Concrete Stator

[loumart]

Hi all

Well I'm pleased with the way my genny is coming along thanks to this forum

I'm wanting to try different stators with my machine and hate the smaell of resins (I have a dodgy chest). I've been searching the board for an alternative (like a good few others) but haven't found anything.

I was wondering if concrete would be any good for a 6" stator. I'm not sure fot the pros and cons but I think it will be better for heat dissapation as its more thermally conductive than plastic! On the down side it will take much longer for the thing to 'cure' but is this the only downside?

Sorry if this has been asked before but I have searched the board for many hours and found nothing on concrete.

I look forward to hearing what you think about this before I go ahead and possibly waste wire.

Thanks in advance

Martin

[wdyasq]

Now snowcrow,

Postings get hijacked through evolution. This may be the first blatant, first post  hijack I have seen. Just WTH does a tail-flipping device have to do with a stator?

Please don't answer here - start a new post or preferably a diary, if you care to elaborate. I'm still wondering the use of your tail flipping device except to complicate things.

Ron

[Flux]

I have no idea if concrete stands any chance of working. I have doubts about the strength but with suitable reinforcing you may overcome that. I wonder about the hard abrasive surface against the wire and even more I worry about the corrosion of the wire itself as the enamel will almost certainly be damaged.

We did cast heavy copper braided cable into concrete supports for fault current limiting reactors, but that was far removed from fairly delicate coils. Be interesting to have the results if you wish to try it.  One of those silly ideas that may not be so daft in the end.

Flux

[electrondady1]

the idea has occurred to me from time to time.

(last week i poured a concrete floor)

Portland cement may not be a good starting point.

perhaps something more like plaster of paris

i believe there are a lot of different types of mortar compounds

perhaps the type used for glass blocks or ceramic tile grout.

you may have to experiment with the proportions of the additives

in order to get the properties you want.

[loumart]

Hi Flux

I've just been told by someone who sells cast concrete garden orniments that a mix of 3 parts peagravel, 2 parts sand(sharp) and 1 part cement will make a strong mix & should be ok. He says if you add PVA glue to the water before mixing then this will weatherproof it.

I've also found that you can add a special fiberglass to the concrete to prevent it from cracking (bottom of this page http://www.cfsnet.co.uk/acatalog/CFS_Catalogue_FILLERS_12.html). It may also add strength - I've sent them an email enquiring about this but havent had a reply yet.

You say you are worried about the corrosion of the wire - do you mean that the copper may react with the cement or the water?

I'm going to give it a go - I'm going to cast staors without the coils at first to get an idea of the strength etc. You never know - it may work!

Thanks

Martin

[spinningmagnets]

The mineral content in the sand and gravel may vary considerably. Might I suggest leaving out the gravel for now, and drawing a strong magnet through the sand before you mix it with the cement. Making one coil in whatever test mix you decide on should answer the question without wasting too much copper. You have a very original idea!

[Tritium]

You might try a non sanded poly blend grout. Been doing my kitchen floor and this stuff is very tenacious.

Thurmond

[loumart]

I've just been told that I will have to wait at least a week and preferably a month for the concrete to reach the desired strength I knew the cure time was long but I didn't think it was that long....

[TomW]

lou;

Yep, to get good strength you need to give it time to cure properly. There are different strengths of concrete also.

I always heard that curing submerged in water creates harder and tougher concrete, too, but never did any comparisons myself.

Cheers.

TomW

[Ungrounded Lightning Rod]

Possible issues with concrete:

 - It's strong in compression but not tension or shear.  You need to add something to reinforce it.  That something has to be non-conductive to avoid eddy current losses and non-magnetic (unless it's magnetically "soft") to avoid iron losses.  Fiberglass sounds good.

 - Concrete can be conductive - especially if it's wet.  You'll need to dry it out to avoid eddy current losses.  (The heat from generation resistive losses should do that, though.)

 - Concrete is strong but brittle so it can crack due to thermal stress.  Don't be surprised if it responds to rapid shifts from idling along to several minutes of heavy generation by cracking and then breaking up.  (Reenforcement should help with this.)  On the other hand, if it can handle going from a "cold soak" (i.e. let it sit and cool off to a low ambient temperature) followed by max generation (furling limit) for a half hour or so, it will probably survive for a long time in service.

 - Concrete needs to be kept moist while it cures - the reaction is driven by water.  Make sure your wiring can stand being wet for a month.

 - When fully cured it is NOT fully reacted.  Crack it and it tends to re-bond across the crack - healing if it's a micro-crack but rebonding at far from full strength if it's larger.  Grind it up and you can wet it and cast it again without re-slaking it (though it will be very much weaker than the first set.)  This means it contains reactive chemicals that may react with your wiring and its insulation, or serve as ions for galvanic corrosion.  So it's important to keep the wire COMPLETELY insulated from the concrete.  (It will also provide a conductive "solution" between your coils and the mounting bolts, again a galvanic corrosion issue due to the external electrical path between them.)

Still it's an interesting approach.

[GeeMac]

Hydrocal might work and it can be cast in a mold. It's similar to plaster of paris but much harder when it's cured. If you add pieces of coat hanger wire or something similar to the mix it might do the job.

[electronbaby]

what about mixtures of hydraulic cement?

[elvin1949]

TomW

 That is right.7 day's in water will give 90% of

maximum strength.It will continue to get stronger

for the next 100 yr's

 Concrete is alkyline so it may damage the insulation on the coil's.

 later

Elvin

 PS the fiber is fiberglass.Makes it a lot stronger.

40 lb's at Lowes is under 5 dollars

[scottsAI]

Hello loumart,

I find concrete an interesting idea.

Remember nothing conductive or magnetic should be in the mix other than the coils.

NO coat hangers.

Elvin1949 has it right, fiberglass concrete should be just right.

The package should give you cure times and strengths.

Do NOT worry about the total cure time. When it's strong enough use it.

Again people getting theory and practice confused.

Who cares if max strength has happened, it just needs to be strong enough.

The torque (power) is inflicted on the stator, must hold the coils in place.

We will let you do the experiment to show it works!-)

Have fun,

Scott.

[sk windpirate]

Hi

Their is a product called Grout. It comes in two kinds. AC is what i use. It can be mixed to a dough like formula. And pressed into the stator. it is a powder, like cement that you just add water and mix.

Or. It can be mixed to a soupy like mix and poured in the stator. it "cures" in 1 to 2 days. at temps of 50 to 70 F (in the shade).

It has no stones or gravel in it. It will not shrink or expand as it cures. I use it to finish concrete the was not vibrated properly. That leaves a honey comb that needs to be filled and finished. I use a rubber trowel to work it into the area. When dry it looks like concrete lasts like concrete. If you are looking for extra piece of mind, you could add fiberglass to it.

NOTE: It sets up quickly, (but it needs time to cure) so be ready to use it. If it gets to stiff water can be added.

I can see no reason that it would not wook.

[TheCasualTraveler]

Concrete for a stator? I wouldn't do it. Wouldn't even think it. It's a cracked stator waiting to happen.

Put your money and time into getting a good respirator if the fumes bother you.

Just my opinion.