Nubee hit's brick wall

[imwithu]

I'm new to the wind power scene but I'm hooked. I had back surgery in early Jan and needed a hobby that was light weight. Shaping PVC blades was just the ticket.

I now have a 4 blade pvc windmill that sits about 16ft up. Tip to tip on the blades is about 5 ft. It's strapped to a 55 gal drum full of water (no guy wires).

I installed a DC motor yesterday and thought I was doing an upgrade. This motor is industrial and 2.5" in diameter. It has huge magnets as it is very heavy and it boasts warning labels for those sensitive to high magnetic fields (pacemaker etc.).

I replaced a 1.5 inch DC motor w/a built in gear box. It was a hard one to turn but it would hit 25 volts in a good wind. Low amps though I'm sure.

This unit hit's 8 volts and typically runs about 4. The windmill runs more as there is less resistance (no gear box). I've got a 4" pulley on my windmill shaft and a 1" on the motor.

I was banging my head against the wall last night trying to find a way to double or triple voltage. All the ICs on ebay a 20mah limit.

Should I make it AC and use a transformer and a full wave bridge? What is the best way to make it AC?

Should I just put back my little 1.5" geared motor and give up on this dc motor?

Please help.

Tom

[windgat]

Hi there, welcome!

What voltage/rpm is the new motor designed for?

You could try and see if its possible to rewire the coils of the new motor to double them up - that would double the voltage.

The electronics you are after (I think) is a DC-DC converter.

[imwithu]

There are no specs on the motor and I'm a little afraid of ruining it (although I used to repair trolling motors). I've never messed with the windings. I ordered a DC to DC converter(still waiting). I got an 8 inch pulley on the windmill and a 1 inch on the motor that hits 30 volts but you need a hurricane to get it going. Most days it sits idle.
I'm wishing my little .5 amp motor was back up there with it's little gear box. It would at least run most days. I used to enjoy hearing those gears whine.

My blades of course are home made. They somewhat resemble your logo. Should I have removed the material from the front or the back of the blade to sharpen the trailing edge? I took it from the back and I'm thinking that wasn't right.

My blades were made 28" but after balancing them out I've one down to probably 25. Yes, sloppy I know. I'm beginning to wonder what the point is in tapering the tip? Why not make like a helicopter and get some flat material (even wood lathe) at a solid 45% and let er go? Would short fat blades get me higher RPM? I can see how the long blades can get the torque.

I'm in Nebraska and wanting for wind. Rediculous. I'm in town and homes and trees really drop my wind. I know a taller tower would help but I need something worth elevating first.

I've invested in a solar array so my batteries are being fed although they are on a starvation diet w/45 watts. I have 3 batteries 2 car batteries and one deep cycle 200 amp hour. I'm going to let the voltage get to 14 I think and then see how long it will provide power. They are at 12.9 now and each day the solar panels bring them up a 10th of a volt or so. I'm suprised at how much power they put out even on a cloudy day.

Thanks for your advice.

[windgat]

By 'front' I assume you mean windward (flat) side? The main issue is that the profile matches what you are aiming for. There is a lot of info on the web about NACA profiles. The windward side is often flat, the leeward side curved, and in that case it makes sens to sharpen the trailing edge mainly from the curved (leeward) face. The sharper the less drag. The tapered tip is also meant to reduce drag (tip travels twice as fast as halfway along). Also lots of info about drag to lift ratio on the web.

'Why not like a helicopter' is a good question. Maybe in that case drag is less important than lift, since the drag cancels out between the tips moving forward and those moving backwards at any point in time.

Short blades will give higher rpm yes. Half the length, twice the rpm all else being equal (like the TSR). Unfortunately, half the length one quarter the avialable power.

I have read that its not a good idea to mix different types of batteries - you may reduce the life of some of them.

[imwithu]

I'm trying to determine the current condition of my batteries. I know what the voltage is but I'm not sure what they have saved in amps. My windmill ran nearly all day yesterday w/a good N wind. I've put back my .5 amp 24volt motor w/gearbox. It is capable of hitting 100 volts w/no load. Unfortunately my total wattage input is only about 5watts. I've been charging them for a week but the voltage is 12.7.

I'm putting a standard charger on them this morning on 2 amps to see how long they will accept a charge. I did a little research on how batteries behave while being charged. I'm trying to get them fully charged before I load them again.

My blades don't have a "flat side" as they are made from PVC 4" sch 40.

I have a second inverter and probably should split those batteries by type.

I ran into some info on line yesterday talking about some quite high outputs from Ac motors rebuilt w/ permanent magnets. My budget and the availability of AC motors may mean that is what I'll try. They were using magnets harvested from old hard drives.

This is an interesting hobby

[windgat]

A fully charged battery will come to rest at about 12.65V, so maybe thats not too bad.

Ok, for the blades, then substitute windward, or concave, instead of flat.

I tried magnets from old drives, and it seems to work well, if you can get the same pole arrangement N/S. Also, you need a LOT of old hard drives!

Have fun with the new hobby!

[imwithu]

Thanks for the advice. I'm thinking about going to 6" PVC blades 6ft long (3x my current blade area). I'm not sure though as I don't have a brake and I can just imagine a heavy 6 foot length of pvc sticking out of my neighbors siding or worse yet though a window. I know I can brake via load. Haven't felt the need to at this point as my 2ft blades aren't that scary and the gear box, belt, and pulleys seem to provide ample resistance.

Thanks for the advice on the trailing edge. My next blades will have the material removed from the windward "front" side to best resemble an airfoil. What "angle of attack" does one use with flat blades?

I've taken your advice and isolated my deep cycle battery. Is voltage any sort of reliable measure of battery charge or can it only be determined under a load?

Regarding the next generator. I ordered magnets and have my rotor down at the machine shop to remove a few mm with a lathe. Found some great magnets (I hope) at a very reasonable price here https://www.supermagnetman.net/login.php. I'm starting with a 1 amp A/C motor that can work with my current setup. I'm anxious to try it. I understand you go N S N S on the magnets so output is AC right? I've got a full wave bridge or the diodes to make one. Is it worth (or beneficial) to use a capacitor to clean up the DC after the full wave bridge? Otherwise I supose it would be a square wave (pulses related to rpm of generator) right? Which is better for battery charging and life?

I appreciate any input and advice. Thanks,

Tom

[windgat]

6ft PVC - wow, that seems long! How thick is the wall? It would be great if you posted a few photos of the process of cutting them out and smoothing them. You could get nearly ten times the power compared to the 2ft blades, so be careful!

Flat blades... are your blades flat, or curved (from a PVC pipe)? Angle I would guess around 6 degrees, assuming a three bladed design. You want to optimise for the tip, where most of the power comes from. I would understand more if I saw a photo...

Magnets NSNS.... yes, so that rotors attract. Note that 24 powerful magnets attracting each other will quite happily crush all the bones in your hand.

AC will not be square, unless design is poor it will be a sine wave, full wave rectified. The three phases combine to form a DC current with a ripple. The battery is basically a big (and slow) capacitor, so I can't see the point of adding a cap.

[imwithu]

Maybe I'll back off a little on that idea. I can't afford to have a blade flying loose in town. I'm using schedule 40 PVC so the wall is probably 3/8" on the 6" pipe and 1/4" on the 4 inch. We recently had some high winds and I don't think a guy wire free set up like mine can safely handle much larger blades. You could watch the 2x4 bending in the wind. I was glad I took time to balance or she would have shaken to bits. I was suprised that little gear box held up.

I've got the smal geared motor up again. I'm getting 250 mah at 30+ volts at the battery. Doubled up my wires to try and help with amperage. Not much improvement. I just got my DC to DC voltage doubler and I'll be putting the larger motor back up. It produced 7 amps and 8 volts with my cordless drill maxed out. The doubler is set to a max of 5 amps in so I'll have to fuse it. It claims 80% pass through and 2amps out. I just need the gumption to pull it down and mount the bigger motor again. Should I put the doubler near the battery or the windmill? Or does it matter?

I make some cuts with a table saw and others with a hand held jig saw. Believe it or not I've had great luck with shaping using the table saw. My blades are curved. Currently my blades are cut from 4" sched 40 PVC. The leading edge has a 45 max angle about 5" from inside tip reducing to 15 degrees on the outside edge.

Thanks again

[imwithu]

Scratch that. I have now put up the larger motor w/8" & 1" pulleys. Takes a strong wind but it puts out a couple amps.

We had high winds all day yesterday 25+ mph and I tried the smaller pulley & large motor with a DC to DC voltage doubler. It would only charge in spurts. It seems the doubler would store a small charge until the output voltage was high enough to open up the diodes on my wiring and then it would dump. Here an amp, there 1.5 amps and mostly nothing. I'm getting more wattage this way. Granted it takes a small tornado to get it going and keep it going but it does provide steady amperage. I have obstructions to the South and get gusts (no steady wind). North to South winds are the best. My rig is too short.

I've got a small AC motor half rebuilt for generating power. They sent me a set of magnets but they were all N. It was just an error and the South magnets are probably waiting in my PO Box. Got the rotor back from the machine shop and mounted the N magnets w/superglue. The motor was a 1 amp fan motor. I'm anxious to get A/C on the 50+ line between my batteries and the windmill.

The only real reliable power I'm getting is from my solar panels. They too have long 16 gaugue wires (I'm losing about 12 watts the way I figure it).

When does a hobby become a burden?

[windgat]

It becomes a burden when you go broke!

As to where to put the doubler, try and minimise the higher current leg, which means make the low voltage run as short as possible.

[imwithu]

Now I'm really frustrated. Got my South magnets and mounted them on my AC motor rotor. I alternated NSNSNS ect all the way around. It cogs as I expected. I grabbed my drill with high expectations. I get 7 VAC an .2 amps. Granted my drill wasn't fully charged (maybe 500 rpms) but I'm disappointed to say the least.

The motor was only a 1 amp motor to start with, 1500 rpm @ 120 VAC. Any ideas on what I did wrong? Or do I just need a bigger motor with stronger magnets?

[windgat]

What load are you testing with? Does the drill strain or turn freely?

Say you getting 500rpm, then that is a third... so you would get .6A and 21V at 1500rpm? That seems a bit woessy to say the least!

I have avoided trying to modify motors to make generators, so can't help from direct experience. If you make your own coils and use a pancake design, you know what you are going to get, and also can use block magnets - no worries about Aouth or North when ordering!

PS: I hope no-one reading your post think you have discovered a magnetic monopole! Presumably it was the shape that was wrong, and not that the magnets were 'south only'.

[imwithu]

I tested it with a multimeter and no the drill didn't seem to strain at all. I guess I shouldn't have expected much from a motor like that. I'll never hit 1500 rpm w/wind (don't think I own a pulley that big).

For now I'm only getting amps from my windmill 1 day in 5. Have to have the wind from the right direction. Too short and too many obstacles in town.

Thanks for all your advice.

[windgat]

Sounds all quite frustrating. Must say it makes me glad I never tried modifying a motor to convert it into a gennie!