Big Wind Genny (dubbed "the bumble bee")

[Dan M]

OK Here Goes:

My personal preference is usually to try something before announcing it to anyone, that way no one will know if (or when) it doesn't work.

I'm abandoning my personal preference and opening myself to any and all criticism and suggestions regarding my next project.

I purchased (REALLY CHEAPLY) a BIG pm dc brushless motor without controls(pronounced "pm alternator").

Specs as follows:

Powertec 60 HP, 1150 rpm, 640 vdc, ferrite magnets, nema 288 frame, presently wired in a 2Y configuration.  It is a little dusty, but appears to have never been hooked up.

Turning it by hand at roughly 50-60 rpm gives about 12vac across any 2 of the three leads.  I would like to modify the wiring to a single Y using 2 of the present coils in series for each "arm" of the Y.  It seems this should roughly double the v/rpm if I get the phasing right.  Shorting any 2 of the leads makes if very difficult to turn by hand.  There are 8 distinct "cogs" per revolution when shorted.

It looks like the wiring is a pair of Y configurations in parallel.  Each terminal has 2 wires coming into it and there are 2 3-wire junctions.

The labels on the wires coming into the 3 terminals are:

T1 - 1 and 7

T2 - 2 and 8

T3 - 3 and 9

The 2 3-wire junctions are 4,5,6 and 10,11,12.

I'm guessing that 4,5,6 represent the other ends of the coils from 1,2,3 respectively.  

Question #1 - Is there any sort of standard regarding the numbering of the leads? or is it best to just get out the meter and check?

Question #2 - Since they are wired in parallel, would the coils represented by terminals 1 and 7 be in phase? (same for 2 and 8, 3 and 9)?

Blades:

I have been desperately trying to come up with some means of building blades without hand-carving them.  Possibly laminating wood into the appropriate twist with a fixture then using a combination of table saw, router and belt sander for finishing.  I've done this with some smaller blades with varying results.

We live on 40 acres, and our nearest neighbor is about 1/4 mile away, so the debris field shouldn't be a problem.

If I can get my hands on the lumber, I would like to build a BIG tilt-over tower (not really tall, just really beafy).  If I don't do the tilt-over, I might get a large dia wood power pole and rent a crane to put the genny on top.  The second option might require running all of the leads to a junction box at the base if I wanted to change the way the coils are tapped without climbing.

I have a friend with a metal fab shop so the hub, tail, and yaw bearing should not be a problem.

In closing (for today) I know I will not get anywhere near 60 hp out of this thing.  But once I get the volts to a useable level, this setup will let me tweak the load to see exactly what the blades will generate.

Any questions/comments from the mundane to the ridiculous (or ridiculing) are most welcome.

I think I should call this thing the "bumble bee".  Since as everyone knows (except the bumble bee) bumble bees can't fly.

The motor is black.  I'm going to keep a lookout for some safety-yellow spray paint for stripes.

Pictures to follow.

-Dan M

[gibsonfvse]

> I have been desperately trying to come up with some means of

> building blades without hand-carving them.

Do you have any experience building model aircraft?  Though I won't have a chance to test my ideas (not for a while, at least), I'm beginning to lean strongly toward built-up construction as a reasonable idea for building a blade.  I hesitate to provide a link to any particular page, since there are so many, and there are a variety of ways to build wings, blades, etc., but take a look at the bottom picture on this page to get an idea of my thoughts.  If you want to flip through that article, you may find the information informative... in fact, I should bookmark that thing for myself  I hope an experienced turbine builder will jump in here, but I believe there are several advantages to a built-up blade:

1. Aerodynamics.  Using a built-up blade with airfoil templates will allow you to carefully select optimized airfoils and come closer to achieving their actual shapes than you could with carving.  This also allows one to achieve better aerodynamic balancing, which reduces vibration.
   
2. Mass.  Centripetal force increases linearly with increasing mass (Newton's third law: F=ma), so you want to keep the mass low.  It's easy to do this with built-up construction, which leaves a bunch of hollow space.  Note that you could carve a blade and then drill holes in it (and then cover them) to lighten up the blade, but you'd still have to carve the thing, leading to the aerodynamics issue I mentioned above.  Also, a reduction in mass means less inertia, so the blade assembly should start up at lower wind speeds and accelerate/decelerate faster.  
   
   

It's true that you have to cover the frame once you build it, but there are also various options for that.  Some on this board have talked about covering frames with sheet aluminum, and sheet wood (properly applied and protected) is also reasonable.  The toughest part is wrapping the covering around the leading edge, which (unfortunately) is also the most aerodynamically critical part of the blade, and also takes the most abuse during operation.  However, built-up construction is definitely worth some thought.  Another option worth thinking about is composite construction using foam, carbon fiber, fiberglass, etc. if you have the proper materials.  This is whole other bag in itself (worthy of investigation, however).  My apologies if I've only confused you!

[gibsonfvse]

My apologies... actually, F=ma is Newton's second law.  Laaaa

[hvirtane]

Someone from Australia, I think some time

ago posted pictures of his project with

built blades with air foil sections inside.

Now I can't find that thread, but probably

someone else can.

I've been working some time with one of my

friends to reinstall a wind turbine of

15 kW with blades, where there is inside

a slightly tapered tube and polyurethane

on the leading edge. On the trailing edge

there is a steel wire. The blade is covered

with a plastic cloth. These blades have been

working faultlessly about six years during

rough weather conditions in Finland.

Some pictures to clarify the idea:

A cross section.

The general dimensions

The fixing system of the blades.

A picture of the blades.

Another more unconventional idea

is to use flat wooden boards.

This six blade rotor has been in use more

than ten years.

http://www.otherpower.com/cgi-bin/webbbs/webbbs_config.pl?read=14319

We quite recently copied that idea and

built a wind rotor using four blades

like that one with the diameter of

3 meters. It seems to be working well.

This Finnish company is making

small blades filled with polyurethane

and a steel pipe in the middle:

http://www.saunalahti.fi/~kkhuolto/pentakone/

However I think that airfoil blades

carved of wood as glued of narrow strips

is one of the best options.

- Hannu

[finnsawyer]

I'm working on a method of milling blades on a planar molder.  They will have to be of constant width, so the pitch (attack angle) will have to vary along the length of the blade.  In principle this should work.  I hope to build a screw powered device utilizing a linear cam to tilt the woodstock as it moves through the planar.  Cutting blades will then cut the airfoil profile.  The flat side can then be milled by running the stock between a roller and the planar head.  At least that's the idea.