My swedish projekt so far.

[Herder from Sweden]

Homemade Alu blades

     

A"Hugh Piggot" coil winder with my daughters twist rope counter



Plasma cutting

Magnet disk for 16 magnets 1"*2"*1/2"(inch),Diameter 36,5cm

Stator whit 12 coils 51 winds and 2mm magnet wire

[dinges]

Very nice, Herder!

I'm not familiar with plasma cutting, but it seems you can make pretty round circles out of plate with it? Do you use any special equipment, or a welding machine, or what?

About the aluminium blades: they look nice, but I wouldn't use them myself; aluminium is VERY prone to metal fatigue (not the correct term, e.g. steel can develop metal fatigue if repeated stress above a certain level is present; however, aluminium will always develop cracks when repeated stress (stress cycling) is present, no matter how big (rather: small) the stress is. Remember the accidents with the English aviation firm BOAC in the '50s? That's how they first learned about it, I think, when A/C came falling down, seemingly without reason).

So I'd not use the aluminium blades, except for short test runs maybe; don't use them in areas with people nearby, if anyone can get hit. I'd not even use it in the desert, because when a blade flies of, the imbalance might cause damage to your generator. This would be a shame, since the genny looks very well made!

BTW, now how does your daughter keep count of the ropes she skipped ?

Peter,

The Netherlands.

[hiker]

nice lookin blades--well thats what planes are made from...havent seen any fallin out of the sky latly...any chance of putting more picts. up on them..

[maker of toys]

remember that 727 that turned itself into a 'convertable' in hawaii back a decade or so?  that's aluminum fatigue in airplanes.  that's one of the reasons you don't see too many 727s around any more; they're reaching their pressurization cycle limits and being retired. (they're also not very fuel efficient, and the engines are old, etc.)

Aluminum airplane propellors have an inspection requirement and usually last about 2000 flight hours for just this sort of reason.  (some make it much longer, but there are hoops to jump though to 'extend' their lives)

[dinges]

Hiker,

The reason you don't see A/C falling out of the sky anymore is because it's now recognized that metal fatigue is an issue and is now being regularly checked for.

Of course, Herder could also install a periodic check & maintenance cycle. I don't know Herder, but I know myself; it wouldn't be an option for me; besides, when I build something, it has to function without interference from me for a long time; don't like things that need constant tinkering & maintenance just to keep it in the air.

Why not simply a wooden prop? Shouldn't be much harder than the aluminium ones (unless you're allergic to wood, like one of my friends who has a professional metal working shop; if it's from metal, he can make, but when wood is involved...)

Peter,

The Netherlands.

[TomW]

Folks;

Trucking companies figured out this aluminum specific metal fatigue in trailers a few decades ago. Aluminum frame trailers are taken out of service and scrapped regularly. The constant flexing of hammering down the road will cause it to fail sooner or later so after a certain period of time they are retired. Come to think of it I know of a couple that were flipped upside down and buried as storage sheds. They work fine for that but are no longer road worthy.

Just another industry that eventually discovered that among it's benefits, aluminum has some drawbacks.

Each individual must determine the suitability of any material before they apply it to any specific use. Fare well and good luck!

Cheers.

TomW

[Herder from Sweden]

Dont have anymore pictures yet, but i will add more later

[Herder from Sweden]

Reply to Peter from netherland.The plasma cutter is creating a very hot beam (plasma) and lets out compressed air in the middle from a tiny hole(½mm).About the blades,lets just say that im curios and wanna try them out.And my daugther sad it was ok for me to have it(of course)

[wil]

Herder,

Plasma cutting was a very good idea. Very low metal warpage with plasma cutting.  I had the same idea for my future project and was trying to figure out some sort of jig for the torch.

My thought was some sort of metal jig or pattern but I never thought of using a wooden holder with the hub in the center.

I have built a couple of plasma torch holders for various track torch machines. (Victor and Buggo)

Did you have much burning of the wooden torch holder?

Wil

[Tommy L]

Hi !

Nice to see that is more RE people i Sweden, nice work. I wish that I have more time for my projekt, so far I just put up a 42W Solarpanel on my roof.

But I planing to do a Savonius gen. out of a tapemotor.

Were in Sweden do you live?

I live 14km west of Stockholm (Vallingby)

/Tommy L

[sahlein]

Maybe aluminum would make a good outer surface for blades.

After all, There are DC-3's still flying!!

Some of the newer "high strength" alloys are quite hard and "work harden"

themselves when stressed.

There are probably 300 or so available alloys currently in use.

Not all ALUMINIUM is ALUMINUM!

Joe S.

[sahlein]

I correct myself... Matweb lists 474 aluminum alloys.

Engineering information on almost everthing known to man can be found

on  "matweb.com"   I've used it for several years.

Try it, you may like it!

Joe S.

[dinges]

That's the problem with aluminium: it work-hardens when stressed. Its tensile strength increases, but toughness decreases. It looses ductility, so when stressed it doesn't yield but breaks.

I'll check out the link of matweb; hope it can replace my steel-tables books ('Stahlschlussel').

Peter,

The Netherlands.

[hiker]

just had to shake up the house............ ;}

[Amptramp]

Howdy folks,

I have some experience with Aluminium rotor blades.

Initially, I used plastic for my rotor blades. PVC pipe, of the sort used on farms, produced brilliant blades.

These could spin at amazing speeds and produce hundreds of watts.

Sadly, the plastic blades had a lifetime of little more than a year, before they would fly apart.

Fatigue would set in, as there was always a bit of flexing in their length.

Typically, the blade would brake off at the hub. Also, failures would occur near the tip, due to minor torsional oscillations at high speeds.

The move to Aluminium occurred over two years ago.

NO failures to report, thus far.

My design is simple. A plywood rotor of 300 mm carries 6 blades. These blades are secured at 3 points to the rotor hub. An aluminium arm extends from the rear face of the rotor, and is attached to the back of the blade, about 1/3 of the blade's length out from the hub.

This helps to minimise lateral flexing.

Torsional flexing appears not to be a problem any more, as the material is so much less flexible than plastic.

These rotors have survived violent storms, and are running sweetly.

At the moment, I feel that Aluminium is a good choice.

A regular inspection, perhaps monthly, would help to provide peace of mind though.

These rotors range in size from 700mm, to 1800mm diameter.

During the Christmas holidays, they'll all be taken down and inspected, just to be sure that all is well.

Here's hoping that this has been helpful.

Best wishes,

Steve  McAmptramp.

[jmk]

  Looks like your building one of Hughs 12' turbines. Looks great! Keep us poasted.