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.....
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".
Only if you are talking about a fully faired recumbent with a Cd around
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.
some candidate fans...
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...
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
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==24mph 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)
EDF Environmental Defense Fund EDF Electricité de France EDF European Disability Forum EDF Edifício (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)
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.
I'd like to know more about that cable from France as apparently we are supplied by DC from France, is there a big DC AC converter in Kent. I was told that this sort of thing is done for very long high voltage lines where DC is used in preference to AC so the conversion must be made back to AC somewhere locally. My neighbour knows a guy that deals with this and he said it was common in long distance power transmission lines but is it efficiency or a phase synchronisation issue.
Yes; there are four pairs of cables running from Les Mandarins, near Calais, to Sellindge in Kent. Capacity is 2 GW, and the link is bi-directional (i.e. it can export as well as import - and sometimes does). Thus I believe there are AC-DC and DC-AC converters at each end.
Yes, it is quite normal. To run on the same AC grid, all generators must be synchronised, otherwise there would probably be a big bang somewhere. Obviously it is too much of a constraint to have the UK grid synchronised with the continent, and indeed I think there are several independently-synchronised grids on the continent. AFAIK, it has nothing to do with efficiency.
For more information, you might find the National Grid Seven Year Statement is interesting:
I used to do quite a lot of work on UK power generation projects - mostly commercial and project development rather than engineering, but I had to get a decent feel for that.
The main reason is synchronisation, but - at least underwater - DC transmission is apparently more efficient than AC. The cable is surrounded by a lossy conductive medium (seawater) which would attenuate the AC signal a bit...