How do i make a 6-8v dc out put rc motor/genterator into a 6v dc alternator

i have a radio controlled cars dc motor that i`m using for a generator on my bike, it puts out about 6-8v on a normal ride, but i would like to make it into a 6v alternator to charge a 6v battery pack while running front and rear led lights so that the lights don't fluctuate and stay con-stint, how can i make it into an alternator, and if i can use parts from like a vcr or some computer parts that i have laying around or is there some thing that is already made that i can just hook up to it?

If it normally puts out closer to 8 volts add 2 or 3 diodes (most any diodes will be OK) in series with the output, they will drop about .6v per diode depending on the current flow. Also, check the output of the motor when connected to the battery pack, it might drop a volt or so as it delivers the power to the pack so less diodes might be required. You're not really making the motor an alternator, just a dc supply for the pack.

To charge a 6 volt battery, you need at least 7 volts, perhaps 8 volts, depending on the battery type, so it seems to me that your generator is about the right voltage to charge the battery. I suspect the generator output may well drop a bit under load anyway.

An alternator is a totally different thing and you can't convert from one to the other.

edit: PS, you need a series rectifier to prevent the battery from driving the generator like a motor when it's not spinning. That will reduce the voltage by 0.7 to 1.0 volts. Use a 1N5400.

You can use it as is. With that little bit of overcharge, that won't hurt anything. The resistors just waste heat to reduce voltage and you want to save as much power as possible.

Your most difficult task will be getting the right rpm's out of the gearing arrangement to the generator.