Navitron Renewable Energy and Sustainability Forum

General Renewable Topics => Inventions, Ideas, Innovation, Bodges etc => Topic started by: Ivan on May 18, 2008, 05:36:30 PM



Title: flywheel bike
Post by: Ivan on May 18, 2008, 05:36:30 PM
Thinking aloud about Ken's bike/trike requirements:

If you keep your motor  below 180W, and have the movement of the bike engaged by pedal assistance, you should find it's exempt from road tax/insurance/mot etc.

The main problem with this is that 180W doesn't give you much power for acceleration, top speed, going up hills and so on. Here's a suggestion: you turn on the bike, and the motor runs immediately. The motor spins up a large flywheel, thus storing kinetic energy. Flywheel is connected to the wheels via a clutch and gearing - perhaps CVT? This gives a short term power boost - say 5minutes worth of acceleration or hill-climbing.

Any comments?



Title: Re: flywheel bike
Post by: martin on May 18, 2008, 05:44:03 PM
steering could be fun! - it'd be a giro too! ;D


Title: Re: flywheel bike
Post by: Ivan on May 18, 2008, 08:16:08 PM
I've figured that one out too - if the flywheel is lying horizontally - eg underneath the storage unit of a trike, then it will be able to turn easily, but will have mind-defying road-handling!


Title: Re: flywheel bike
Post by: northern installer on May 18, 2008, 08:58:15 PM
Nice idea,but what about the weight of the flywheel?


Title: Re: flywheel bike
Post by: Ivan on May 18, 2008, 09:07:28 PM
I agree, weight is an issue, but flywheel energy is defined by err, 'angular momentum' (starting to falter - been 100 years since I studied this!). The further out the weight is on the flywheel the less heavy it has to be for a given energy. Also, floating on magnetic bearings and housing in a vacuum will reduce frictional losses, allowing it to store energy more efficiently, and allowing it to be spun up to greater speeds.

Anyone care to do some calculations? What amount of energy are we looking to store? Let's assume we want 3-5minutes of power from the flywheel. What power are we looking for? 800W?


Title: Re: flywheel bike
Post by: guydewdney on May 18, 2008, 09:12:05 PM
twin, contra rotating flywheels will help...


Title: Re: flywheel bike
Post by: Ivan on May 18, 2008, 09:15:22 PM
Even cleverer - and we can then mount them in the vertical plane which might be easier for vari-belt driver power transfer.


Title: Re: flywheel bike
Post by: northern installer on May 18, 2008, 11:01:02 PM
How about a very small flywheel running at ENORMOUS rpm,a bit like the push and go toys? the smaller flywheel would reduce the(very real)effects of precession on navigation,and the whole unit could fit in a small space  bike:


Title: Re: flywheel bike
Post by: mespilus on May 19, 2008, 01:03:51 AM
Is this flywheel spoked?

I rememeber a few years back the Italian Pursuit team were disqualified for having spherical weights on their spokes
which acted as incremental flywheels.

The faster the cyclist the longer the weights stayed at the rim throughout each wheel revolution.


Title: Re: flywheel bike
Post by: Ivan on May 19, 2008, 01:36:23 AM
I've found an online calculator - http://www.wa4dsy.net/robot/ring-flywheel-calc

Let's assume we are looking for storage of energy equivalent to 5minutes at 800W output - which should help us over small hills and accelerate away from traffic lights at respectable speed. That's 5/60 of an hour x 800W = 0.0666kWh (=240 000 Joules)

Using the calculator:

If we go for a 24" ring flywheel (22" inside diameter) of 5.11kg weight, spinning at 10 000rpm, we get 239681Joules.

So it's feasible and realistic.

I have a vision of a cyclist (pedal-power), arriving at a set of traffic lights, but whilst stationary, pedaling furiously, spinning up the flywheel. When the lights change to green, he releases the clutch and the bicycle accelerates from 0-30mph in a couple of seconds, leaving the combustion-engined vehicles for dead.


Title: Re: flywheel bike
Post by: KenB on May 19, 2008, 03:19:15 AM
Ivan,

Find me a material that will survive 10,000rpm, 24" diameter without bursting??  Cast iron craps out at 1000rpm for this diameter - trawl the net for flywheel explosions if you need any visual convincing of the destructive nature of flywheels.

The gyroscopic forces would be astronomical.   What you need is a series of small flywheels shaped and sized like beancans, running at approx 100,000 rpm.

The Sandia Labs in New Mexico investigated these about 15 years ago, as an alternative energy storage to batteries for electric vehicles.


Ken



Title: Re: flywheel bike
Post by: guydewdney on May 19, 2008, 08:14:07 AM
spin at that sort of rpm, and the losses become huge. However, I agree that 10K @ 20 odd inches is phenominal...


Title: Re: flywheel bike
Post by: northern installer on May 19, 2008, 08:43:46 AM
There shouldnt be any losses in the flywheel itself,just in the bearings that support it;but the reduction gearing-now thats another matter!but all feasable,the bearings on a turbo charger survive huge rpm,and violent extremes of temperature,but have to remain free running to allow the turbine to start;
The flywheel would have to be automatically decoupled from the bicycle on overrun,or the lollipop lady might get a nasty shock!  bike:  sh*tfan:


Title: Re: flywheel bike
Post by: paul on May 19, 2008, 06:37:46 PM
Petty to de-couple on overun as going down hill and breaking could 're-charge' the fly wheel.


Title: Re: flywheel bike
Post by: guydewdney on May 19, 2008, 08:15:24 PM
The bushes (note) are phozzy bronze or similar, supported on a film of oil in turbos. They are balanced to within an inch of their life, and also tiny (relativly) and very very light (relativly) - they are designed to have the lowest possible rotating energy to reduce turbo lag.

You cant use this method with high RPM heavy things.

High speed heavy things - like grinders (for making precision cylinders) run on air bearings - the air has to run, before the thing spins. similar for magnetic.  Bit impractical for a 'bike  ;D

Compressed air maybe as an energy storage? Light, simple, proven technology. There was a tread about an air car a bit back wasnt there? cylinder can be a sphere for extra lightness...

and fillable from a house (using a cheap 5 quid compressor...)....

Um?


Title: Re: flywheel bike
Post by: billi on May 19, 2008, 08:27:10 PM
I think or heared ( is there a difference ? banghead:)

these are in the flywheel buisness ..... but perhaps its cheaper to go for a PV charged battery  :P

http://www.beaconpower.com/

billi


Title: Re: flywheel bike
Post by: Gnidrolog on May 19, 2008, 08:29:42 PM
Some years ago there were experiments with a flywheel tram. The motor made electrical contact at stops to charge while the passengers got on. What I thought was very clever was the gear arrangement. Power output from the flywheel was taken from the centre at pull away, then the drivers lever pulled the output jockey wheel towards the edge to increase speed (CVT?). To slow down the lever pushed the jockey wheel towards the flywheel centre to put the trams inertia back into the flywheel. The flywheel was horizontal so it aided stability on cornering.

I think the experiment took place in Barking, probably 15 years or more ago. Presumably it failed as I've heard no more about it.

Gnidrolog


Title: Re: flywheel bike
Post by: Gnidrolog on May 20, 2008, 12:45:50 AM
but perhaps its cheaper to go for a PV charged battery  :P

billi

Here's a link to a PV bike: 900 Kilometer race, average speed 40Km/H. 150W motor. That's if I understand it fully http://www.flighttechdistribution.co.uk/News/open_article.asp?articleNo=456&parent=technical

Gnidrolog


Title: Re: flywheel bike
Post by: renewablejohn on May 20, 2008, 09:28:23 AM
You could use the rear motor bike tyre  as the compressed air cylinder and the technology to inflate and deflate tyres on the move as your powerline. link this with a screw compressor which can be used as a motor and you have an air powered bike.


Title: Re: flywheel bike
Post by: Ivan on May 20, 2008, 01:17:45 PM
Flywheel-powered buses are very real. Used in Switzerland:

http://en.wikipedia.org/wiki/Gyrobus


Title: Re: flywheel bike
Post by: KenB on May 20, 2008, 03:26:52 PM
Ivan, List,

Correction,it was the Lawrence Livermore Labs that did the research in the mid-1990s using a bank of very high speed composite flywheels as power storage.

The flywheels incorporated rare earth magnets to get the power in and out and were run on air bearings, with the flywheel in an evacuated vessel IIRC.  Turn around efficiency (energy out / energy in ) was stated as 99% compared to about 65% for a lead acid battery.

I found this Livermore paper for some of the details, but I think the original article that got me interested was in the Scientific American October 1997.


http://www.osti.gov/bridge/servlets/purl/358801-vtzl8B/webviewable/358801.pdf


 Flywheels in Hybrid Vehicles; October 1997; Scientific American Magazine; by Rosen, Castleman; 3 Page(s)

The search for an alternative to the internal-combustion engine used in today¿s cars is motivated by two societal concerns: the need to reduce fossil-fuel consumption and the need to reduce air pollution. Unfortunately, most car buyers do not make their purchases based on these criteria. Instead, when looking for a new automobile, most consumers consider issues such as cost, safety, performance and fuel efficiency. (This last factor does, of course, have an effect on fuel consumption and pollution, but it is rarely a car buyer¿s primary concern.)

In 1993 one of us (Rosen), along with his brother, Benjamin, founded Rosen Motors with the goal of producing a new type of powertrain for cars that would not only address concerns about pollution and fuel efficiency but would also be something that consumers would actually want to own.

http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ISSUEID_CHAR=55FFD523-BFC2-4006-87AB-B49A4B9B4A1&ARTICLEID_CHAR=40A5048D-1AE0-4AED-B8B7-1472C964FBE


Title: Re: flywheel bike
Post by: KenB on May 20, 2008, 03:50:59 PM
Ivan, List,


After some hunting - Here is the link to the electro-mechanical battery EMB - developed by the Livermore Labs

https://www.llnl.gov/str/pdfs/04_96.2.pdf



Ken


Title: Re: flywheel bike
Post by: mespilus on May 20, 2008, 04:23:23 PM
Were ever/are any embs commercially available?


Title: Re: flywheel bike
Post by: KenB on May 20, 2008, 04:48:18 PM
List,

EMBs failed to get out of the lab.

Whilst the rose tinted spectacled scientists referered to their failure mode as "benign" - there is nothing benign about 1kWh of flywheel dissipating that energy in under a second, when the bearings failed.   TNT has a lower energy density than the flwheels used in the EMB.  whistle

Ken


Title: Re: flywheel bike
Post by: Ivan on May 21, 2008, 01:33:23 AM
The link that Billi mentioned - Beacon Power are producing 25kWh/100kWh units!! I haven't dared to ask a price, though.

I did speak to an American company a few years ago that was developing home-scale 25kWh units, to be burried in a hole in the basement. The idea was that if the flywheel failed, the impact would be absorbed by surrounding earth. Seemed sensible to me. They were planning to produce their machines for a few thousand dollars, but I can't find them, now