Flattening sheet metal

[bcarwell]

Hi folks,
I just got an antique 10 foot Dempster windmill I am going to rebuild. There are 15 fan blades which are variously bent up and dented quite a bit.
Could someone suggest some techniques for getting the dents out and getting them flat and straight again.
First (and call me stubborn), I do not want to take them to a metal working shop to be rolled but want to do it myself. Second, the most obvious thing is to get a rubber mallet and start pounding away. And third, I am aware that you can purchase replacements for maybe $20 each but don't want to do that unless necessary
But are there some better home techniques ? For example, does heating them with a brush torch first help ? Or is there some clever jig I can fashion using a hyraulic shop press ? Or are there some tools I should get used by auto body repair men. Can I rent a mini-steam roller for 1/2 hour and roll over them in a parking lot (partly serious, partly in jest).
And and all suggestions or pointers to websites/forums are welcomed.

Thanks,

Bob

 

[6sunset6]

Hammering will strech the metal and the problem will get worse. Rolling actually will kind of do the same thing.
A techique an old welder told me about a long time ago ( I am old now) was to shrink spots. I tore the door off a BH and was contemplating it when he wandered by. Heat up small spots with a torch, I think it has to be a red spot so oxy acet or mapp and then cool it with a wet rag. Shrinks really great and pulls out dents. Th only issue is it only works in one spot once. In other words you can only shrink a specific spot once. You also have to figuire out a pattern. But it's kind of neat when it works.

 

[AlanB]

Probably one of the best modern day metalwork guys out there, and he writes and explains it real well.

Fournier Metal Work Questions & Answers

That said, a Stump, or an anvil, a hammer, some wooden mallets and blocks, some wedges, a vice, some pins driven into the stump to twist against, a leather bag filled with lead shot or sand are tools that could help you get there.

Time is money, for all of us it is just a different ratio. $20 a blade seems pretty cheap.

Got a picture so we can see how bent, bent is?

 

[john_bud]

Eastwood sells a "shrinking hammer". The head twists and that pulls the metal. You do need to heat the metal.

Nearly all beating methods will expand the metal. Heating ones will shrink, but harden. You will probably want to anneal the metal later.

 

[zzvyb6]

Place them on some wet sand and drive over them with the tires of your car with some air let out. Make sure you align the fan blades with the curvature of the tire. Yeah, they may stretch out a bit, all you want for this job is for them to look good at 50 yards. My Flint and Walling looks brand new. (Came down twice: once when the former owner sawed the shaft to get the thing down and once when it blew off its mount while I had it mounted on a basketball backboard to fix it). An old washing machine wringer makes a good curve bender, too. but your blades are probably too long.... Lets see a picture ! Mine still looks as good as new (1932 Star, 8' on a 30' tower).

 

[ray66v]

Stretching and shrinking sheet metal requires considerable experience to be done properly. There is no simple technique, or instruction for this.

I have spent 30 years practicing this, and often have to draw on all of my experience to be successful.

Yes, its possible you will be lucky, and have some degree of success. You also could quickly make the repairable, unrepairable.

If you can, find an experienced metal man to help you, at least rough them out. Then you could possibly take it from there.

 

[RWolf]

Working metal is an "art" and a "science". I've been working metal as a hobby for awhile and still can't get that finished look very oftain. You will need a variety of body hammers, bag of lead shot or sand (as been said) and plenty of time. I'd start with some scrap metal of the same type and thickness and work on that first. Metals come in different "types" i.e. cabon content. The higher the content the more brittle it is and harder to work. Heating will go a long way to help but you need to be at the right temperature to work it or you could possibly make it much worse. If you can find someone to show you how to work the metal you will be much better off. Maybe someone you know has a forge setup. Maybe you can find an old blacksmith that would be willing to show you the techniques. In the long run you will be happier when your done because you will be investing a great deal of time on this project.

Good luck.

 

[Farmerford]

zzvyb6:

Glad to hear about the windmill.

I am about to dismantle a Flint & Walling on my grandparent's farm, where I grew up. The tower is very good, the tank almost completely rotted, and the blades and wheel are gone, apparently the shaft snapped when the oil finally gave out. How about a picture of yours to give me something to anticipate?

Have you found any source for parts? All the antique windmill sites I found have parts for Aermotor, etc, but nobody seems to carry F&W. They were very popular here in the southeast before electricity made it to the farms in the 1930's. I can't decide whether to try to replicate the F&W wheel (assuming I can find the dimensions) or just make another brand fit.

Thanks.

Farmerford

 

[mwb]

depending on what kind of damage you are trying to remove try a few searches on "English Wheel" and how they work. Might be just the machine for you and not very $ (I think HF sells them).

Mike

 

[ray66v]

depending on what kind of damage you are trying to remove try a few searches on "English Wheel" and how they work. Might be just the machine for you and not very $ (I think HF sells them).

Mike

An English wheel is for forming curves in light sheet metal. It is not going to help to straighten fan blades.