Ametek 30 Blades

[wphfl]

Severel recent forum posts have dealt with Ametek 30 tape drive motors using PVC blades. I fly an Ametek 30 with a two bladed wooden prop which has performed quite well.  Perhaps this information may be of use to those having problems with PVC blades.  Following is a picture of my unit on it's storage stand in my garage.  Unfortunately, political issues prevent me from flying it full time.





The prop is 48" (1219mm) in diameter with a set angle of approximately 4 degrees, giving a TSR of about 5.5.  This is from Hugh's blade design tutorial, freely available in a pdf format on the Scoraigwind website.  The wood is a piece of straight grained nominal 1x4 fir (19mm x 89mm actual), which I got from Home Depot for $2.35 USD.  It tapers from 3.5" (89mm) at the root to 2.625" (67mm) at the tip.  The thickness at the tip is approximately 5/16" (8mm).





There is no twist to this prop.  I don't believe twist is really necessary in a prop of this small size, as it spins up quit nicely at about 9 - 10 mph (4 - 4.4 m/s) which is about the cut-in speed for this motor.  I think my next prop, assuming I'll need one, will be a TSR of 5 to extend the range up a bit.

I bought the lumber for this prop a Saturday afternoon and had it completed by the next afternoon, using only a couple of homeowner's wood chisels, a small block plane, and a palm sander to complete it.

One word of caution.  After reading numerous posts about vibration issues with two-bladed props, I was absolutely meticulous with balancing.  I used a small plastic cone that pivots on a plastic spike I had for balancing lawn mower blades.  This device is available in the lawn & garden section of the hardware store.  The blade shows absolutely no vibration issues from imbalance.

Regards,

Kevin

"At what point does intellectual curiosity become a thought-crime" ...unknown

[elvin1949]

 Nice blades

later

Elvin

[Flux]

I would guess that with that symmetrical aerofoil you are seeing a tsr higher than you predict. The solidity looks suitable for something over tsr6 and the angle may not be too far wrong for tsr6 as well.

I agree that it is likely to perform much better than any crude pvc blade.

I suspect that you could do better still by reducing the profile thickness and making it asymmetrical as most others do. In which case you would need to reduce the angle.

Vibration from 2 blade props comes from yaw and can't be avoided. Good balance is needed for smooth running when not yawing. Small props such as that should be perfectly ok with 2 blades. You could no doubt manage what you need with 3 blades if you wanted to but 2 is nice and simple and strong for a non furling machine.

Flux

[asheets]

Can you go into a bit more detail with the "political issues" you mentioned?  I ask because I had to take down my Ametek recently as well.

[wphfl]

"Political issues" basically amounts to the Zoning and Building Departments not knowing how to handle residential small wind turbines.  The codes don't expressly forbid them, but neither are they expressly permited.  This is a problem in many jurisdictions throughout South Florida.

In the most supreme measure of absurditiy, I can park a sailboat in my yard and mount the turbine on the mast without permits or questions (Air-X machines abound around here), but take it off the boat and put on a pole and the entire bureaucratic landscape changes - engineer's calculations, UL certifications, zoning appeal applications and hearings, building permits (complete with two structural and one electrical inspection), installation only by State Licensed contractor, etc.  

I'm afraid I don't have the $15,000 - $20,000 USD to educate the County on small wind.  It would be less expensive to buy a sailboat - a thought which has occurred to me.  BTW, they do tell me that if I were in an agricultural zoning it probably would be approved as it is usual to see wind turbines in conjuction with agricultural buildings.

End of Rant.

Regards

Kevin

[ghurd]

Maybe try a different approach if they aren't already PO'd at you.  It could all be semantics anyway.  Just try not to frighten them.

Don't use the word "Power".  Call it "A hobby battery charger, like the HF PVs, but wind driven"?  Point out it only charges a battery, it won't be connected to the grid, and it won't make enough power to run a regular light bulb?

Maybe bypass the confusing pipe and cable structures and mount it on a 20' treated 4x4 sunk 4' down, with a 6' pipe rising 3' above the 4x4?  Inspectors here love 4x4s.

Looking closer at the photos, I don't think that is actually a scary 4 foot diameter blade, I think it only has 2 airfoil blades about 22" long.  

Gosh, 22" is less than twice as long as the guys desk ruler!  ;-)

G-

[Old F]

Lawn art any one?

OldF

[Ungrounded Lightning Rod]

Lawn art any one?

YES!

Put an aircraft fuselage around the motor, some wings out the sides, and call it a decorative weathervane.  B-)

[TheCasualTraveler]

Also in Florida in a small town I anticipate someone pointing the finger. I don't think we have any ordinances against a wind generator but all the same I am flying my setup without the generator. It is nothing more than "yard art". Once everyone is used to it I will add the rest. For now it's on the pole and I'm waiting to see if anyone salutes. If they ask me to take it down I will and replace it with the ugliest assortment of antennas ever seen.

[Capt Slog]

I've "gradually" put up my present wind generator.  I started with one of Ed Lenz's Minigens, which then grew bigger blades and I then replaced that with the current gen BUT kept the same blades for a while.

From then on, the blades have grown almost magically, a casual observer might even suspect that someone must go up there at night time and change them!  The same strange thing happens to the pole it's sitting on, it must be very fertile soil where I am, because it's able to make a  steel scaffold pole grow about 2 inches a week.

[RP]

I wonder just how small or seaworthy a boat could be and still be a boat.  What about something the size of a bathtub under the base of your tower.  With a pillowcase for a sail of course...