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turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 04:56am 26 Feb 2010
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Just had a quick read of roger miller's book
This caught my eye on dementions
He writes
"The width of the blades must equal the radius of revolution of their central vertical axis about the fixed shaft. The height of the blades should not be less than their width"
Still reading
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 05:12am 26 Feb 2010
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good to see you have the book turnymf this bit has lost me.
"The width of the blades must equal the radius of revolution of their central vertical axis about the fixed shaft"
the second part I get lol.
thought I should add that my miller isn't as good performance wise as I had hoped. it takes at least 20kmph wind to start it and has less torque than I expected. I am going to make some new panels 1.2 metres wide and try and figure out the optimum distance to place them apart.Edited by clarence 2010-02-27
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 05:34am 26 Feb 2010
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I guess ...chord=0.5 x distance apart
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 02:07am 27 Feb 2010
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Here is Miller's wing
And one of Miller
No revelations in the book
He describes it as a wing and a sail
He also wanted to use a centrifigal clutch to apply the load depending on rpm
Back to the test stand
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 02:50am 27 Feb 2010
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[quote]"The width of the blades must equal the radius of revolution of their central vertical axis about the fixed shaft" [/quote]
To me this says if your blade is 23" (cord) than the blade will be mounted at 11.5" central to the shaft at a radius of 23" to the face of the blade.
He means the radius is measured to the central point of the blade not to the tips.
The camber is what makes the difference in balance to make it spin then.
Pete.Sometimes it just works
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 04:53am 27 Feb 2010
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"To me this says if your blade is 23" (cord) than the blade will be mounted at 11.5" central to the shaft at a radius of 23" to the face of the blade.
He means the radius is measured to the central point of the blade not to the tips"
Exactly
The camber adds torque according to Miller
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 03:42am 02 Mar 2010
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ok miller enthusiasts, what do you reckon about the camber? is that going to help starting and efficiency? it looks like it should.
Re my miller, the wind has been constant from the south at about 30-40 kmph for 3 days and its been wizzing around at about 60 rpm constantly, but I cant get near the bloddy thing to attach the load wires . I should have wired it up properly first but in my enthusiasm to see how it would work I neglected too.
Anyway I now have the load wires on. 40 rpm is approx 20 volts on my f@p neo mod, and the wind is now 20 kmph. Without load the voltage varies from 10 to 25 volts in gusts, but as soon as I put a 1.5 amp load on it quickly stops the miller. I really think it needs to be twice as big to produce useful power in 20 k winds.But then it wont turn fast enough for cutin voltage so gearing would be neccessary. But I will do some load tests in 40 k winds and report back asap.
So from what I have observed so far, my miller in its currant dimentions is probably good for about 1/2 an amp @ 12v in 20 k winds. Hopefully with all the camber and sail spacings ect optimal, a miller with the same swept area as mine "could" put out over 1 amp in 20 k winds.
And a Miller with twice the swept area as mine might be good for 10 amps or more? very rough estimations I admit.
Any thoughts?
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 04:50am 02 Mar 2010
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Hi Clarence
I can't help thinking a curved camber would be better than a straight one
I don't think you would lose rpm by playing with the blade area and leave the spacing alone
Mine is still inside, I do now have a f&p hub on it
I have done this to apply a brake for comparisions
It would be nice to have the f&p hub move up and down on the stator with rpm, like a clutch
If the rpm of the miller falls too low then it won't get in it's power band, won't fly so to speak
I have this problem with my lenz
Here is Miller's idea from his book
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 05:45am 02 Mar 2010
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yes I suppose you are right, decreasing the distance between sails should gain higher rpm too, but lose torque I imagine.
Turnymf, are you going to do some tests with camber?
I will try and find some time this week hopefully.
I want to redo the whole frame on my miller using lighter gauge square tubing and extra bracing , and make the sails 1.2m x 1.8m. I might hold off for a bit until I can get some data on the effect of camber.
Your input is very much appreciated re miller .
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 06:01am 04 Mar 2010
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Got some 30-40 k winds and did a test.
With a 16 ohm length of nichrome wire across the output the miller seemed to maintain about 15 volts so I guess it is good for 1 amp in 35 k winds. not world shattering.
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 06:33am 04 Mar 2010
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"not world shattering"
Was never going to be but it's a start
What sort of rpm did you get?
Cheers
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 06:39am 04 Mar 2010
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It averages approx 30-40 rpm with the 1 amp load and shoots up to 60-90 unloaded. With the nichrome thing, I'm not sure what the resistance is doing as it heats up. I think it increases? by how much I dont know. it certainly gets warm.
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 07:09am 04 Mar 2010
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"what the resistance is doing as it heats up. I think it increases"
6% from 60 to 2000f according to Wiki
Have you tried it with a amp meter?
Cheers
Note to self
Must read posts more carefullyEdited by turnymf 2010-03-05
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 07:20am 04 Mar 2010
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will try amp meter soon as the wind comes back.
cheers.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 03:20pm 04 Mar 2010
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The whole idea of using nichrome wire is that it does *not* change its resistance very much as it heats up.
Unlike the tungsten wire in a light bulb, which has a much lower cold resistance than when its red hot.
Nichrome wire makes it easy to calculate the load wattage.Klaus
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 06:54am 10 Mar 2010
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I made a test model miller. 27cmx36cm panels with adjustable camber and panel radius spacing.
using a pedistal fan about a metre away [very unscientific I realise] I got these results.
panel radius. rpm
26cm 72
30cm 66
35cm 60
40cm 51
Adjusting the camber either way made no difference at all
for rpm or starting.Increasing the camber to more than in turnymf's diagram decreases rpm. The panel radius also made little difference to starting.I didn't take any torque/camber measurements.
I think I will make my next miller without camber and make the panel radius about the same as the panel width.
cheers clarence
Edited by clarence 2010-03-12
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 09:26am 10 Mar 2010
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Hi Clarence
Got any pics?
Having some sort of camber would be advantagious
The spacing / chord seems key, I can't get it out of my head that the back wing is working a little off the wake of the front wing
Cheers
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 04:42am 12 Mar 2010
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yes the wake or shield effect thing. Need a wind tunnel!!! I have been a bit busy but will get some pics up soon.
Have you gleaned any more insights from millers book?
clarence.
turnymf Regular Member Joined: 04/10/2008 Location: AustraliaPosts: 84
Posted: 03:43am 16 May 2010
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Hey Clarence, how's your mill going?
I haven't progressed very far
I do have the frame done, and have worked out the vane configuration
Just have to decide on the vane( 300mm x 600mm) material
It's not to Miller's or Ron's spec, more to make the 4 tier easier to build
and not get too tall
cheers
clarence Regular Member Joined: 27/10/2006 Location: Posts: 63
Posted: 01:06am 18 May 2010
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My next miller has been put on hold for a bit, but I have the steel ready for the next model. Should be able to get it built in the next month. My original miller is still up and in one piece. I had to short the output in fierce wind a while back, but it survived really well. I hope I didn't damage the alt.
cheers clarence.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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. I should have wired it up properly first but in my enthusiasm to see how it would work I neglected too.
so gearing would be neccessary. But I will do some load tests in 40 k winds and report back asap.
