Helical digression back to savonius(sorta)

[rotornuts]

Here's where all my Vawt experiments have taken me. The solid center two cylinder digression back to a savonius but with a twist, literally!

It's a foam core, fiberglass skin with a 3/4" center shaft. Tried it in a straight blade and a helical before the fiberglass went on and the twist was a clear winner. Someday after I hook this up to an alt. I'll build a striaght blade to confirm the diff.

12" diameter x 26" high so I'm still experimenting but I hope this will suffice as a test bed I can add flow augmentation devices to and actually see results.

It's clearly not done yet. Needs three more layers of fiberglass, the ends need shaping into a convex dish shape and the center shaft needs to be properly secure before the ends get glassed. So far it weights in somewhere around 8 pounds with the shaft.

Having fun and perhaps actually getting closer the production of a small amount of power.

Mike

[drdongle]

Nice looking work I hope it meets or exceeds your expectations.

[Norm]

   Don't be surprised...On of these days you'll walk into Walmart's

and see something this shape 4 x 8 ft. ... an

inflatable! hooked to a small generator and lit

up inside...A yard ornament! In with the solar

yard lights.

               ( :>) Norm.

[windstuffnow]

  Very Nice Mike!  I'm a bit skeptical about the helical design.  When I was testing some multi wing units I found you get a small "band" of power from the wings that were exposed to the incomming wind.  Although, the torque was continuous as opposed to pulsing you end up with far less than the pulsed torque.

  I like the idea of augmentation or adding a diffuser(s).   This really increases the power of a small turbine and we have them built in to our normal environmemt.  May as well use them.

  How soon before you'll have this one up and ready for testing?  I'm interested in the outcome!  

.

 

[hvirtane]

Really nice.

I hope that you will publish some

test figures soon.

It resembles 'Windside' turbines:

http://www.windside.com/products.html

There is an interesting

machine in development here:

http://www.me.dal.ca/~dp_01_10/index.htm

---

Some time ago I started to think

about making a kind of Gorlov

machine using a metal drum.

A draft for the machine was like this:

Then I made a very small

scaled-down model:

I've also made a model like that

of a PVC tube about 80 cm X 40 cm.

Unfortunately it became quite heavy

and it seems to need quite a storm wind

to start. No pictures of that one yet.

- Hannu

[cr8zy1van]

Wow, Nice. I do have to ask some questions.

What kind of foam/resin combo did you use to get past the melting of your foam? Someone on this board has told me that if I cast my blades out of expanding foam, and try to glass it, it will melt. Would you suggest any retailers that carry the right materials?

[cdg378]

Blue styrofoam made by Dow will resist melting with both vinylester and epoxy resins such as west system. Even the pink stuff will work too but you have to remove the protective film. I suggest you use the blue...

Lowes, home depot has the foam and vinylester resin.

[rotornuts]

I share your concern Ed, I taped the sections together (1 1/2 HD CC extruded polystyrene cut in identical sections and stacked) in a straight format and a helical format. The helical format had a much higher unloaded rpm and a greater range of operation. I'd like to someday try both but the staight was disappointing in comparison, could be the shape.

My greatest concern about the helical design is how it will effect the use of flow augmentor such as the tubercles. I just can't reconcile if they will still work right if they don't in pairs at the same time. The experiments will be fun.

Unfortunately but good for me in other ways, I've started my training for CNC machining this week so for the next 6 months I'm in school so I may be too busy at times to get much done but I'm going to do the best I can to keep at it.

I'm eager to produce some measurable outputs.

Mike

[electrondady1]

ive often thought of inflaitable vawts norm .it would be excellent for portability mobility. the low mass would allow one to go very large and sculptural .

[electrondady1]

its gonna be sweet!! looks like you've got the windside shape down mike and maybe one better by eliminating the cross bars. i hope it blows your meter!! because you've made it so smooth, you could  use IT, as a mold to cast dupelicates .two dupelicate could form a female fold.  nice work mike.

[rotornuts]

I like the model Hannu. Keep at it and you'll eventally have a test unit to further your ideas. My model resembles the windside's helical shape but the profile is quite a bit different. We are going to start making much better progress with Vawt's as soon as we can can develop apropriate profiles which require a recognition of the difference between them and how they work in a Vawt application.

There's still so much progress to be made.

Mike

[electrondady1]

a female mold !! (thats got to be froidian)

[rotornuts]

The foam I used Owens Corning's Celfortec 200. It's a high density pink closed cell extruded polystyrene foam and as cdg378 said an epoxy resin will not melt it. I don't know about vinylesters and the pink foam has no protective film on it. I read recently that some RC modelers have been using Minwax Polycrylic clearcoat as resin with good success as it's safe as well. I won't vouch for the strength of the polycrylic but it may make a good "sealer coat" allowing you to finish with a typical polyester resin.

Polyester resins definitely melt polystyrene foam products.

The blue and pink foam have subtle differences mainly with respect to their densities and compressive strengths. Both are closed cell extruded polystyrene so both should work. The key is to find the compressive strength that suits your needs. For my need I could go with a lower strength of 20 psi but for Hawt blades I would get the highest possible. In the pink you can get up to 100 psi for industrial applications but the highest your likely to find in a home center is 25 - 30 psi depending on brand. The Celfortec 200 is 20 psi the Foamular 150 is 15 psi the 250 is 25 on so on.

Have a look here:

http://www.owenscorning.com/around/insulation/products/foamular.asp

I used a polyester resin but do not recomend anyone else use it. I used a primer sealer as a barrier coat but there was still some deformation. I will try the polycrylic for the ends with structural layers of polyester after and post the results in the future.

The safe but expensive bet is an epoxy resin.

Hope that helps.

Mike

[rotornuts]

See my post below. I'd like to add that the rigid foams such as the blue or pink are very easily machined, hand sanded, power sanded, filed or even power planned.

I don't know about the expanding foams.

Mike

[rotornuts]

oops! I guess that should be see my post above!

Mike

[free energy64]

Hi, Rotornuts, seems you have done the work that I want to do already.

Love the Windside design and want to construct a unit for myself, as you have done.

How did you get the details of the curve shape and over-all details? Would you be prepared to help me make a similar unit?

I like the idea of having a number of these coupled together and mounted horizontaly on the peak of my house or garage, thus very unobstrusive while still being able to generate a useable amount of power from low wind speeds.

I live in suburban Adelaide, South Australia so a whacking great tall rotor way up on a pole in my back-yard would attract lots of unwanted attention from neighbours and the council as well. This great design overcomes all of that, if I can get the details to try and construct one.

Looking forward to your reply.

Regards

Paul