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Forum Index : Other Stuff : exercise bike conversion
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| adric22 Regular Member  Joined: 06/08/2008 Location: United StatesPosts: 47 |
I'm planning to do a conversion of an exercise bike into a generator. I know this has been done before, as well as those flimsy things that you sit a regular bicycle into that turns it into a generator. But there isn't much data out there on them. So, I have a few questions. 1) What size generator (wattage) should I use? Imagine the system is grid-tied. I wouldn't want it to draw so much power that the pedals are too difficult to work, but I wouldn't want to have one that was too small to be able to capture all the energy created. That being said, how much electricity can a person generate with their feet anyway? 2) Would the system be better if I had a large, heavy flywheel to keep some inertia going? I've seen this one guy's setup where he has a giant wooden flywheel. I'd rather have something that was smaller, but spins faster. I was thinking of using one of the electric scooter motors I have laying around and making sure the chain was geared up so that it would spin it the correct speed. |
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| Robb Senior Member  Joined: 01/08/2007 Location: AustraliaPosts: 221 |
I think a humans expected cycling output is in the 200 - 300 wattish area if I remember right. Some sports cycling sites may be worth a read. Just remember your not Lance Armstrong  |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
RE: The grid feeding aspect. You could supplement power to an existing gridfeeding system. The costs of a stand alone system at the 100-200W intermittent power level would be high. I would justify adding an exercise bike to my 24VDC wind/battery setup into 160VDC solar to 240VAC gridfeeding system. I only top up the solar system. You would have to consider the safety aspects. Low voltage at the bike, and conversion to what the grid connect system needs. There are anti islanding delays with grid connection,2 minutes usually. Any power produced during this time would need to go to a diversion load. Gordon. become more energy aware |
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feix62k Newbie  Joined: 30/07/2008 Location: AustraliaPosts: 36 |
Hi there were some pics of excercycle someware gill or gizmo cant remeber .I to have just picked up a bike from the tip $5 bargain could someone please send me the link to the pic link again thanks he had some real good shots of mounting moter electris ect dont the days seem lank and long when nothing gos right and everthing gos wrong |
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| BjBlaster Regular Member Joined: 04/04/2008 Location: AustraliaPosts: 55 |
I can get around 40W of power out of my F&P mounted exercise bike. It's quite interesting how much effort is required to generate that sort of power constantly! Here is my bike Check out my projects here in: Bj's Shed |
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| dwyer Guru  Joined: 19/09/2005 Location: AustraliaPosts: 574 |
Hi I just wondering if Your F&P made of gold or just Gold plating 
Dwyer the bushman |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
You know I think these exercise bike conversions deserve a web page of their own. Its an interresting topic and I know there are several forum members who have built them, there is even one using a PicLog to record amp/hours. I might put together a pedal power links page this weekend. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Could anyone who has put together a exercize bike conversion and would like the details put on the web site please send me a email gizmo(at)thebackshed.com A photo or two would be helpful. Dont need a lot of written detail unless you want to include it. I'm thinking of a page showing a few exercise bike conversions and some links to other sites about the same. I see Gill, Kiwijohn, tinymf, BjBlaster, and I think there are others, have posted messages about their bike, so I'll send them a message to see if I can use their photos and bikes details. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Ok Glenn, I will try to see what I can find about mine. I certainly learned a few things making mine it!
Some of the things I recall from when I added a F&P to an old exercycle: 1. A F&P is really too big (OK maybe not for Lance Armstong)! 2. You need some way of smoothing out the load as you cant put much effort in when the pedals are at the top and bottom. 3. A realistic sustained output for most people would be about 50 watts. I remember the book by the aforementioned Lance Armstrong mentioned 500 watts in training but that was his effort as measured by the machine. If you suppose the bike and generator is 50% efficient then you are putting in 100 watts. Easy enough then to realise the F&P is really too big and it is a heck of an effort just to overcome the cogging drag so I took my trusty jig saw and cut about 60% of my stator away! On the question of efficiency the chain and sprocket is not going to be more than about 95% efficient. To keep the pedals in motion you need some kind of inertia, I kept the exercycle flywheel but it did not spin at the speed required for the F&P so I needed two stages of gearing, that 95% of 95% or in other words 10% of my effort wasted right there! There are pictures of my exercycle and F&P on the forum somewhere. The guy with the big wooden wheel was on the right track but using a highly geared up generator spoiled his effort a bit, in my opinion. In my view the most efficient practical pedal generator would be a single big flywheel direct mounted on the same shaft as the pedals with a few magnets spaced around the rim that passed stationary coils to generate the voltage. You would not need many coils as remember the generator will only be a couple of hundred watts (for most people). The cream on the cake with this idea is that the magnets could be spaced around the rim in such a way that the maximum generator output coincided with the points of the cycle where you can put maximum effort on the pedals. There is a short topic with this idea on the forum somewhere. Pedal generators are fun, for a while! I made mine and demonstrated it to a radio group one evening. Connected to a 12V motorcycle battery, a laptop, and a small radio transceiver I was able to pedal continuously, talk to the meeting, run the laptop and send a bit of morse code while keeping a steady output of 50 watts or more. I think some people thought this was silly, which is not the first time that has happened to me, but in a real extended natural disaster situation, such as hurricane Katrina or an unusual cold spell we had in NZ a few years ago, telephones eventually die and generators run out of fuel but with a pedal generator and a HF radio you have basically world wide communications capabilities until you run out of food! KiwiJohn |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thanks John. I've spoken to Gill, OK to use his photos and details too. Looks like we have a pedal power RE web page in the pipeline. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I've put together the pedal power page. Its online at http://www.thebackshed.com/Windmill/articles/PedalPower.asp. Let me know if you think there is anything I should add. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| BjBlaster Regular Member Joined: 04/04/2008 Location: AustraliaPosts: 55 |
Here is an update :) I made a curbside pedal powered TV with the kids on the weekend. Here is the page I made this one smaller by design so they kids can pedal it. I was surprised that they have taken to it like they have. This is much more kiddy aware as if they stop pedaling it stops working! Check out my projects here in: Bj's Shed |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
A friend had such a setup and I tried it out one day. Everything was fine until a load was applied. At that point, I felt like the little train that said, "I think I can, I think I can." Man, it was like all of a sudden 50 people on roller skates latched onto the bike -- very hard to pedal. If it were me doing something like this, I'd design a contraption that swung a very massive flywheel with a ratcheted drive so I could "coast" and the flywheel would keep spinning. Once I had the flywheel somewhere approaching light speed, there'd be a clutch, which could be applied to transfer the angular momentum of the flywheel to a generator. That way, the generator's speed could be increased with something as simple as a belt transmission and some meaningful power could be extracted (albeit for only a short period of time) at such time the clutch could be released and momentum regained through exercise. Maybe someone else could run with this idea; I already have way too many plates in the air to juggle any more! M Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Sounds like a classic case of poor loading. Another example where more careful selection of the load, or adding series Capacitors, to get matching would make the system usable. Gordon. become more energy aware |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
MacGyver, there is such an exercise bike. Its called a "Monark", you find these at the gym clubs. They use a belt around the circumference to apply the (friction) load. But, its still "power in to get (a little less) power out" so, while you could 'coast', you'll soon find its then even harder to get the thing back up to speed. I think your speeding up and down idea would be much more tiring than a steady beat on the pedals, with a load set to match the input power  Klaus |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
[quote=MacGyver]A friend had such a setup and I tried it out one day. Everything was fine until a load was applied. At that point, I felt like the little train that said, "I think I can, I think I can." Man, it was like all of a sudden 50 people on roller skates latched onto the bike -- very hard to pedal.[/quote] Try reducing the load. Unless you're Eddy Merckx it's silly to try to produce 500W for any reasonable amount of time. I've found I could produce about 150W maximum electrically with my setup; not sure how much power that was mechanically (have to take efficiency of the drivetrain and generator into account for that). If you can sustain only 50-75W, then don't load the generator any more than that and you should be fine, without needing to resort to enormous flywheels, clutches, ratchets etc. as you propose. Having the correct cadance (I prefer around 75-80 RPM) will help your power output enormously too. Just like with windturbines, matching of the generator and powersource (i.e. you) is vital. I'm curious as to how much power I can deliver with my legs these days. Should have it professionally measured sometime as I've made a lot of improvement over the past few years. Actually, sometimes my leg muscles scare me now. My arms, however, are still as thin as they've always been.
[quote=MacGyver]If it were me doing something like this, I'd design a contraption that swung a very massive flywheel with a ratcheted drive so I could "coast" and the flywheel would keep spinning.[/quote] Sounds like a complicated mechanical contraption that would yield only very little power. But should be technically doable to build. Whether it's worth the effort?.... Everyone has to decide that one for himself. One thing I'm thinking about is bolting a generator to a bicycle trainer as these: 
or 
Should be relatively easy, and should be able to use all the bikes as powergenerating devices that way. Could use a basic, non-modified bicycle. It's project number 143(c) at the moment, so low priority, but that could change once I can scrounge such a trainer. The generators for it I have already lying on the shelf, so shouldn't be too much work to build one. [quote]I already have way too many plates in the air to juggle any more! [/quote] Join the club.... Peter. |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Dinges: You have brought up a couple interesting points. First, there appears to be a vast gulf between our ages. I used to ride 100 miles a week and think nothing of it. My legs looked like Popeye's arms. Not so 20 years later! I still ride regularly, but my goals have changed from "looking fit when I get there" to just "getting there"! Hide and watch; it'll happen to you too sooner or later. Secondly, if you look at the second picture you posted, that little contraption is basically a bicycle dynamometer sort of a thing. It looks impossible to ride, but I had one and it's actually really easy as long as you keep your focus. If you look away even for a second, you could find yourself hitting the tarmack "at speed" and hurtling across your garage floor! My point here is, this is basically a design I cooked up to let a car's drive wheel(s) sit in and turn a generator for remote-site electric power. I never built the car-sized model, but I can tell you one thing for sure: If you put a generator on it similar to the first picture you posted, you'd better have a way to engage and disengage it or you'll never get it started. You'll need your wheels spinning, so their angular momentum keeps you upright. Installing a little generator really places a drag on the wheel being situated on the circumference of your wheel. If you build one of these contraptions, please keep us in the loop, eh? Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
This is true if you use an iron cored generator or a resistive loading. If you use an AxFx, or other ironless generator and a battery loading, coupled with Capacitors, the loading will be proportional to the rpm, above cutin. Below battery cutin there will be only bearing and drivetrain resistance, and angular momentum of the alternator. Gordon. become more energy aware |
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| Jarbar Senior Member Joined: 03/02/2008 Location: AustraliaPosts: 224 |
Talking of riding rollers try doing some of these.Amazing!!! http://www.youtube.com/watch?v=b36Yi-Pb1wM&eurl=http%3A%2F%2 Fwww.rotorburn.com%2Fforums%2Fshowthread.php%3Ft%3D183870&fe ature=player_embedded#t=86 Anthony. "Creativity is detirmined by the way you hold your tounge".My Father "Your generation will have to correct the problems made by mine".My Grandfather. |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
[quote]Talking of riding rollers try doing some of these.[/quote]  
I'm already happy when I don't fall off during normal riding - let alone any off this stuff. I can't help but wonder how many times they fell off and how many bruises they've sustained before they managed to perform it flawlessly. 
Peter. |
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