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New prop
By Peppyy, Section Wind Posted on Wed Nov 24, 2004 at 05:55:04 PM MST
Think it'll fly

Here is the up-scaled prop I have been working on. It is 21" in diameter with 6 blades. At the moment it is lagged to the end of a 2x2 that is nailed to a short post in my front yard. It seems to spin pretty eaisily but I can't help but wonder if it would work better if I faced it the other direction.

It turns about 120 rpm in a 4 to 5 mph wind with no load. It is pouring rain here tonight so I don't really want to go out and mount it the other way. Would there be benifits of having the blades on the back instead of sticking out the front?
By the way, where did the ad photo button go in the board? I think I only used it once.

New prop | 7 comments (7 topical)

Re: New prop (3.00 / 0) (#1)
by baggo on Wed Nov 24, 2004 at 06:20:12 PM MST

Hi Peppyy,

That's quite a neat way to make a set of blades. I've followed your previous posts and wasn't quite sure where the plastic lid fitted in but now all is revealed! I think I'm right in saying that you have the blades the right way round i.e. the concave surface of the blades should face the wind. Turning them around will lower efficiency. You could turn the whole thing round and have the rotor behind the motor and thus make a downwind turbine which would not need a tail vane (check out Windstuff Eds site).

John

Re: New prop (3.00 / 0) (#2)
by Mentally Moribund on Thu Nov 25, 2004 at 01:03:17 AM MST

Neat blade. Has anyone triied using a utillity fan blade, such as the ones in Central air conditioners? There is a junk yard not too far away that has 100's of those. There would definatly be less torque but highr RPM.

Re: New prop (3.00 / 0) (#3)
by Reno on Thu Nov 25, 2004 at 06:35:10 AM MST

I don't know about AC fans but have a look at industrial wall fans or air movers(the ones on wheels) I have looked at them they have twist taper and are areodynamically designed except the flat is a little concave. The other interesting feature is the blade pitch is adjustable is some. THese things move air so well the actaully place blades in both directions so it can be setup as an exhaust or blower by changing the rotation. One draw back is if you can't find then scrap they aren't cheap not even the blades alone.

[ Parent ]

Re: New prop (3.00 / 0) (#4)
by wooferhound on Thu Nov 25, 2004 at 09:26:09 PM MST

Cool Peppyy

You have me wanting to cut out a set of those blades.

On the lookout for some strong flat large round thing . . .

)}=- W o o f -={(

Re: New prop (3.00 / 0) (#5)
by Peppyy on Fri Nov 26, 2004 at 06:31:36 AM MST

The thing I like most about this design is that it is one piece. We had sone really strong winds last night and I got to observe the behavior in gusty conditions. I only have it mounted a few feet above the ground in a terrible location, (Just to watch it spin) until my motor arrives. I noted several interesting facts.

Since there is no furling system and no load it tends to spin really fast, (A complete blur)whenever there is wind gusts above about 15mph.
The balance point is quite a ways back from the prop, almost 1/4 of the length. This seems to make it yaw slowly and smoothly so it looks very gracefull.
With no load it keeps spinning for a long time between gusts and when it is hit with a big gust it flexes slightly upward slightly, (might be due to the location close to the ground)?

I know the balance point will move forward with the weight of the motor/generator and frame and this will make the machine yaw more rapidly. I really like the current action and am wondering if extending the length of the frame is a good idea. Perhaps I will male it adjustable length.

My other question is do you think there would be anything to gain by reducing the pitch on this prop? I made it adjustable.

Have a great day.
Pep

Re: New prop (3.00 / 0) (#6)
by gumshine on Sun Dec 19, 2004 at 09:57:50 AM MST

Hey Peppyy

complete newbie with two left thumbs here. I got really excited when i saw this genny! I thought " I think I could do that ", and I have. My question is this how did you attatch the little green prop to the vcr motor? Please be gentle I am extremely mechanically challenged.:)

Also, have you had a chance to put the bigger white prop to a motor yet?

thanks for being patient with me.

gums

Re: New prop (3.00 / 0) (#7)
by Peppyy on Mon Dec 20, 2004 at 08:35:09 AM MST

Hi Gums. I am a newbie too, until I can afford to build a big one :)

The little mini had a tape drive pully on the end. I slid a tight fitting washer onto the pulley and then I cut a Y shaped slot in the center of the lid and pushed it on to the pully. Here is the story of that one.
http://www.fieldlines.com/story/2004/11/15/191526/10

My bigger mini is flying now too. The genny is not matched to the prop very well though so I don't get the power I want. I think this prop would work great if paired with the right one. This is where I am at with that one.
http://www.fieldlines.com/story/2004/12/16/134525/71

I am currently building a new set of blades to try on my medium mill. I hope to get better rpm out of them but I am a bit concerened about the overall power. You can see what I want to make here.
http://www.fieldlines.com/story/2003/10/29/17144/245

I will warn you! This stuff is addicting! Once you have one flying you can't stop. It is just too much fun.

Welcome and have fun.
Pep
[ Parent ]

New prop | 7 comments (7 topical)

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