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#Post#: 2485--------------------------------------------------
Diy75 Re-Build
By: nessprojects Date: April 30, 2014, 9:22 am
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So my diy75 was doomed a failure for a multitude of reasons and
ended up tucked away in the back of the shed.....Not for much
longer though as I dug it out and decided to try and get it
going again.
A few blades were damaged and after testing the PMA I found at
800 Rpm it would only deliver about 40w so a few questions arose
that hopefully can be answered here.
I wish to use the original blades, original rotor, and the PMA
to re-build this turbine to keep the costs low so here comes the
questions...
I will be cutting the blade length down to 12" but will it be
best keeping the rotor diameter the same or bring the blades in
towards the bearing ? Hence giving a smaller diameter. HELP
Please.
My original thought would be about 20"-24" diameter rotor and
24" of blade (12" of blade is all I can salvage from each blade
I have). Unfortunately I am stuck with the 6" chord.
Any help would be appreciated.
#Post#: 2486--------------------------------------------------
Re: Diy75 Re-Build
By: lynx wind Date: April 30, 2014, 10:12 am
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You can go with 24" diameter and be fine. It will hit higher
rpm but with less torque. The chord length is good. Try it.
Make sure to put some kind of bracing on, the wood dowels only
serve to locate the blades and prevent twisting.
The DIY 75 suffered from not enough poles and too much
resistance. It was more an introductory DIY turbine so people
could see the action of how this type VAWT works. Theoretically
it could do 75 watts, but theoretical doesn't make people happy.
The DIY 175 will be a full performance kit.
#Post#: 2490--------------------------------------------------
Re: Diy75 Re-Build
By: nessprojects Date: April 30, 2014, 2:12 pm
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Many thanks for the info, I will give 24" a try.
The reason for lack of power on this PMA was that I used some
spare 1" diameter neo magnets by 1/2" thick.
My whole thought on this was that it was doing nothing at the
moment so why not try and put it back into service at minimal
cost. I have nothing to loose as all the parts are there anyway.
It will be getting the steel strap back on to the blade tips.
Mine failed at the rotor sheering the dowels so I will pay more
attention to this, maybe epoxy because silicone is not too good
at sticking to wood (Maybe why it failed).
Many thanks again.
#Post#: 2491--------------------------------------------------
Re: Diy75 Re-Build
By: lynx wind Date: April 30, 2014, 2:18 pm
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Ness,
I want to understand. You had strapping on the blade tips but
the blades broke the dowels at the rotor? What kind of wind?
Wow
Ok, this wont happen with the fiberglass spars and bracing.
#Post#: 2492--------------------------------------------------
Re: Diy75 Re-Build
By: nessprojects Date: April 30, 2014, 2:48 pm
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Being all metric wood here I used 9mm dowels, It simply sheered
both dowels clean off flush with the rotor.
It carried on spinning with only the blade tip strap kind of
like a lawn mower blade (glad I was no where near it or it could
have decapitated me).
Not sure on the wind speed but I did have a amp meter in line
and it got to about 3/4 amp before I heard that familiar ' Thud
' sound. I can say that it was a freak build up of wind because
1/2 hour before that there was no wind (Strange but true).
#Post#: 2497--------------------------------------------------
Re: Diy75 Re-Build
By: nessprojects Date: April 30, 2014, 8:36 pm
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@ jerrym
Well the way you see it you would say yes it was a bird strike
but I can assure you it was not, Firstly it was about 10pm at
night and I was about to call it a night + the shed that has all
the gear in was only about 10ft away and I was actually taking
some readings as the power increased with the occasional glimpse
outside to see it spinning (Something hypnotising about spinning
blades). I think it was just a constructional weak point on this
turbine that I had not noticed. I have to admit though that the
wind increased very rapid in a short period of time, Always
happens at test time !!!.
#Post#: 2501--------------------------------------------------
Re: Diy75 Re-Build
By: sut Date: May 1, 2014, 7:33 am
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That windmill must of been spinning extremely fast ! you would
of thought your strapping would of gave first (screw pulled out
of wing tip)
@LW so what on this windmill gives it its torque wing chord
or rotor diameter
#Post#: 2502--------------------------------------------------
Re: Diy75 Re-Build
By: lynx wind Date: May 1, 2014, 7:45 am
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Both. Imagine a torque wrench. Its not moving. You put it on
a stubborn bolt. You hang a 10 Lb weight at one foot from the
bolt. Now move the weight 2' out and you have doubled the
torque. The chord length represents the 10#, and the lever arm
is represented by the diameter.
The blades of a VAWT when spinning fast need to withstand 100#
or more spread across the inner sqin area of each blade. In the
case of Ness' blades the weak point was the two wood dowels. I
like to fiberglass the blade join on the Seagull 75 where it
meets the rotor.
#Post#: 2507--------------------------------------------------
Re: Diy75 Re-Build
By: nessprojects Date: May 1, 2014, 4:24 pm
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@jerrym
See post #4, It did have a 12v battery connected.
#Post#: 2509--------------------------------------------------
Re: Diy75 Re-Build
By: nessprojects Date: May 1, 2014, 5:07 pm
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Day1 of the re-build....
Blades had to be cut down to 11" in the end.
Rotor was cut back to 24" diameter.
Blades are hot wire cut polystyrene blades covered in brown
packing paper and plenty of water proofing paint.
There were too many pictures so I made this slideshow of the
progress.
Sort of looks a little small and dumpy now !!
Still got to glue it all up, add blade tips and straps and
another paint job.
HTML http://youtu.be/EMOC6B2Mitk
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