Cost Effective Rotors

[brokengun]

A friend of mine helped me draw up some wind turbine rotors in Solidworks. These are the standard 12 inch diameter rotors used on the Dan's ten footer. I gave the drawings to a local machine shop and they gave me the following price quote:

$244.55 for the pair machined to +/- 0.010" or better

$158.21 for the pair cut on a plasma to +/-0.125 or better.

I thought $158 was a bit steep for rotors cut from a CNC plasma cutter (pretty rough from my understanding). Especially when Otherpower sells the completed metal work for their 10 foot turbine for $159.

Is this quote about on par with what other charge? Is there a more cost effective way to get relatively precise rotors? I was thinking I could mark them and cut with an air grinder then maybe smooth it out with a lathe. The rest of the holes could be done with a drill press. Does anyone have a recommended method for cutting these out that they have tried? Is it better to pay for some machine cut ones and shop around a bit?

Thanks!

[Perry1]

Wow, those are seriously gouge prices. Don't do it. send your drawings/IGES files to a couple different waterjet shops. I had to but finally got quotes for $50/disc. Still a little high but I was buying them one at a time so you don't get to amortize the programming costs over hundreds of parts.
To save money, don't have them tap the front rotor disc jacking holes. tap them yourself. i have the entire 10 footer in Solidworks as well.

perry

[Boss]

I had a blacksmith shop do a set for ours, they came out terrible,  We too have the solidworks files, next set are coming from "the Dans" They deserve every order we can send their way

[mbk]

Wwwdotshopwagnerdotcom has 12 inch steel disk 1/4 inch thick for 22.43 these maybe to thin but it's a good price. Someone from this site posted that lastyear I think .

[luv2weld]

You need to start thinking along different lines. Just because the plans in the book or online said
to use a 12 inch disc, waterjet cut, that does not mean you are locked into that.

To begin with, who says you can't use a square piece of metal for a rotor?? May not look cool, but who cares???
OK, you don't like the looks of it. So take a hacksaw or grinder and knock the corners off. There is nothing that says
the rotors have to be perfectly round down to a thousandth of an inch. As long as you can find the center and
balance it, Who Cares???

Use the discs referenced by mbk. You think they're too thin, then tack weld 2 of them together. You got a half inch
rotor plate!! For $45.

What about using a disc brake rotor??? I bought a couple of 12" rotors from the auto parts place for about $22 each.
That's brand new. Go to an auto salvage yard and they are probably cheaper.
They are already drilled to fit the hub and balanced. What more do you need?

The point here is to not get locked into using only what someone said to use. Yeah, it might make it very easy
to follow their instructions. But at a cost of hundreds of dollars.
Start thinking---"What else can I use to do this that doesn't cost a lot of money?"

How about going to a yard sale and buying an iron skillet for $2. Then go home and use a hacksaw or grinder
to cut the bottom out. You have a disc for a rotor.

Start thinking outside the box. Hell, cut the side out of the box and use it!!!!

Ralph

[bob golding]

i got 2 14 inch discs 3/8th  thick laser cut for  40 uk pounds including the cost of the  material. i just gave them the diameter and the size of the centre hole plus the pcd of the hub studs over the phone. you dont really need to do a drawing for something so simple. thats around 60 dollars.

[fabricator]

I had the rotors for my 17' machine lasered with all the holes for 90 bux for both, the cast iron skillet bottom would not work very well, cast iron is only mildly magnetic.

[jlt]

I had a local water jet cutter do my 15" rotors. he only charged me about 60 bucks for them, and that included making the holes to fit my hub and the metal.

[brokengun]

It's not so much that they do need to be round you guys are right on that one. I am just going for something that looks good as this machine might get used in an academic setting. Also if I end up doing bench tests I'd like like everything to be nicely put together so I know it's not going to fly apart or knock into something. It's really just preference I guess.

Anyways, I got another quote from a machine shop a couple hours away. They can do it for $55 a disc COD at a +/- .01 inch tolerance. So, I think I'll try for those guys.

[luv2weld]

OK, now I understand why it must be perfect.
For display and teaching purposes, you really don't want a pile of junk.

I don't want to hurt your feelings, but I don't think that is the best use of your money.
You are going to have $110 in 2 discs and nothing else.

Look at this link.

http://69.175.14.181/catalog/product_info.php?cPath=22_30&products_id=175&osCsid=4bfe09ba2e9f4bb8dd39b38b2af659b0


All of the flat metal pieces for just a few dollars more. Might be a better bargain. All of them water jet cut.

Ralph

[Dixie]

Prices for this sort of work can vary a lot.  If you want to go on the cheap... brake rotors really do work nicely and there's lots of nice big ones to be had for cheap that fit standard hubs.  For free... you can often get slightly warped or slightly too thin ones at brake shops.

We sell ours which are water jet cut, the water jet does a nice job - but if you want to save money, I'd totally encourage anybody just to cut them out.  You can cut nice rotors out with a torch, by hand, on a compass.  I've also seen folks cut nice rotors with a jig saw.  I've seen very high quotes from machines shops so be careful if you go that route ~ especially if they think you need precision parts and get into lathe work.