Suggestions for VAWT rough dimensions

[makenzie71]

So last year I picked up a TESUP Atlas 2.0 which was an (unsurprising) absolute bust.  I'm wanting to start a new project, though, to try and actually get some power out of the the generator.  I think this is going to be a tough job because voltage is still way too high, but I'm going to take a stab at it anyway.

I'm going to convert the thing from the ghetto savonius style rotor it came with to a three bladed H-Darrius style rotor.  The generator is rated (allegedly) for 2000w so that's my target wattage.  The generator is running a 10:1 gearbox to keep the PMA at a high RPM.  I'm pretty sure paek rotor RPM will be 100rpm tops.

I would appreciate some input on the rough dimensions of the rotor assembly.

I am thinking a 6ft rotor diameter with very simple wings.  I'm thinking the blades should be either 3ft or 4ft with maybe a 8" cross section.  I don't know whether or not I should try and do airfoils or if I should make the inside "faces" scooped...I know there's a word for that design but don't know it.  The blades will be wood ribs with steel 28g flashing wrapped around them...although I'm considering having a local shop cut me some aluminum or thin steel ribs since they got a cnc sheet cutter.

Thoughts?  Should I be leaning a different direction with rotor design?  Keep in mind this project is purely for fun just to see if something useful can be extracted from this generator.  A lot of people have fallen for TESUP's poor design because of the price, I'd love to come up with an economical solution for them to actually get something from these machines.

[Bruce S]

I watched your U-tube vid on that unit, a good  ghetto Savonius. Not sure way they cut the top part of the blades to match the cut out bottom of the cut-out wasn't necessary IMO.
Now that you have the gear box down, will you be doing measurements on the gen itself before deciding which way to go with the blades?

[makenzie71]

I watched your U-tube vid on that unit, a good  ghetto Savonius. Not sure way they cut the top part of the blades to match the cut out bottom of the cut-out wasn't necessary IMO.
Now that you have the gear box down, will you be doing measurements on the gen itself before deciding which way to go with the blades?

Everything about the Atlas models is about packaging.  The package generates the sale.  That's why their demo model is nice and sleek and has all the right bits trimmed and cut...it's for looks.  Trimming the blades is just an aesthetic touch to make it look a little more pretty.

I've got it down on my bench now with all her clothes off just to poke around.  The PMA actually looks pretty decent but it is not particularly high quality...all aluminum and mild steel.  I'm going to do a couple bench tests this afternoon just to see what kind of wattage I can get out of it but just like when I started I think the voltage is so high that I won't be able to do much.  A quick twist of the wrist sends this thing up over 150vac lol

[Bruce S]

I'm guessing they used thinner wire on the coils to get to voltage up( saves $$$ too).
Sad that the unit you received was so poorly built; it is pretty :-/
It would've interesting to see how well it would've done had you had the chance to lock down those bolts

[makenzie71]

I think even with proper hardware it wouldn't have performed well, but hard to say.  I finally got a good bench test done and the thing is seriously making 300~325vdc turning it by hand.  I put it on a 48v battery and it just jumps the teeth on the pulley.  Once you get over 25w on the meter it doesn't want to turn.

[Adriaan Kragten]

This isn't a Savonius rotor because for a Savonius rotor, the blades have a certain overlap in the centre. This creates a certain flow through the rotor which causes a lift component. As all three blades touch each other in the centre, there can be no flow through the rotor. Therefore this is a pure drag machine and that is the worst thing you can make (see public report KD 416). In my public report KD 703, I describe a 4-buckets Savonius rotor which will have much less fluctuation of the torque than for a normal 2-buckets Savonius rotor but the maximum Cp might be lower.

[MattM]

What about a little unconventional but oversimplified scoop?  Use some 1x4 arms coming off your hub and use some 12" roofing metal to fold in half in the shape of a 'V' for the scoops.  Fasten the metal to the 1x4 using spacers, so it can cup air.  Spacer material can be simple tubing sections cut into 1" or 2" lengths; run your screws through a washer that will suck down to the tubing.  (Screw goes through tubing, to creat a stiff strut.)  If you use screws with high thread counts they will never back out.  Fastenal sells capped roofing screws about 2 per buck.  Flat metal straps every so often can run from the 1x4 out to the point of the V to keep the v-shape taught against your spacers, limiting flapping.  So it will be a long cup facing away from the wind and the V-shape will be like an arrowhead into the wind.  Simple design.

[Mary B]

I think even with proper hardware it wouldn't have performed well, but hard to say.  I finally got a good bench test done and the thing is seriously making 300~325vdc turning it by hand.  I put it on a 48v battery and it just jumps the teeth on the pulley.  Once you get over 25w on the meter it doesn't want to turn.

Good candidate for a 4:1 step down transformer then rectify and feed an MPPT controller. Toroidal transformers have a wider operating frequency than E core common power transformers. step the voltage down under 100, your available current goes up by 4(approximately!)... but I don't see an H-Darrius rotor having enough torque to get the gearbox turning, cup style drag machines have a LOT of startup torque but poor performance after that...

[Bruce S]

IF you have a nice sized squirrel cage, you could always attach it for a nice test run.

[makenzie71]

Well I've sorted out that whatever I do to try and drive it, the belt can't handle it lol

https://youtu.be/SoSx4Q7v7Kw

I won't have that one published publicly until tomorrow but all the same you guys can still see what's happening to it.  Once any drive is put on it, it starts skipping teeth.  That belt will have to go and a I'll use a chain maybe?  Otherwise we just rip the PMA out and direct drive it.

[MattM]

Looks like the wrong belt to use.  Probably would have been fine with a v-belt with a bit of tension.  The electric scooters with 500W motors used belt that size, though I don't believe they really reduced gear ratio on them by much.  It may simply be too much gear reduction putting too much stress on the teeth.

[makenzie71]

I don't think there's any saving it with that belt and that gear ratio...voltage is just too unreasonable.  How they expected this turbine to ever work with a 48v circuit is beyond me.

I'm going to ditch the case and see what the PMA by itself can manage.

[MattM]

The good thing with a VAWT you can get massive start-up torque if a steep gear ratio comes back into play.