Bike Generators (Do you have one? easy to build?)

[MattTuck]

After Hurricane Sandy, I saw a few threads on people using stationary trainers to charge cell phones and small electronics.

Knowing that on a good day, I might be able to produce 225 watts for 30 minutes, I don't have any delusions of grandeur on powering a whole house.

But I wonder if a bike generator could be hooked up to a battery that could power essential systems in a house (I'm thinking oil furnace, water pump, some LED lights; as secondary systems maybe fridge, cooking stove, etc.)

Any engineers here that could build such a system?

It seems to me that a purpose designed stationary trainer (like a spin bike) might be engineered better for the task, and cause less wear and tear on a geared diamond frame machine, which would run through gears, chains, tires, etc.

[esldude]

My approach for cost and simplicity would be to use an automotive alternator. I believe those are roughly 85% or so efficient. One could use a voltage regulator and power an inexpensive inverter to get AC or recharge batteries directly with the DC. Actually one can do some mods and get AC directly from them, but my approach means you don't have to know much about such things.

If you are sticking to DC around 12 volts, you can get 20 amps at 12 volts for about 280 watts input on your part. Enough to charge a dead car battery in about 3 hours. Cell phones, laptops etc. would take much less.

Taking into account inefficiencies, you will need about 400 calories of food to generate about 100 watt-hours of electricity. About 12 calories of food should recharge a cell phone battery.

[AngryScientist]

My approach for cost and simplicity would be to use an automotive alternator. I believe those are roughly 85% or so efficient. One could use a voltage regulator and power an inexpensive inverter to get AC or recharge batteries directly with the DC. Actually one can do some mods and get AC directly from them, but my approach means you don't have to know much about such things.

If you are sticking to DC around 12 volts, you can get 20 amps at 12 volts for about 280 watts input on your part. Enough to charge a dead car battery in about 3 hours. Cell phones, laptops etc. would take much less.

Taking into account inefficiencies, you will need about 400 calories of food to generate about 100 watt-hours of electricity. About 12 calories of food should recharge a cell phone battery.

building on this idea: it would not be difficult at all to take an old or broken stationary trainer and weld up some tabs to secure an automotive alternator as the resistance mechanism. outfitted with a marine deep cycle battery and a power inverter, you would be able to keep up with some small loads, and have the battery as a buffer so you wouldnt have to pedal all the time.

i would consider it more of a novelty thing to have than a viable power source, but in this storm, we definitely saw the value of a fully charged smart phone, and i could definitely run my steam boilers thermostatically controlled electronics (totally minuscule load) off of a deep cycle battery and inverter, so this is a neat idea!

[yngpunk]

When I was in Beijing several years ago, one of the "shopping malls" had a Christmas tree display powered by several stationary bikes. The faster and more people who pedalded, the brighter the lights on the Christmas tree.

More of a novelty, but it can work...

[esldude]

Exercycle conversion. Low tech, but works.
http://www.youtube.com/watch?v=R_-wVuEkk2E

Other ideas on the same approach:
http://www.magnificentrevolution.org/diy/single-bike-generator/

http://techvideohunter.blogspot.com/2010/09/exercise-bike-generator-using-car.html

Other people use a bike in a training stand. Take off the rear tire, and put a fan belt over the rim which then spins an alternator or generator. Most DC motors will also provide generation if spun. So lots of possible ways to rig this up if you wish. Just a matter of what kind of free or cheap parts you can scrounge up and then work out the details to make it happen.

[ultraman6970]

http://www.youtube.com/watch?v=kVAZIDFMRXY&feature=fvwrel