Author Topic: Another new 12 foot diameter turbine  (Read 37622 times)

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Warrior

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Re: Another new 12 foot diameter turbine
« Reply #66 on: November 26, 2010, 12:33:31 PM »
Hi Chris,

I for one am really interested in your geared up 12 foot. Your post seems like someone took the words out of my mouth. I've always thought about how the Jacobs machines have been so succesful, both in terms of reliability and kwh production.
In my country, magnets and copper are very expensive, yet a gearbox is just steel and can be found cheap. I'd rather make the blades a few feet longer to compensate for the gear loss which usually is small.

Plus the more someone tells me "it's the only way to do it"..the more I try to go the other way. What would've happend to Newton & Galileo if they listented to everyone else telling them it can't be done... ;)
Good Luck,

Warrior

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Flux

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Re: Another new 12 foot diameter turbine
« Reply #67 on: November 26, 2010, 12:48:24 PM »
Once again a lot of of interesting issues and we shall probably never agree on any of it.

It is possible to make very good machines with high solidity rotors using gearboxes to increase speed to a practical level. The Danish Windflower design is a good example. Normal water pump type rotors are not very efficient but even then they can give good results.

Speed increasing transmissions have their problems so you have to decide whether it is worth the nuisance to use them and again the thing will be site specific. In very low wind regions it is difficult to gain much , the losses in the speed increasing gearing usually take most of the power. In the days of iron cored machines with wound fields the losses were too high already to accept any more from transmission loss. With modern low loss air gap alternators the problems are less and you can make cheaper alternators if you use speed increasing gearing.

Size of machine comes into this as well, below 8ft it seems unlikely that any gearbox is worth the effort but beyond that you can argue some sort of case. When you have tried and found that gearboxes can be a real source of trouble you may change your mind but like everything else if cost is no object then most of the problems go away.

My experience of gearboxes is that they need to be capable of about 10 times the expected power to have a useful life and you need hardened and ground gears for a decent life span. This doesn't come cheap and I still suspect that roller chains with a proper oil bath will prove better for machines in the 12 ft region. Belts of all types are a real pain and not worth bothering.

In decent winds a machine with good gearbox can probably compete  with direct drive machine in the 12ft region and you can save a lot of cost on the alternator, the gearbox may not work out cheap in the long term.

For lower wind areas then direct drive will give better performance. I have seen no evidence to suggest that a slow speed high torque prop will be any more efficient than a typical prop running at tsr6 or 7.

In the days before neo the bias was definitely in favour of speed increasing drives from the typical props that we use now, there seemed no virtue in using more speed increase with high solidity slow props. Now that neo has solved many of the alternator problems the case for the gearbox is much less especially with direct battery connection, it is now cost effective to produce alternators that can hold back a 20ft prop with direct drive. In the old days an alternator capable of this would be a monster and cost a fortune so the case for the gearbox was obvious.

At one time even small grid tie machines were forced to use gearboxes but they are now unusual in smaller sizes and becoming less common in big ones. The cost and reliability has always been a big issue.

I am sure those such as Chris have the mechanical ability to make a satisfactory geared machine and it may work out well but I think the average constructor would be well advised to steer clear of such things, unless properly engineered they are a major source of trouble.

There is a lot to be said for trying things rather than basing results on theory. Those new to the game will not have the experience of what has been done before and will think they see advantages in all sorts of things and want to try them, they will be going over ground that has been covered before, they will have some success and some failures, nearly everything works up to a point and in some specific conditions may prove beneficial but I have moved away from most of these ideas and gone with direct coupled ironless ( or at least slotless) alternators as the best approach in low wind areas but if you regularly have winds over 10mph the case is not clear cut.

Flux

ChrisOlson

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Re: Another new 12 foot diameter turbine
« Reply #68 on: November 26, 2010, 01:44:54 PM »
This doesn't come cheap and I still suspect that roller chains with a proper oil bath will prove better for machines in the 12 ft region. Belts of all types are a real pain and not worth bothering.

Hi Flux,

I've played with several different designs and settled on an oil bath roller chain and sprocket using synthetic transmission fluid for lubricant.  These type of drives have been used successfully for years in four wheel drive truck transfer cases, engine camshaft drives, industrial and agricultural equipment drives, and many other applications.  They're about 97% power efficient and I believe more gains than the 3% loss in the gearbox can be made by spinning a low resistance delta generator at high speed with it.

I have at least 20 stators just laying around from different things I've tried, and this 12 footer is going to use a stator that I originally used in wye on a 10 foot rotor, rewired delta, with a 12 pole generator, driven at 1:2 overdrive with 12 foot blades.

I know from testing the generator on the bench that it's about 20% more efficient, with roughly double the amp rating in delta, than it has in star.  Taking that 20% gain in generator efficiency and subtracting off the roughly 3% loss in gearing, I think I can build a more high-performance turbine out of the deal.  I'm going to use a homebrew gearbox, made of sheet steel, and just weld it together.  Again, for the uninitiated, this is an experiment, not to be considered the cat's meow.  Just because I like to play with things.

Hopefully, in the next couple weeks when I get caught up on other projects, I can get started on it.
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DanB

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Re: Another new 12 foot diameter turbine
« Reply #69 on: November 27, 2010, 10:31:58 AM »
Quote
They're about 97% power efficient and I believe more gains than the 3% loss in the gearbox can be made by spinning a low resistance delta generator at high speed with it.

Lots of good machines have been built with fairly low friction gearboxes, and I expect the larger the machine, the more likely it is to save on weight and cost.  The 97% bit...  hard to say.  I do not know about these things or have much experience, but I would guess that the efficiency of such boxes depends on how much power they're dealing with, and at what rpm.  I doubt the gearbox capable of handling several horsepower (perhaps 3000 Watts) for the long term is 97% efficient at the fractional horsepower(say 1/4 horsepower or 200 Watts) that we'd see in lower (perhaps 10mph) winds.

At any rate....  I look forward to hearing about your experiments as usual!
If I ever figure out what's in the box then maybe I can think outside of it.

Flux

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Re: Another new 12 foot diameter turbine
« Reply #70 on: November 27, 2010, 01:08:17 PM »
Chris has a decent wind site so I suspect the geared unit will work out ok.

My experience has been that with iron cored alternators and speed increasing you can manage from about 10mph upwards, not much available below that.

When I first replaced wound field machines with permanent magnets bur with slotted iron cores I found the start up problems to be a big issue, the iron loss is manageable with direct drive but with speed increase starting is an issue. I got good results once it started but the gain from permanent magnets was small and the wound field was more flexible.

With neo magnets and slotted cores the start up would likely be even more of an issue but once you move away from slotted iron cores much of this changes. The gearbox or better still chain drive has no efficiency issues worth worrying about at full load you can easily make it up with the gains from more speed on the alternator.

Bearing and oil drag losses willbecome a greater factor as the power is reduced and at a few watts out the efficiency will be low. I would avoid delta here as it is an additional loss, winding star with 53% of the turns will bring the characteristic back to that of delta with no start up drag.

In the end you have the same old problem, you can match a small band of wind speed well and get high efficiency with a cheaper alternator but when you try to cover a wide speed range you have to compromise something. At least in the wound field days I could match the load reasonably well and with speed increase you could over build the alternator without too much cost penalty.

I look forward to the results and I am sure it will be fine but it requires decent engineering and I would advise against it for anyone without a lot of mechanical experience and facilities.

Flux

ChrisOlson

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Re: Another new 12 foot diameter turbine
« Reply #71 on: November 28, 2010, 10:36:04 AM »
The 97% bit...  hard to say

One of the best illustrations I can think of that demonstrates the efficiency of a roller chain drive, that most people are familiar with, is on motorcycles.  The early 80's Honda CB750 with the 16-valve engine made 62.7 hp at the transmission pinion shaft, measured on a Taylor eddy current dynamometer.  That same motorcycle, driving the chassis rollers on the dyno with the rear wheel, made 62.1 hp - exactly 99% efficient with the factory Daido #50 roller chain.

The thing with roller chain drives is that they can run at very high speeds with proper lubrication and the temperature of the chain components barely rises above ambient.

My transmission with be oil bath, so there will be some losses due to viscous drag.  But I think I can keep that to a minimum by allowing only the larger drive sprocket to run in the oil in the sump, using windage from a CCW rotation to push the sump oil up against the side of the transmission case instead of "carrying" it around on the chain.  And keeping the faster turning pinion sprocket up well clear of the oil level in the sump.  We're only talking about input shaft speeds of about 350-400 rpm and generator speeds of 750-850 rpm, so the windage losses will be quite small.  I figure maybe 1% viscous losses, 1% in friction in chain components, and another 1% in the pinion bearings.  And the losses in the bearings might not even be that high because I'm using ball bearings instead of rollers.

At any rate, we're getting into my area of engineering expertise here, as that's what I did for Cummins for years before I left the Big City Rate Race and moved back to the farm.  I don't want to hijack your thread on your 12 foot machine, Dan, but somebody did say they were interested in this when I mentioned it.  So I uploaded some photos of the transmission case that I started building last night after getting motivated to start on it.  If there's any other interesting information on it later I'll put it in a new thread:
http://picasaweb.google.com/christopher.w.olson/WindTurbineTransmission#
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don1

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Re: Another new 12 foot diameter turbine
« Reply #72 on: November 28, 2010, 08:31:55 PM »
Hey Chris,

  Looks like a good start. Nice heavy box. How will you tighten the chain in there? and what do you think will make a good lube in the box?
 Most skid steer loaders have used roller chain in an enclosed oil bath to drive the wheels with great success. I bet you would have a durable low maintenance drive there.  Good luck..Don.

don1

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Re: Another new 12 foot diameter turbine
« Reply #73 on: November 28, 2010, 08:39:15 PM »
Chris, sorry I didn't read back a bit as you have answered my oil question there. Not intending to be a bother. :D
 Don.

ChrisOlson

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Re: Another new 12 foot diameter turbine
« Reply #74 on: November 28, 2010, 10:25:22 PM »
Chris, sorry I didn't read back a bit as you have answered my oil question there. Not intending to be a bother

Oh, no problem - I've been transmissioning (is that a word?).

I really hate to hijack Dan's thread here so I posted a new thread about the transmission:
http://fieldlines.com/board/index.php/topic,144577.0.html

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poco dinero

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Re: Another new 12 foot diameter turbine
« Reply #75 on: December 02, 2010, 08:47:47 AM »
I guess I'm still a newbie when it comes to the mechanics of posting.

Quote
  If you don't observe the proper torque sequence and spec (72 lb-ft) you'll have problems with tip tracking.   
Posted on: November 28, 2010, 09:25:22 PMPosted by: ChrisOlson 
 [/quote]

Chris, could please describe what is the proper torque sequence for tightening the hub bolts on your powermax blades.  I have two exmork 2 kw wind turbines flying and their fiberglass rotor blades have those steel inserts in the roots.  Maybe exmork uses powermax blades.  There were no instructions on assembling the rotors.  I may have done it wrong, although the machines seem to be working fine.  Please send me a PM if you think it more appropriate.  Thanks.

poco

ChrisOlson

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Re: Another new 12 foot diameter turbine
« Reply #76 on: December 02, 2010, 09:15:27 AM »
Chris, could please describe what is the proper torque sequence for tightening the hub bolts on your powermax blades.  I have two exmork 2 kw wind turbines flying and their fiberglass rotor blades have those steel inserts in the roots.  Maybe exmork uses powermax blades.

No, I think it would be good to post it here.  I'm pretty sure Exmork and Talon both use PowerMax blades, although the PowerMax version used on some of the Talon turbines isn't the same as the blades you buy for DIY turbines because they're variable pitch.  What I was told when I called CMS Magnetics is that you're supposed to torque all the inner bolts first, going around the rotor in a circle to 45 lb-ft.  Then go around the outer circle of bolts to same 45 lbs.  Then back to the inner circle and take them 72 lb-ft, then do the outer circle at 72 lb-ft.

Because the blades are sandwiched between the two aluminum plates, and everything is a tight fit (it fits so tight that there's not even any "play" to adjust tip distances), if the proper sequence isn't observed you'll end up with the blades not tracking properly.  I've heard other people who have had Exmork turbines that have had a problem with a noisy blade, and I would guess that's why.

They don't send any instructions with the PowerMax blades either when you buy them for a DIY turbine.  After I had problems with one rotor I called them and told them one of the blades wasn't built right or something.  That's when they told me how it has to be torqued to properly seat the blades on the big (rear) hub with the taper in it.  They also told me that the hub is labeled A, B and C, and each blade has a tag on it that's labeled A, B and C and each blade has to go to its corresponding place on the hub.  This is the same as an Exmork turbine too, and I had already figured that out as it was pretty obvious.
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piglet2

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Re: Another new 12 foot diameter turbine
« Reply #77 on: December 02, 2010, 11:09:13 AM »
Hi.

I have two Exmork 2Kw turbines with 3.8m dia rotors and my hubs are cast steel, not aluminum.

/piglet

ChrisOlson

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Re: Another new 12 foot diameter turbine
« Reply #78 on: December 02, 2010, 12:48:51 PM »
I have two Exmork 2Kw turbines with 3.8m dia rotors and my hubs are cast steel, not aluminum.

Hi, yes I guess you're right.  They're painted with aluminum paint but they are steel.

Do yours say "New Energy" on them?  Just curious if they come from the same outfit.
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piglet2

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Re: Another new 12 foot diameter turbine
« Reply #79 on: December 02, 2010, 01:24:41 PM »
Nope, no "new energy" anywhere. A, B and C, yes.
Also Your hub seems? neater somehow? Maybe?
My blades were numbered with 1, 2 and 3 and the numbers were stamped on relevant places on both parts of the hub too.

/piglet

poco dinero

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Re: Another new 12 foot diameter turbine
« Reply #80 on: December 02, 2010, 08:36:29 PM »
Chris, thanks for the torqueing instructions.  I'll re-torque mine when I bring them down for their next six month checkup.

Quote
I've heard other people who have had Exmork turbines that have had a problem with a noisy blade, and I would guess that's why.

Other than properly torqueing the hub bolts, I was pretty careful assembling my rotors.  I carefully checked and adjusted both the tip spacing and tip tracking.  Up to about 50 mph winds, they make a nice, relaxing swishing noise kind of like a babbling brook, or wind blowing through tall pines.  But they roar at winds over about 45 mph.  No helicoptering sound, just a near constant roar.  I guess that's okay.  Suckers are putting out 65 amps at 53 volts when the roaring starts.  When I first put them up I shut them down in advance of stormy weather, but now I just let 'em rip.  Honeymoon is over.

poco

poco dinero

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Re: Another new 12 foot diameter turbine
« Reply #81 on: December 02, 2010, 08:49:31 PM »
Quote
Posted on: Today at 10:09:13 AMPosted by: piglet2 
 
I have two Exmork 2Kw turbines with 3.8m dia rotors and my hubs are cast steel, not aluminum.


 

Piglet, you got those things flying yet?  How're they working out?

poco

piglet2

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Re: Another new 12 foot diameter turbine
« Reply #82 on: December 03, 2010, 03:10:01 AM »
Hi Poco.

Mine work beautifully and produce much more than expected!

I have also ordered a water heating controller from Exmork.

/Piglet

bobfandango

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Re: Another new 12 foot diameter turbine
« Reply #83 on: December 10, 2010, 04:34:55 PM »
Another instance - there's a fellow not too far from here that has an old 8 foot Aeromotor windmill and he rigged up a bunch of roller chains and jackshafts and he drives a 200 amp Leece-Neville truck alternator with it.  I have seen that thing put out 100 amps continuous at 14.5 volts in a good stiff wind and it makes 60-70 amps without even breathing hard.  With just a 8 foot rotor on an old 40 foot windmill tower turning at not more than about 200 rpm.

If by a "good stiff wind" you mean ~50 mph, then these numbers make sense. 


Another illustration on torque vs speed - you can take a Freightliner powered by an N14 Cummins that makes 525 horsepower and 1,970 lb-ft of torque @ 1,200 rpm, and climb a hill with that truck with the rig grossing 80,000 lbs with no problem.  Now, pull the Cummins out and replace it with a 600 hp small block Chevy dirt track engine, change the gearing so the engine can run at 7,000 rpm, and try to climb that same hill with it.  The small block will run out of steam less than 1/4 of the way up the hill.

I think what you intended to convey requires at least a few unspoken assumptions.  The example as it stands is not correct.  Yes, torque is work.  Power is the rate of doing work.  If you could get up to speed, the chevy would pull the load fine since at peak, it can actually do work faster than the Cummins.  The problem is the fact that the Chevy would have trouble getting up to speed for the lack of torque in the low rpm range (an rpm range that cannot be avoided since you have begin from a standing start).  Gearing multiplies torque.  If you could gear down the Chevy enough, you'd have more than enough torque at the wheels, and enough horsepower as well, to pull this load.  Therein lies the rub...  such a gear ratio would not be practical to build and maintain within the confines of an ordinary transmission.  In that light, your example is good in that it illustrates the tradeoffs that one must consider.  One *could* build a chevy-based tractor towing solution with crazy amounts of gearing.  But why bother when you can just spec a high torque monster engine and gear more normally?


Wind doesn't carry torque and wind doesn't carry power.  It carries energy.  The turbine is a transducer that converts that energy from one form into another.  Some of the energy stored in the wind may be used to do work on the turbine and vice versa.  That is, the wind does work on the blades (makes them spin) and the blades do work on the wind (slows it down).  Since the blades are spinning, the work done on them is converted into a torque at the shaft.  So, let's keep in mind that we are interested in making power, and that power is the rate of doing work (i.e. the rate of applying torque).  As you've noted, Power = k*torque*rpm, where k=1/5252.  So, power is proportional to BOTH torque and rpm.  Said another way, for a given power there is a linear relationship between them.  You can increase torque and and decrease rpm proportionally and still have the same power (or vice versa). 

Thus, it is axiomatic that neither is more important that the other.  As with the truck example, the choice of building the turbine for torque vs speed involves weighing the various tradeoffs.  On balance, I tend to think the simpler, high speed, low torque solution is best. 

Janne

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Re: Another new 12 foot diameter turbine
« Reply #84 on: December 10, 2010, 05:17:32 PM »
Hi Poco.

Mine work beautifully and produce much more than expected!

I have also ordered a water heating controller from Exmork.

/Piglet

Hi Piglet,

Once you receive the heating controller, I'd be interested if you could share your experience about it. Quite a few people around my place are interested about a cheap direct heating controller.
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galeforce jones

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Re: Another new 12 foot diameter turbine
« Reply #85 on: December 17, 2010, 05:34:26 PM »
Hi Dan, thats a very impressive power curve on your 12 foot turbine. What magnets are you using? Also what will be the TSR of your blades? What wind speed would you expect the cut in of 125 rmp?

12AX7

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Re: Another new 12 foot diameter turbine
« Reply #86 on: December 17, 2010, 10:48:52 PM »
Hi Dan...

Today was the first time I watched some of your youtube videos.
I enjoyed those I've watched but it was a challenge weeding through the hundreds of other videos there.
By chance do you have a "list" of your youtube videos?

Was also wondering about the one where you have the alligator clips fastened to your ears.
Some new method to charge the old batteries?

ax7
Mark

ChrisOlson

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Re: Another new 12 foot diameter turbine
« Reply #87 on: December 17, 2010, 11:18:22 PM »
Was also wondering about the one where you have the alligator clips fastened to your ears.

That's called a "dummy load".   ;D

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12AX7

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Re: Another new 12 foot diameter turbine
« Reply #88 on: December 18, 2010, 11:53:29 AM »
Was also wondering about the one where you have the alligator clips fastened to your ears.

That's called a "dummy load".   ;D

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*ouch*

wllshaw

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Re: Another new 12 foot diameter turbine
« Reply #89 on: January 02, 2021, 05:22:47 PM »
Dan a quick question.  I have finally got back to working on a 17 foot diameter turbine.  I have the Dexter hub.  Do you suggest machining the back side to true it up relative to the front side.  Also, should I leave this as thick as possible and just clean it up and possibly provide an inner face so the rear magnetic hub is centered?  I'm just interested in your thoughts.  Many thanks.

SparWeb

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Re: Another new 12 foot diameter turbine
« Reply #90 on: January 02, 2021, 06:17:33 PM »
Hi there
And welcome back!

I doubt Dan will see this message any time soon - best to locate him here: https://otherpower.com/
We haven't exactly parted ways, just interests have diverged.

I didn't build a kit from Dan, but I did use a Dexter hub for an axial I built about 10 years ago.  In my experience, the Dexter hubs will have a rough cast surface on the back face, plus thickened pads to hold the studs, all of which you'll be modifying to hold the rotor plates.  Spinning the hub on the lathe to cut a true face on it sounds like a very good idea to me.  I don't think the body will be very concentric to the bearing axis, either, so be careful how you mount it.  Do you have a 4-jaw chuck on your lathe?
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wllshaw

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Re: Another new 12 foot diameter turbine
« Reply #91 on: January 02, 2021, 08:59:18 PM »
Thanks for the reply.  Yes, I do have a 4 jaw chuck.  I was planning on mounting the Dexter hub in the chuck and then indicating it on both the front machined face and the rear coned bearing surface.  What I was wondering is how thin I should make the hub.  I had done a search on the Dexter hubs and found the pictures on page 1 of this thread.  Based on the pictures I was planning on taking the pads down about 1/3 of their thickness.  It could be less, or more, and that is really what I would like advice on.  Should the hub be as thick as possible or  match the pictures on page 1.  Also I would turn the outer cast surface on the rear of the the hub so I have a concentric surface that matches the bearing axis that the rear magnet rotor will align with.  I just don't want to take too much off.
     Penny for your thoughts?  Tks

SparWeb

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Re: Another new 12 foot diameter turbine
« Reply #92 on: January 03, 2021, 12:55:59 PM »
I think you could just skim it until all 6 of the pads are smooth and flush surfaces, no need to cut them down further...  unless the total thickness is too thick for the rotor-stator-rotor assembly to have the right gap spacing.
IIRC you end up with spacers and jacking nuts between the two rotors when you put it all together, so maybe that is not a problem, or maybe the combination of hub's thickness and jacking nut adds up too much.  Then you would want the hub flange turned down more.  Some careful measurement of the thickness stack-up should answer.

As for the hub's body, not sure why you want to turn it, hopefully just another skim cut.  It's the internal bearings that have to be concentric (and supposedly the bolt hole pattern).  Is there too much slop in your rotor's bolt holes to locate the rotor disks?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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wllshaw

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Re: Another new 12 foot diameter turbine
« Reply #93 on: January 04, 2021, 07:39:12 AM »
I was just going to take a skim cut on the hubs body so the rear magnet rotor would self center on the resulting machined surface.  The bolt holes are centered on the bearing and if I cleaned up the outer hub then it would be centered with the bearing as well.  Everything should have lots of mechanical support that way.

     Thanks for your input!  This forum is great.

Generator

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Re: Another new 12 foot diameter turbine
« Reply #94 on: January 04, 2021, 03:01:36 PM »
Very impressive DanB

Your video link is not working.

Curious to know how much Power it generates [under load] at 13 m/s wind speed or any other speed at which you measured. I'd like to compare it with my Windmill. I don't have results based on RPM but based on Windspeed. I have 8 ft ducted windmill with 16 blades and I calculate the power output under the load {either by using Heater or 300 watt lights}. If you have power output results, then it would be easy to compare them.