Author Topic: Wind Turbine Transmission  (Read 73702 times)

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ChrisOlson

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Wind Turbine Transmission
« on: November 28, 2010, 08:19:48 PM »
I made a short video of the .46:1 overdrive transmission for my new 12 foot turbine:

http://www.youtube.com/user/OlsonFarms?feature=mhum#p/u/5/zml8zvxT4sA

Note:  That's not the input shaft that will be used in the transmission - I just had that shaft laying around from another turbine so I used it to build and test the transmission.  The actual shaft will be much shorter and won't use a 1:10 taper hub.  I also didn't bother mounting the stator support for testing - the stator support mounts right behind the generator rotor on three studs that stick out the rear of the transmission case.  Nor did I weld a flange to the top of the case yet to bolt a top cover on.

The transmission case will be integral with the yaw tube and the offset is built into the transmission case.  The tail boom will also mount to the transmission case.

Thought I'd post it because some folks asked me to.

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Chris

bvan1941

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Re: Wind Turbine Transmission
« Reply #1 on: November 28, 2010, 09:51:25 PM »
Chris,
Strong and simple system-- May work better than anticipated. Video is very good !
Will you use furling alone or possibly a disc brake combination for speed control??
Bill

ChrisOlson

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Re: Wind Turbine Transmission
« Reply #2 on: November 28, 2010, 10:28:26 PM »
Strong and simple system-- May work better than anticipated. Video is very good !
Will you use furling alone or possibly a disc brake combination for speed control??

Hi Bill, this will be just a furling machine, no mechanical brake, just stator braking.  I'm flying a set of blades on this machine I haven't flown before - they're 12' Gottingen 222 blades from Royal Wind & Solar.  So it make take a bit of "tweaking" to get it tuned in.
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Chris

picmacmillan

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Re: Wind Turbine Transmission
« Reply #3 on: November 29, 2010, 06:05:35 AM »
good job chris  :)....good video also ...very clear...puts me in the mood to get at my own project :) have a good one...randy


bj

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Re: Wind Turbine Transmission
« Reply #4 on: November 29, 2010, 08:18:35 AM »
   Very robust, as always Chris.  Don't know  what rpm you got to, but your rotor looked dead on true.
  Interested in the final outcome.  Thanks.
"Even a blind squirrel will find an acorn once in a while"
bj
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ChrisOlson

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Re: Wind Turbine Transmission
« Reply #5 on: November 29, 2010, 08:58:20 AM »
   Very robust, as always Chris.  Don't know  what rpm you got to, but your rotor looked dead on true.

I would guess the output shaft was approaching 2,000 rpm in that video.  I was using a ground off socket extension to drive it, chucked in a hand drill, and that thing wobbles all over the place, making it a little hard to run it at high speed.

On the turbine I doubt the generator will exceed about 800-850 rpm.  When I get a yaw tube welded to the transmission case so I can mount it on my test stand properly, then I can do some testing while driving a real generator with it.
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Chris

freejuice

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Re: Wind Turbine Transmission
« Reply #6 on: November 29, 2010, 01:50:38 PM »
Chris,
 Nice deal you have there!
 I saw the video...dont let that thing get away from you :D
It looks like a good cavity for an oil bath!
Are you going to use a light weight oil for those frozen winters you have up there....diluted it with a little kerosene maybe?
 millions and zillions of "R's", I wonder what kind of juice I could pump out on a 17 footer?

Auto's have timing chains that go 100,000 miles much less all the RPM's in between. An old Ford Pickup I had used a  timing chain and was not in an oil bath and that thing was wore out when I replaced it but it  had like 175,000 miles on that 302 engine.

a good clean oil bath will go and go and go and go...well you get the point!

 Keep us posted!
 Gavin
« Last Edit: November 29, 2010, 01:56:07 PM by freejuice »

DanB

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Re: Wind Turbine Transmission
« Reply #7 on: November 29, 2010, 02:17:59 PM »
Chris - I think it would be fun, and easy for you to finish that up (looks like you've basically got it done) - put some oil in it, spin it at different rpm/measure foot pounds and find out just how much power is required to turn it ~ especially at lower rpm (what you'd see in perhaps 7-12mph winds).   You could play with different oils then and test it at different temps.  It'd be interesting to me anyhow.

You certainly will save lots on the alternator here.  At the end of the day I expect it will be just as heavy/expensive as a direct drive machine but it's very interesting, and I do believe that the larger machines get, the more such gear trains probably become attractive.  Roughly speaking - I figure the cost of a direct drive alternator to be related to the cube of the blade diameter.  At some point a gearbox might make sense, although the trend seems to be moving away from that, even in some very large megawatt + machines.

That said - it's very interesting and looks pretty efficient and robust, and always refreshing to see something new.
If I ever figure out what's in the box then maybe I can think outside of it.

fabricator

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Re: Wind Turbine Transmission
« Reply #8 on: November 29, 2010, 04:03:07 PM »
That transmission and those high torque blades that Royal fabrication makes would be a match made in heaven.
I aint skeerd of nuthin.......Holy Crap! What was that!!!!!
11 Miles east of Lake Michigan, Ottawa County, Robinson township, (home of the defacto residential wind ban) Michigan, USA.

ChrisOlson

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Re: Wind Turbine Transmission
« Reply #9 on: November 29, 2010, 06:54:24 PM »
Chris - I think it would be fun, and easy for you to finish that up (looks like you've basically got it done) - put some oil in it, spin it at different rpm/measure foot pounds and find out just how much power is required to turn it ~ especially at lower rpm (what you'd see in perhaps 7-12mph winds).

Dan, I put two 11" diameter rotors on it today, with magnets installed, and the flywheel effect from the rotors is quite significant.  I ran it up to about 1,800 rpm (the mags are pinned) and when I took the drill off the input shaft it coasted for almost a minute before it came to a stop.  It takes a considerable amount of torque to accelerate it due to the mass of the generator rotors gaining energy, but once spinning at a certain speed the amount of torque required to keep it spinning at that speed is not measurable with the equipment I have - especially at the 400 or so rpm the input shaft will run at, max.  At slow speeds of around 150-160 rpm (10-12 mph wind) it would take very accurate equipment to measure the input torque and I haven't come up with a good idea on how to build anything accurate enough to measure it.

When I first put it together it was a bit "draggy" because of new bearings and the seals cause a lot of friction.  After the first run at 1,800 rpm the seals broke in and it spins freely.  I was going to remove the seals from the bearings, just leaving the outer seal in place on the input and output bearings, and lubricate the bearings with the oil bath.  But that would require additional work to build oil channels to catch throwoff from the chain and channel it to each bearing for proper lubrication.  Plus it would require more oil in the sump.

After the bearings broke in I've decided to leave the seals in the bearings, as ball bearings are very low friction in the first place, and secondly I can run only enough oil in the sump for the bottom of the chain to barely dip in it to keep the chain and sprockets wet.  I'm going to use a synthetic SAE 10 hydraulic fluid for lubricant in it, which flows freely even in -40 degree weather.

It's a simple unit and there's not much more to test on it.  It'll work fine.  What I'm more interested in finding out is how the turbine reacts spinning the mass of the generator at high speed.  Typically, the wind is never constant.  A 12 mph average wind maybe varies from 8 to 15 and it probably spends more time at 8-10 than it does at 15.  With a direct drive turbine, when a gust hits, the turbine quickly accelerates and puts out more power, even if for a brief time.  Then the gust dies out and the power output drops.  The amount of power the turbine produces in kWh, or amp-hours, adds up from the peaks of the gusts and the most constant "push" from the lower wind speeds.

With this turbine, say the wind is blowing at 10 mph and there's a gust to 15.  Based on "feel", running the transmission with real rotors and a hand drill, I know it will take longer for the machine to accelerate simply because of the amount of energy that has to be transferred to the generator rotor mass that spinning at 2.14x what it is with a direct drive.  Once that energy is stored in those rotors, it seems to transfer very well thru the gear reduction to the input shaft to keep the input shaft spinning.  So when the wind dies out I expect that the turbine rotor rpm will not drop as fast as a direct drive.

The above is based on gut instinct of what it SHOULD do - the real story will be learned when it flies to see how it affects that.  I have a feeling that the generator rotors will end up being too heavy and that a smaller, more compact 8" diameter 8 pole 6 coil generator might work better.
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poco dinero

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Re: Wind Turbine Transmission
« Reply #10 on: November 30, 2010, 06:11:28 AM »
Quote
  it would take very accurate equipment to measure the input torque and I haven't come up with a good idea on how to build anything accurate enough to measure it.
 

Chris, you might try strain gages.  The gages themselves are cheap.  You'd need to put some slip rings on your input shaft to get the readings off the spinning shaft and out to a homemade resistance bridge.  Then a little calibrating and there's your torque readings.  Strain gages are very accurate.

poco

ChrisOlson

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Re: Wind Turbine Transmission
« Reply #11 on: November 30, 2010, 08:00:31 AM »
Chris, you might try strain gages.

Hi poco - yes, I know there is equipment that can measure it.  I was simply looking for something I had laying around the shop that I could rig up to measure it.  I've pretty much decided that it's immaterial because it spins so freely that I just don't think it will make much difference.

I do believe the bigger challenge is going to be to build a generator that matches it.  A permanent magnet generator puts out amps (or watts) based purely on the open voltage minus the clamped voltage divided by the resistance.  The open voltage is going to climb very fast with the generator spinning at 2.14x input speed, which means the wattage (and load on the rotor) is also going to climb very fast with only a small corresponding increase in input speed.  With a wound field generator it would be no problem.  With permanent magnets it might take something like using 1/4" thick magnets with only 20 turns per coil or something, to prevent the power curve from being too steep.

I think the generator is going to be the fun part.  I'm already satisfied with the transmission - it's so simple it'll "Just work".  And I built it heavy duty enough that it won't break.  Building the transmission case from 1/4" sheet steel was probably a bit of overkill.  I can beat on it with a 10 lb maul and can't bend it or flex it.  But it ended up not being overly heavy so I'm happy with it.
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Flux

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Re: Wind Turbine Transmission
« Reply #12 on: November 30, 2010, 08:41:51 AM »
Chris, I think you will find that you will have to keep a similar efficiency electrically to get the same sort of blade loading or you will have to work over a smaller speed range.

What you will find is that you need a lot less magnet and copper for the same efficiency, if you don't make efforts to lower the efficiency somewhere the alternator will be very stiff indeed and will clamp you to near constant speed. unless you use star /delta or some other form of voltage matching you will not be able to run at higher efficiency and gain much. This may be a case where you could try to incorporate that gap changing mechanism we discussed previously.

As for accelerating I have no experience with large inertia disc alternators but with normal radial slotted machines used with a gearbox the acceleration was very quick, it's pretty amazing how quickly a prop will accelerate even with a lot of inertia.  Unless you can do something about the speed range of the alternator you will probably find it very responsive indeed as the load will come on very quickly with only a small increase in the speed.

I never have seen why people are so paranoid about light blades and low inertia, I really don't think you gain anything significant.

Flux

ChrisOlson

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Re: Wind Turbine Transmission
« Reply #13 on: November 30, 2010, 09:33:17 AM »
What you will find is that you need a lot less magnet and copper for the same efficiency, if you don't make efforts to lower the efficiency somewhere the alternator will be very stiff indeed and will clamp you to near constant speed

Hi flux - yes indeed, that's pretty much what I have figured out.  The generator is very easy to change on this machine, due to being mounted on a PTO shaft and not requiring disassembly of the entire machine to change it.  So I'm going to try it with one of my 10" diameter generators first, that was originally wired wye, except wired delta.  That generator requires 225 rpm for cut-in in delta, which will match the blades nicely at cut-in.  And the power curve in delta is not nearly as steep as it is in wye due to requiring more rpm for each volt it puts out.

Once I fly that I'll have a much better idea of what sort of power curve I need, and design the final generator for it accordingly.  Like you say, it should take a lot less powerful magnets and considerably less copper than a direct drive.  But at the same time, what I'd like to see from this machine is good performance in the 12-18 mph wind speed range, and I don't really care about peak output in higher winds.  So the first generator I'm going to try on it might work fine too.

My hydraulic drive generator testing stand will only go to 500 rpm, which is 230 rotor rpm thru the transmission.  At 500 rpm, in delta, it was a 1,550 watt generator at about 62% efficiency.  At 18 mph wind speed and 5 TSR, the blades I'm using should be spinning at about 205 rpm, which on paper still looks like a good match.  I tried running that generator direct drive with 13.1 foot PowerMax blades before, and the blades couldn't run near fast enough to get any decent power out of it in delta.  I tried running it in delta with 10.6 foot PowerMax blades, and the blades still couldn't really run it fast enough to get decent power from it, although it would put out about 800-850 watts, which is more than I got out of it with 13.1 foot blades.

So, for me, that's what is kind of fun about trying a geared drive - instead of using powerful magnets and lots of copper density as is used with a direct drive, I might have to use weaker magnets and less copper to reduce the power curve of the generator.  Which is something I've never tried before.
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Chris

DanB

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Re: Wind Turbine Transmission
« Reply #14 on: November 30, 2010, 04:41:42 PM »
It could have lots of merit - time will tell, but Neodymium is sort of rare stuff and the price is skyrocketing.  Combine that with issues of rust, not very good tolerance of high temps and stuff...  maybe a gearbox and ceramic magnets make some sense.  At any rate... looking forward to more updates as usual.  Thanks Chris!
If I ever figure out what's in the box then maybe I can think outside of it.

ChrisOlson

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Re: Wind Turbine Transmission
« Reply #15 on: November 30, 2010, 08:58:25 PM »
Some photos showing front, both sides and rear views of the turbine head.









I didn't weigh what's on the stand right now, but I would guess somewhere between 60-70 lbs.  The tail assy will use my standard vertical hinge with a spring loaded tail.  The turbine rotor is offset 6" from the center of the yaw shaft.

Typically I've built my machines with right hand offset, right hand rotation.  Using the precession forces of the rotor to aid in the machine tracking the wind properly has worked really well for me, without having to use a radical amount of tail offset.  I'm not too worried about furling because my vertical hinge system is pretty much fool proof and it just works.  I like my machines to look nice, and using a lot of tail offset to get them to track the wind head on makes the machine look goofy, IMHO    :)

So, since my new blades for this machine will be CCW rotation viewed from the front, I decided to go with left hand offset on this one, and not change what I've done in the past on my other machines.

The other thing I decided was that it would be better to have the pinion just rubbing the top of the oil in the sump instead of the bigger drive sprocket, simply because it's the highest wear point in the transmission.  I would expect 10,000-12,000 hours out of a chain before it has to be replaced, and 50,000 hours out of a set of sprockets in an oil bath drive.  The service life of the smaller pinion would probably be cut in about half if it was lubricated only by oil carried by the chain.
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Fused

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Re: Wind Turbine Transmission
« Reply #16 on: December 01, 2010, 06:07:30 AM »
Chris, can you share the details of the flange bearings you use?
I see you using the same type on all builds. They look handy.

Thanks
Fused

ghurd

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Re: Wind Turbine Transmission
« Reply #17 on: December 01, 2010, 06:30:41 AM »
Nice!
That is some amazing work in an incredibly short time.
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ChrisOlson

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Re: Wind Turbine Transmission
« Reply #18 on: December 01, 2010, 06:32:14 AM »
Chris, can you share the details of the flange bearings you use?

They are Fafnir self-aligning ball bearings that can be used in either cast iron pillow blocks or pressed steel flanges.  They're available in either relube (greaseable) type, or permanently lubricated (sealed).  The main difference is that the relube bearings have a hole drilled in the outer race so grease can get into them when they're mounted in a cast block, and they use a neoprene single lip seal on each side of the bearing designed to keep water and dirt out, but still allow grease to escape when they're over-lubed.  The sealed bearings use a metal shielded double lip seal on each side designed to keep the grease in and water and dirt out.

I get them at the local implement dealer for about $15 each.  I use the sealed bearings in wind turbines because they're designed for severe duty applications like combines and grain augers.
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poco dinero

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Re: Wind Turbine Transmission
« Reply #19 on: December 01, 2010, 06:48:21 AM »
Wow, what a clean workshop compared to previous pictures.  That cleanup must have taken more time than building the gearcase.  Or did youn start with a new building.

poco

jlt

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Re: Wind Turbine Transmission
« Reply #20 on: December 01, 2010, 07:36:29 AM »
If any body can make it work it is you.But why? Looks like your trying it make a  1930 thirtees wind charger with neo mags.

ChrisOlson

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Re: Wind Turbine Transmission
« Reply #21 on: December 01, 2010, 07:48:51 AM »
Wow, what a clean workshop compared to previous pictures.  That cleanup must have taken more time than building the gearcase.  Or did youn start with a new building.

No, same building.  But my shop is pretty good sized and it depends on what room I'm working in on what day.  This is the type of equipment that I normally work on:






ChrisOlson

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Re: Wind Turbine Transmission
« Reply #22 on: December 01, 2010, 07:51:12 AM »
If any body can make it work it is you.But why? Looks like your trying it make a  1930 thirtees wind charger with neo mags.

Why?  Just because I can.  As far as I know, those 1930's Winchargers worked pretty good too.
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clintonbriley

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Re: Wind Turbine Transmission
« Reply #23 on: December 01, 2010, 05:25:24 PM »
Nice progress Chris, it will be interesting to see what results you find once you get it up and spinning.
Are you going to add a way of adjusting tension on the chain to compensate for wear?
Clint

fabricator

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Re: Wind Turbine Transmission
« Reply #24 on: December 01, 2010, 05:58:10 PM »
Wow, what a clean workshop compared to previous pictures.  That cleanup must have taken more time than building the gearcase.  Or did youn start with a new building.

poco

LOL, I've thought about taking that route a few times.
I aint skeerd of nuthin.......Holy Crap! What was that!!!!!
11 Miles east of Lake Michigan, Ottawa County, Robinson township, (home of the defacto residential wind ban) Michigan, USA.

12AX7

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Re: Wind Turbine Transmission
« Reply #25 on: December 01, 2010, 06:08:37 PM »
Hello...

Was just wondering,  how are you going to seal the box?  The last picture you posted (smallest sprocket down),  you're not going to weld a cover over the opened end...   Tap/thread into the edge and fasten a clear plastic cover?  I assume you'll all so add a fill hole and a vent?

I like your work!

ax7
Mark

ChrisOlson

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Re: Wind Turbine Transmission
« Reply #26 on: December 01, 2010, 07:10:22 PM »
No chain tensioner is necessary.  It's about like a timing chain in the Detroit built V-8's.  The chain is a pre-stretched unit made by Diado, it has chrome pins and brass bushed rollers.  With the short length, even totally worn out, it will barely loosen up.

I still have to weld a flange to the open side of the gearbox to put a cover on it.  The cover will be heavy duty like the rest of it - 3/16" thick steel.  Since the cover will be facing down towards the ground with the tower lowered, I'll put a drain hole and plug in the bottom of it.  Once I get that on there I'll determine how much oil it takes to fill the case to the bottom of the chain, tip the box on its side to the position it will be when the tower is lowered, drill a hole thru it at the top of the oil level and put a fill/check plug in it.

It will have a vent on the top off an automotive drive axle.
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