GPS that does not run out of power, easy access to music for the monotonous sections, and light on demand (all things a dynamo hub will provide) will help to keep stress free and happy. I certainly think these benefits will outweigh the watts lost!

As far as weight is concerned, the SON28 model I'm using weighs 430g — a Hope Pro 2 Evo hub weighs 185g — a difference of 245g. This might seem like a lot (I thought so when I first started looking into this), but when you factor in the amount of charging gear and batteries you don't have to pack it doesn't seem so bad! For starters, a dynamo powered front light has no battery, so that's a 100-200g saved instantly. 

I also thought I'd write a bit about why I chose the SON28 over the SONdelux, which offers slightly less drag in a marginally lighter package. The SON28 builds a stronger wheel, due to the wider flange spacing (66mm vs. 54mm), and outputs at 3W rather than the 2.4W of the SONdelux (this is better suited to larger 29er wheels and slower off-road speeds). I can't speak for hubs other than the SON, having not used them, but I have had a great experience so far.

With the hub I'm going to be using an Exposure Revo light, along with a Supernova Plug II+ to power my iPhone and Garmin 800. I have used an E-Werk in the past but it required a cache battery to charge most devices — this worked fine in the rain and the cold but as soon as the temperature went up the battery cooked and failed. The Plug also houses all the electronics in the steerer tube, sheltering them from the elements, unlike the E-Werk which straps to the top tube.

(http://h1987995.stratoserver.net/magento/supernova-the-plug-ii-plus-usb-dynamolader.html)

[sthig]

I've fiddled with solar panels only to have them result in fail.  Not to mention them standing up to the elements is not very great either. 

So far - the shimano hub has been awesome, I've noticed zero for drag and it's very comforting to have 400-800 lumens jumping out as well as the ability to hook up a USB port through the light (although it charges very, very slow). 

A solar panel is another "part" that has the potential to fall off the bike and it honestly does not work well (at least it's been my experience).  That said, Voltaic's batteries that come with their solar panels are the best damned rechargeable batteries I've ever had.

[Mental-Miles]

Hey man, you do some hardcore calc. ... if you compare the systems: Think about time for finding/buying/storing batteries. And your brainwork when thinking about if your bat-storage is large enough for the next no-support-section ... and what about rainy days in Montana no solar-loading at all ...

All in all for me the SON-Hub-Dyno is the best choice ... and having real good light when night riding is a big pro ... having mounted the new Busch & Müller Luxos ... providing 70 lux with an extra large light-field (right term?) and entering towns late at nite with a serious rear light could be a real lifesaver!

But in the end: one could find all systems at winner/recordrider/midpackracer/DNF ... it is like all TD-aspect: find your way, fell your discussion!

Cheers

M-M

[sthig]

this has been most helpful too - I've already been through the gamut of stuff and found the shimano/revo works best for me.  but who knows...10 feet down Banff and everything may splode on me.

[THE LONG RANGER]

Whatever you all do, please *after the race* compare notes, however subjective they come. It's a looong race and a million things can go wrong.

[sthig]

Justin, speaking of notes - can you let me know your thoughts about the surly chain tensioner ont he SS thread? 

[sthig]

For what it's worth, here is my review of the Alfine/Revo setup. I love it
http://www.driven2divide.com/2013/02/06/gear-review-alfine-revo/