Falcon mach 5 blades observations

[madlabs]

Hi All,

A while back (say 6 weeks) I put a set of the Falcon mach 5 blades on my treadmill motor mill. I have some observations and I am wondering if they make any sense.

First, some specs: The Falcons: 5 blades, 62" swept area. My home made blades: 46" swept area, 3 blades, NACA airfoil maybe 2512, I'd have to check. I have good data logging for amps/watts output, but my wind speed is currently screwed up. So I don't have a complete set of data to work from, just my observations.

Firstly, the Falcon blades spend a LOT more time spinning than my DIY blades. However, it doesn't seem to spend that much more time actually making electricity. And the peak output seems less. With my DIY blades I have seen around 150 watts, but the most I have seen with the Falcons is about 100 watts.

Of course, I am not comparing apples to apples. I don't know the wind speed was when my DIY blades hit 150 watts, but I'm pretty sure I've hit the same wind speed at some point. But it seems like when unloaded the Falcons get it spinning in lower winds but then stall or something when the RPM's get up enough to start loading the mill. Does this make sense?


Jonathan

[bj]

Jonathan    I'm no expert, but from what I've seen here, yes stalling.  A test I did to make sense of it, (for me) was to temporarily unload the alt in
a decent wind.  It screamed right up, then connected it again.  The output would of course be high, then fight it's way back down to where it
was.  It wasn't instantly by any means, slow enough to kind of tease you.
Almost sounds like your previous blades were a better match for everything, in the winds you are seeing.
Just my take on it.

[ChrisOlson]

As far as I know those Falcon blades are just bent pieces of aluminum.   They don't have any real airfoil.  So the results aren't all that surprising.
--
Chris

[Dale S]

The reason they seem to be spinning more is they are lighter and will start in lower wind, but there is no power in that lower wind until you reach cut in.
I would also think that they slow down faster also they are not as good a flywheel as the wood blades, so the power curve drops quicker.
Chris is 100% correct, those things are not an airfoil at all, so it is stalling alright, it reaches a point where the non airfoil just quits generating any kind of lift, if you can actually call what those things do making lift.
That shysters claim to fame is "Look at all the big airliners now they all have winglets" Yeah they do, but that winglet is attached to an actual airfoil.

[Rover]

I have a set of these, as well as many other types.

They spin more because you have more of them and they are larger. IMHO they are pretty useles.. I've used them on ECM's , treadmill motors etc. One of theings you also need to realize is that in most cases the larger the swept diameter, the lower the top speed. Pretty much why they don't put large blades on an AirX (Although putting any blades on an AirX doesn't really help it, works as well with just the shaft pointing into the wind )

You might want to try just using 3 of blades, might increase your top end. These blades have a lot of drag.

Means getting another hub... the 5 point hub obviously will not work

As an aside .. I'm getting really tired of seeing the "More blades is better" crap on Ebay... yes they will spin up.. but not to where you need em.

Rover

[madlabs]

Thanks for the replies. The Falcons are noisy buggers too, as compared to my DIY blades. While I am curious what a DIY set of larger blades would do on this mill, the sad truth is that while I had a lot of fun and learned a lot building this one, it's time to make a "real" mill. I knew this one would be a toy when I started, so I'm by no means disapointed. And I have seen that I get enough wind here to make it worth while. Plus, I just like watching it spin.

So, if anyone has parts or gen for a 6-8' mill, let me know!

Jonathan

[Dale S]

If you put larger meaning longer blades on a treadmill motor you will get less power, on those motors you need speed, shorter blade and less of them, you could try your original blades but just use two, and see what happens.

[Wolvenar]

After reading this I remembered i have a couple treadmill motors here,
So it might work as a good temporary wind gen to take advantage of all the wasted wind we have had here recently.
Unfortunately though it seems at least the one I tested will not fit the purpose.

The tested ones label says 95v and 21.4 amp no RPM or none readable.

Turned with a drill at ~ 600 rpm it just touches on 22volt

For a 24v system, without gearing, this is certainly not going to work.
Or is there something i am missing?

[ghurd]

I do not think it is "stall".
I think it is the opposite of stall.
I think it is high torque (and NOT efficient torque), and low TSR.
Sure they start in low wind, but they do not make the RPM required to be efficient in high wind.

Those 100' GE (whoever) long blades are efficient, but the RPM is never going to get fast enough to make any power with your PMA in a 20MPH wind, right?  That does Not mean it is stalled.

The 'bent bits of metal' (not my term) would probably be better suited to something else, which goes back to the 'matching', but matching is only a fix for inefficient blades on a highV lowA motor conversion for low wind speed, if you know what I mean.
Might get something useful with a ECM reconfigured to match the blades, but it won't be a power house in high wind.
G-

[ChrisOlson]

I think it is high torque (and NOT efficient torque), and low TSR.

That's where these bent aluminum barn fan blades fall on their face, aka "Falcon" or "TLG".  You need tip speed to reach Cp much above .25.  It's all about that power coefficient.  The big utility scale turbines, Vestas V82 as an example, only run at 17 rpm.  But the tip speed on the blades is 8 or better and they reach efficiencies of 49%.  Slow blades (TSR 4 or less) are not going to capture what's available in the wind and the kinetic energy contained in the wind flowing thru rotor's swept area just slips right thru without being converted to mechanical power.

These bent aluminum blades, because there's no real airfoil and therefore they run with a lot of drag and turbulence coming off the trailing edge of the blade, are never going to achieve decent tip speeds.  Just think about a fan with a 5 hp motor on it.  It moves air but the fan don't take off across the floor when it's running.  Put an airplane prop on that same motor with a real airfoil on it and now it not only moves air, the fan will take off across the room when you turn it on.  That's because the lift/drag ratio on the real prop is a LOT higher than fan blades.
--
Chris

[tomw]

These bent aluminum blades, because there's no real airfoil and therefore they run with a lot of drag and turbulence coming off the trailing edge of the blade, are never going to achieve decent tip speeds.  Just think about a fan with a 5 hp motor on it.  It moves air but the fan don't take off across the floor when it's running.  Put an airplane prop on that same motor with a real airfoil on it and now it not only moves air, the fan will take off across the room when you turn it on.  That's because the lift/drag ratio on the real prop is a LOT higher than fan blades.
--
Chris

Chris;

Good analogy and the thing most folks miss and have to make statements like "These babys really crank!. "Which means absolutely Doodlie Squat, right up there with "80 open volts and 30 short circuit amps which only fools the uninformed because the simple facts of electrical power are ignored. shorted means zero volts and 0X30 is Zero watts. But you know this too bad many do not.

Tom

[ChrisOlson]

Good analogy and the thing most folks miss and have to make statements like "These babys really crank!. "Which means absolutely Doodlie Squat

Yeah.  "These baby's really crank".  Except mine are 11.5 feet.

Interesting - I've seen these YouTube videos of people who have put up one of these wind turbines on a 30 foot piece of pipe on the end of their house.  The ones that say, "they really crank".  And they're happier than a pig eatin' sheeite because the turbine is going around.  They don't give a crap how much power it actually makes, as long as it wiggles the ammeter off zero now and then.  They got a wind turbine and it's fun, and they like it.

The truth being told, there's a probably a bigger market for folks like that than for folks like me that need a wind turbine to actually WORK and make serious power.
--
Chris

[ghurd]

I recall a guy, popeye(?), who was selling a 4' dia blade made from a 1x3"?  One piece of wood, 4' long, 2 blades in that piece.
He claimed the sound change from Voc to Isc was demonstarting the efficiency or something.
An experienced ear could hear it was in a run-away condition, but he just kept arguing.
He sold a few, but stopped selling them shortly after that, thank goodness.

Hucksters selling crap is why RE has a bad name, IMHO.
G-

[Norm]

On my wish list is a simple 2 blade that will turn a treadmill motor fast enough
to charge a 12 volt battery in a 7-10 mph wind.....so I would need to know what
size and what tip speed ratio to use.

Chris has me convinced that plastic and metal blades are a waste of time.

Course I would like to start smaller like with a few stepper motors first......

Norm.

[Wolvenar]

Well from my experiments, direct driving one of those motors wont happen, it will need a gearing system of some sort, especially in that kind of wind.
Plus the shafts of those motors just aren't up to the task of a big wind, and they certainly wont be able to brake by shorting well enough to stop much of any blade.
Just will need to build the blade and hub heavy enough to handle some serious over-speeding.
I had a 6" that took it with no kind of braking or speed control of any kind.
It eventually failed in a spectacular way, but I am not sure if the blade breaking caused the shaft to bend, or the shaft bending caused the blade to hit the tower, either way the blade came apart in the end destroying the alternator.