Around the world on a solar ebike

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Cowardlyduck   100 MW

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Re: Around the world on a solar ebike

Post by Cowardlyduck » Jul 21 2020 3:56am

I find this interesting as I've found the opposite.
After I first put a solar panel on the front of my semi-recumbent I noticed a significant improvement in cruising speed (45-50kph) efficiency of about 50W+. I've increased the size of the panel over the years from 15W to 40W now and the efficiency gains only seem to increase with it.

Image

Maybe it's related to the 'semi'-recumbent nature of my bike as well as the higher speeds I cruise at, but the irony is for me I get better gains from the efficiency gains than I do from the solar energy generated while riding. :lol:

Cheers
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solarEbike   100 W

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Re: Around the world on a solar ebike

Post by solarEbike » Jul 21 2020 11:34am

Cowardlyduck wrote:
Jul 21 2020 3:56am
I find this interesting as I've found the opposite.
After I first put a solar panel on the front of my semi-recumbent I noticed a significant improvement in cruising speed (45-50kph) efficiency of about 50W+. I've increased the size of the panel over the years from 15W to 40W now and the efficiency gains only seem to increase with it.

Maybe it's related to the 'semi'-recumbent nature of my bike as well as the higher speeds I cruise at, but the irony is for me I get better gains from the efficiency gains than I do from the solar energy generated while riding. :lol:
That is interesting. I can't explain why you seem to be getting significant gains from your front fairing. Air resistance increases as velocity squared so it would be about double at your speeds compared to the 20 mph (32 kph) I have been testing at (45^2/32^2=2.0). Small reductions in drag or area would result in more noticeable reductions in power needed to maintain the same speed.

I spent a lot of time reading through posts in human powered racing forums where enthusiasts discuss the benefits of various home-made semi-faired and faired recumbents. The consensus seemed to be that tail fairings are far more effective than nose fairings with anecdotal evidence like "0.5 mph gain from nose fairing, 1.5 mph gain from tail fairing" being common. The explanation was that vortex shedding from the back of the vehicle causes a low-pressure region of turbulent air which "pulls" on the vehicle from behind whereas a long, smooth tail box results in more laminar flow, reducing this effect. Even the maker of the Windwrap nose fairing I used emphasized increased rider comfort in winter and downplayed expectations of speed gains. This all seemed consistent with my own experimental findings so I've focused on tail boxes and reducing the frontal area.

I even paid for a subscription license for a CFD (Computational Fluid Dynamics) software package from AutoDesk for a couple of months hoping I could model the effects of different tail box designs before building physical prototypes but I never mastered the software well enough to get meaningful results. From what I understand, the most effective design strategies are often not intuitively obvious. Just because something looks fast doesn't mean that it has low drag. Small, seemingly insignificant changes in draft angle or the gap between the rider's body and the fairing can make a surprisingly large difference.

I also found the testing procedure more difficult than I anticipated. It's hard to find a long stretch of flat road what is shielded from the wind. I tried doing multiple runs in each direction with and without the fairing(s) and found that the variance between individual runs was greater than the average difference between faired/unfaired runs. I could only hope that the wind was the same throughout the experiment. Even something simple like maintaining a constant speed with no acceleration/deceleration was tricky. I never got the Cycle Analyst dialed in so that it wouldn't oscillate about the target speed setting. Next time, I think I'll just set it to maintain constant power and compare the difference in speed.
SWB recumbent, Grin DD hub, Phaserunner, 6x LiGo battery, 238 watt sun-tracking solar trailer and 76 watt solar roof with 3 Genasun MPPT boost controllers, CA3 w/ solar FW & GPS Analogger, Rohloff hub. Solar ebike build, Website, Instagram

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Cowardlyduck   100 MW

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Re: Around the world on a solar ebike

Post by Cowardlyduck » Jul 23 2020 4:47am

solarEbike wrote:
Jul 21 2020 11:34am
Small, seemingly insignificant changes in draft angle or the gap between the rider's body and the fairing can make a surprisingly large difference.
This is what I think makes the difference in my case.
I think that in my semi-recumbent position, my body catches a substantial amount of air basically turning me into a wind sock. With the panel upfront it forces a large amount of air to balloon around me and rejoin at my sides or just behind me. This effect is obviously greater at higher speeds.
I can even feel this when riding, particularly on very cold (-7C) mornings I can stick my head or hand our past a certain point and feel a stream of dense air streaming around me at speed.
So while the flat panel up front may not seem like it helps much just looking at it...under the right circumstances I think it greatly improves things in the right direction. All this is anecdotal I must admit, but I hope it helps inspire none-the-less. :D

Cheers
My stuff:
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Cowardlyducks - Videos - Ride videos
BikeE recumbent commuter - 9C, 6Fet Grinfineon, internal 17AH, 52V, + on-board solar.

For Sale:
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ScooterMan101   10 MW

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Re: Around the world on a solar ebike

Post by ScooterMan101 » Jul 27 2020 1:54am

Here is a good article , I first saw pictures of a vetter full fairing scooter many years ago , Have been waiting for a commercial product to come out like it for some 20-30 years .
In this article the faired electric Zero S gets great efficiency despite such a rear tail that does not look better than one that comes together at the rear .

https://ridermagazine.com/2013/12/20/th ... r-fairing/
and
a picture of the blue scooter bodywork .
https://www.pinterest.com/pin/705094885386226659/

https://en.wikipedia.org/wiki/Vetter_Streamliner
My first conversion ... Sold

viewtopic.php?f=3&t=71378&p=1077497&hil ... 1#p1077497

It's 2018 already, ( now 2019 ) lets get some real , improved e-bike / e-velomobile / e-motorcycle designs .

Warren   100 kW

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Re: Around the world on a solar ebike

Post by Warren » Jul 27 2020 10:06pm

There was lots of research done from about 1975 to 2005 on the aerodynamics of recumbents, by university engineering departments, and independent developers. They found that, as cowardlyduck suggests, an upright seating position acts as a parachute. Laying the seatback back reduces that effect. Also, putting the windmilling cranks and legs directly in front of the torso does wonders to reduce drag. This is why a full front fairing is most effective on a LWB, low bottom bracket bike like the BikeE, but does little to improve performance on a bike like solarEbike rides.

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Cowardlyduck   100 MW

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Re: Around the world on a solar ebike

Post by Cowardlyduck » Jul 28 2020 7:30am

Warren wrote:
Jul 27 2020 10:06pm
There was lots of research done from about 1975 to 2005 on the aerodynamics of recumbents, by university engineering departments, and independent developers. They found that, as cowardlyduck suggests, an upright seating position acts as a parachute. Laying the seatback back reduces that effect. Also, putting the windmilling cranks and legs directly in front of the torso does wonders to reduce drag. This is why a full front fairing is most effective on a LWB, low bottom bracket bike like the BikeE, but does little to improve performance on a bike like solarEbike rides.
That makes perfect sense and explains exactly why I see the difference I do where others with lower bikes do not. Thanks for explaining!

Cheers
My stuff:
Ebike Garage - My YouTube Ebike ramblings.
Cowardlyducks - Videos - Ride videos
BikeE recumbent commuter - 9C, 6Fet Grinfineon, internal 17AH, 52V, + on-board solar.

For Sale:
Custom made 18650/21700 battery packs - Australia only
High Power LiPo wiring harnesses - 4P - XT90, HXT4mm, 5.5mm. 200Amp+ capable. Global shipping.

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