large bicycle flywheel 150 watt average

[etyler88]

My goal is build a bicycle powered flywheel ( large about 200 pounds or more) that would average a 150 watt output.  The rpm and therefore the watts would start much higher and spin down over the course of the day.  I want to connect it to the grid with a net meter to avoid battery inefficency and cancel out my currenct utililty bill of 800 KW a month with the credits from my net metered flywheel.  I've seen a few bicycle generators but nothing with a large flywheel.

I envision using the 45 pound freeweights used for bodybuilding as the flywheel.  I imagine using at least four, don't know what the limit would be.  I would build the flywheel frame using bicycle parts:  A bicyle headtube on each side of flywheel (flywheel spins perpendicular to the ground, the flywheel mounted on a bicycle fork steerer tube, the steerer tube mounts in the headtubes with standard bicycle headset bearings.  The headtubes are built into a metal frame to support all this.  The bicycle is mounted in a standard rear wheel exercise stand. Take off the exercise resistance device and have bicycle rear wheel make direct contact with flywheel, just like the exercise resistance device does.  I envision using a mountain bike with the wide gearing range of the triple crankset.  I would hope I would only need to spin up the flywheel once a day but twice a day would be fine also, of course the bigger the family the more help.

I'm just a suburban husband whose wife thinks he is crazy already, so I need to build this thing slowly so the money spent won't be too noticable.  I'm thinking a budget of 2-3 thousand, mostly for inverter and net meter.  I'm a handyman but I do not even own a voltmeter; recommendations very much appreciated.  My only concern is I could be wrong about how long the flywheel could spin, if it is only about an hour this won't work.  My therory is the human body is an efficient torque machine, this  combined with the triple crank set gears will make this work.

Many thanks for anybody's input.

[PHinker]

Maybe I'm misunderstanding your plan.  Let me see if I have it right.  You want to build a heavy (200 lb) flywheel that's going to be driven by a person.  Presumably this flywheel will then drive some sort of generator which will feed the grid through an inverter.  So far so good.  The next part is where you lose me.  You are planning that this flywheel will continue to spin and produce power for 12 or 24 hours?  This won't work since power out is necessarily less than or equal to power in.  Once the person stops pedaling, the flywheel will quickly decelerate and the generator will stop producing electricity.

I'm afraid the flywheel won't spin for even close to an hour once the pedaler stops pedaling.  150 watts is possible for a person to produce for an hour or more if you're in very good shape.

If I'm not understanding your plan, I apologize.

Paul

[etyler88]

Hi Paul,

You got the idea.  The part about how long the flywheel would spin is the keystone to this plan.  I really have no idea.  I was hoping that with gearing and my torque I could get the flywheel to spin in the 3-4 thousand rpm range and it would take hours to stop spinning and the watt output would drop per hour by something like 600, 500, 400, 300, 200, 100.  That would be 2.1 KW per spin up of the flywheel with a 6 hour spin down.  I'm expecting my torque and the bicycle gearing loading the flywheel to be more efficient than steady state pedalling.

[nothing to lose]

"I'm just a suburban husband whose wife thinks he is crazy already"

I agree with her

Just joking of course, but I think there is many problems with this idea.

" My only concern is I could be wrong about how long the flywheel could spin, if it is only about an hour this won't work."

I may spin not quite as long as needed to almost produce the power you put into it as electric back out of the genny, there will be some losses so it's not equal in/out.

First the way I see it (but could be wrong) is that 150watts is 150watts no matter how or when you make it, right. SO, if you rode the bike all day constant making 150watts direct to the gennie you have no bearing losses extra gearing losses and all the other things that may cause extra losses when using the flywheel. You have to produce that much power then to drive the flywheel and cover any extra losses I mentioned like bearing frictions so you have to provide a little more power even.

So 150watts x 24 hours = 3600watts per day. I order to power the flywheel 2x's a day and produce that in electric you have to put in over 1800watts each time. 4x's a day is still over 900watts each time. Take in for losses and you jump to 2000 and 1000 or more input each time. Don't know if that would even work really myself. But still if you could do that, might as well just go direct and forget the flywheel, power is power and if your feeding the grid who cares if it's all at once or spread out durring the day? Now if you were trying to power your own needs then spreading it out might be worthwhile.

 Now it is said a person in decent shape can produce about 100watts continous for a while or a little more maybe, about 150-200watts for a short burst, if I remember the figures correct.

 No matter how you gear the flywheel you still have to provide that power. Either peddal HARD and slow, or peddal really fast but easier, depending how your gears are setup or changed. BUT, either way it is still the same basic effort and result. You put out 100watts of your engergy to make the genny provide 100watts of electric.

 Now by using a flywheel it might help make constant running a bit easier, eliminate the lummpy spots, provide for a brief break to relax, keep the genny spinning while changing riders etc.. but the gennie has a load on the flywheel equal to the power it puts out plus a little. So if you have 150watts electric being made you need to power up the flywheel to about 300watts if you want to take a short break. Now this would be good for changing riders, the first gets it going which takes alot of work, the next just keeps it going at a constant rate and so forth.

I try to keep the pedal power a person can produce in mind, though my mind is full of many other things so I get a bit slow at times with numbers. Since I am thinking of electric vehicles like bikes and 3 wheelers this info is useful to eliminate false statments by others supposedly knowing more than me (mostly local). In other words when someone tells me it takes 2HP and 10amps 120Vac to move a 3 wheeled bike down the road, I KNOW they are wrong! If a person peddals a bike at 100watts per hour and can move the same bike down the road then it takes .83333amps at 120Vac or 8.3333 amps at 12VDC. FAR less than any 2HP motor I ever saw

 So at 115 amphrs per deepcycle battery at 50% discharge I get 57 amps/9= 6.3333 hours at normal peddaling speeds (aproxamate).

 Now add in wieght of batteries and motor etc.. I might get into the 10-15amp 12Vdc range or 1-1.5amp 120Vac. Even 15amps is close to 4 hours at half cycle on 1 battery, plus your not always using power, sometimes you can freewheel or downhill brake.

 If you have many short hop type trips you make alot, might be a bike idea for you better than the flywheel genny. Still have to pay for electric and maybe more to charge the bike, but look what you could save on gasolene! Could build a small wind genny to charge the bike. OR a peddal powered genny from the exercise bike as direct drive. Just sit there and casually pedal at night in the comfort of your home while reading a book or watching TV over a long period of time taking breaks whenever. THEN when you got the long hard ride in the hot sun you ride free and comfy letting the batteries do the work

My plan I am gathering parts for is a powered bike trailer. Some places have lots of laws and restrictions on motorized bikes, I no of nothing about motorized trailers

 The bike is still pedal power only

Also as a trailer unit you could use one for several bikes, just have to mount the controls when you change bikes and connect the hitch. So a 3 wheeler, 2 wheeler, etc.. could use the same trailer at different times and you always have peddal power as a backup. If you wanted to make long trips to the same place often like I might, you build 2 trailers, one for each end of the trip. Charge one at home and one there, ride one way swap trailer and ride back

 I do have a place to store and charge the second trailer at the other end and that of course is very important. No advantange of leaving a dead trailer to stay dead.

 I will also be able to haul things on the trailer as a trailer. Car parts, groceries etc..

[kitno455]

dude, law of conservation of energy. this is pointless. think about it this way:

assume you are capable of putting out 100W for a solid hour before you collapse, you've got 100Wh of power into pedals.

now, say bike and bearings are 90% efficient, and electric gen is ~80%. now you've got 72Wh.

now your grid tie inverter is ~80% efficient. you've got 57Wh of power into the grid.

even if the efficiency of those components is far higher, the max you've got is 100Wh.

adding in the flywheel makes things worse! more bearings, lower efficiency. in fact the higher rpm will kill you in bearing loses.

you cannot 'create' more watts out of a flywheel than you put into it, you can only spread it out over time. the power meter does not care if you grid tie 100W for an hour, or 10W for 10 hours. there is no point in stretching it out.

allan

[nothing to lose]

"I was hoping that with gearing and my torque I could get the flywheel to spin in the 3-4 thousand rpm range and it would take hours to stop spinning and the watt output would drop per hour by something like 600, 500, 400, 300, 200, 100."

This being my second reply and the above being posted while I typed the first one I probably covered a lot!

However!

If I were you, before spinning anything up to 3-4 thousand RPM I would go far far into the woods, bolt it to the crank flywheel pully of the car or truck engine, make sure no-one is within 500' at least and start your engine from a safe distance!!!

Also you might want to have some-one waiting for you to give you a ride back home or call the tow truck BEFORE you arrive at the remote test site, pretty sure you won't be driving that one home. :O

First didn't you say something about wieghts like maybe bar bell lifting wieghts? Perhaps I mistook that part but if so, they are for lifting, not spinning!

 They will shatter at far lower RPM I am almost certain and they are not going to be very well balanced either so they will rip anything you put them on apart at high RPM if they do not shatter first.

There are differnt type of weights, cast iron, plastic coated that looks to be filled with pressed slag iron etc... but I think what I said is probably true for all of them at anywhere near the RPM you want.

As for gear ratio, count how many times your bike pedal goes around in 1 minute!

Say maybe 120? 2 times a second? Ok, now 3000 rpm divided by 120rpm= 25/1 ratio.

Now if you have 3' legs maybe you could use a 30" sprocket on the peddals and connect to a rear sprocket of 3", is that 10/1 ratio?

Now your driving a 26" wheel at 1200rpm. Go from that wheel to your flywheel direct and the flywheel needs to be less than 1.7333" to get that other 15/1 ratio you need. Well that's not going to happen right. So if you use a belt on the bare 26" rim and a 2" pulley at the flywheel you get ALMOST the 25/1 ratio total for close to 3000rpm.

You get the point. Now how many RPM do you need to run your genny? Go from 3000rpm down to that RPM. If it's say 500rpm for 150watts then 3000/500= 6/1 ratio. Okay that part is easy to do. BUT, now when the flywheel slows to 2500rpm you will be below 500rpm at the genny, about 416.6666 rpm so your not going to get your 150watts. You'll have to over speed the genny at the full 3000rpm to acount for this ratio effect. So if you go for 3/1 ratio your genny will spin at 1000rpm when at full speed, can it handle that?  When the flywheel drops to 2000rpm the gennie will be at 666.6666rpm and still producing power. BUT at 1500rpm you are hitting the bottom limit of the 500rpm needed. You either have to peddal it back up to speed at this point or you have lost all the energy it takes to get the unit up to 1500rpm from where ever you do start pedaling again. If it totally stops then you lost 1500 rpm of energy, 0 - 1500rpm. If you start peddling at say 1000 rpm then you have lost 500rpm of energy. It may be free, may be help you lose wieght, it may give you a heart attack!

 Once you hit any of these ratio's I also think you will lose the ability to peddal at 120RPM also.

Now if you r genny produces power at any speed above say 300rpm, you still need 900 rpm at the flywheel unless you go 1/1 and run the genny at full 3000rpm. If you do that how will it effect your power output and genny life. If gthe genny is producing more power at faster speeds it also slows the flywheel down faster, but at least you have less losses like from belts and pullies. Plus under these conditions that 2" pully is going to let the drive belt slip alot probably when trying to peddal up the flywheel.

All this is figuring the low of 3000rpm, if you want to try for 4,000rpm your on your own for math

I am not that up on gear ratios, I geuss I figured them correct, if not forget this whole thing I typed and refigure it correctly. Same idea applies numbers will be different.

[kitno455]

i should have said at the end, that your flywheel lets you CHANGE the amount of time the power is applied over, not just lengthen it.

if you are only capable of 100w for an hour, but you use that power to spin this huge flywheel, and then connect it to a 1000W genny, it would actually work, but it would slow down at 10 times the speed you spun it up at, so 6 minutes of 1000W. i assume you could even get a hundred KW, for about 1/6th of a second

in the end, though, 100KWh in, >100KWh out.

oh, and using barbell weights at the outer rim of a 2k rpm flywheel? really, really bad idea. spinning the bearings in a bike headstock at 2krpm with a few hundred lbs of weight on them, also a really bad idea.

allan

[Nando]

Let me state it in a different way.

You want to inject 150 watts for 1 hour and recuperate 150 watts for 6 hours !!

This is not free energy --THIS IS ETERNAL ENERGY ---

The DREAM of humanity

Clear indication that you do not know any principles of energy, energy producing, energy harvesting, efficiencies and etc. and etc, Human power capabilities, and etc in physics and other sciences.

YOU HAVE SAID:

>>>>I'm just a suburban husband whose wife thinks he is crazy already

Tell your wife: Yes I am crazy !! And give her this message

Nando

[orochi8]

Ok, where this is going to actually prove usefull is in getting a little extra incentive to exercise. More than that really, it is not going to acomplish much. You have to remember, that you are only going to get how ever much energy out of it that you burn in calories. Your fat is nothing more than stored chemical energy, and your muscles are converting it into kinetic energy and heat. All the fly wheel is going to do is give you a little momentum so you dont can spread the effort out over time, the same way that pedaling your bicycle untill you have some speed would make it easier to maintain that speed. The magnetic field of your dynamo is going to be constantly creating resistance as it produces electricity from your kinetic energy though. Basicly your generator is like putting on the brakes.

-Orochi

[nothing to lose]

Hey be nice now

We all have our moments.

I once built a working magnetic motor, once started it increased in speed till it blew itself apart! Almost got myself hurt, I had nothing built in for breaking or loads etc... as I was not expecting anything to happen and did not think of such things before hand.

Hmmm, I thought I was on to something there.

Sometimes I make the mistake of mentioning that experiment and get kinda reamed.

OOps, I did it agian didn't I ??

Well anyway it was explained several various things that could have had an outside effect on what I had built. Never have been able to build another that works like that one did, or works at all for that matter, so I can't test any thoughts of what could have actually happened.

Was it outside interference, did I discover something that does not exist, was there a very fast mouse running inside it trapped somewhere trying to get out??

Does the universe have limits, or is it like the earth, once you start moving in a straight line and never stop you just keep going on the same path in a gaint circle. Or fall off the end?

I geuss someday if I ever get my real workable projects done I may give it another shot just for fun of trying. If it was outside interference and it provides useable force to turn a genny what do I care where it came from as long as I can harness the energy for free and use no feul to do so. Maybe it was a too strong radio station or faulty power lines nearby???

[orochi8]

You know, with a much less powerfull generator, he could probably put enough energy into it to keep going at a reasonable rate, then use it to say, power one of those little lcd tvs while he works out. At least it would be accomplishing something usefull, would look cool, and give him some incentive to exercize.

-Orochi

[MelTx]

  Hello etyler88 I am currently building a pedal genny[see diary].It is not finished but so far after reading your post I sort of timed it.

   Guesstamates:pedal= 2 rpms per second = 120-150 rpm

   50 LB solid iron flywheel Ratio 4:1 = 480 or 600 rpms

 This is not compleate there are more coils to go on stator.But turning as fast as

   posible will produce 13.5 volts with a parralel capacitor it takes only 30 seconds for the volts to drop to 12vdc... The wind drag on the flywheel and mags realy slow it down....

    By the way for what its worth I had 1 x1/2 x1/4 neos on the flywheel,no glue they stayed just fine no problems.....So I put 2x 1 x 1/2 neos on the flywheel and realy rev it up..DONT DO THIS AT HOME... the large mags that are much stronger went flying into orbit I ran for cover....Some of the mags went 40' away, strange things happen at high R.PM.s......   MelTx

[commanda]

currenct utililty bill of 800 KW a month

I presume you meant 800KWH.

Your real problem is the size of your utility bill. Your problem can be solved with one word; CONSERVE.

Replace most of your lamps with compact fluoros. Turn them off when not in use. Turn off the heater & put on a jumper. Turn off the air-con & open the windows instead. There's lots of others. The first few simple ones won't cost much, and will save heaps.

Amanda

[halfcrazy]

yes if you are trying to make the hole 800 kwh with a pedal bike you will be busy that figures out to be like 26kwh a day so presuming you could pedal 150 watts a hour steady for 24 hours you would have 3.6kwh so you will need a little over 7 bikes and people to erase the utility bill without counting losses.

[pyrocasto]

For every hour you pump yourself on that bike, you'll save less than a dollar here. I would spend that time working to buy some CFLs and a windmill. ;-)

[Victor]

Hi Chris.

 150 wh would be about a penney.

Victor

[wdyasq]

Gee Chris - you must pay high rates there.  Rates here were highest in the nation at one time - ~14 cents a kWH a 6.5 hours a kwh, to get to a $1 it would take near 45hours - so.... pedeling 24/7 at athlete power one could  produce about $15 a month in power.

Changing 2 light bulbs used all month from resistance bulbs to CF bulbs would do the same.

Ron

[Tyler883]

Hi I just wanted to re-state things one more time...

instead of pedaling a flywheel for an hour, you can make more power by pedaling a larger generator for an hour and 5 minutes.

[troy]

If you can erase a monthly electric bill of ~800kwh by peddling a generator, with or without a flywheel, with only your muscle power, you need to be a professional cyclist.  After you win the Tour de France the third time, you can buy all the electricity you want from your promo money, or even better, all the renewable/alternative energy gear you want.

Seriously, having built a pedal driven custom made hand wound permanent magnet alternator myself, I can state with pretty good certainty that you'd do extremely well to put 100 watts into the utility system after you acount for losses.  50 watts or less would be more realistic.  A flywheel of any kind will not change that number appreciably.

By the way, the economics of your scheme don't work any better than the physics.  A typical grid tie inverter, by itself without the installation or the permits or the other bits and baubles will generally cost a couple grand at least.  Cheapie MSW inverters CANNOT hook up to the grid without very bad things happening.

Good luck and have fun!

troy

[jomoco]

Hey there Tyler,

I'm afraid your expectations are in for some serious adjustments, but I encourage you not to give up hope that you can make a dent in your electric bill.

I have built a few spring motor powered prototypes with very heavy flywheels and found that anything over a five minute spin down to zeroe requires a huge imput and minimul generation drag to achieve. That said, your idea of utilizing a multi geared bike to spin up a ( balanced ) 200 lb flywheel to generate electicity has merit as long as you modify your power output expectations accordingly, and are willing to do a little research as well.

Again I encourage you to keep trying, there's a law of physics that states you get out of a project what you put into a project, the more you put in the more you get out.

Best of luck.

jomoco

[stm]

Hello,

The flywheel will be good for decogging the generator, and to maintain the torque on the generator in those (very short) moments where you are not pedaling at full power (the pedals in the vertical position)

If you want to "work like hell" for a few minutes, and in this time produce a large amount of electricity, then you can use a bicycle with some heavy gears as the basis for the generator - you will not get more energy than you put into it, but you will save some time, which i guess is what you want.

With a budget like yours: What is your reason for not buying a soladin grid tied inverters and 145 watt of solar? - this will do the trick for you....?

/Steffen

[pyrocasto]

Dont know what I did for my math... :?

It would take over 5000 hours to pedal off your monthly bill.

[georgeodjungle]

man = 1/5 hp ><

1 hour 1/10 or less ?

horse = 3 hp  ><

1 hp = 700 watts

it will take a 3.5 hp to run a 62amp gen.

could work for short time and loads like laundry.

any way sounds like a lot of work.

ok ok maybe lance could run a tv N dvd for that all important must see 2 hour show.

you could cost a lil with a flywheel.

how about a battery?

i wouldn't try to spin it...

[Norm]

 Sounds logical...

 Before I retired I made $12 an hr. , my electric

 bill was less than $90 but for simplification

 we'll say it was $90 so that would be $3 a day

 so 15 minutes pays my electric bill for the day

 we had quite a few 15 minute breaks during the

 day so in a way my electric bill was being paid

 for while I was smoking a couple of cigarettes

 and drinking coffee! What a deal! Why bother

 with flywheels!

               My wife thinks I'm crazy too!

              ( :>) Norm.

[JeroenH]

I've heard that you can feed bike-produced electricity into the grid by spinning a synchronous electric motor faster than it wants to when it is connected to the grid.

Is this true? And, more important, is it practical and efficient?

[etyler88]

Thanks for all the responses.  I'm glad I posed the question before getting to far along only to be stopped by the laws of physics.  I am trying to conserve first.  I have all fluorescent bulbs now.  Bought a Prius couple months ago, that has gotten me into this.  Was frustrated by places like this

http://www.wholesalesolar.com/index.html

All alternative energy stuff I've seen so far has 15 - 30 year paybacks, but I know there must be better options out there.  I live in Delaware with many trees in the yard so solar might not work too good and a wind turbine would have to mounted maybe 75-100 feet up to get above the trees.  There may be a good spot for solar on my roof though.

I'm paying about 9 cents per KWh and would like a payback of no more than five years. My state has a 50% refund grant program for solar and wind.

Steffen's suggestion of "With a budget like yours: What is your reason for not buying a soladin grid tied inverters and 145 watt of solar? - this will do the trick for you....?"  gives me hope.

Ed

[etyler88]

With a budget like yours: What is your reason for not buying a soladin grid tied inverters and 145 watt of solar? - this will do the trick for you....?

/Steffen

Sounds good

Can you tell me the FAQ on this.  A parts list and sources.

Thanks, Ed

[Vernon]

KE (Kenetic Energy) = 1/2 MV^2.

Consider a 200 pound flywheel rotating at 5000 RPM with a center of mass 2 feet from the hub. The diameter is 4 .. so every revolution is 12.57 feet, 62,831 feet per minute or 1047.2 feet per second. Square that and you get 1,096,628 multiply by 200 ... 219325568 ... divide by 2 ... 109,662,784.

The stored energy is 109,662,784 foot pounds and since 550 foot pounds per second is one HP you can get 199,387 horsepower for one second or 55.38 horsepower for one hour.. and for home generation 5.538 horsepower for 10 hours. I would cut that in half because you will have aero and friction loss.

The problem is the army of men necessary to pedal it up to speed in a time similar to its output time. I would start an excercise studio, charge memebership, gang the excercycle pedals to a shaft that is clutched and geared (50 to 1) to a 200 pound flywheel at each end. When one flywheel is up to speed it is connected to the generator and the other, depleted unit is spun up by the cyclists.

If you want to get greedy you can locate your human generating plant in San Francisco, contract for a dominatrix to beat those cyclists who will pay large sums for this treatment and really cash in both from the power generated and the clients. I don't know what this really accomplishes however because I don't think that a human is a very efficient converter of energy. The postulated pedaling submissive probably eats beef and that requires all that tractor and transportation diesel needed for the associated agriculture.

Kenetic energy recovery could work well applied to a pickup truck .. put some batteries in the back, install an oversize alternator and connect it to the batteries when the brake lights come on. Charge the batteries from energy used to decelerate the truck when stopping for traffic.

[troy]

Theoretically yes.  If you can overdrive a motor like that at just the right speed, it will pump watts onto the grid without an inverter.

Legally and practically: very bad idea and won't work.  It would be very difficult to regulate the speed well enough to do this safely and efficiently with a humam as the prime mover.  Furthermore, no utility in North America will allow you to pump watts onto the grid without their inspection, permission, code issues, etc.  The setup you describe would never pass.  That would also make your house and liability insurance null and void.

Sorry...

troy