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6 inch radial air core
By windstuffnow, Section Homebrewed Electricity Posted on Sun Oct 22, 2006 at 12:20:31 AM MST
A larger attempt...

Another fun project to see if its possible to get some decient power from a radial air core alternator.
Started with some plastic and a section of 6 inch sch40 pipe for the drum. Mounted the magnets and drilled the end plates. It uses 18 magnets and 54 coils. Each coil is 11 turns. I wanted to keep the magnets and wire as close to each other as possible. Below is a photo of the magnet rotor and drum completed...

Another shot of the bearing assembly attatched to the drum and rotor installed... The drum spacer is an .050" thick sheet of PVC...

And finally all wired up...

Since this was a test machine I really didn't want to waste any good wire on it and wound it with some used stuff I had. ( Hence the really sloppy coils )
So with a quick turn, and wired in star, it jumped to 15 volts right off. Turning it slowly with the tach it makes 12 volts at 106 rpm. I haven't had it on the lathe for any tests yet so thats all I have right now.
This was a fairly quick simple project overall. I'm not sure what type of plastic the black drum is but I'll never use it again... It is a nightmare... I spent more time cleaning it up than drilling the 108 holes in it.
If I made some molds for the plastic parts I'd bet this thing could be built in a few hours...
This design definately needs a considerable amount of refining but has quite a bit of potential overall.
Lots of fun in anycase... kind of disappointed when it was finished, guess I'll have to build another one...
.

6 inch radial air core | 28 comments (28 topical)

Re: 6 inch radial air core (3.00 / 0) (#1)
by vawtman on Sat Oct 21, 2006 at 07:09:22 PM MST

Hi Ed
Even your disapointments look great.Nice work
Just a thought
What if you coated the coils with jb,bismuth or other brews for a test.

Re: 6 inch radial air core (3.00 / 0) (#2)
by windstuffnow on Sat Oct 21, 2006 at 07:29:06 PM MST

Thanks Vawtman, it's really not a disappointment it seems to do fairly well. The plastic I used, what ever type it is, for the stator loom really sucks. I have a few small sheets of it... good for project bases only.

I'm not sure JB weld would work very well, it has steel in it and could create some cogging. Bismuth wouldn't really do anything as far as I know, a steel sheet around the outside of the stator drum might increase output a bit. It would have to be a continuous ring though no gaps or breaks or it will cog at the break.

.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#5)
by vawtman on Sun Oct 22, 2006 at 08:46:46 AM MST

Ed i have this 20inx1.5 aluminum flywheel hangin on the turbine and just thought maybe i could convert it to an air core.What do you think?

I know 60 1.5x.75x.5 mags would be around 200 bucks and then the wire another couple hundred but then i could direct drive it.

[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#9)
by windstuffnow on Sun Oct 22, 2006 at 09:13:25 AM MST

I've had pretty good luck with the axial air core units as well as this one. The key is keeping the magnets as close to the wire as physically possible for the best output.

The aluminum flywheel would need to be wraped in steel to get full benifit from it but it could be done. If you matched the coils to the poles similar to the single phase but adding 2 more phases ( the way this one was done ) the turn per coil count would be extreemly low and easy to wind.

Don't give me any new idea's Vawtman... I have enough projects... You have me thinking of modifying my 24" flywheel into an RACA.. unfortunately it weighs over 200 lbs, not real easy to move around.
.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#11)
by vawtman on Sun Oct 22, 2006 at 10:30:18 AM MST

Ed this might be stupid but just need to ask.
Why would you need a steel backing for the mags when theres no return path?

Wouldnt the flux go from mag to mag and thus through the coils has its spinning.

Shoot me!

[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#12)
by windstuffnow on Sun Oct 22, 2006 at 12:06:30 PM MST

If you measure the gauss at the surface of a magnet, I'll use the readings I get from one of the 1 x 2 x .5 blocks as an example...

In open air the reading is about 3500 gauss at the surface of the magnet (either side), on a 1/4" steel plate the reading jumps to 4900. It helps to bring the flux where you want it. If you add a flux path on the top it increases dramatically depending on the gap. Thus the use of a blank steel plate or a second disc of magnets to close the loop for the flux to flow.

On an air core we're depending on the flux to flow through the coils in a small area above the magnets where its trying to get back to its neighboring magnet to complete the path.

Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#15)
by vawtman on Sun Oct 22, 2006 at 05:32:17 PM MST

Hmmmm Ed 180 little coils.

The flywheel has a 1in x 1/8 slot for a belt that i could wrap with steel its from a exercise bike.
Maybe i could run both alternators?
Dammit i need to take a tub and come to bed so says the wife:>))

[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#3)
by wayne on Sat Oct 21, 2006 at 07:51:09 PM MST

Hi Ed

This one looks so good and works very well. I am impressed. Did you ever take a break from last week! I know your next one will get even better. I had some on that black plastic and its very strange stuff. Did you make one big loop or one wire a time? I did a small test on mine and with 40 turns with #20 single phase only getting 5-6 volts. With short wires on drill got 1.7 amps. I think I did something wrong try again.

Great work
Wayne

Re: 6 inch radial air core (3.00 / 0) (#4)
by WXYZCIENCE on Sun Oct 22, 2006 at 01:40:30 AM MST

Super Ed, I am very impressed.What gauge of wire did you use on this wind?

I have been doing spin tests on my unit will post in my diary results. Probably tomorrow.

Joseph

Re: 6 inch radial air core (3.00 / 0) (#6)
by windstuffnow on Sun Oct 22, 2006 at 08:57:17 AM MST

Hi Joseph,
I used 18AWG wire to wind it first time up. I had a salvaged spool of it and didn't want to commit any pricey wire to it as yet.

At this point with the wire thats in there I'd say the overall output would be in the 100 watt range. I believe I can get 14AWG in there with about 8 turns per coil getting a 14 volt cut in speed at around 170 rpm and it should do 30-40 amps without any problems. Would be a nice unit for a 6ft prop.

The black plastic would be the drawback I think. Cutting it with a band saw it tends to pile up under the work piece so it wouldn't take much heat. I think if the end plates of the drum were made of nylon it would be fine with the higher power.

All in all, it definately proves your RACA design would be a viable competitor to the small DIY turbine market. Easy to build with some basic tools. I used a drill press to build the entire thing except for the bearing hub itself which could be purchased in another form complete such as a trailer hub.

It definately deserves some more thought and another more refined version.
.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#7)
by electrondady1 on Sun Oct 22, 2006 at 08:59:49 AM MST

now we're really getting some ware.
i realized a while back that a radial design might give some advantages,
but everything i drew turned out looking cup shaped and requireing perfect machineing and alighnment .
by turning the rotor and stator into a drum your supporting them in two places and making then stable and eliminating the alighnment problem.
really clever.
if time and resourses permit i wonder if you would consider takeing the next step,
that is to form another, open ended mag rotor that would slide down over the existing devise and become a dual rotor radial?

[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#10)
by windstuffnow on Sun Oct 22, 2006 at 09:28:28 AM MST

It would be really easy to do a "Brake drum" style internal stator which would actually require less wire. Doing an external drum is also simple. When you combine both as a single unit then the magnet drums become more difficult and need to be very precise. It would also remove the coil cooling ability and require some hi temp plastics. It could be done, and I'm sure it would double or more the output but I'm not sure I want to go there right now. The air cores are simple to construct because you don't have to find or make precision parts, plastic is easy to work with to a certain point. At least for now I'm going to play with the KISS units and see if I can refine the construction a bit.
.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#8)
by powerbuoy on Sun Oct 22, 2006 at 09:10:26 AM MST

Nice nice, impressive work. I am wondering, aren't the magnets on the rotor to close to each other? The magnetic field will rather go from "magnet to magnet" then from magnet -> coil -> magnet ...right?

Powerbuoy

lathe test (3.00 / 0) (#13)
by windstuffnow on Sun Oct 22, 2006 at 12:14:19 PM MST

I made up a 3.5 ohm load from some nichrome wire and connected everything up in the lathe and here is the results...

Rpm Voltage amps watts

7.1 2.02 14
13.8 3.95 54
20.5 5.85 120
28.57 8.16 233
35.71 10.2 364

I couldn't get it to run any faster than that without changing alot of belts around. The readings probably aren't 100% accurate in the upper range because the wire was heating up a bit which most likely changed the resistance a bit. Close enough to get a fair reading of its potential.
Have Fun! Windstuff Ed

Re: lathe test (3.00 / 0) (#14)
by RP on Sun Oct 22, 2006 at 01:25:34 PM MST

Ed, If you're willing, I'd be really curious if iron wire would have an effect as an external laminate core. If you have a few pounds of it handy, could you try spooling a least a couple layers around the outside of the stator and check the output again?

[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#16)
by veewee77 on Mon Oct 23, 2006 at 07:54:16 AM MST

Do not wrap the outside with a sheet of steel in a effort to help the magnetic circuit. All that will do is introduce eddy currents and place unnecessary drag on the rotor and waste energy to heat. If you want iron back there, use laminates but much trial and error will have to happen to find the best shape and thickness of the laminates. It might be worth the effort it if doubles the output but that would have to be determined.

Doug

Re: 6 inch radial air core (3.00 / 0) (#19)
by Ungrounded Lightning Rod on Mon Oct 23, 2006 at 07:13:46 PM MST

If you want iron back there, use laminates but much trial and error will have to happen to find the best shape and thickness of the laminates.

I'd think a stack of "washers" of transformer/motor-core material would do the job nicely.

Find a fried motor with a stator whose laminates have the bottom of the slots about the same distance from the center as the clearance around your coils. Strip out the coils, grind off the poles, clean out the shorts between the laminates from grinding down the poles, and drop the remainder around your genny. (You'll need to clamp it down because it will want to slide off-center and will have a slight drag trying to rotate it with the rotor. That torque corresponds to your iron losses.)

[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#20)
by Ungrounded Lightning Rod on Mon Oct 23, 2006 at 07:16:49 PM MST

Or just take one where the inside clearance is about right, strip out the coils, and stick that over your genny with no grinding. Split it in two and offset one of 'em by a half pole-width to eliminate cogging.

[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#21)
by windstuffnow on Mon Oct 23, 2006 at 08:18:40 PM MST

Hi ULR,
What you propose would work, probably quite well as a matter of fact. I think if I was going to go to the trouble of doing that I might go ahead and convert the original motor the laminants came from. I was looking for a KISS genny that would work reasonably well with the least amount of effort. This one, based on Joseph's original idea ( aka WXYZcience ) fits the bill quite well and performs reasonably very nicely for an air core based alternator. The entire thing could be built with nothing but a drill press. I complicated the build by using the external bearing set up as the bearings could have been set into the end plates using an end mill in the drill. Overall the alternator could be made in one full days work with nothing but a drill press, a few drills and an end mill. Also a plywood jig to cut the circles.
.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#17)
by RobD on Mon Oct 23, 2006 at 08:14:45 AM MST

I like the design Ed,

A couple of things.
First, I don't see a problem with the wires vibrating. I use waxed string on my alts to stop that and it would be an easy task to run several 'lines' around the perimeter tied to each coil.

I would also make the final outside housing large enough to give about an inch clearance from the coils. If you built in a cooling fan this area would work in accord with it.

Rob

Re: 6 inch radial air core (3.00 / 0) (#18)
by windstuffnow on Mon Oct 23, 2006 at 01:58:15 PM MST

I agree about the wires being tied in place. I think they could be varnished as well without any problems.

The outside housing could actually be a simple shield with stand offs but definately needed. Those magnets will pick up anything in close proximity.

The challenge is most of the fun, building it is the balance of the fun. When its done its just another project in the pile...

.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#22)
by Capt Slog on Thu Oct 26, 2006 at 06:23:54 AM MST

Hi,

First time on here, so go easy!

Just wanted to know whats holding the magnets onto the drum? and what du you think is the maximum revs it will take before they are likely to let go?
"Slowly changing the world, one watt at a time!"

Re: 6 inch radial air core (3.00 / 0) (#23)
by windstuffnow on Thu Oct 26, 2006 at 08:39:35 AM MST

The magnets have quite a bit of magnetic force holding them in place, as well they were epoxied using JB weld. As a safety precaution they were also banded with strapping tape although, if I were going to run it above 1000 rpm for extended periods I would recommend a non magnetic stainless band. This one will only see 500 to 700 rpm max so I'm not real concerned about it.
.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#24)
by Capt Slog on Thu Oct 26, 2006 at 09:55:08 AM MST

Thanks Ed,

Minigen is working well by the way!
"Slowly changing the world, one watt at a time!"
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#25)
by force9BOAT on Thu Oct 26, 2006 at 10:58:54 PM MST

From the last photo it looks like you would need to unwind all the coils if you wanted to disassemble the machine. Is that correct? Just trying to understand how it goes together.

Rob

Re: 6 inch radial air core (3.00 / 0) (#26)
by spinner on Fri Oct 27, 2006 at 07:58:22 AM MST

hiya Ed,
you are the master at three phase stuff...'specially in theese smaller units(jealous here<G>..hats off to ya!
btw: what size caps ya runnin' in your volt doubler?
thanx
spinner

Re: 6 inch radial air core (3.00 / 0) (#27)
by windstuffnow on Fri Oct 27, 2006 at 11:58:30 AM MST

The smaller units I've been using some 1800uf 80volt caps but on my rooftop I used 2 1F caps rated at 24 volts.

They all seem to work well but the larger caps seem to push the amps better. I tried some 140F caps isolated from the batteries and when their at low voltage the turbine seems to see them as a short circuit until their up to working voltage.

.
Have Fun! Windstuff Ed
[ Parent ]

Re: 6 inch radial air core (3.00 / 0) (#28)
by spinner on Sun Oct 29, 2006 at 07:16:33 AM MST

hiya ed
probably the wrong way to ask this, for which i apologise

isolated from the batteries, can ya scketch the hookup diagram for other mentally challenged people like me?

second ?: re three phase winding w/ a flat stator, on your minigen vs a "conventional" 9/12 generator....you use open slots on the minigen and holes/slots on the flat unit you make from scratch, if i understood your site correctly.
The minigen kit also has precut wires which are laid in the slots...
when making a unit like the ones you make from scratch, do you also precut your own winding wires first, then put the unit together, or?
sorry for what must be redundant ?...am just TRYING to get the whole thing straightened around in my tiny brain...never tried a flat stator before and am very interested in the how-to thing..any help/thoughts would be much appreciated

thans
spinner

[ Parent ]

6 inch radial air core | 28 comments (28 topical)

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