Powerful EDFs

i have an idea!
i want to make a EDF powered bicyle that can reach 40km/h but i only have space for 4 100mm fans. What type of EDF will give me the ability
to do this, oh and i want to be able to control the speen of the EDFs from my handle bars. Any sugestions on what i can use for this? And i weigh about 70KGs and my bike is about 15KGs.....
--
Jason 123
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On 07/08/12 19:52, Jason 123 wrote:

A motor directly connected to the wheels will be many times more efficient than EDFs.
EDFs are horribly inefficient when used at low speeds, especially if the area of the fans is limited - a really big DF (like the powered paragliders use) can be marginally efficient at low speeds, but not a small one.
In the UK you will need a driving license, MOT, tax and insurance to ride it on the public streets if the design speed is more than 25kph or if motor output is more than 200 watts continuous, or if it weighs more than 40 kg without rider. Tax is free though, but you have to get a free disc.
There are some more regs, and even DOT have been known to get them wrong. so check first.
All that said, supposing you are fairly streamlined on your bike and only need 100 W of delivered direct power to remain at 40 kph. That's about 9 Newtons of force, or 900 grams of thrust.
I don't know the modern available EDF models, but I don't think you will have too much difficulty getting hold of 100mm EDFs which produce 225g of thrust each.
500g or more each would be better, the 100W mechanical figure is ballpark for a streamlined bike with racing suit and helmet etc., not a fat wally on a pos bike.
But EDFs will use a whole lot more than 100W to keep you at 40 kph. Probably ten or twenty times more.
Which translates into "using a direct drive the batteries will last 10 to 20 times longer than using EDFs".
YMMV,
-- Peter Fairbrother
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On Tue, 07 Aug 2012 22:29:17 +0100, Peter Fairbrother wrote:

Definitely...
To bear in mind.

Only if you are talking about a fully faired recumbent with a Cd around 0.1.
For a conventional bike, 100W might get you to 20kph. At design speed the power requirement will be at least 250W and maybe closer to 400W (remember the added equipment will increase frontal area).
So call it 36N of force, or 9N per fan.
http://en.wikipedia.org/wiki/Bicycle_performance#Power_required is about right
http://www.ductedfans.com/Ducted_fan_impellers_EDF_units.html has some candidate fans...
http://www.ductedfans.com/Wemotec_mf_480.html has some useful numbers. For 8.7N thrust, they show 11.5V, 30 amps, or about 345W per fan, or just under 2 horsepower total.
Incidentally you can divide thrust (force) by the open area in the duct to give pressure, and use Bernoulli's theorem to convert that to airspeed through the duct. (On examination, Bernoulli turns out to be good old e= 0.5m.v^2 in disguise). That way you can derive the power you will require, assuming 100% fan efficiency. Add say 30% more for fan/motor efficiency, and compare with the numbers above.
The mismatch in efficiency comes from the fact that you need to drive air at probably over 200kph to create the pressure you need to generate the thrust to get you rolling at 40kph.
Using this, you can run different scenarios in a spreadsheet and it'll turn out more efficient to use a slightly larger fan running at a lower speed.

I have a feeling that "coolness factor" outweighs efficiency in this project...
- Brian
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On Wed, 8 Aug 2012 09:45:00 +0000 (UTC), Brian Drummond

<snip>
The link calculations sound almost right, if only based on the fact that as a 16-17 year old, I could regularly put in 20 minutes=$mph over the 8 miles from home to school on Wednesday afternoons (sports time in the curriculum). Mind you, in the summer Holidays before that year, I'd done 750 miles in 7.5 days of cycling as an adventure. (sad git)
Mark Rand RTFM
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An Unicycle, however, is not legally a vehicle - the Road Traffic Act and Construction and Use regulations refer to a "vehicle having two or more wheels in contact..." - a mate was prosecuted and went to court after riding his unicycle on a pedestrian crossing - he was liable to points on his driving licence if convicted, so he took copies of the RTA and C&U to show the magistrates, and was commended for his knowledge of the law...
In theory, a powered unicycle needs no registration, insewerants, Road Gnk, the driver (pedestrian in question?) needs no licence, can't be convicted of any motoring or vehicular offence (including drunk in charge...) BUT can't use motorways or other pedestrian-free zones?
Dave H. (the other one)
Rules are for the obedience of fools, and the guidance of wise men - Douglas Bader
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Jason 123 wrote:

??
EDF    Environmental Defense Fund EDF    Electricit de France EDF    European Disability Forum EDF    Edifcio (Portuguese: building; postal usage) EDF    European Development Fund EDF    Earth Defense Force (game) EDF    Earliest Deadline First EDF    Expected Default Frequency (finance; credit analysis; Moody's KMV) EDF    Educational Foundations EDF    Erbium-Doped Fiber EDF    Empirical Distribution Function EDF    Export Development Fund EDF    European Data Format EDF    Environment and Development Foundation EDF    European Dystonia Federation EDF    Anchorage Elmendorf AFB (airport code, AK) EDF    Eritrean Defense Force EDF    Eritrean Development Foundation (Washington, DC) EDF    Engineering Data File EDF    Engineering Design File EDF    Earth's Defence Force (freeware game project) EDF    Employee Data Form EDF    ECS Development Facility EDF    Emergency Decontamination Facility EDF    Engineering Development Facility EDF    Electric Dream Factory EDF    Electronic Design Fixture EDF    Engineering Design Fixture EDF    End Upstream Data Flow EDF    Enterprise Documentation Framework (NCID documentation in the DoD on the GIG) EDF    Engineering Design Format EDF    Elliptic-Disc Filter EDF    Effective Direct Fire EDF    Executive Dining Facility EDF    Enterprise Data Fabric (computing) EDF    European Dermatology Forum (est. 1997)
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Expert Delivery (of) Farce
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F Murtz wrote:

Google gives Electric Ducted Fan when a search of "EDF powered bike" is done.
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David Billington Wrote: > F Murtz wrote:

> ability

> EDFs

> i

> KMV)

>

I'm still trying to understand why you want an electrical duct on a bicycle, let alone why you would put a fan in it.
--
rsss
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rsss wrote:

The duct improves the efficiency of the fan, I suspect the whole assembly is required as the rider is not eating enough beans and needs some further wind assistance.
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On Tue, 14 Aug 2012 21:37:30 +0100, David Billington

But, since efficiency is lower with high velocity flow than low velocity flow, wouldn't it be better to have a nice little epicyclic gearbox and a _BIG_ propeller?
Mark Rand RTFM
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wrote:

Well if it's efficiency that's important, why doesn't the fellow fit a couple of sprockets linked by a chain that he can turn with his feet? Can't get more fuel efficient than that.
Cliff Coggin.
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I was tempted to 'choose' Electricit de France and suggest a long piece of flexible cable would be needed!
Henry
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Dragon wrote:

I am finding it increasingly difficult with the propensity of posters writing epistles full of what is now known as acronyms (incorrectly sometimes)and having to waste time looking them up.
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Well, if you find it tedious, just ignore them - I usually do. If posters don't ask questions of make points in a way which is considerate to the reader, they probably deserve to be ignored.
David
--
David Littlewood

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It wouldn't need to be a particularly long cable here in Kent, as we have foreign electricity from EDF.
Cliff Coggin.
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On Mon, 13 Aug 2012 16:26:42 +0100, "Cliff Coggin"

And the locally made stuff (Kingsnorth, Grain CCGT) is made by E.ON !
Bring back the CEGB :-|
Mark Rand RTFM
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And keep Dungeness in operation.
Cliff.

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On 08/13/12 17:56, Mark Rand wrote:

Absolutely. At least we would have some semblance of forward planning that didn't depend on profit...
Regards,
Chris
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I was thinking more of the length of cable from the mains to the bike! The cable from France is probably already there despite the locally generated stuff. I am by the way a 'Man of Kent' though haven't lived there for many years.
All this 'nonsense' makes for a bit of fun to pass the time.
Henry
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