Low RPM Generators

This is the main page on this site regarding the construction of generators. While many of the examples are regarding wind driven generators, the principles regarding the generators themselves apply equally to other motive sources. Anyone contemplating building a low rpm generator should look through all the sources on this page. Those persons specifically building a wind generator should also look at our "WIND" page which has on it many things specific to wind generators such as towers, blades, tails and testing them.

Comparison of Generators and Alternators

Most generators and alternators (like off of a car) need to revolve at around 1800 rpm (that is they have to make 1800 revolutions per minute in order to generate power) and it is often difficult to get a third of that speed with most homemade wind, water or other sources.

Overview: Comparison of Alternators and Generators

Low RPM Generators and Alternators

Since the difficulty with most generators is that you have to turn them too fast before they start generating power these low RPM ones are neat because they put out power at low rpm and so will work with a bicycle, a low head water source, or lower wind power.

The low RPM generators will start generating power at around 100 rpm and remain efficient up to about 600 rpm. Their "sweet spot" is often around 400 rpm but it will vary from generator to generator.

Brakedrum Generators and Alternators

Brakedrum: Use the brakedrum off an old pickup truck to make a low RPM generator!

      Although the literature says these brakedrum generators are easy to make, we made ten of them and found it a considerable challenge. Nevertheless, they all worked reliably and are very durable.

Front Disk Generators and Alternators

There seems to be a trend away from brakedrums to disks. Talking with Hugh Piggot, he tells me that he is writing a new book on this subject.

Disk 1: Forcefield Low RPM Disk Alternator

      More details from the same source - on the same idea. The ideas keep changing, but it may be that only some of the older ideas will work in the future because of materials available.

Perm Magnet Generator Assembly

      This 49 page manual is by Hugh Piggott.

Wooden Generators and Alternators

Some wind generator designs can be put together very quickly. You can carve less elegant blade designs in an hour or two. Some motors can be used as generators. People have gone out and stuck their wind generators up on top of a hydro pole that is not being used. Hopefully the need is only temporary anyhow, until a more permanent source of electricty is re-established.

These may not produce so much electricity as a metal based generator and may be not as durable but they may be more accessible for one of the main components.

Simplest: Wood Axe

      This one is particularly fast to build. Even if you don't build it you should study this one because the pictures and explanation by Force Field are so excellent.

Wooden 2: all the plans and information for another wooden one
    BUT these are 9 pages of plans mirrored in .pdf format from Home Power Issue #88 are ones that you can download and print off NOW.

Wooden 3: A key set of plans to study

These are 49 mirrored pages of plans in .pdf format are ones that you can download and print off NOW. While you may not build this unit - you should definitely study these plans from Hugh Piggot because they give you details on many subjects such as how to build a coiler, the winding of a coil and how to wire the coils together.


On-line Info: Lots of info on build it yourself windmills

      This is a link to Hugh Piggot's website. Hugh lives in Scotland. This is probably the world's most authoritative source for build it yourself windmills. For those who look into it ahead of time they can get Hugh's book. We also have a .pdf file from Hugh (available on our low rpm generators page) - that gives LOTS of details.

Other Generators and Alternators

Microwave Oven: Making a Microwave Oven into a Generator

          This is a particularly neat idea and there are lots of neat ideas at the Windstuff Now site.