Am I going to melt this little motor/generator?
 

A couple of people have expressed doubt about the suitability of my little motor/generator. I have to admit, I decided to use it based on a W.A.G. of its specs. Am I'm going to burn it out?

I just tested the blower in my car (it's the same size motor I pulled from the older - same - car). On the highest setting, it pulled 9.1 amps @ 12.5 volts or 113.75 watts (car not running).

That's great, since that must be its continuous "rating".

How does that measure against the amount of power I can transmit through it? Well, based solely on remembering the readouts on the stationary bikes at the Y, 100 watts is a light-moderate amount of effort. Sustain that long enough and you'll break a sweat.

Of course it's possible to put out peaks of much more than 100w, but I'm not going to be riding this thing for long periods or doing sprints on it.

So I'm thinking it's going to be just fine.

cool idea!

heres a thought though. belt drive. take the tire off the rim, and run a belt to the motor. the shape of the rim should keep the belt in place. an old v-belt (or maybe even a serpentine) should work.

i once took the cover off my elliptical machine to see how it worked. resistance was increased by tightening a belt around the "wheel" in the back. now you got me thinking........

That's funny: I took apart my dad's exercise bike over Christmas. (Was mulling over this project, and wanted to see how it worked.) Same deal with the friction belt on what amounted to a chain-driven flywheel.

The belt/rim idea works, but then it complicates using the bike as a bike if I have to keep re&re'ing the tire. That's where Doofus' idea of finding another rim would be good.

Great idea, metrompg. We need one of these because we are off the grid, and have to use a generator from time to time this time of year. I would love to make one that is belt driven. I had a light that hooked up to the wheel of a bicycle when I lived in B.C. and I found that it sapped an amazing amount of power. you should use it to charge the battery in your metro and then run alternatorless.

Hey James - off the grid! Nice. You should post up your details.

You're right: it's not going to make a lot of power. Even if I can squeeze 10 amps @ 14 volts out of it (the output of a common car battery charger), it would take forever to completely charge a car battery. Which means I'll only be putting light loads on that battery.

If I ran my laptop from it all day (it pulls about 25 watts, and it's in use for about 10 hours a day on average), I'd then have to ride the bike for about two or 3 hours to replace that energy.

Here's how I made the bike stand
 

I wanted the uprights to contact the frame at two points on each side: lower chain stays, and the seat stays.

So I started by putting the bike on a sheet of paper and laying the boards against the bike to find the right width/angles at the base, which I traced out. As a result, the uprights have both negative toe-in and negative camber, to use some car terms:

http://ecomodder.com/imgs/stand-trace-base.jpg

To keep the thing from collapsing over sideways, I needed to buttress the uprights from the wide base. Triangulate! I checked to see how high I could attach the brace with some string (to make sure my heel cleared it when pedaling):

http://ecomodder.com/imgs/stand-check-tri-clearance.jpg

The chainstays rest in these cradles attached to the inside of the uprights:

http://ecomodder.com/imgs/stand-chainstay-cradles.jpg

Here's the finished stand, from above. Fore/aft stability is provided by that piece screwed to the base that runs underneath and inline with the tire. You can also really see the "toe-in" adjustment in this pic:

http://ecomodder.com/imgs/stand-above.jpg

It's not quite as strong in the "fore / aft" plane - no triangulation. But it doesn't feel like it needs it. I can add something if need be (I'd like to watch someone else riding it).

And from the rear:

http://ecomodder.com/imgs/stand-rear.jpg

Whole thing took a couple of hours tops, to make, and seems to support the bike solidly with the rear tire about 2 cm off the base.

http://ecomodder.com/imgs/bike-stand.jpg

Attached the motor to the stand...
 

I liked Tim's drawing, so I basically did what he suggested:

http://ecorenovator.org/forum/attach...ratorstand.jpg

Truth be told, I hadn't considered the idea of the hinge. But it's really useful for 2 reasons:

1) can easily swing the motor away from the stand and down to lift the bike out when it's time to be a bicycle again.

and, 2) the pivot means I can adjust the pressure against the tire via the bungee cord:

http://ecomodder.com/imgs/stand-motor-side-front.jpg

And here's the view of the motor hub contacting the smooth side of the tire:

http://ecomodder.com/imgs/stand-motor-looking-aft.jpg

And... it works! And... I already busted something!
 

So I couldn't resist. I figured I'd give it a try since I happened to have a one of those million candlepower rechargeable 6v flashlights sitting right beside me. Popped the bulb out, hooked it up and presto! A million candles courtesy of my legs.

Funny: I could see the light pulse on each down stroke of the pedal. I'll have to wear my bike shoes and clip in if I want to apply smooth power all the way around. :)

So then I hooked up the voltmeter to see how much the physical effort corresponded to the output. And then it immediately became a game of "what voltage corresponds to what amount of light output", which immediately became a game of "I guess 8v is too much voltage for a 6v bulb". Oops.

It was funny though: when the bulb expired, the pedal effort immediately became easier. But powering the light certainly wasn't "hard". I wish I could have taken a current reading to know how many watts I was pushing before it blew up.

Next steps:

Commence the junk car battery hunt tomorrow!

I laughed at that part. Haha, who woulda thunk?

I think its really cool you could feel the difference with even that small amount of load vs no load.

Yeah I couldnt believe how much the light I had on my bike slowed the bike down. And thats just a flashlight bulb! Really makes you think about how much energy is being used to power the typical house. You would need a team of cyclists riding 24-7 to keep it running.
Where should I post the info on my off the grid system?