What a difference a blade makes!

[billymc]

I have been messing around with a 1 hp conversion.  Have split the wye connection and turned the rotor and added 48 - 1/2 x 3/8 round mags (12 per pole, 4 pole).  Have been less than satisfied withe the results going into a 12 volt battery. Have been through 3 props and finally broke out Hugh Piggots book and "carefully" followed his dimensions for the 8' prop.  All I can say is wow!  This baby really flies.  I got all excited and promptly blew out the shunt on the amp meter in my control box so I don't have any hard numbers yet.  Had a 100 watt load on the battery and the voltage was still climbing. Now to start trying different delta and wye connections.  I guess the only way to get lots of power is to go to a higher voltage. I only have a 300 watt 12 volt inverter but I can connect my batteries to the control panel at 24 and 36 volt just to play with power outputs.

I took a video with my camera and noticed that the prop appeared to be spinning slowly and then start spinning the other way!  Believe me, that baby was really spinning fast.  I guess it was the old wagon wheel effect you see in old westerns. My camera shoots video at 15 fps so can I calculate an rpm?  Seems I saw something about that several months back.

I posted the video in my files. Not sure how to insert link, but here is a static pic.

[willib]

billy is it my imagination or does it start turning CW , then start turning  CCW ?

oh just point to it like this..

http://www.otherpower.com/images/scimages/3617/1hp_with_Hughes_Blades.AVI

[Titantornado]

HA, neat video.  It looks posessed!   You are right, that you can determine RPM that way, though, the prop will appear stopped at every 15 RPM step. (15, 30, 45, 60, 75 and so on)  Just how you plan on determining which step you're at is the tricky part.

[willib]

nevermind i see what was going on..

[willib]

maybe if you marked one of the blades , a different color , so you could tell which one was which , as it was "frozen" ,

it might be easier to measure the rpm in a different way

amanda has a tach circuit floatng around here somewhere

there are many ways to measure rpm

[Chagrin]

Just stick a multimeter on it and look at the frequency. Divide by the number of poles.

Piece of cake.

[sPuDd]

Dang !!

That video had me stumped for a while.

I just use the multimeter on frequency, then go

Hz / Poles x 60 = RPM

Nice work billymc

[commanda]

Isn't it half the number of poles? It takes 2 magnets (one North, one South) to make a complete sine wave of current in any particular coil.

Amanda

[jimovonz]

As each pole passes over both legs of the coil (hopefully not at the same time!), it only takes one magnet to make a complete sine wave. The current moves in the same absolute direction in each leg, but as the coil is, well, a coil, the result is a change in current direction in the wire. (this has been thrashed on the board a few times in the past...) If you had only one magnet on your rotor, you'd still get a sine wave.

[Flux]

Yes it is pairs of poles.

A 2 pole machine makes one cycle per rev. 3000 rpm = 50 Hz   3600 = 60Hz.

Flux

[dinges]

So. You've proven that the blades are an important part of a windmill...

Think I'm going to nominate you for a Nobel prize

Good to see it's finally working out for you. And an important reminder for the rest of us not to skimp on the blades.

Peter (who is elegible for a few Nobel prizes too)

[zubbly]

hi billmc!

great work!

you are reminding me of what i went through with my 1.5hp conversion. actually had a 11 foot prop on it and all it would do was stall very soon and badly. that was in the 1 star connection. basically, it just hit charge voltage to soon and the prop could not exceed what the genny was putting into the 12 volt batt i was using. i was limited to just a few amps output (stalling).

you will probably find that 2 delta will yield you the best performance as it really allows the prop to speed up and have lots of watts available. however, you really miss out on the lower wind performance. you may find also that the prop will still stall in the 2 star connection, but with a little more output as the prop can run a little faster before stall.

in the end after you confirm just how it picks up speed in 2 star or 2 delta, you will i think agree that a star/delta switch will help get the best of both worlds.

i know its a little work to lower the mill and re-connect trying the different connections, but it really does open your eyes and make you understand the relation between prop/speed/cut-in and overall performance.

don't be surprised if you see your mill hit 500-600 rpm with strong winds as i can just about guarantee that you will. i also suspect you may find your mill giving you 750 watts plus.

hope your prop is well built and balanced.  you will find it scary at times  

have fun,

zubbly

[billymc]

The blade carving wasn't as random as it might sound.  I was kind of going off of plans from the old LeJay manual. The twist is a straight line from root to tip. That was a starting point and then I modified the twist as I saw fit.  Tried different diameters:5', 8', 7' and even emailed Art about his blades.  He is not far from me.  Then the Hugh blades, very nice.  The other blades were just prepareing me for the real thing.

[billymc]

Hey Zubbly, thanks for the words of encouragement.  I actually do have it in 2 delta now. The 2 star seemed to be stalling the last prop too soon and in 2 delta the old prop never really got fast enough to give good output. At least not at a reasonable wind speed.  It will be interesting to see if the extra foot of swept area will let me run in 2 wye configuration without stalling.

Looks like I need to upgrade my multimeter to one with frequency measuring ability, get my smoked shunt figured out for the amp meter and then start gettin some hard data.

[jimovonz]

What I didn't say above was that in our 'typical' air gap alt, two oposite poles act at the same time on each leg of a coil - both contributing to the output. So while only one is needed for a sine wave, we use two to get double the voltage. This means that you are correct in dividing the number of poles by two, but not for the reason you state.