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magnet rotor
By windspeed, Section Wind Posted on Fri Aug 15th, 2008 at 08:44:41 PM MST
flaking paint

I live near the sea in a very corosive enviroment ...........moist conditions
I notice on my magnet rotor the paint is flaking away from the surface where the magnets are almost flush with the surface can moisture get between the magnets and the epoxy
will the nickle plating rust or will the moisture make its way into the steel plate and start to rust
windspehed

magnet rotor | 16 comments (16 topical, 0 editorial)

Re: magnet rotor (3.00 / 0) (#1)
by tecker on Fri Aug 15th, 2008 at 03:17:40 PM MST
(User Info)

I assume your talking about an axial rotor the answers are yes , yes , yes The nickel varies but won't take much stress another sanding and good coat of paint is in order . But you have to do the maintenance . Sooo maybe someone will suggest a brand for you that has a good track record in Marine environments get er done.

Re: magnet rotor (3.00 / 0) (#2)
by Dave B on Fri Aug 15th, 2008 at 06:24:37 PM MST
(User Info) http://www.madbbs.com/users/bruggelog

Windspeed,
Just a comment and suggestion if you were to make another machine. Others may agree, some will not but I have found that the magnets do not have to be fully cast to or near their thickness if properly adhered to the rotors.

A quality epoxy adhesive very thin on the back and then maybe gussets along the edges with chopped glass added is plenty if using Neos. Sure this will not look as nice but it also allows for better cooling with the magnets acting to swirl the wind around a bit.

The old thinking that casting was necessary was brought on by using "bondo" fiberglass in an attempt to secure the magnets. As many unfortunately found out, bondo is not an adhesive and cracks very easily besides. Magnet adhesion problems were brought on by cracking of the bondo and water getting in and under the magnets then corrosion setting in.

The current process now indicated is to use super glue to secure the magnets into position before casting with the now tried and true Epoxy adhesive with chopped fiberglass as a casting. Full casting and now banding being used also looks nice but the thicker the casting the more water can be held if any cracking ocurrs. I believe others who originally "glued" their magnets on with the proper preperation and adhesive may not have experienced the problems originally associated with the "bondo" and casting method to secure the magnets from moving.

I hope you are not into a loosing maintenance battle with cracking, water and corrosion. Rotors constantly flex, to me the less on there the better. Dave B.

Re: magnet rotor (3.00 / 0) (#3)
by wdyasq on Fri Aug 15th, 2008 at 09:08:55 PM MST
(User Info)

I will agree with Dave on this with the exception of using <s>'Stupid Glue'<s> oops Super-Glue as I don't think much if the stuff. I will recommend abrade, clean, degrease and use a small bit of epoxy to attach the magnets. Then apply the light layer and fillet around the magnets.

GOOD epoxy seldom comes in small tubes. The bes commonly available are 'Boatbuilders epoxy' and can usually be purchased in units about a quart in size and up. Each has their favorite 'brand'. I have used WEST, System3 and MAS and any of those work well.

Ron
Adventure is just bad planning." -- Roald Amundsen
[ Parent ]

Re: magnet rotor (3.00 / 0) (#4)
by Flux on Sat Aug 16th, 2008 at 01:34:16 AM MST
(User Info)

Yes this is a problem in damp areas especially near the coast with sea air.

Not sure what the original construction was or whether you potted the magnets. I don't trust the nickel coating alone under these conditions. The steel/nickel interface is even more of a problem.

I am inclined to think that for this sort of environment galvanising of the steel discs is the way to go.

Regarding the other factors I agree with DaveB and I agree with Ron that superglue is one of the things best forgotten, It sticks paper but other things do as well. I see no use for it in this field.

I believe Hugh has had some luck with some form of bitumen/epoxy paint and that may be a way of keeping the problem in check with what you have got to deal with.

If you can satisfactorily protect the magnets without completely potting them I go along with it but potting may give better protection in the long run under these conditions. If you pot with satisfactory material I see no need for the stainless band round the outside but that is an individual choice. My concern is corrosion not magnets falling off.

Flux

[ Parent ]

Re: magnet rotor (3.00 / 0) (#5)
by Dave B on Sat Aug 16th, 2008 at 03:02:13 AM MST
(User Info) http://www.madbbs.com/users/bruggelog

If I'm not mistaken I think (they) are using the super glue to just tack and hold the magnets in position until they can be secured with epoxy adhesive and chopped fiberglass surrounding them. The extra banding idea now again stems from the past when it became very obvious that bondo was not an adhesive.

If the magnets were mounted flush to the edge of the rotors (as many still are) there was no way then (if bondo or similar was used) to keep the magnets from being thrown or at least kept from moving as there is tremendous torque on these trying to break them free.

Bottom line is still the same, the magnets need to be secured to the rotors in such a way that they can take the temperature changes, flexing of the rotors and constant torque trying to rip them sideways and still remain as one with the rotors. Dave B.

[ Parent ]

Re: magnet rotor (3.00 / 0) (#6)
by tecker on Sat Aug 16th, 2008 at 08:18:40 AM MST
(User Info)

One of the problems is getting a brand of metal epoxy that has no metal and other filler ,for the initial stick down . The ferrous material migrates away from the magnet surface to the magnet sides . I think some one suggested Golfsmiths shafting epoxy some time ago .I tried if and it sticks to clean metal well seems to do better with the surface scuffed up Very sticky stuff takes a little time to dry. I can't see not encapsulating the mags the rotors really need to be smooth to keep the weather and other bs from that area. There' not much that is fly around that sticks to the mags but weather will take a toll . As far as paint goes I have'nt found anything other than urethane or two part epoxy that works with an unsanded surface ( you cant' really sand the rotors once they're assembled ) . I have rotors running above 5000 rpm for long periods using super glue for the tack down encapsulated in epoxy and a steel band with no problems and I have had rotors crash from loose mags just sticking them down. The other thing that's neat with a band is it provides a ready mold and very little cleanup.

Re: magnet rotor (3.00 / 0) (#7)
by vawtman (vawtman(at)charter(dot)net) on Sat Aug 16th, 2008 at 09:13:51 AM MST
(User Info)

Hi Teck

That was me.

In the clubmaking business it's a practice to prepare the shaft properly.The shaft is rough sanded and small divots are created using a center punch.

My rotor is cast iron and allowed to surface rust and each mag spot is center punched multiple times.The mags are sanded with 40g paper.

I switched to this: http://www.fieldlines.com/story/2008/7/27/204224/519

Then the plan is a one part ureathane caulk around the perimeter of the mag and thats it with no potting.The ureathane would work for mags but takes a week to cure.

To windspeed:
Hugh did a posting about corrosion problems he had.If you didn't read it i could bring it up for ya.

Mark

[ Parent ]

Re: magnet rotor (3.00 / 0) (#8)
by windspeed on Sat Aug 16th, 2008 at 09:46:52 AM MST
(User Info)

thanks alot fellas
I did stick down the mags with an industrial super glue
and put strips of glass fibre right around the pirimeter
then potted over the mags with west epoxy
I suspect the coating over the mags was very light I think this is a weak spot (a case for not potting fully)
I gave it 3 spray coats of cellulose auto paint over an auto udercoat
have not had any trouble yet but I think the moisture might get in
Windspeed

[ Parent ]

Re: magnet rotor (3.00 / 0) (#10)
by vawtman (vawtman(at)charter(dot)net) on Sat Aug 16th, 2008 at 02:53:32 PM MST
(User Info)

Any pics?Always a good thing.

[ Parent ]

Re: magnet rotor (3.00 / 0) (#9)
by tecker on Sat Aug 16th, 2008 at 02:53:22 PM MST
(User Info)

Man I could use some Popsicle sticks. I take more than my share of coffee stirs at my coffee stop mornins and they're gettin wise to me . If I stop now I 'll be out of stirs by May 2010 but they break so easy Popsicle sticks are far superior . Hook me up
if you can if you can't give me your source so I can avoid a possible line up[].

[ Parent ]

Re: magnet rotor (3.00 / 0) (#12)
by vawtman (vawtman(at)charter(dot)net) on Sun Aug 17th, 2008 at 06:22:50 AM MST
(User Info)

Do you have a Wall Mart in your area?They should be in the craft dept.

[ Parent ]

Re: magnet rotor (3.00 / 0) (#13)
by tecker on Sun Aug 17th, 2008 at 06:25:44 AM MST
(User Info)

OK I'll look

[ Parent ]

Re: magnet rotor (3.00 / 0) (#11)
by bob golding (photoman290 at yahoo dot com) on Sat Aug 16th, 2008 at 05:41:25 PM MST
(User Info)

hi i also live in a marine environment with lots of rain. i just paint my rotors with hammerite primer. hammerite is a UK brand but i am sure there is a equivalent US product. my magnets have got rusty over 3 years but are still working ok. i don't think you can avoid rusting in this sort of environment unless you completely seal the rotor somehow. i just live with it and do what i can when i take the turbine down for servicing. the nickel
plating came off after a very short time. maybe the epoxy coated magnets might last longer,but everything made of iron or steel rusts around here eventually. just had to scrap yet another van due to rust!!!

cheers
bob golding

Re: magnet rotor (3.00 / 0) (#14)
by scoraigwind (magnet@scoraigwind.co.uk) on Sun Aug 17th, 2008 at 04:02:13 PM MST
(User Info) http://www.scoraigwind.co.uk

If you plan to glue magnets to the disks and rely on the glue alone, then you need something a bit special such as Araldite 2021 methacrylate adhesive in 2-part cartridges. It needs to be tough and flexible. Epoxy is not really ideal.

I like to fully encapsulate the magnets and I use polyester or lately vinyl ester for this. To give strength I like to put a sheet of glass cloth over the magnet faces. I would not recommend bondo at all and never have.

Hammerite looks nice for a little while and then peels and harbours water to enhance and accelerate rusting.

I do find that epoxy bitumen paint is better but I still worry about rusting of the magnet rotors and the magnets themselves corroding. I no longer worry about magnet flying off since that has been a non-issue for me since I started encapsulating the magnets in resin.
Hugh Piggott http://www.scoraigwind.co.uk

Re: magnet rotor (3.00 / 0) (#15)
by dashting (mshtingATyahoo etc.) on Sun Aug 17th, 2008 at 07:04:13 PM MST
(User Info)

I am on the coast too and just experienced rotor magnet adhesion failure due to corrosion also. I think my stator is going to be ok but I am unsure if I can reuse the mags and what to paint them with. Any suggestions? And what surface prep can I give the rusted magnets without destroying them?

Re: magnet rotor (3.00 / 0) (#16)
by bob golding (photoman290 at yahoo dot com) on Mon Aug 18th, 2008 at 09:56:05 AM MST
(User Info)

hi all,
i was thinking of trying this stuff.
http://www.isoflex.ie/prodshowind.asp?groupID=0&prodid=94&groupname=Isoflex%20High%20Perform ance%20Liquid%20Rubber&intext=int
i know it works on flat roofs and skylights. they do a primer as well for extra flexable surfaces.
Hugh, it was the hammerite primer i was refering to not the normal hammerite. it does not seem to flake so much. just waiting for my field to dry out enough to get the turbine down. at the moment it is far too wet to get the truck onto it.

cheers
bob golding

magnet rotor | 16 comments (16 topical, 0 editorial)

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