Friction driven alternator experiment?

Speedy Wilson · Mar 16, 2009

I was looking around the forum, just reading and such, then out of left field it hit me. I hear all these guys talk about the range they get or lack of on an electric powered bike. My idea is to mount a GM style Delco one wire alternator onto a bike and drive it with a friction setup. Use the Juice generated to charge the battery or batteries while in motion. They are hardly any parasitic drag to turn. It has an internal regulator and come in 12 and 24 volts.Most are light and would be easy to mount up. If a car engine can idle at say 800 rpms and the ratio is about 2:1 between crank pulley and alt. pulley it would spin at 1600 rpms. Most will make about 50 to 60 amps i would think at this speed depending on output rating of the alternator. The key is to find a way for it to spin up this high from riding on the tire in a friction setup. Could use a friction drive mounted to a gearbox to spin it up faster at a slower wheel speed? I'm not that great at the math of calculating the ratios but If I had the parts I would try it just to see if it would work. If anyone has tried this or have any thoughts let me know. All great inventions started with an idea right?
.bld.

toytime · Mar 16, 2009

I'm just not sure if the power used to drive it will be equal to what it gives you back in return.

cityevader · Mar 16, 2009

perpetual motion machine?!?!

toytime · Mar 16, 2009

That's about it-nothing comes for free.
The thing is that if it even gave you an extra hour of use, that can double your mileage and with ebikes that is large.

Speedy Wilson · Mar 16, 2009

True,it would be some drag but i can spin an alternator pulley fairly easy by hand. With some type of low friction bearings in the drive setup,use aluminum mounts it may add about 8 to 10 pounds. Or i was thinking about those really old (indian or harley) bikes that had a big pulley mounted on the rim,at a say 20 to 1 ratio that thing would really spin up.

cityevader · Mar 17, 2009

You can easily spin an unpowered alternator by hand. With the field energized, considerable torque is required to spin it. A car's computer will increase the idle air valve to maintain steady rpm when electrical loads increase.

Doesn't make sense to run an electric motor to spin a generator.

deacon · Mar 17, 2009

Here is the only problem I would have my bike is 24volts the alternator is 14max. I doubt that it would do much good.

It takes several hours to charge the batteries from the bike so I'm not sure the alternator would do much even if it was 24volts. But if you have one, I would give it a try.

On a car the battery is only used for a few seconds then the alternator charges it as long as you drive the car. Still Give it a try I would if I had one laying around.

Speedy Wilson · Mar 17, 2009

The 24 volt alts. usally come off small diesel engines or backhoes. I had a 12 volt alt and a couple car batteries here somewhere,but i need a 12v motor for my tests. I was going to bench test the idea by the running time of the motor on a battery alone versus the running time with alt. backup. Spin the alt. at about 1500rpm with a washing machine motor to simulate being driven by the wheel.But then that is constant and riding is varied speed. Im starting a gas weedeater/mt.bike build so i don't want to go in an opposite direction on my only bike, though I am going to give this idea a shot once I get the funding for parts and another bike. I will keep you posted on what happens...be it works or bombs.

deacon · Mar 17, 2009

Speedy Wilson said:
The 24 volt alts. usally come off small diesel engines or backhoes. I had a 12 volt alt and a couple car batteries here somewhere,but i need a 12v motor for my tests. I was going to bench test the idea by the running time of the motor on a battery alone versus the running time with alt. backup. Spin the alt. at about 1500rpm with a washing machine motor to simulate being driven by the wheel.But then that is constant and riding is varied speed. Im starting a gas weedeater/mt.bike build so i don't want to go in an opposite direction on my only bike, though I am going to give this idea a shot once I get the funding for parts and another bike. I will keep you posted on what happens...be it works or bombs.

Good luck and let us know sounds like an interesting experiment. They say you can run a car's starter motor on the bike as a friction drive and that is 12 volts.

Speedy Wilson · Mar 17, 2009

hum..i may have an old chevy starter...wont it burn out? I'm thinking that because when cranking an engine its on for what,5 seconds max? Will consider that too. Thanx for idea,will keep you posted on it.

deacon · Mar 17, 2009

some say they will burn, some say they won't.. I would use it in pulses not for extended time. Like run it on the hills but turn it off going down hill. Kick it on to get the speed up on the flats then let the bike coast some before you bring it back on again. that kind of thing. When i was young stupid and poor I used a household switch for my starter button on an old toyota. So you can use one of those as your on off switch.

Now that part fascinates me. How the starter will work. Those should be very easy to find in almost any town.

cityevader · Mar 17, 2009

I too would be interested to know your experiment results. But to get the most simple results, use a 12 volt drive motor instead of a 120 volt one.
With a proper amp meter, get a baseline measurement of drive motor current draw, then see what additional draw draw is required while the alternator is charging (not merely spinning), then compare it to the amp reading coming out of the alternator. This will show any viability.

Do friction drives not allow regenerative braking? Wouldn't that be easiest without additional componentry?

deacon · Mar 17, 2009

okay my understanding. I'm not at all sure that I'm right, is that all brush type motors convert to generators when spinning faster than they are drawing current. However you need a diode to pervent the current from running back to the motor. The controller on some motors do that have the diode built in. So when the throttle is turned off or low the motor is free wheeling and becomes a generator. I have run my friction drives both ways and have never seen any significant difference. On the hub brushless motor absolutely a difference.

Auto alternators have the diode pack built in which allows power to travel only one direction. If you ran a starter motor for push and an alternator for charge you will probably get the same effect only a little more so since the alternator will be charging even while the starter motor is pushing. that's my guess

Speedy Wilson · Mar 17, 2009

Somebody tossed my alternator! Probably went in trash pile when my Pa cleaned up behind the barn. First rule of being a gearhead is never throw away parts even if you think they are useless. I went to wally world today and seen a "hybrid" e bike for 399.00. I will give 50 for a back wheel and the drive motor...lol..the setup looked sweet...very compact. Anyway,I have to find an alternator and starter or twelve volt motor...I wonder about electric wheelchair parts. I think I know where one was...got to check on it. The next challenge i see is adapting a drive wheel to the starter motor. Could dremel out the nose cone and fit a sprocket somehow. Will be a few weeks on this one...the bill collectors cometh...untill then ride on guys...

deacon · Mar 17, 2009

I really am curious to see what a starter motor does. I think I would like to try one as a friction drive.

ottolynx · Apr 5, 2009

I also interested in finding out if this work, I current working on my senior project for school and our group idea is to take a electric moped and attach a alternator to it to charge the battery but where lost on ideas that why I interested in knowing the resultof your experiment.

Cabinfever1977 · Apr 5, 2009

2 stroke gas bike engine,small lightweight and powerful.
hook it to a 12 or 24 volt alternator.
use the alternator to charge deep cell batteries to power electric motor.
then you can say: officer im running off of the electric motor,the gas engine is a generator to charge the batteries.

cityevader · Apr 5, 2009

I'm kicking myself for not taking a picture...I just sold my gym-type elliptical excercise machine and tried to lighten it by removing panels, etc. Surprised to find the sole component for resistence was that the pedals/handlebars spun an alternator, an exact car alternator wired to two large resistors to dissipate heat. That thing would put out so much resistance that the Hulk would have a hard time spinning it. I apologize for being such a negative nellie here, but the only way to get any reasonable charging on an E-bike is coasting downhill. From what i've read about electric bikes, it doesn't take much headwind to slow them way down and reduce range. High resistance from "charging" would do the same.

toytime · Apr 6, 2009

That is interesting "city". Where did this power go to?
You are so correct about wind slowing you down on an ebike.
There is no such thing as free power and if anything, cabinfeaver has the right idea but a small generator can be had for under $200.
I've always followed these threads but they always die off with nothing ever being accomplished

cityevader · Apr 6, 2009

The power went into gigantic resistors and dissipated as heat.

Friction driven alternator experiment?

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