Author Topic: Newbie help with bike axial flux generator  (Read 18574 times)

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HomeBrewer

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Newbie help with bike axial flux generator
« on: July 02, 2015, 06:11:40 PM »
Hello, after 28yrs 3mo active duty and almost 5yrs defense contracting in the middle east I am leaving in less than 2 weeks to live in the Philippines where my wife and 5 year old triplets are.  I also have property in USA but will stay out the tax year there and occasionally return to USA till ready to move back to USA in a year or so.  Have been following otherpower for a long time now and have the book in storage in USA so bought Hugh's metric kindle edition for reference.  Have solar that will need to be hooked up upon arrival to the Philippines.  When a typhoon hit last year people could not charge cell phones and laptops for about a week with no electricity. So, to make my first contraption would like to make some exercise bikes attached to axial flux alternators.  I have a Philippine born 2nd generation Chinese friend who owns a hardware store and imports so will have connections for getting the magnets.  See a couple possibilities.  Option 'A' would be to source 2" x 1" x 1/2" magnets and build Hugh's design from the Kindle book.  I was on Magnet4less and shipping is not an option overseas but see two types of which one has alot more protective coating on it and black colored, a very nice looking and affordable magnet.  Option 'B' seems to be the wedge or trapezoidal magnets that are 14" OD and 8" ID and possibly a smaller generator but also possibly could have other benefits such as lower RPM.  Option 'C' could be to buy a premade alternator out of China and build some bikes from them in the Philippines.  Here is an interesting possibility on Alibaba that I am waiting on a price response from.  They look to be made for VAWT and 250w at low RPM

http://www.alibaba.com/product-detail/200W-350rpm-Axial-Flux-Permanent-Magnet_1784769276.html?spm=a2700.7724857.35.1.qgkL0i   

  My intention is to get my workshop and makerspace going there soon. Already have different types of welding machines and woodworking equipment on the property and access to machine services is low cost there.
  It sure would be nice to make several of these as a first project.  Would be very thankful for advice.

Best regards,
Mike
« Last Edit: July 02, 2015, 06:19:27 PM by HomeBrewer »

Flux

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Re: Newbie help with bike axial flux generator
« Reply #1 on: July 03, 2015, 03:59:05 AM »
Good luck with the project. For exercise bikes the quality of magnet protection is not so important as for a wind turbine but if the better magnet is not excessively more expensive, then quality in one area may be a reflection of better manufacture. 

I don't have much experience of this type of thing but I would look at it a bit differently from a wind generator For wind you need some inherent inefficiency to match the blades. If I have to pedal something I would like the highest possible efficiency.

You may have to do a bit of experimenting or research on the energy source, it is just as important to match the man in this case as it to match the blades on a turbine.

You can get the speed range you want by altering the winding ( number of turns) or you can play with chain drives. I certainly would want to keep the alternator speed fairly high and use a chain drive than wind with lots of turns for direct drive.

Your sustained power will not be high but keeping the alternator up to something like 500 rpm will get you a decent efficiency.

How a man reacts to change of speed to load I have no idea but I have a strong suspicion that a choice of gear ratio will be needed unless you always want to work flat out.

My personal feeling is that using a buck converter would let you get the best power match easily. At the power levels involved it will be much simpler and cheaper than for wind ( you won't need a Classic and small off the shelf converters ought to be available )

Done properly I suspect you could manage to maintain an overall efficiency of over 80%. If I had to pedal it I would be reluctant to throw half the energy away.

Flux

electrondady1

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Re: Newbie help with bike axial flux generator
« Reply #2 on: July 03, 2015, 08:43:26 AM »
i had a heart attack last year and i am supposed to be doing cardio exercise. i don't like the idea of an exercise bike but have been thinking of building a kind of stand for a regular bike that would allow me to pedal indoors and  that would produce electricity. but still allow me to go for a bike ride outdoors when i wanted to. your post has made me think it  would work for an emergency power source as well .

« Last Edit: July 03, 2015, 08:48:36 AM by electrondady1 »

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #3 on: July 03, 2015, 03:52:32 PM »
Hi Flux and Electrondaddy1,  thanks for the responses.  This gentleman did a fine job using one of Hugh's alternator designs.  Here is his web page and also link to his article in Mother Earth News:

http://www.gulland.ca/homenergy/lindabike.htm
http://www.motherearthnews.com/renewable-energy/pedal-powered-generators-zmaz08onzgoe.aspx

  This gent has a professional unit that is very nice as a DIY kit for 850 USD.  His grid tie inverter is the same as what is on Amazon and the efficiency has been documented to not be high as seen in Amazon reviews.  In the review the mfg stated the better than 90% efficiency was "theoretical".

http://www.thegreenmicrogym.com/the-story-of-the-upcycle-eco-charger/bicycle-generator-diy-kit/

  This guy used a bicycle hub on his axial flux alternator and two sawblades.  It likely is not optimal construction and may have all sorts of problems like blade warping?  think and one would need to be protected from a saw blade biting into flesh but it nevertheless is an idea.

  Not to change the topic too much but I am a big rower and have been thinking of making a homebrew rowing machine as well after seeing the over two times mark up in the Philippines for new units.  It would be alot of fun to open a gym using the bikes and rowers powering axial flux alternators.

https://m.youtube.com/watch?v=l4r1VgPFF70

  I agree with the idea of using the bicycle chain drive in a multiple speed bike but that of course drives up price while making it easier to match people to load requirement.

  I have a midnight classic charge controller for my panels currently so was thinking to start with a 24vdc design and optionally make a 12vdc design for a standalone charging station.  I will likely be buying a second midnight classic. 

    Maybe a good design is to use an axial flux alternator on a side stand and it's own bearing then have a new/longer shaft to couple the bike hub into the alternator stand to simplify things?

  I am very very serious about this project and my biggest decision is hiw to source the magnets and get them there.

Best regards,
Mike


Flux

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Re: Newbie help with bike axial flux generator
« Reply #4 on: July 03, 2015, 05:09:20 PM »
Thanks for the link, that is a nice design and probably on the lines I would have tried. I think the quoted output is good proof that when done properly the output can be useful.  There may be far cheaper ways to just get exercise but if the intention is to produce useful power then the axial alternator properly matched will be hard to beat. If you can include the classic then you can keep the efficiency right up and a fixed single chain drive may be good enough. Connecting lead resistance is not an issue here but starting with a good alternator speed will let you minimise the winding I^2R loss. There is no iron loss so you may get close on 90% efficiency.

To get the best possible you may even have to start thinking about windage losses, stator heating is not going to be an issue so smooth magnet castings with little fanning effect should be a good idea. Also keep any metal well clear of the magnet leakage field to avoid any eddy loss. All metal is bad so just avoiding ferrous is not the answer.

This certainly looks to be an excellent starting point.

Flux

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #5 on: July 03, 2015, 06:05:10 PM »
Hi Flux,

  You mentioned keeping metal away from the flux lines.  Unfortunately I have zero experience in actually making one yet but I am an electronics guy by trade for 33 years and have alot of mechanical skills and welding equipment as well.  I saw the design of an axial flux alternator on a stand that is metal.  Would you be wiling to do a little "elmering" as the HAM radio operators call it and tell me more about distances to keep the metal away and maybe some examples to?  It is starting to sound like I need to make one of the smaller designs that use the 2x1x1/2" magnets as they are very affordable and it is a proven design like the gent in the link did.  If I made a stand on the left side of the bike then just maybe I could take my existing bike, remove the tire using the quick release and set it on the stand with a sprocket built into the stand.  This would save the bike for future use and not make it single purpose.

Best regards,
Mike

Flux

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Re: Newbie help with bike axial flux generator
« Reply #6 on: July 04, 2015, 02:37:38 AM »
The place you need to watch is where the magnets sit on the discs, there should be no flux on the discs if they are thick enough but on the edges of the discs you will get some flux fringing from the stator gap. For wind turbine use, keeping things over 1" from this region is good enough but if you are trying to minimise all losses perhaps 2" would be better. In the picture it looked as though there were some metal parts that may be having a small effect.

I tend to agree that the common magnet blocks are the best value for money as demand dictates the price, some of the wedge shapes come out very expensive and it is often possible to use more of the cheaper rectangular blocks to get the same result.

I think the 2 x 1 x 1/2 magnet design should be more than adequate here. By mounting the alternator to one side where you are not crammed in between the back forks I think it will be easier to avoid the flux leakage regions, although it will not look as pretty as the design shown. If the attachment is quick and easy then dual purpose sounds ideal.

Flux

hiker

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Re: Newbie help with bike axial flux generator
« Reply #7 on: July 04, 2015, 03:25:57 AM »
Built a few bike gens--try this link--go to YouTube.com. And enter--hiker71453- on  their search bar--should be a few of my old pedgens their..might give you a few ideas..
WILD in ALASKA

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Re: Newbie help with bike axial flux generator
« Reply #8 on: July 04, 2015, 12:22:19 PM »
Hiker,

  I looked with your search on youtube.com....no joy.  Maybe you can send a link.  I am actively looking at using the 2x1x1/2 magnets but was surprised to see the 2f smashbooks ebook from Hugh was using the ferrite type that is impervious to corrosion and tempting. My first how to book with plans for an axial flux generator I think used the same type of magnet.  That big yellow book cost me alot of money to ship directly from New Zealand in 1998 and to my knowledge was the first axial flux alternator plans (1kw) even before Hugh was doing them.  Unfortunately, that book was destroyed by a burst water pipe.  It was a collector type book IMHO.

Best regards,
Mike

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #9 on: July 04, 2015, 05:55:34 PM »
Hi again,  I found this amazing post on ferrite magnet alternators. 

http://www.fieldlines.com/index.php/topic,145700.0.html

  Hugh posted on it and man does he know his stuff.  The ferrites are a small fraction of the cost of the neos and this is what I need if several are to be made.  Looked on Alibaba and there are several sources for them.  With an alternator off to the side of the bike the larger size of the magnets could easily be accomodated and with a simple shroud over the alternator all would be safe. 

Best regards,
Mike

electrondady1

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Re: Newbie help with bike axial flux generator
« Reply #10 on: July 05, 2015, 09:21:06 AM »
there have been quite a few posting about bike driven generators over the years.
 if i can remember correctly humans can only put out about 100 watts maximum for any length of time.
  i would think you could do a ferrite mag  based alt. that would do the job and it would be much more economical.
« Last Edit: July 05, 2015, 09:29:59 AM by electrondady1 »

electrondady1

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Re: Newbie help with bike axial flux generator
« Reply #11 on: July 05, 2015, 09:53:06 AM »
in using ferrite magnets, much thinner iron rotors can be used to contain the flux. i used cheap 10" table saw blades for backing on ferrite mags. worked fine .

with all the gears involved and a big bike wheel as a driver you could get quite revy with the alternator. allowing  you to use less mag and less copper

 you are  developing  a product for commercial use so you will need to  experiment to find the optimum set up.   
 

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #12 on: July 05, 2015, 10:06:50 AM »
Electrondaddy1,

  So you are suggesting that the bike be left entirely intact and the rubber tire drive the alternator for higher speed to increase speed?  I was stuck on the idea of not using the rear tire at all and removing it while generating electricity with the generator likely to the side.

Best regards,
Mike

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #13 on: July 05, 2015, 11:04:58 AM »
electondaddy1, I know cost is everything for this but I am hesitant to use saw blades and have to wonder if it is a cheaper material cost to just use 1/4 or 5/8" (6mm in the f2 hugh design)?  Have seen some posts while studying and one where you talked about measuring leakage flux on the back side of sawblades but think that is with neos.  Doubling saw blades may be a good alternative for used blades but think maybe not with new construction.  With ferrites the whole thing is going to be too thick to mount in place of a tire and likely needs to go to the side anyways.  In order to get 100 watts at the lower RPM's it seems like a 400 watt alternator like the 2f would work but getting a higher RPM seems to be the trick with ferrite alternotors.
 
  However,  I may be 100 percent off on all assumptions so would appreciate any schooling on the best approach even if that means using sawblades and a different scheme to get RPM's higher.
 
  Looking on Amazon I see some belt and tire driven ideas but they don't appear to be heavy duty and long lasting at first glance.

  Cost is monumentally important so any schooling is appreciated.  Cost is what appears to be keeping these from being mainstream in the first place.   Ability to use the bike for regular use is also important.

Best regards,
Mike

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #14 on: July 05, 2015, 11:51:15 AM »
Hello all,  Just did some cost comparisons on steel rotor costs (in USA).  One website had 1/4"x4'x8' sheets at $205 making a material cost under $10 each 12" diameter rotor for the steel. I am assuming use of a plasma cutter with a round jig would be fine for use.  After reading Hugh say he is experimenting with galvanized coatings I looked at G90 1/8" thick 36" x 36" at $75 per piece which is even cheaper.  Cutting galvanized with a plasma cutter is certainly something to do in the open air is my assumption and may require special respirator so would have to look into that or maybe someone has a better idea for that (maybe 12" squares that are somehow cut into circles but don't know how).  It looks like the sheet steel is cheaper and I am assuming better than saw blades unless given used ones for free on a very limited basis.  Question, is 1/8" galvanized suffient for rotors on an f2 design using ferrites or not stiff enough and thick enough?  Seemed thicker than 1/8" galvanized is not as common.

Best regards,
Mike

hiker

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Re: Newbie help with bike axial flux generator
« Reply #15 on: July 05, 2015, 08:12:06 PM »
http://youtu.be/1JOOGBqNd4c    test...cant seem to find my pedgen fliles..so heres a old one - on how i build my gens...works great--thats a plywood stator with holes cut out for the coils -then their epoxyed down..simple design -but holds up to a lot of strong wind...any ?  just drop a e mail...my regular isp is down--and i hate using a cell phone..so might be a bit slow on return.............have fun
WILD in ALASKA

hiker

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Re: Newbie help with bike axial flux generator
« Reply #16 on: July 05, 2015, 08:32:01 PM »
WILD in ALASKA

hiker

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Re: Newbie help with bike axial flux generator
« Reply #17 on: July 05, 2015, 08:43:06 PM »
few picts on the build.....
WILD in ALASKA

electrondady1

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Re: Newbie help with bike axial flux generator
« Reply #18 on: July 06, 2015, 08:53:23 AM »
product design is what is studied in school. what ever i learned about producing electricity i learned right here at otherpower listening to guys like flux, hiker, Hugh and the Dans.

you have to figure out your market.
 I'm thinking a lot of people in the Philippines already have bikes .
so build a bike stand with an alternator attached.
you need a clamp at the front to lock it in and some rollers at the back that the drive wheel can sit on and the rollers can transfer the rotation to the alternator.
maybe the drive wheel sits on the alternator itself .









Flux

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Re: Newbie help with bike axial flux generator
« Reply #19 on: July 06, 2015, 03:26:03 PM »
I am not sure whether this is a commercial venture or a project to make a few efficient machines for producing power.

If a commercial venture the requirements are quite different and absolute efficiency will not get you a viable product you will have to compromise.

For this application I see no concern about the life of neos, there is an issue with wind turbines in hostile climates.

If total efficiency is the aim then ferrite will be a challenge, the alternator will be bigger for the same output and considerably bigger to keep a similar efficiency. You will need to go for higher speed and consider the windage issue.

For direct charging with wind turbines you can't use a high overall alternator efficiency and that makes ferrite more attractive.

Everyone to their own choice but if you have a plasma cutter I wouldn't give saw blades a second thought, just stick to mild steel.

Much depends on the magnet cost in your area and the ease of getting them.

Flux

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Re: Newbie help with bike axial flux generator
« Reply #20 on: July 06, 2015, 04:32:36 PM »
Everyone,  thanks for the help so far.  Yes a plasma cutter would be nice and an older lincoln capable of doing the job but thinking to buy a hypertherm.  The model 65 would lead to a probable need for a generator to go with it.  A CNC table would be the ultimate but I saw this device called "the ultimate plasma jig" that cuts circles and has different models for different amperage 75 degree handles and is 80 bucks.  I think I am going to give them a call as this may be all I need along with the plasma cutter

http://www.ultimateplasmajig.com/Model-II.html

  To answer the question about it being commercial, it is both.  I would like to make some for my house, for sell, and potentially for a green gym in the city. 

  I am currently thinking a couple variations may be the best bet so it may be used with existing bicycle or a variation that is stand alone as a pedgen exrecise bike.  Hugh stated the efficiency of the 2f in an email after I asked him.  He said 80 percent efficiency and 100 watts at 240 RPM and 99 percent at 400 RPM.  Have emailed a bunch of magnet sources out of China and still researching so more to follow.  NEO is going to give the low RPM efficiency.  The one manufacturer actually adds weights to their alternator to make it act as a flywheel so alternator weight is a non issue from a pedaling perspective it seems.  Thanks again everyone.

Mike

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #21 on: July 06, 2015, 05:21:21 PM »
Big typo, 90 percent at 400 rpm stated on the 2f

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #22 on: July 07, 2015, 03:04:23 AM »
Hello all,  i received a quote for the c8 magnets from a recommended supplier for the 2f design.  This is in quantity but the price is 36 cents each before shipping.  I only received 1 quote at just under 4 dollars for 2x1x1/2 n42 nickel plated neos (i think that was for 1k pieces at $3.92ea from memory) but am waiting for more.  Really big price difference.  That is $8.64 for 24 magnets for a 2f design before shipping to the philippines in quantity. 

Best regards,
Mike

Bruce S

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Re: Newbie help with bike axial flux generator
« Reply #23 on: July 07, 2015, 09:09:09 AM »
HomeBrewer;
I've read with intertest, and NOW must ask. ;D
Which city on which island?
A fellow poster here and I had a wonderful travel and time in the Banaue region!
The Mall of China was MASSIVE!
Bruce S
A kind word often goes unsaid BUT never goes unheard

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #24 on: July 08, 2015, 07:50:28 PM »
Hi Bruce,

  About 15 minutes outside Batangas City, The capitol of the Province Batangas on the southern part of the main island Luzon.  Beautiful American style house with a large pool and a slide that I have counted 11 children going down at the same time on.  Two poeces of property connected at the corner.  Back property is 1/2 hectare (5000 square meters or 1.2 acres) that has a small house on it and a Kubo.  Property off the road is 1700 square meters with the big house, pool, and other stuff.  Was thinking to put a 90 ft tower for HAM radio but maybe next year.  Have no idea what wind potential is but think there likely isn't any.  Plenty of solar panels however.

Mike

HomeBrewer

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Re: Newbie help with bike axial flux generator
« Reply #25 on: July 10, 2015, 01:46:59 PM »
Have a couple questions after looking at some of Hugh's 350 watt design.  It has two rotor plates but only 1 of them has magnets.  If the rotor plate without magnets is stationary this will not make a difference correct?  Is there a drop in efficiency with this design?  Lastly, has anyone built or know how many RPM's for 100w out?  His 2f design gets 100w at 240rpm which is ideal.  Best regards, Mike

hiker

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Re: Newbie help with bike axial flux generator
« Reply #26 on: July 10, 2015, 04:46:53 PM »
It needs to spin as well--other wise it will create some drag..the mags interact with a sat, disk,,have you thought about using a treadmill motor as a gem,,they work out great on a pedgen,,or you just like the idea of building your own ?
WILD in ALASKA

Flux

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Re: Newbie help with bike axial flux generator
« Reply #27 on: July 10, 2015, 05:30:27 PM »
Yes both steel discs need to spin otherwise the thing will be virtually an eddy current brake, you will get the exercise bit of the deal ok but the electrical production will be very poor.

Hugh tends to use standard readily available magnets and in some cases this works out with magnets on one disc only. It has little effect on efficiency as long as the blank disc spins. It does need a thinner stator and the mechanical gaps needed for clearance become a more significant part of the useful space. It lets you use magnets available rather than getting specials at higher cost but life is probably simpler with the conventional design with magnets on both rotors.

The designs are near enough that you can use the wind turbine stator but for this application, unless you use a buck converter you will be better off with higher rotational speed and less turns of thicker wire on the stator.

You are not faced with matching turbine blades so aim for a speed somewhere over 500 rpm to reach 12v and gear to suit. Keeping the speed up will give you higher efficiency or will let you use less magnets for the same efficiency. Although the 2F will get you 100w at 240 rpm, running it with a stator of half the number of turns and twice csa of wire will get you a lot better results for this use. It would not be a good option for a wind turbine but this application is different.

For commercial pedgens treadmill and various servo motors will work fine but for your own use where you value the electricity the ironless axial flux alternator will get you a higher efficiency.

Flux


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Re: Newbie help with bike axial flux generator
« Reply #28 on: July 15, 2015, 09:20:39 AM »
Everyone, thanks again.  I continue to work this project and have been working on a partnership with a spin bike factory in China but discussions are still ongoing. Have a question, there is a guy who is selling them on the internet for 850 dollars for just the alternator.  Looking at his product it is nothing more than an electric bike hub motor with zip tied weights.  I am not so sure about the safety behind zip tying weights with plastic zip ties but maybe that can hold to the centrifical forces without a problem.  I can see the hub motors on the internet for as little as $200 and higher in price. they look to me to be similar construction to those Australian washing machine motors people convert to turbine alternators.  I never paid much attention but remember seeing somewhere a listing of potential problems using them.  Found this picture of a disassembled bike hub motor so am asking the crew here about comments regarding use of one of these.  I think it is cheaper to use an axial flux that I make but want to ask opinions based upon the pic in the link

https://www.electricbike.com/wp-content/flagallery/hub-motors/leafmotorinside.jpg

Best regards,
Mike

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Re: Newbie help with bike axial flux generator
« Reply #29 on: July 15, 2015, 09:26:23 AM »
Just found another link and it is identical looking to the one that has everything except the weights (motor plus hub) selling form$148

http://www.leafmotor.com/hub-motor.html

Best regards,
Mike

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Re: Newbie help with bike axial flux generator
« Reply #30 on: July 15, 2015, 10:16:41 AM »
Ok, need to slow down before posting.  These motors are definitely not matched for 100w output of a human as efficiency is low on both the bldc hubs and brushless pm hubs like the picture sent.  They have links for performance data on each type of motor and they all look dismal at 100w output.  I have heard that the neos when properly designed are 90% efficient at target torque and RPM.  I was told Hugh's 2f ferrite design is 100w at 240rpm and 80 percent there climbing to 90% at 400rpm.

Best regards,
Mike

hiker

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Re: Newbie help with bike axial flux generator
« Reply #31 on: July 16, 2015, 12:55:27 PM »
ceiling fan motors work out ,,,if it's just a 100 watts you need,,their easy to rewire,,toss some neo mags on,,or  if you don't care to rewire,,use the stock windings and just use a battery charger hooked up to it for power out,,,,then just toss a flat belt on it  and the wheel on the exercise bike,,,real simple,,
WILD in ALASKA

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Re: Newbie help with bike axial flux generator
« Reply #32 on: July 20, 2015, 07:35:04 AM »
Hello everyone.  I ordered some ferrite C8 magnets 50mmX50mmX20mm for Hugh's 2F design and experimenting.  I paid also for nickel 2"x1"x1/2" N42 neos from same supplier.  Then I paid for nickel plated 2x1x1/2 from a different supplier who has since emailed me wanting to substitute zinc coated for nickel.  Looking through the threads I can see that zinc coated "doesn't really stick and forms a shell" that can peel off if cracked and many mention of the pitfalls of nickel coating.  It seems nickel coating is the way to go.  Should I email back and tell this person to absolutely not sell me the zinc and I'm willing to wait for the nickel?  Lot's of different subject on the threads about painting/preserving rotors, not to use polyester resin, and super glue not working well for glueing magnets in place but nothing I've found stating to use nickel as the only coating.

Best regards,
Mike