VAWT new proto-type

[GoVertical]

Hi, I have no training with aerodynamics. The work on the transmission is complete, it is low cost and it is something I can fabricate. I agree with your observation but I have to keep the blade configuration within the parameters of the fabrication method being used.
The problem with a classic Savonious is snow fall building up and adding to the weight.
I still have to fabricate new stators and this will improve test results. I am also considering a inverted J or Lenz design for the blades. The increased cost of the rare earth magnets more then justifies the addition of the transmission. Thanks for pointing me in the right directions. 

[GoVertical]

If your tsr curve is not a peak and levels off at a max TSR of 0.3 unloaded (or even loaded for that matter) you have aerodynamic issues to deal with.

-KBwind

Hi, I do not understand what you are saying. Why is important to have the TSR peak and level out? Can you elaborate? Any help received would be greatly appreciated. 

[KBwind]

This concept is important because each unique aero rotor will have TSR which yields the highest power coefficient. This coefficient directly affects potential turbine output because it is a constant multiple in the traditional power calculation based on swept area and wind speed. It is important to Try and design the turbine to operate at its optimal TSR for power output. For example the cut in of the alt needs to be at fast enough speed that the turbine rotor is making significantly more power than the alt at that speed. Otherwise your turbine will accelerate great to cut in and then "hit the wall" that is the load applied by the alt and will never speed up fast enough to reach it's proper TSR for making real power.
Something for you to consider would be to run a road test and carefully record windspeed vs. RPM for the rotor without load or transmission. I emphasize the word carefully because its not typical practice to road test like this but you seem set up for these tests. And only test within real world wind speeds or don't bother for now testing at the really high end over 9 m/s. From this data set you can graph TSR vs windspeed and this is very valuable info.
I recommend finding this data before more transmissions because you may be building fantastic drivetrains but getting awful turbine performance solely due to aerodynamic inefficiency. For some perspective I built a drag turbine last year of similar dimensions to yours which would run 90 rpm in 7 m/s all day loaded. I later changed the blades to my first lift type and this ran at about 120 in the same wind. My latest turbines run at 135 rpm in 4.4 m/s at a TSR of 1.4. The task of matching an alt to this turbine is much much easier because we aren't dealing with such horribly low speeds.
Have fun!
KBwind

[GoVertical]

Hi, thank you taking the time to post a response. Does your method apply to geared systems? Is it possible for a Drag design to have more power because you are converting the torque to higher RPM at the alternator using a transmission?  A lift design has a higher TSR, but a Drag design has a larger surface area with a lower TSR, is it possible that the Drag design would transfer more power even with the lower RPM?  Is Cp and TSR used just to evaluate the performance for a discrete system or can they be used for universal comparison between different style turbines?  Comments welcome.   

[GoVertical]

Greetings, results from today's road test:
at 5 MPH it started charging @ 0.5 amps. The belt again started skipping at a 2 amp output. I tighten the belt and started over. At  4 amps output the belt started skipping again. At that point the belt was so tight that it caused a increase load on the bearings and to me it did not make any sense to continue. I was expecting to see 8 to 9 amps @ 20 MPH because of the 7:1 ratio but only had a 4 amp output and the belt was still skipping.  From today's test results I am concluding that auto timing belts at such a high geared ratio can not handle the forces being produced and the current blade configuration started to stall at a 2 amp output caused from the accumulative load of the belt drive and the PMA. The current system looks good in the picture but does not perform well. It is a learning experience and a first attempt. I am fabricating new blades and reducing the ratio of the belt drive. Comments welcome.  

[GoVertical]

Hi, I was able to exam my PMA and  belt drive more closely after the road test and I found that the main shaft was flexing off center as I tighten the timing belts. This allowed the belt to walk over the teeth on the pulley. The more I tighten the belt the more the center shaft was pulled off center. I have to include another bearing above the bottom pulley to prevent the problem. I also believe that the small pulley is to small and not enough teeth on the belt are engaging the pulley.  I did find out that my current blade configuration does need to be improve. I purchase some 6 inch pipe and I should be able to configure a C rotor style blade or  J shape blade and do another road test in a few days. Thanks again and enjoy the day.

[GoVertical]

photo of completed assembly

[KBwind]

Govertical - Nice photos, nice work. The concepts I explained do apply to geared turbines as well - my turbines have transmissions based on a chain and weld-on sprockets. Cp and TSR apply to all turbine types and when you are talking about turbine 'surface area' you are talking about what is refered to as solidity ratio. Its measure of how much of the turbines swept is filled by the turbine blades. Your turbine has 100 percent solidity like an s rotor. This concept is important and somewhat counter intuitive as the turbine needs to let the wind flow through it and not stop it. With higher solidity a low speed zone of air can build up in front of the turbine causing high speed winds to flow around the slower air and eventually flow around the turbine as well. I have observed this in wind tunnel and real world testing but am not sure if road tests will exhibit this effect since the turbine is moving through the air. In terms of the potential for a drag turbine versus a lift turbine if you consider power as the product of speed and torque then theoretically you can get the same power from each type - but - the upper speed limit of a drag turbine is about the speed of the wind and lift turbines can go several times faster than this. Thus the drag machine will end up being larger than the lift for the same power output.
Ofcourse, now you are looking to change your blades to a J- type. I haven't heard it called that before but I am thinking you are talking about a lenz blade with the cup facing in. I have used this a modified version of this set up before - I believe you will be pleased with the results and this will definitely bring your TSR up to about 0.6 or 0.7 which puts you in a position to use a smaller drive ratio - a 2 or 3 to one should be good in this case. Have fun.

[GoVertical]

Hi, results of today's road test:

MPH_____DC Amps_______using 12 volt deep cell as test load  

10_______0.15
15_______0.5
20_______1.0
25_______3.0
30_______4.0
35_______5.0

The added top bearing made all the difference. The belt did not skip. I tighten the belt and ran the test again and the added bearing load greatly reduced the output. I have to find the ideal belt tension.  Today's test also showed the that belt drive ratio is to high for the blade size and design being used and was creating a stall condition. Comments welcome  


Hi KBwind,  thank you for responding. The information you are providing is a great help and is supported by today's test results. I look forward to seeing some photos of your project. Thanks again and best regards.

[GoVertical]

Hi, I am comparing the data from today's test with the results from the data posted with the 3:1 gear drive. The results were almost the same until the wind speed reached 30 MPH. Than the blades started to stall.  It appears that doubling gear ratio just increased the load and did not increase the output. I wonder if this is always the cast? Comments welcome
  http://fieldlines.com/board/index.php/topic,143852.342.html

[XXLRay]

Perhaps this is just the efficiency limit of your wind turbine?

[GoVertical]

Hi, Yes I believe your correct. My blades are to small and the geared ratio is to high. I have completed the new blade assemblies and hope to road test soon.  Enjoy the day.

[XXLRay]

Maybe you should build a simple Savonius to generate reference data. R.E. Sheldahl, B.F. Blackwell, L.V. Feltz: Wind Tunnel Performance Data for Two- and Three-Bucket Savonius Rotors might help you to create a meaningfull model.

[GoVertical]

Hi, thanks for the info. I am using the data from previous tests as reference data. When I make a change to the current design I compare the test results with earlier recorded data.
I have only recently been able to observe all the relationships that affect the output at different wind speeds. I am experiencing information over load from all the new information, it will take awhile to review all the content. Thanks again, all the help is greatly appreciated. Enjoy the day.

[GoVertical]

new blade photos


The core structure allows the scoop to be positioned as Lenz, C rotor, or internal J style.

[GoVertical]

photos of new blades

[KBwind]

Great work, you sure know how to build using plastic. When testing the Lenz or J type blade try to have the back section of the blade flush with the front cup part as if it were one seamless piece. For a hybrid turbine like this one it is crucial to eliminate as many ridges or extrusions that will add to the overall drag coefficient of the blade. I am interested to see the comparison between the three types.

[GoVertical]

Hi, a short video of the new blades. Sadly winter is here, I hope to have enough time to just test what I have, reduce the belt drive ratio, and place it on a pole for a winter test. Everything else will have to wait for spring.
I really appreciate the information you given me, it has pointed me in the right direction. I hope to post road test results soon. Enjoy the pool. I plan on moving south as soon as possible, to old for the cold.

 http://www.youtube.com/watch?v=uffHDWlGQ6Y

http://www.youtube.com/watch?v=uffHDWlGQ6Y

[GoVertical]

Hi, just complete the road test. Results using three blades, very bad, startup 25 MPH and 1 amp at 40MPH. Results for 6 Blades, about the as the fin style last tested. Conclusion, the fin or C rotor configuration produced the same results. Style of blade will be based on ease of fabrication because they produce the same results for this size blades.  I am primarily interested in produce as many amps as possible at low wind speeds, 10 to 25 MPH. I am reducing belt drive gear ratio, increasing blade length, and replacing stators.

[KBwind]

Govertical - your results are somewhat confusing. Looking at the photos above I do not quite understand how your  blades are configured. Are the outer blades j type and the inside blades lenz style? For your three blade test were the blades set to lenz (with blade surface on inside of cup) or J type (with surface on outside of cup)? Aerodynamically the three blade should work better than the six. For the j type, I have experienced that the performance is very sensitive to blade pitch angle. A difference of a half inch of positive pitch (blade trailing edge pitched toward center) would make a 40% difference in rpm.

Also your chord length is very large. For VAWTs the blade aspect ratio is very important. This is the ratio of blade length to chord length and many have found that ratios should be greater than 5. I'd say your turbine would perform much better with three blade jtype with proper blade pitch and half the chord length. There is an important step for most people who are tackling VAWT design when they finally understand that less blade makes a faster turbine. Ofcourse there is a limit where solidity becomes so low the turbine can no longer self start and that's where all these hybrid designs come into play.
A proper three blade j type should self start in 2-2.5 m/s.

[GoVertical]

Hi, when I started the project I was trying to create a blade configuration similar to a cross flow turbine. I have  slowly been changing the design. If a change showed a increase in output I would continue to make modification until it had a negative affect.  The only thing I can say that increased RPM is moving the outer edge of the larger blade farther away from the center.  After experiencing the force needed to produce a higher amp output I am conflicted regarding which blade configuration to pursue. I asked myself the following questions, what style blade would be used to pump water, if your on a sail boat and want to increase speed what would you do, what is the shape of the fastest whale tail, is there a difference between pushing something through the water or flying through the air? Then I considered what I am able to fabricate and what materials I have available. After all this I have concluded that a shape similar to what you are using and the shape I am testing, would work best for my project. Winter is here in the north and future testing may have to wait until spring but the next blade modification will include a larger C shape with end caps. Thank you for the help I receiving, there is a lot to consider. Enjoy the day.

[GoVertical]

Hi, because I am increasing the blade length I have to install a blade support bearing. Fabrication was not difficult but I do not know how long it will last.  Bearing ID is 4.26 inches and will fit beneath the PMA and ride on the PVC mast supporting the blade evenly during rotation. Comments welcomes.

[12AX7]

I think it's damn pretty!

good luck!

[GoVertical]

Hi, any suggestions on what would be the best type of grease to use?

[12AX7]

I don't know!   maybe none?   lite coat of silicone?
Maybe slice it through  the center line so you can remove and check it (without having to pull everything apart)??

[Madscientist267]

I would say the same, silicone or maybe even moly? Lithium?

Depending on what its made of though, you may end up with not much more than just a number of pressure points and a lot of rubbing with very little "bearing" action regardless of what you use for lube. Particularly under significant stress.

A non pressurized bearing (ie ball and race) relies heavily on the balls, races, and guides being hard. Not sure how well I really see this working with the pvc and (whichever) race material you're using.

Guess we will see, eh?

Steve

[GoVertical]

Hi, I purchased ¾ bearing balls and fabricated new bearing housing. I am using a 4 inch PVC coupler as a shaft collar. After I added some high temp grease the bearing spins freely and has a reduced noise signature. Spinning the assembly manually on the test fixture it is very stable and appears only one assembly will be needed for the lower blade rotor. The cost of a large ID bearing is over $500 US and at this time it appears to be a cost affective solution.

[GoVertical]

Video link that shows the need for lower blade rotor assembly
http://www.youtube.com/watch?v=o-GuG3u-450

Once the lower blade rotor is installed below the PMA larger blades can be installed.
When you consider the national wind speed average is 10 MPH, are you going to produce more current with a feather or a main sail?

[Madscientist267]

When you consider the national wind speed average is 10 MPH, are you going to produce more current with a feather or a main sail?

Neither.

One is only useful if you're a bird, or need a primitive writing device (ink well not included).

The other is only of use on a boat.

That said, I vote "generator"

Hope it all works out, you've put enough effort into it!

Steve

[KBwind]

Govertical - I cannot see how a 500 dollar bearing could be cost effective on a turbine your size. The whole turbine, bearings, magnets and all should not top 500. I also recall the whole point of the multiple stators and rotors was to use smaller, less expensive magnets. For 500 you could get the standard 1x2x0.5 neodymium mags and build a 4 pole standard axial flux and have it cut in at 60 rpm no prob.

Just trying to offer some context.

[Madscientist267]

He wasn't referring to his version of the bearing, but the commercial version of the one he would need to do the same thing.

 

Steve

[GoVertical]

Hi, yes to buy a large ID bearing is very expensive.

http://www.vxb.com/Merchant2/merchant.mvc?

check the bottom of the page

The new blades will be 8 feet tall by 2 foot chord and it that is not enough then I will try 8 by 4 blades and if the is not enough ……….

[GoVertical]

Photos of lower mast blade rotor.