Author Topic: DIY axial PMA from free recycled parts. (Read 8498 times)

stag · « **on:** November 30, 2012, 12:44:13 PM »

Here are details of my diy PMA. It is axial flux based on hugh piggotts' design . Laser cut steel discs and Neodymium magnets are expensive,so I put out the word and started collecting scap microwaves,each of which contains 2 round magnets 2 1/2" diam x 1/2. The 2 magnet rotors have 12 magnets on each. the discs are plywood with sheet metal from the microwave cases glued and screwed on. The metal is cut larger than the ply, then the overlap is snipped in from the edge every 1/2" and bent upwards to create a raised edge like a pie dish, to contain the magnets which are then glued and resined in. I used body filler diluted to a custard like consistancy with extra polyester resin. The stator has 9 coils, 3 phase, star, made from a square of plywood with a ring of holes to accommodate the coils. It then was given a layer of GRP on each side. (no mould) All ply was resin saturated.In situ ,the alternator has a cover over the top to give some protection from the weather. It works well,but not as powerful as hughs' design but it cost nothing,nada,zilch ,zero.

gww · « **Reply #1 on:** November 30, 2012, 03:40:44 PM »

Pictures?
gww

fabricator · « **Reply #2 on:** November 30, 2012, 06:11:02 PM »

Did you do anything to pot the coils?

stag · « **Reply #3 on:** December 01, 2012, 12:11:53 PM »

Coils are potted into the holes with resin,and channels cut into the ply for the tails,so as to keep everything flush. If repeating the process ,I would glue some thin sheet laminate to one side, then lay the coils in place, set them in resin,then glue another sheet of laminate on the other side,before sealing the edges with resin and maybe glass fibre tape. As the coils need to be very close together,I left just a wafer thin piece of ply between the holes. Without this ,the whole middle would fall out of the stator when the holes were cut out. Oh! It didn't actually cost nothing. I paid Â£15 for the winding wire as spool ends from a guy who rewinds motors, the threaded rod,nuts and washers were donated by a friend,and the resin and ply were leftovers from other projects. Sorry, I did not take any pictures of the alternator construction,but I will post some pictures of the completed turbine which is up and flying. Early tests look promising generating good voltage,but I am awaiting delivery of an ammeter from ebay to measure current and thus calculate the output. Thanks for your interest. Pete.

gww · « **Reply #4 on:** December 01, 2012, 04:44:01 PM »

Don't feel bad about the pictures. I took ten microwaves apart and used the wires and magnets to make one also. I have since replaced the ferrit magnets with neo's and the turbin is stalling. I wired it jerry and it seemed to help a little but I won't know more for a couple weeks when I go back on vacation. I believe part of my problim is also using a front chrysler bearing which has more drag then the trailer hubs I use now. I believe this is due to the bearings being sealed an me not being able to remove some of the grease. on the trailer hubs I also remove the rubber seal on the back which helps greatly. Hope to here more.
gww

stag · « **Reply #5 on:** December 02, 2012, 06:42:43 AM »

HI! gww. I used a hub from a Ford Focus(UK)which has a little initial stiffness which my motor mechanic friend assures me will free up when it has run for a while. It can't be too bad, because boy is my rotor fast. I emailed Hugh Piggott some time ago about the project and he made three observations, that he was dubious about ply in the stator,and that his 8ft blades would be too slow for this alternator. and that the thin sheet metal would not get the best out of the magnets. Less flux = the need for more speed. My blades are untwisted GRP from navitron.org.uk as used on an 8ft machine but instead of bolting them onto the hub, I brought the ends into the centre of the hub as in the piggott design. This brought the rotor diameter down to 6ft 8", which seems ideal, bearing in mind that my priority was to build something that worked reasonably well at minimal cost. I guess you can achieve almost anything if you throw enough money at it, but that's not what I'm about, even if I could afford it. Pete

gww · « **Reply #6 on:** December 02, 2012, 05:57:33 PM »

Mine wasn't free. I had to buy the all thread, hubs. Then I was building a different hugh turbine so I ordered extra magnets. I tried the tin covered plywood hubs and was not satisfied. I tryed the chrysler disk but they took too much room. I had better volt match for my eight foot blades with the microwave magnets but I thought I could do better with the neos. If I don't get it worked out I may just wire a 48 volt stator and be done with it. I tried to do it cheep also. I did some expermenting that cost but was worth it for the learning experiance. I have made lots of junk IE; cieling fan, geared leason moter etc. I may make more junk but have also been learning. I still like the actual plan turbine the best and consider it money well spent as it seems to work best. I am living away from home and lost my free junk resorces or I would probly still be messing with the recycle stuff.
Cheers
gww

stag · « **Reply #7 on:** December 04, 2012, 10:50:58 AM »

I'm thinking there may be some differences between your alternator and the one I've built. My coils are round to suit the shape of the magnets. They are 90 turns of 1.40mm wire which with the weaker magnets and a dose of wishful thinking,I was hoping to top 24v . all a bit unpredictable. I have no instruments except a clamp multimeter. when I got it up on the pole we had some very strong winds. I hooked it direct onto 24v battery(2x12,series) they were very flat showing 19v. Most of the time it recorded around 20v and higher in the gusts peaking at 25v for a brief second,so my hopes for a 24v system don't look good. I switched to 12v battery and cut in is much earlier.and it is charging consistently around 12/13v-15v in winds less strong than before.I'm on a steep learning curve here so any comments will be most welcome.

gww · « **Reply #8 on:** December 04, 2012, 04:40:12 PM »

I wired round coils to fit the microwave magnets. I had different size wire as the microwaves were not consistant in wire size. I would guess the smallest was about 20 awg. I first wound with about 70 turns. I then re wound with 120 turns. I was getting about 4 volts rectified dc at about 60 rpms just turning buy hand and counting seconds in my head. I would say that your turbine could be less voltage as you have shorter blade which if shaped simular to the hugh blades will be much faster.

What amps can you get at battery charging rate. from your post something doesnt sound right. When hooked to the batteries you should be getting no voltage swings from the turbine. 12 volts to 15 volts sound wrong unless it climbed very slowly to this rate. I guess you have no way to check the amps while charging.

Mine after I put the neos on it would get 12 volts open at sixty rpm. When in a heavy wind it would go to two amps but never above. This was due to stalling. The altinator was keeping the blades turning too slow for the wind to work well with them. I only have 6 coils.

You really need to see the amps "in my opinion" while charging to really know what you have. I dought the ferrit mags is making the turbine stall but you kind of need the current to tell. I hope you are enjoying yourself what ever the out come. I am still working through having too many turns in my coils. I wish I could think of a good use for a 24 volt system as I am sure my turbine would work better then it is on a twelve volt one.

If you have spicific questions, the guys on this site have answers.
cheers
gww

Mary B · « **Reply #9 on:** December 04, 2012, 05:43:16 PM »

19 volts on a 24 volt battery means the batteries are toast, at least one them is.

Quote from: stag on December 04, 2012, 10:50:58 AM

I'm thinking there may be some differences between your alternator and the one I've built. My coils are round to suit the shape of the magnets. They are 90 turns of 1.40mm wire which with the weaker magnets and a dose of wishful thinking,I was hoping to top 24v . all a bit unpredictable. I have no instruments except a clamp multimeter. when I got it up on the pole we had some very strong winds. I hooked it direct onto 24v battery(2x12,series) they were very flat showing 19v. Most of the time it recorded around 20v and higher in the gusts peaking at 25v for a brief second,so my hopes for a 24v system don't look good. I switched to 12v battery and cut in is much earlier.and it is charging consistently around 12/13v-15v in winds less strong than before.I'm on a steep learning curve here so any comments will be most welcome.

stag · « **Reply #10 on:** December 05, 2012, 09:30:13 AM »

Yes I guess the batteries are shot. I never got them above 11v on mains power or turbine. They were a gift and I think had been discharged for a long time.Now trying another battery. Charging rate is steady 12v rising slowly as wind increases. the 15v was a brief peak in very strong gusts. Other factors are that when testing at 24v, the batteries were at the foot of the tower,whereas at 12v I now have a 40yd cable run( 3 phase AC). Each phase/cable is 4.5 mm. but will soon be beefed up to 6mm. I obviously need to know the current and am awaiting delivery of an ammeter from ebay. At present, I can only measure single phases of AC on a clamp meter. I got 9v when cranking the alternator by hand with a meter across 2 phases. My blades are not piggott type. they are GRP untwisted, thin aerofoil shape as used on chinese turbines sold very cheaply by navitron.org .uk. the turbines look a bit like a copy of Bergeys'. I set them at 4degrees and they seem very fast with lots of lift.

stag · « **Reply #11 on:** December 05, 2012, 09:35:51 AM »

gww. how did you get the wire out of the micriowave transformer. I found them impossible to dismantle and gave up. Even if I had succeeded, I would never have got the winding wire out without serious damage.

hiker · « **Reply #12 on:** December 05, 2012, 05:04:29 PM »

stag....sounds like one of my mills..but i use saw blades for the rotors..
your sheet metal is to thin..so you might want to try blades..you can double up on them as well..i use ceramic mags topped off with neo"s or just ceramics...
i mount my mill on the back of my motorhome..lasted for years..in the winter it goes on top of my shop..made a few like this -never had any real problems at all.
not to say ive never had any..the early modles were like duck and cover!!
good luck with yours.......................

gww · « **Reply #13 on:** December 05, 2012, 05:54:41 PM »

hiker
love pictures

stag
I used an angle grinder to cut the lamnits "metal" surounding the coils. Once they were lose they seemed to unwind with no damage to the wire. It did leave some chunks of varnish but did not short when made into coils. It made the coils a little bumpy but when I clamped them in the mold they came out smoth and the proper thickness. I also did another no no, I soldered them to make enough turns. I have gotten 65 volts unloaded an it didn't seem "that" fast but was not slow. I haven't got it to working well as it stalls the turbine when running 12 volts and I have tried nothing else. I only get to mess with it a couple weeks a year as I am not home yet due to work. I have not got a shorted coil with this wire yet but I also haven't heated it up yet due to stalling.

Good luck
gww

Ps
I read some where that if you unwind the wire while in hot water they unwind easier. I have also taken some de=gussing wire from around tv tubes but it has been much smaller wire then the microwave wire.

stag · « **Reply #14 on:** December 06, 2012, 06:07:56 AM »

Hiker. Saw blades look like a good idea if you can get them. Probably available in the ideal diameter to. Mine are 11". I thought it may be possible to laminate the microwave sheet up to a greater thickness. I like the recycle/reuse attitude. gww.I have a shedload of magnets and transformers so will try again with the wire.Now that the word is out, the microwaves just keep on coming.

stag · « **Reply #15 on:** December 12, 2012, 05:48:25 AM »

Yes, first batteries were shot. The turbine got them up to 11v,but when left for a few days, they went down to 8v. I now have 2 tractor batteries which quickly came up to13.5v. turbine now charging between 13& 14v in light to moderate winds. In strong wind it very briefly peaked at 16v at which point each phase AC read 6amps. ( still waitng on DC ammmeter from ebay).Turbine will probably furl close to this. To my newbie eyes,this looks like a perfect match all round.Am I right?? Comments please. It is frustrating, not being able to accurately measure max output when furling as the strong gusts pass so quickly, it is difficult to measure at just the right moment. Trying to figure how to reduce file size so that I can post pictures. OH! As charging is mostly under 14v,does this mean that it can be left without a controller,and not fry the batteries?

,or will charging rate rise with battery voltage ??.

southpaw · « **Reply #16 on:** December 12, 2012, 09:42:56 AM »

Here is a good article on battery charging http://www.progressivedyn.com/battery_basics.html
You stated in an earlier post that you had seen voltages of 25v when connected to the 24v battery, thus your mill is capable of producing at least this voltage.
You will definitely need a dump load controller otherwise the batteries when fully charged will start gassing and overheating turning the water in the batteries into hydrogen gas and oxygen. The power from the mill will mostly be turned into internal heat in the batteries, if your mill can produce 1000 watts of power think how hot your batteries will get if this power is dumped internally into your batteries.
A dump load controller takes this power and dumps it externally using air or water cooled resistors.
The dump load controller is hooked directly to the batteries and is set to dump at the proper voltage for the type of battery you have.

stag · « **Reply #17 on:** December 12, 2012, 02:25:56 PM »

Southpaw. Thanks for your valuable comments. Do you think I am right in thinking that the mill seems ideal for a 12v system , with dump load controller, of course?

gww · « **Reply #18 on:** December 12, 2012, 04:43:22 PM »

Stag
Just a guess, but I would say if you get about 4 volts turning it by hand at about 60 rpms you are good to go for a 12 volt system. This is unless you blades are really slow. I can't remember but arn't they just strait angle from root to tip?
good luck
gww

southpaw · « **Reply #19 on:** December 12, 2012, 07:39:13 PM »

Stag
When it comes to wind turbines I'm long on theory and short on experience.
I used to install and service PV solar for 4 years before I retired last year so I know quite a bit about flooded lead batteries but there are many on this board better qualified to advise you about your turbine. My lack of practical experience with turbines means though I have read almost every post for the last 6 years most of it doesn't stick. The answers are all in the archives but one can spend weeks searching and reading.
Hopefully one of the Gurus will chime in.
Southpaw

stag · « **Reply #20 on:** December 16, 2012, 10:47:52 AM »

Southpaw. Thanks for the link re batteries,very informative. I think I get it now. The battery will clamp down the turbine voltage until it is full,after which the turbine output has to go some where. I already understood this but was confused by the relatively low charging rate, thinking that it may stay low enough to do no harm. gww. I will post details of the turbine when I figure out how to reduce file size so I can post pictures.

midwoud1 · « **Reply #21 on:** December 16, 2012, 11:29:39 AM »

Hi Stag.

Reduce picture format .
Camera format is 1,5 Mb or more.
Use Printscreen Gatwin or download it free.
That makes your pictures to 60 Kb in one second .
Put them in a new folder and from there on the forum.

stag · « **Reply #22 on:** December 18, 2012, 07:41:43 AM »

Here is a picture of the turbine..Blades are untwisted GRP, thin aerofoil, 4" wide,set at 4 degrees. Rotor diameter 6ft 8".It is very fast and shows no signs of stalling and responds quickly to gust and increases in wind speed. Appears to have plenty of lift. However! I thought that start up might be a problem so it has since been fitted with wider, more steeply angled fins at the blade roots to aid start up. These were curved pieces cut from the bottom corners of a scrap GRP domestic bath tub. The turbine is now mounted on a 30ft tilt up tower sited to take full advantage of the prevailing South Westerlys.

News:

Author Topic: DIY axial PMA from free recycled parts. (Read 8498 times)