Aerodynamics

General Discussion about electric bicycles.
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Chalo   100 GW

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Re: Aerodynamics

Post by Chalo » Mar 01 2016 5:37am

LockH wrote:`Been saving/collecting corrugated plastic sheets ("Coroplast", like Kleenex (TM) is to tissues) from past political elections. Good thought re "thermal molding". Was just gonna overlap and "Zip tie".) :)
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

BILL1953   1 µW

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Re: Aerodynamics

Post by BILL1953 » Mar 01 2016 12:32pm

teklektik wrote:
WASYLBRYTAN wrote:I cannot express how disappointed and frustrated I am with this forum. I discover something interesting and tell people about it so that they can try it and give me their feedback. But all people want to do is discredit me as if I am trying to cheat them or get money out of them.
Seriously, dude -try what and why?

There are two entirely different concepts here:
  • The Nullwinds 'headwind-negating' fairings
  • WASYLBRYTAN's 'range-improving' fenders
fenders.png
  1. Nullwinds is very clear:

    In still air, the Nullwinds fairing has been tested to give no significant improvement.

    Of particular note (see Nullwinds Drag Mechanics Document):
    1. [quote="nullwinds"]Under null headwind conditions, the predicted gains are minimal, which is consistent with road test results.

Importantly, both their new drag formulae and their road tests are consistent on this point.


[*]The Nullwinds maximum estimated potential speed improvement of 16% using their unreleased computational model are for a 10mph bike in a continuous 40mph headwind and only where the spoke drag is a large percentage of the overall vehicle drag.

These Nullwinds estimates are unsubstantiated by testing - the largest recorded savings by actual test were "in excess of 10%".[/list]
In any case, large heavy riders with upright posture on heavy ebikes using fat 26" ebike tires certainly fall in the category of bikes with low spoke-drag-to-vehicle-drag ratios. Nullwinds observes that such vehicles will show substantially reduced improvement.

Nullwind's claims of improvement may mislead those who believe that the power required to propel a bike at 10 mph in a 10mph headwind is the same as that required to propel the bike at 20mph in still air. However, this is certainly not the case and simply traveling at higher speed without headwind will not make the fairings work - and Nullwinds states this clearly.


[*]You claim a repeatable 20% range improvement with your DIY fairings in essentially uninstrumented tests:
WASYLBRYTAN wrote:I continue to see at least a 20% improvement in battery range everytime I test this.
...
I ride the same route 2 or 3 times each day at the same times, speeds, terrain, weather conditions.
...
Three days ago I obtained 217 kilometres range from an 8.8 amp hour battery.
...
36 volts, 8.8 amp hours. 217 kilometres at 18 kph.
So - on a heavy draggy ebike in presumably still air (or certainly not continuos high speed headwinds day after day of your tripping) you are claiming 200% of the best test gains claimed by Nullwinds. Confusingly, your vehicle and riding conditions are flatly stated by Nullwinds to reduce or eliminate any gains by their technology.
  • Looking at the figures you have supplied we see that you go 217km on 36v with an 8.8 Ah pack yielding an energy consuption of:
    217km / (36v x 8.8Ah) = 1.46 Wh/km travelling at 18kph (2.35wh/mi at 11mph).

    With a little math we know that a 60lb hybrid bike with 170 rider requires 7.6Wh/mi to achieve 11mph in still air.
So - you are puttering along at 11mph and are providing 69% of the power by pedaling. Your 'tests' are based on results that rely on unmeasurable and subjective rider pedal power input that is 222% of the applied motor power - hardly a compelling test scenario to claim a 20% increase in ebike range.[/list]

Returning to the question of 'what to test and why?':
  1. By their own statements, Nullwinds appears to offer insignificant improvements for the ebike world - wrong style bike, wrong speed, and wrong headwind requirements.
  2. You offer claims that contradict the testing and physics presented by Nullwinds and substantiate them only with vague and subjective tests that rely on 69% of the vehicle power from the rider at speeds that are generally considered undesirably/unrealisticy slow.
Nothing to test in either case.[/quote]

I recently visited the Null Winds site and decided to try the concept with aluminum sheets and duct tape. I ride a step-through e-bike with a 500 watt 8fun motor and a 48 volt 13 amp hour battery. I normally get about 34 km. of range out of the battery when I ride at full speed over a set course at 30-35 kph. With the so-called wheel fairing on the front wheel only, I notice 38 km. of range under the same conditions. I repeated the test with and without fairings and consistently see upwards of 10% improvement with the fairings which cost me nothing to construct. It appears that this idea may have some merit. Also, the Null Winds site has something new they call spoke fins; if these work as well as the fairings they may catch on.

Hummina Shadeeba   100 MW

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Re: Aerodynamics

Post by Hummina Shadeeba » Apr 19 2016 1:46am

LockH wrote:`Been saving/collecting corrugated plastic sheets ("Coroplast", like Kleenex (TM) is to tissues) from past political elections. Good thought re "thermal molding". Was just gonna overlap and "Zip tie".) :)
Wow that's pretty wild. But does it work?

Hummina Shadeeba   100 MW

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Re: Aerodynamics

Post by Hummina Shadeeba » Apr 19 2016 1:48am

Chalo wrote:
LockH wrote:`Been saving/collecting corrugated plastic sheets ("Coroplast", like Kleenex (TM) is to tissues) from past political elections. Good thought re "thermal molding". Was just gonna overlap and "Zip tie".) :)
Great video thanks

I paid a fortune for the stuff at tap plastics.

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LockH   100 GW

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Re: Aerodynamics

Post by LockH » Apr 19 2016 5:09am

Hummina Shadeeba wrote:
LockH wrote:`Been saving/collecting corrugated plastic sheets ("Coroplast", like Kleenex (TM) is to tissues) from past political elections. Good thought re "thermal molding". Was just gonna overlap and "Zip tie".) :)
Wow that's pretty wild. But does it work?
TBA. I'm already riding recumbent, so thinking is to hood/cover my lower body enough to deflect rain and snow. More aero is the objective but currently thinking about vision forward and down at street-level bumps and cracks and debris. May go with some clear hard plastic flexible sheeting inserts and for a wind shield. (Cabin heating and cooling also on list of stuff to play with.)
ES changed my life (for the waaaaay better).

Eff. June, 2014 Phoenix Ebike Promotions

(Current ride? High speed lawn chair.)
viewtopic.php?f=3&t=57408

Phoenix Ebike Promotions conversion kit (work in progress. More drink holders, etc etc)
viewtopic.php?f=15&t=60564

Joined yer local chapter of EA yet?
(Ebikers Anonymous - Where we're all miserable failures, but the parties are hilarious...)

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spinningmagnets   100 GW

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Re: Aerodynamics

Post by spinningmagnets » Jan 14 2021 1:47pm

Mythbusters had an episode years ago (Bubble Motorcycle) about taking a motorcycle and adding a full body fairing to actually see how much of an improvement in fuel consumption there would be.

250cc enduro style, single-cylinder. Fuel mileage went from 56 to 70 miles per gallon. An extra 14 MPG from 56 is a 25% improvement. Rider also mentioned the riders comfort and percieved noise were dramatically improved.
AeroMoto1.jpg
A
AeroMoto1.jpg (107.04 KiB) Viewed 123 times

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Stealth_Chopper   10 W

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Re: Aerodynamics

Post by Stealth_Chopper » Jan 16 2021 9:03am

I didn't know of any good use for that 'sign' material.
I have thought about finding some use.

In 2016 I could have filled truckloads of common "Vote for Me" { ~ 2' square pieces and steel wire frames. }

Could used signs be laminated, Again , they are made by lamination
Creating big sheets ?
For projects like campers
A gardening structure like small agricultural green houses ?

Thanks
I hope something good happens to you today.
Mike

donn   10 kW

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Re: Aerodynamics

Post by donn » Jan 16 2021 10:28am

Fluted polypropylene / "coroplast", very popular for home made inventions - light, strong and cheap if you can use discarded campaign signs.

It isn't miraculously easy to work with, though. Its durability comes at the expense of being so chemically stable that there's no practical way to really bond it or form it, so the ideally you design your enclosure so each panel needs to bend in only one direction, and the edges can be fastened with something like pop rivets or zip ties, or maybe rubber cement.

Recumbent enthusiasts probably account for the majority of home made fairings. I have a couple commercial Zzipper fairings, one that came with my recumbent bicycle and one that I bought back in the '80s for my upright bicycle. They're good for weather protection, maybe a little good for aero drag but that's hard to measure; otherwise they can be more nuisance than they're worth.

Conventional wisdom in the recumbent scene is that a "tail fairing" may do as much good for aero as a front fairing. There was also some enthusiasm for fabric "sock" fairings for a while, don't know if that's still a thing.

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