Blade shape for low speedwinds on an Ametek

[Norm]

Here's the blade



I need it to drive an  Ametek 30VDC at 325 RPM

The blade is about 7 x 14 inches.

I was thinking of cutting it at the slanted black

mark to maybe make it run at a higher speed.

The goal is to make about 2amp charging rate for

a 12 volt SLR 75amp/hr. (Walmart $40 special)in a

6-7 mph wind....well maybe better than that in the winter....9-12?

I'll make a steel hub about like Jerry's

3 bladed....

Anyone got suggestions? ....more narrower blades

the whole assembly will be about 3ft diameter.

....Maybe I'm expecting too much from too little?

           Well it's fun anyway....even with

about 14 inches of snow.

  ( :>) Norm.

[ghurd]

Well... Mine was faster with the tip narrower,

but it wasn't that narrow.  

In faster winds than normal, maybe 10~14,

they tried to fold back.

There was a stress mark a couple inches from the ribs.

It didn't do too bad, but wasn't flown very long.

G-

[Norm]

  These blades as is traveled pretty good...

but that was free wheeling....no load

A whole different ball game when you put a load

on them...ain't it?

 Time to start shoveling a path out to the

 shed.

              ( :>) Norm.

[luckeydog]

you would be better off making blades from PVC pipe

short fat blades have a lot of drag. a root chord of 6  inches and each blade 2 to 2.5 foot long. wit a tip chord of 1.5 to 2 inches

Look into my files and you will see some blades i made from fiberglass. they work very well and you can make the same thing from PVC pipe

 

[Jerry]

Hi Norm.

I'm in the prosess of trying my hand at the PVC pipe blades. Today I assembled a 4ft set.

This first blade set is made from 6" diameter 1/16" thin wall pipe. I'm using a hub made from 2 pices of 3/4" plywood laminated for a 1.5" thickness.

The hub is tryangle shaped. I used an 1/8" wood cutting blade on my Roto Zip with the circal cutting atachment set at 6" diameter. I cut a groove on the side faces of the tryangle to set the blades into. Then I drilled a screw through the hub and blade to secure the blade.

This is just a test blade to get the feel for this design. I'm building another the same way but with 6" diameter pipe that has a foam core and is 5/16" thick. The core stuff is very strong.

I'd say with the curve of the pipe it may be stronger then wood.

After I finished the thin blade I took it outside. At this point there no shaft hole yet, just the 1/4" hole in the center. I put a bolt through the hole.

There just a very slight wind 2 to 4 mph maybe. The blade began to spin to a point I was getting a littel nervus.

Its 28 degrees at the root and just a few degrees at the tip. I think the cup of the blade at the root makes for good startup tourque and the small tip zings through the air with the greatest of ease.

Here a couple pictures.

                             JK TAS Jerry

[ghurd]

Mine were too small for the big PMA,

So they stalled at a few amps.

Could be they bent back in higher wind and self-stalled?

It was a flimsy bucket.

G-

Remember this one?

[luckeydog]

here is a photo of the blade. the square tips are a bit noise in high winds so a round tip chord is much better

this blade was made from fiberglass foam and carbon fiber.

[luckeydog]

wrong photo here is the correct one ..... wish we could edit thees postings.

[Norm]

That's a really nice looking blade....  the one you made from plywood...didn't look too bad either.

        ( :>) Norm.

[luckeydog]

the one made from plywood ended up breaking in some 60+ mph winds. I don't recommend plywood. it was an experiment that did not pan out. but the fiberglass ones did much better than I expected. I was seeing 180 watts out of an Ametek 50 vdc motor.

 when I get my website in full swing

I will post the entire process  building a quality fiberglass carbon fiber blade.

[luckeydog]

Jerry

I like the way you built the hub.

 Simple and effective. and the blades look great.

Is the hub made from plywood?

[Norm]

  Like your's Jerry but with a 4 in chord for the

root....problem would be using a 6 inch pipe,

the root would have too small of a radial curve...

unless I could heat-form it to a larger radial

curve at the root?

  (love my new 1500 watt hot air gun )

 I have a little bit of insane fun at times.

           ( :>) Norm.

[Jerry]

Hi Norm.

Ya the root is a littel narrow. Thats another reason to try the 8" foam pipe.

                           JK TAS Jerry

[Norm]

Yes a 5gal bucket is too big in circumference

and the piece of plastic pipe I have would be

about what you have in the picture....

  I think I'll try making some like yours

Jerry....soon as it warms up, 2 degrees this morning

but it warmed up to 22 degrees and the wind kicked up to 15-20.

    Thanks everyone for the help.

           ( :>) Norm.