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Forming an elliptical coach roof in brass.


John M

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Hi

 

I am looking for suggestions for forming an elliptical coach roof from brass sheet.

 

The idea is to form the basic roof in .015" brass half etched in order to represent raised detail in a similar manner to the old etched brass loco kits.

 

I have done some experimentation using rolls, but wonder if a wooden former or some form of simple press and die would give a better result.

 

John

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I would not half etch the detail it makes it more difficult to form. First anneal the brass and then form main raduis with a set of rollers or broom handle and mouse mat. if it has the tighter radiis at the edges the can be done in the vice with a smaller diameter bar.

Half etched groves tend to lead to a curve with lumps in, which need loads of work to get rid of.

If you were going to make 100's or 1000's yes a press tool might be viable. They were expensive 30 years ago when I was still making clocks. You also need the flypress to work them.

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If my understanding is correct, an ellipse is part of a circle therefore I would have thought that metal bending rollers would be the tool to get the desired amount of bend needed.

Sandy

 

An ellipse is part of a stretched circle. An 'arc' is part of a true circle. An ellipse has different radii at different parts of the ellipse. If you use rollers you will need to slightly unbend the outer parts of the etch to do this.

I would echo the concerns about half etch or an etch with lines. Use thinner brass and a camping mat or mouse mat.

John

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For me, coach roofs of the type mentioned in 10thou brass were impossible to get straight along there length, there was a slight bowing. I agree with N15 in that any etching of the surface will probably make the job even more difficult. For my own etched coaches that have an elliptical type roof, a wooden former was used to vac form dozens of styrene roofs at a local toy manufacturer ( a college might be able to help ). I've also used thin card.

 

Regards Snitzl

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