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kenrinc
04-08-2013, 11:07 PM
I'm working on the tender sides for my locomotive. These are specified in copper but because I'm building double size, copper is out of the question. I'd like to just use what I have which is 22 gauge steel. I tried this out a couple times, once with 16 gauge which was very difficult. I've seen ways to do this but not many using hand tools. I've made a wood pattern, the size of the side with the intended round edge. I clamp the metal with another piece on top to hold in place. For the straight sections the metal goes over fine (to be expected) once I get to the corners it's another story. As you can see, I tried using some shears to see if that helped and it did. So my question is, is there some logic to it? How many, what size, etc... I have one 90 degree corner one 30 deg corner and this one which is basically another 90 degree. I have no problem slitting the corners if that gets me a nice round edge in the end. I'll just weld up what's left, dress with a grinder and smooth with filler.


http://kenrinehart.org/corner.JPG

Ken-

whateg01
04-08-2013, 11:18 PM
It can be a lot more work, but tuck shrinking will do the same thing without the need to weld. Still have to finish it to suit. Tucking forks are used to form the tucks, then each tuck is beat into itself causing shrinkage.

Dave

RussZHC
04-08-2013, 11:37 PM
Not sure if there is any "set" number or size etc.of slits. Maybe the best way to explain it is to say its like the idea of a curve being a series of straight lines, the more you have the smoother the curve.
So a single slit would allow you to make a nice 90 degree corner etc. etc. etc., now, to me, there are a couple of ways to approach this "method". Start at the mid-point of the desired curve with a slit and then split the remaining two sides in half, each getting a slit and continue until the curve is as smooth as you want it (i.e. good enough for your purposes). Or you could estimate (sample?), start with fairly large gaps and then go back and split each gap until the curve you want is reached.

Your photo looks like it is actually a compound curve (the top of the shape is sort of rolled), if this is the intention it makes it quite a bit more complex as you now have two curves you will want to have fairly smooth and that's more work. If that edge can be "square" instead of rolled, bit simpler process.

Mtw fdu
04-09-2013, 01:32 AM
The term you are looking for with the way you are doing things is called "hammerforming". This is a technical used when panelbeating a sheet of steel to make the shape you are going for. The process however, should be an easy one as you described it. If you google "hammerforming" on the net, it will give you some pointers of how to go about it with some helpful tips and "tricks" of the trade if you have not done it before. I have done it myself quite a few time without any trouble with the corners. I can't see where you are going wrong. Normally when you hammerform the corners the metal will gather together (similar to a door skin) on a car. Here is a website that may help.

http://www.bevenyoung.com.au/index.php?main_page=product_info&cPath=28&products_id=188

Mtw fdu.

kenrinc
04-09-2013, 02:01 AM
Thanks guys. Yeah, I was just unsure on how to proceed. The curve is compound, everything is rounded and then curved. I just can't seem to get it "flowing" without a bump somewhere along the way. If I slit once in the middle of a 90, I can see the opposite section begin to come the other way sliding over the previous metal. I was then going in with tin snips and snipping that part of the "pie" out and then continuing. Thanks for the tip on the hammerforming, I was doing some searching around and I wasn't sure what terms to use. I'm thinking the slits will get me where I need to be but wanted to ask around.

Ken-

whateg01
04-09-2013, 02:15 AM
A hammerform is certainly a doable thing. The nice thing about sheetmetal is that it can be moved. You can shrink the edge and get it roll over. You can stretch a section of it and put shape in the flat side. It does take some practice to be able to read the metal and know whether you should shrink a spot or stretch it. Check out some metalshaping sites for techniques on shrinking and stretching. I personally think you'd be better off avoiding that much welding on the panel, as you'll still have to tweak the shape after it gets done moving, but that's just me.

Dave

Georgineer
04-09-2013, 04:18 AM
You may be astonished at how much easier the metal can be formed if you anneal it (heat to red hot and allow to cool slowly) before, and if necessary again during, the forming process. Although annealing can cause slight distortion of the metal sheet, you will be ideally placed to correct it.

George

J Weber
04-09-2013, 05:44 AM
Check out the You tube videos of Eric Dubé He makes full medieval plate armor all by hammering.Some of the curves he uses are very much like what you are trying to do.He has a bunch of them.

Stepside
04-09-2013, 08:37 AM
I have built parts like what you have shown. I used the the same system with the mold/form on the bottom and a similiar shape on the top. the top board was as large and the same shape as the flat portion. The thing that worked for me was using a piece of wood, old hammer handle, and a large hammer. The rule being , if you want to shrink the metal use wood or hard plastic between the metal and the hammer. If you wish to stretch the metal, use a metal hammer. On steel, annealing isn't necessary, but non-ferrous metals will work harden and need to be annealed several times in the process.

kenrinc
04-09-2013, 02:08 PM
Yeah, I guess the trick is "reading" the metal. That's the part that I'm not educated on. Using a metal hammer for stretching and a wood hammer for shrinking makes sense to me, what seems harder is when and where you'd shrink vs stretch.

Ken-

whateg01
04-09-2013, 02:50 PM
You probably know this, but the wooden hammer in and of itself doesn't shrink. You still have to be forcing the metal into a space smaller than it already occupies. The reason a wooden hammer is used is that when the metal is smacked between the metal hammer and a metal form, it will stretch it. The wooden hammer isn't hard enough to do that.

Dave

micrometer50
04-09-2013, 07:25 PM
metalmeet.com has a lot more on forming sheet metal.

wierdscience
04-09-2013, 08:37 PM
Also -

http://allmetalshaping.com/

vpt
04-09-2013, 09:24 PM
Would those eastbay metal shrinker/stretcher deals work for this?

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcTJycCLRNGTAfvpV5YLt3f993jB6bWVk uIJmthHhVGdyMcTVeSXLg

http://www.youtube.com/watch?v=0jGCt-CtrxY