Steel or Iron

[thumbnail101]

Just wondering the steel disc people are useing

for there windmill, would cast iron be better

for the disc???

[nick02]

I would think steel because cast iron is heavy as hell and magnets love to stick to it. You cant pry neo's off cast iron (well maybe you can)

[Psycogeek]

cast iron is that the stuff that breaks

strips out threads, and causes people heck

acts like pot metal when in cheapo products

what about the danger of "throw off" ?

what if a rock smashed into it while it was flying 600Rpms?

[Aelric]

Steel would most definatly be better.  Steel is an alloy of Carbon and Iron, with a few other elements if we are talking stainless steel :-)  I would think just 1/4" steel plate would be ok, Oxygen Acetylene cutting torch, (if you are a glutton for punishment a hacksaw and a few replacement blades) or better yet a CNC laser, with a little cad work a Laser could cut those parts lickety split.

[Jessum Dumguy]

If weights not a problem and a ( best possible )FLUX path is

your goal, Nickle Iron is probably the best blend.

But Psycogeek is right, Iron is ussually a B#$&@ to

deal with in it's stand alone castings. EASY to Turn on

a Lathe, EASY to drill holes in,Easy to Tap a thread Ect...

But Over tighten that bolt and you'll be cuss'in.

   But Iron has been used to make flywheels in the past so

the strength is there just don't expect super high rpm's.

Add Nickle to the equation at about a 50(Fe) - 48(Ni) with a

dash of this or that accounting for the remainder and

then you got something.  But be prepared to

Pay for it if you can find it.

Go here and search for Alloy 49 Nickle Iron.

http://www.matweb.com/index.asp?ckck=1

And if you go forward and acctually find someone that

makes and sells it in PLATE FORM, Post here and let me know.

I've since moved on and am looking at Steel now.

   Several of the Stainless Steel ALLOYs are low on the

magnetic spectrem do to low Iron Content and

by no means is ALL Stainless steel that magnetic.

I've got a 1/8 inch thick SS door Kick plate

( ie: The silver plate at the bottom of a resterants kitchen door ).

I can't get a NEO to stick to it in the vertical possition without GLUE.

Turns out it has a Iron content of less than 15%. GREAT if RUST is your worry.

On the other hand I dropped the same NEO in the home SS sink and

nearly broke my fingers getting the dam thing loose. So I really

had to wonder why my sink hasn't Rusted away.....

It's the quantities of those other elements that Aelric was

mentioning that makes the difference. So with that said,

Steel with a high (Fe)Iron content alloyied with STUFF like

Nickle(Ni), Manganese(Mn). As it turns out the

more corrossion resistant the Steel is, The less benificial to

the flux path.  So again it's a game of Trade-offs.

Then again a good enamel paint job could make up the difference.

Stainless Steels 410, 416, 430, 434. These seem the

best blend of iron content ( 80 to 85 %) with a fair resistance to

rust and structuraly sound for a fast spinning disk.

   I really can't coment on Carbon steels as I've found

little in the way of element contents for it.

I would imagine the same holds true about them aswell.

    As a SIDE NOTE to thumbnail101's original question,

I've kind of been wondering if a cast iron Ring embedded in

say an aluminum disk or SPOKED steel wheel might not work.

It's probably making more work for myself and I question the

possible benifit values of doing so. Dollars to Dougnuts kind of thing.

Hehe, Well thats my BOOK on the subject.

Sorry for being so Gabby, Cafine buzz....

.

[dconn]

I think the disk brakes are cast iron?  I'd say it would turn into a load of rust fairly quickly if you were by the sea - on that note its a pity that the rotors cant be stainless.

Derek

[kitno455]

i come from the automotive side of things, where cast iron (now cast Al) is considered a wondermetal. Brake disks are pretty much always cast, usually with a higher nickel content that most other things (engine blocks, diff cases, etc). This tends to give them better dimensional stability and fatigue resistance during heat cycling. Buick and Caddy cylinder heads and blocks are high nickel too, thats why they use induction hardened valve seats rather than inserts. they make good raw material.

whether you should use a iron rotor over a steel disk, is an entirely magnetic question, the strength of the rotors will be comperable with any kind of thickness. the cast iron is slightly lighter than steel (higher carbon content).

allan

[darde]

I have access to a lost foam foundary. They make lost foam castings of anything that you can make out of eps foam. I also have acces to a cnc router that I cut out parts for them to cast. How would this ductile iron work for a rotor.

[Aelric]

Personally I wouldn't use Iron as a rotor.  But like I said thats just me.  I justify this by the ammount of strain put on the props.  All the other components and even the hub for the props I would make of steel for its durability but the props, foam or wood or abs plastic.  Thats just a personal preference though hehehe

[Psycogeek]

i understand more now

i forgot that brake drums ARE a cast iron.

just not the same junk they made the engine blocks and other cheap cast iron stuff.

so i take back what i said, them rotors are pretty tough.

[redeyecow]

 I've been wondering about the possibility of stacking

sheet steel to get the desired thickness.  Maybe rivet

them together.  What about using old car body steel?  

 Would the lamination effect be a good thing or not?

 Alway's looking for way's to use my scrap cars for material.

[Ungrounded Lightning Rod]

Laminations are unnecessary on the rotors.  The magnetic field is not moving through the metal.  It just provides a return path for the steady-state field from the back of the magnets that are riding on them.

Laminations are to interrupt parasitic "eddy" currents in the magnetic pole pieces, reducing the losses that occur when they create drag and heat the pole metal, converting some of your mechanical power to waste heat.

If you got your sheet steel pieces smashed together REALLY CLOSE, so they didn't have little air (or paint) gaps for the mag field to jump, they'd do about as well as a solid piece.  Otherwise they'd do worse.

[Ungrounded Lightning Rod]

If your disk is thick enough to do a good job carrying the mag field it will be enormously stronger than is needed for the mechanical loads on it, regardless of whether it's steel or cast iron.  (It should NOT be stainless steel, which does not guide magnetic fields well.)

Cast iron is convenient because you can get brake rotors cheap, they're already the right shape and size for some designes, with holes in the right place, designed to mount on a very good (and cheap) standard bearing, can be easily made flat by standard brake-job tools, etc.  Cast iron rusts out somewhat faster than steel.  But brake drums are thick, so it will take a long time.  Also: you can epoxy-paint any of the exposed metal that isn't already buried in epoxy from mounting the magnets.  (No heat issues with the rotors.)

Steel is easier to work if you're having a rotor custom-made rather than recycling a used brake disk.

[kitno455]

hmm, ungrounded, i think you are closer on your second post here, the rotor most certainly carries the flux from the back of the magnet (unless i am missing something)

rotary laminations would seem to perform worse than solid, but you could use them if you had them. but unless you have old cars like me, you will be cutting alot of sheet steel to make any kind of thinkness. also, you are going to find that almost no surface on any car is completely flat, unless its a jeep

as far as strength is concerned, i dont think that anyone suggested that you mount the blades to the magnet rotors directly. cast iron does not take that kind of fatigue well enough. but for issues like foreign object contact, you could hit the average vented rotor with a sledge while it was turning, and its not going to fly apart at room temperature.

hot tip: ford suv's with rear disks often use a small drum brake inside the hat on the rotor as a parking brake. with those as your two rotors, if you cand find a way to keep the parking brake working, you could have automatic overspeed or manual lock down, inside the rotors.

allan

[nothing to lose]

I generaly shoot down all UFR's  if flying under 100FT above my property. Fresh Unidentified flying rocks are actaully rather good with oat meal in the mornings, adds a sort of crunch to it.

Actually I might think about the other things, but it's not a lawnmower blade so rocks aren't a very big worry for me.

 I think parts of my car and 1 ton truck (like around the brakes) are cast iron, so I don't much fear using it myself, though it is heavy.

As I think about it, the rear axle housing supporting the entire wieght of the 1 ton truck and everything I put on it is also cast iron. This take the force of everything and transfers it to the springs and tires, also holds the bearings and gears that drive the wheels hitting all those bumps.

I geuss I don't worry about cast iron much except for heating it for welding and the weight of it.

And I still preffer cast iron engine heads and blocks any day over these junk aluminum things.

[nothing to lose]

Clean well after turning, mount mags, epoxy, paint nicely. Should never rust if you do a good job. Remember you can't paint rotors for brakes, but a rotor as part of a gennie is not a brake and that you can paint easily.

[nothing to lose]

Basically I think a rotor should not be taking much strain itself. Depending on the type and how it is mounted, the strain should be on the mounts and bearings, the rotor itself just spinning along for the ride. If it can take the stress of driving down the road, it can take a windmill.