Quote from: MrTeal on March 16, 2015, 05:04:02 PM

Quote from: mikenekro on March 16, 2015, 04:30:00 PM

Quote from: MrTeal on March 16, 2015, 04:09:13 PM

If you want to save yourself some time and effort, consider buying a motor kit. I've wound a couple helicopter motors that needed an extremely low RPM/volt using kits from Scorpion Power systems, and it makes the job much easier. It's still a fiddly process, but since you get the casing, shaft, bearings, etc it's nothing like trying to make everything out of resin.

I'll look into that. If I can find some good old motors or motor casings I'll probably get that instead.

That'd be cheaper, although removing the existing windings can be a huge PITA.

Honestly, you might just be better off buying an automotive alternator from a wrecker and using that. It'd be the cheapest and least time consuming.

I looked at that, and the RPMs needed to create any useful amount of energy is way to much. Even for a wind turbine it's not recommended.

Here's a quote from a site which explains the car alternator for wind turbines better than I can. You can imagine human power would be less than wind power in terms of longevity and, at some points of wind speed, RPMs.

Quote

Im thinking about using an automobile alternator for a homebuilt wind generator. Will this work?

Ron Johnson Albuquerque, New Mexico

Hello Ron, A car alternator is a bad choice for a wind generator. The efficiency in normal use is never more than about 60 percent. The bearings are too small to reliably support large blades (more than about 1.5 meters diameter). It is designed to be lightweight and robust, and to withstand running at very high rpm. At low rpm it produces nothing, and low rpm is where wind generators spend the majority of their time running.

If you use a car alternator in a wind turbine, the speed problem can be addressed in one of several unsatisfactory ways:

Use a small blade area so that the short blades can spin at high rpm. This means that you cannot catch much wind, and even so, you will need a high wind speed to get the necessary rpm. It will also take a lot of wind to produce high enough power to excite the magnetic field and actually have energy to spare.
Use gearing to increase the rpm. This involves extra cost, extra losses, extra unreliability, and overall ugly and clumsy engineering.
Rewind the coils to work at lower speed. This means more turns of thinner wire in each coil. This reduces the cut-in rpm, but also increases the losses in the coils themselves, limiting the power output and further reducing the already low efficiency.
A car alternators rotor needs to be powered to excite the magnetic field. The field has to be at a maximum to get output at the lowest speed. This represents a constant power loss of 30 to 40 watts during operation. You will also have to remove and bypass the internal regulator. The internal regulator in the alternator is not suitable for charging a deep-cycle battery via a long wire run.

While it is cheap and attractive at first look, the car alternator is more trouble than it is worth. It is better to build a purpose-built alternator for a wind turbine.