How to curve a brass coach roof

David Thorpe

How to curve a brass coach roof

Postby David Thorpe » Mon Feb 21, 2022 9:25 pm

I'm currently building a Caley Coaches kit of a 65' Grampian coach. Having done the bogies, underframe and body I've now got to the roof which is supplied as a nicely etched flat piece of 0.3mm brass 40 x 260mm. I have to curve it to fit onto some formers and am having great difficulty in doing so. One of the problems, of course, is that it's not just an even overall curve as at the edges of the roof the curve becomes much tighter. I've tried rolling pins, brass piping and one or two other items in an attempt to curve it in a similar way to what I'd do for a tumblehome, but as yet without much success in achieving the required curvature, or indeed much curvature at all. Before I resort to plasticard (which I don't really want to do) has anyone any tips as to how I can curve this roof to the proper shape?

DT
Last edited by David Thorpe on Tue Feb 22, 2022 12:13 am, edited 1 time in total.

Phil O
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Re: How to curve a brass coach roof

Postby Phil O » Mon Feb 21, 2022 11:01 pm

When I rolled a boiler, I used 1/2 inch dowel, two hands width longer than the length of the boiler barrel, the flat barrel was placed on top of a couple of magazines. For the tighter curves, just roll in that area. The alternative would be to invest in G W boiler rolls, if they are long enough.

Cheers

Phil.

Jeremy Suter
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Re: How to curve a brass coach roof

Postby Jeremy Suter » Tue Feb 22, 2022 8:43 am

Hi David
3 arc roof's are notoriously hard to make in metal. As when you roll the first curve it work hardens so doing the second curve becomes harder to form and get in the right place. I supply 2 roof skins in the railmoter kit because of this and rolling problem

It might be easier to throw away the roof you have for a wider one so you have something to grip when you pull the second curve in. I form the shallow curve first in my long rollers then the tighter curve is made using rods screwed to a bar and clamped in a vice then pull round with a ruler.

Although this is a half etched roof all the correct size for what I want the principle is the same.
Rolling the gentle curve first. I use paper on the etched side to work as a cushion against the etched rain strips etc. As well as getting a tighter grip on the middle part of the roof even with 1 inch diameter bars the middle just wants to be a little tighter so the we don't get tight ends and a shallow middle. and more paper can be added if needed.
IMG_6148.JPG


When I am happy with the shallow curve the tighter curve needs to be put in. This is done using a rod of the right radius (needs to be less than the radius of the final curve you want as the metal will spring back). screwed to a square bar long enough for the roof to fit in.
IMG_6189.JPG

Then clamp in the roof and clamp in vice and pull the roof round the rod it will need the centre clamping so that the curve is uniform I have tabs in the base of the roof to slot into the floor and gutter roof former. This gives the bar tool something to grip which is why I suggested you got a wider piece of material.
IMG_6188.JPG

Once you have the second Curve turn the roof round and repeat but first you will need to work out where it will go. when all curves are done trim the length to near where it needs to be. and then rub on emery paper on a flat surface to get the level correct. Although I have no photos of a roof rolled unfitted at this point but here is some LYR Ones fitted.
I have rolled the roof's as mentioned above cut to length and soldered to a shaped flat piece to form the gutters and also something to screw the roof to the body and then the body to the underframe.
IMG_5558.JPG
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Daddyman
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Re: How to curve a brass coach roof

Postby Daddyman » Tue Feb 22, 2022 8:44 am

David Thorpe wrote:I'm currently building a Caley Coaches kit of a 65' Grampian coach. Having done the bogies, underframe and body I've now got to the roof which is supplied as a nicely etched flat piece of 0.3mm brass 40 x 260mm. I have to curve it to fit onto some formers and am having great difficulty in doing so. One of the problems, of course, is that it's not just an even overall curve as at the edges of the roof the curve becomes much tighter. I've tried rolling pins, brass piping and one or two other items in an attempt to curve it in a similar way to what I'd do for a tumblehome, but as yet without much success in achieving the required curvature, or indeed much curvature at all. Before I resort to plasticard (which I don't really want to do) has anyone any tips as to how I can curve this roof to the proper shape?

DT

If you're not making any impression I'd say either that you're not pressing hard enough, or that the brass is very hard: the tools and methods I use on Eileen's 10 thou (which is very soft) did nothing when I tried them on some 10 thou that Dave Bradwell gave me. If it is very hard, then annealing won't do any harm, as working it will make it hard again. However, if it's the soft stuff, then I'd avoid annealing as it will leave it soft - in my experience anyway, though I know the grown-ups dispute this.

I use a mouse mat and a rolling pin for roofs with an even curve, but remember that the roof needs supporting in its middle section on thin card to ensure the roll is even. So it's: mouse mat, then card, then roof.

Personally, though, I wouldn't hope for much from rolling without rollers [edit: I mean with me using rollers - no disrespect to Jeremy who posted at the same time as me, and who is of course doing it the right way with the right tools], and if it was for me I'd make a former from layers of plasticard, anneal the roof, and press it down on the former. Long-winded, but guaranteed results... Here you can see the end profile being used to gauge the width of layers of plasticard needed (upper corner aligning with the end profile), though I did it in a rush to illustrate the principle, nothing glued, so some of the sheets of plasticard are not aligned properly in the photo. Milliput smooths the steps between the layers out, and using black plasticard and white filler helps show that the curve is even.
20210424_110035.jpg


Same principle for my Y9 and Manning Wardle tanks:
20220222_083706_resized.jpg


Alternatively, what about contacting Jim at Caley Coaches and see what he suggests?
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Will L
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Re: How to curve a brass coach roof

Postby Will L » Tue Feb 22, 2022 2:35 pm

Jeremy has it right of course.

However before you get too fixed on producing exactly the right profile before attaching it, you should remember that a "roughly the right shape" roof can be transformed to something much closer to the truth by bending it round and soldering it to, formers that are the right shape. That is the edges of the coach if you want it fixed on permanently, or if, as I would prefer, you wish it to be removable, fixed to a flat ceiling with profile pieces to match the roof profile. A roof produced this way is very robust, I do plastic roofs more or less the same way and the results are remarkable rigid.
The late Dick Petter was very keen on a properly engineer approach, and occasional got a bit sniffy about some of my methods, but I did get him doing coach roofs my way.

David Thorpe

Re: How to curve a brass coach roof

Postby David Thorpe » Wed Feb 23, 2022 3:45 pm

Thanks everyone for your help on this one.

Will, the kit came supplied with a roof base and formers which I have duly made up. (see below). I had hoped to do something like you suggest, i.e. bend the roof round the formers and solder it to shape. Unfortunately that hasn't worked. First, the roof base does not allow for soldering into the edges of the formers where the roof would have to be attached, and secondly even when attached the distance between the formers means that the roof edge bends up between them whileas it should of course be dead level.

roof1.jpg


David, I probably didn't persevere long enough with the rolling and I'll give it another go. However, even if I get the basic roof onto the correct shape I really don't know how I'll manage with the edges which are at a much tighter radius. The only instructions in the kit suggested that I form the roof in the same way that I formed the tumblehome, i.e. a pipe and the edge of a 12" rule. With every respect I don't think that's going to get me very far. Your plasticard system looks interesting, and I assume would probably work best with a plasticard roof, which would not in itself be a problem.

Jeremy, thanks for going to the trouble of posting your photos. Your system is ideal, as evidence from your results, but sadly I don't have to tools to do it and even if I did I wouldn't know how to use them. I don't suppose you'd take a commission to do my roof would you?

Otherwise. I'm wondering whether to do what I've done with all the other coaches I've built and fit an extruded aluminium roof. It almost certainly won't be the exact profile but it shouldn't be far out. I assume that these are available from the trade - anyone know of a supplier?*

DT

+Addendum: It seems that Wizard/Comet do them.
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Will L
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Re: How to curve a brass coach roof

Postby Will L » Wed Feb 23, 2022 4:48 pm

David Thorpe wrote:Thanks everyone for your help on this one.

Will, the kit came supplied with a roof base and formers which I have duly made up. (see below). I had hoped to do something like you suggest, i.e. bend the roof round the formers and solder it to shape. Unfortunately that hasn't worked. First, the roof base does not allow for soldering into the edges of the formers where the roof would have to be attached, and secondly even when attached the distance between the formers means that the roof edge bends up between them whileas it should of course be dead level.

Image

David. I think its doable, my method, once you've cleaned off any stray solder from previous efforts, would be something like this.

The trick is that you need to over-bend the roof a little to give a reasonable but not exact and slightly too curved shape to the roof.

On a hard flat surface, press the former into the roof until the curved formers touch the roof in the centre, (which forces the roof to straighten a little) and solder the centre section of each former to the roof. You may need 3 hands to do this.

With luck, if you got enough curve into the roof edges, they will now be in contact with the edges of the former and you should be able to run solder down the edge joints.

If not the assembly will already be reasonably rigid so if the edges don't quite meet you can now force them together against a hard flat surface while applying solder.

Daddyman
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Re: How to curve a brass coach roof

Postby Daddyman » Wed Feb 23, 2022 5:30 pm

David Thorpe wrote: David, I probably didn't persevere long enough with the rolling and I'll give it another go. However, even if I get the basic roof onto the correct shape I really don't know how I'll manage with the edges which are at a much tighter radius. The only instructions in the kit suggested that I form the roof in the same way that I formed the tumblehome, i.e. a pipe and the edge of a 12" rule. With every respect I don't think that's going to get me very far. Your plasticard system looks interesting, and I assume would probably work best with a plasticard roof, which would not in itself be a problem.

I wouldn't have much hope for the tighter edges either, David, and bending over spasmodic metal formers in the way the kits suggests has never worked for me (though it clearly does for others): even with something as short as a saddle tank's tank, the distance between the supports is enough to allow distortion between them, hence my use of the plasticard former, which provides support along the full length of the bend. Here are the deep, crisp and even bends which resulted:
20220222_084736_resized.jpg


As for the carriage roof, you're right that I used the former with a plastic roof. But then I question whether 10 thou (or even 15 thou) brass is thick enough to represent some carriage roofs. As I've said elsewhere, when I use 10 thou, I always thicken it up with strips of 5 thou along the undersides of the edges. That's OK for NER arc roofs and clerestories, but it doesn't work for NER ellipticals, which look much thicker. I had a look at one or two books, and the CR carriages I could find are somewhere in between. Anyway, to get the thickness I wanted on the elliptical, I used "planks" of 30 thou x 2mm plastic and laid them over the former in the way the planks are laid on the real thing. My thinking behind the use of 30 thou was - rightly, as it turned out - that by the time I'd sanded the planks smooth, I'd be down to about 20 thou, which looks right. The whole "plank" thing was based on an idea in MRJ 275, but I swapped out the writer's intermittent supports for the solid former that I've already shown. This is the closest I have to a photo of the plank-laying stage, showing how, with care at the former stage, the roof is an exact match to the end profile:
20210502_202625.jpg


And here's the finished roof (with the damage from dropping it down the stairs nicely hidden at the far end...)
[Any NER-in-LNER-days aficionados: please note the incorrect domed lamp tops have now been replaced with cylindrical ones.]
20210630_093420.jpg
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David Thorpe

Re: How to curve a brass coach roof

Postby David Thorpe » Wed Feb 23, 2022 6:07 pm

Will L wrote:With luck, if you got enough curve into the roof edges, they will now be in contact with the edges of the former and you should be able to run solder down the edge joints.


The snag about that is that if you've got a roof on the formers there's no way you can then get a soldering iron into the edges of the formers - the L shaped base gets in the way. I suppose it might be possible using solder paste and an RSU. I'm also a bit concerned in that the formers are very thin and I fear that they might not take too much applied force although that shouldn't be necessary if the roof is sufficiently bent as you suggest. Still pondering.....

DT

David Thorpe

Re: How to curve a brass coach roof

Postby David Thorpe » Wed Feb 23, 2022 6:36 pm

Daddyman wrote:And here's the finished roof (with the damage from dropping it down the stairs nicely hidden at the far end...)


Well that looks absolutely perfect. I'm now wondering if I could use that method with the base and formers I've built as that fits very neatly between the two ends of the coach, tight enough not to require any fixing so the roof can remain removeable. Not that that's of vital importance.

DT

Daddyman
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Re: How to curve a brass coach roof

Postby Daddyman » Wed Feb 23, 2022 6:47 pm

Yes, the supports might be close enough that the planks would not sag in between - that was certainly the MRJ275 chap's method. You could always use brass planks... Expensive though! And heavy!

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Will L
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Re: How to curve a brass coach roof

Postby Will L » Wed Feb 23, 2022 10:21 pm

David Thorpe wrote:...The snag about that is that if you've got a roof on the formers there's no way you can then get a soldering iron into the edges of the formers - the L shaped base gets in the way...

You would need to do it from the outside and clean it up afterwards.

Bill Newstead
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Re: How to curve a brass coach roof

Postby Bill Newstead » Thu Feb 24, 2022 12:54 pm

A roof forming tool is described in the Great Western Study Group Newsletter No 147 (Winter 2019). The tool is based on a design by Dave Smith of Blacksmith Models. The original was made of steel for commercial use but the tool described is constructed from wood sections and so would be suitable only for small batch work. I could scan the article if you are interested.

Bill

Mark Tatlow
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Re: How to curve a brass coach roof

Postby Mark Tatlow » Thu Feb 24, 2022 4:42 pm

Bill Newstead wrote: I could scan the article if you are interested.

Bill


Yes please!
Mark Tatlow

Jeremy Suter
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Re: How to curve a brass coach roof

Postby Jeremy Suter » Thu Feb 24, 2022 6:29 pm

David Thorpe wrote:
Jeremy, thanks for going to the trouble of posting your photos. Your system is ideal, as evidence from your results, but sadly I don't have to tools to do it and even if I did I wouldn't know how to use them. I don't suppose you'd take a commission to do my roof would you?


Hi David
If you really cannot do it I can skin it for you.
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David Thorpe

Re: How to curve a brass coach roof

Postby David Thorpe » Thu Feb 24, 2022 6:36 pm

Bill Newstead wrote:A roof forming tool is described in the Great Western Study Group Newsletter No 147 (Winter 2019). The tool is based on a design by Dave Smith of Blacksmith Models. The original was made of steel for commercial use but the tool described is constructed from wood sections and so would be suitable only for small batch work. I could scan the article if you are interested.


I suspect quite a lot of people would like to see that, Bill!

Bill Newstead
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Re: How to curve a brass coach roof

Postby Bill Newstead » Fri Feb 25, 2022 11:18 am

By popular demand here (i hope) are PDF scans of the description:

Coach Roof Tool 1.pdf


Coach Roof Tool 2.pdf
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Paul Willis
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Re: How to curve a brass coach roof

Postby Paul Willis » Fri Feb 25, 2022 12:26 pm

Hi Bill,

I'm not a member of the Great Western Study Group. What is the position with regards to copyright of that article?

members of the Forum may not realise that it is generally publicly viewable (and there are very good reasons for that, highlighting the excellent modelling and skills here) and archivable but that does mean that we need to be respectful of the wider environment.

Whilst there are exemptions for selected extracts, publishing material as a whole without the explicit permission of the author or copyright holder is generally frowned on.

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Terry Bendall
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Re: How to curve a brass coach roof

Postby Terry Bendall » Sat Feb 26, 2022 8:49 am

David Thorpe wrote:when attached the distance between the formers means that the roof edge bends up between them whileas it should of course be dead level.


I have never tried to do this job but given that there are kits in the cupboard that need this type of roof it may happen some day. It seems to me that if there are insufficient formers, or if they do not seem sufficently robust, one solution would be to make up some extra ones proably using the scrap from the etch. Mark round an existing one with a sharp scriber before it is fixed and file to shape.

Terry Bendall

Phil O
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Re: How to curve a brass coach roof

Postby Phil O » Sat Feb 26, 2022 10:00 am

David,

Can you unsolder, the horizontal pieces? If you can, I would suggest that you remove one, attach the roof on that side, replace the horizontal and remove the other one and repeat.

I hope that me be of some help.

Phil.

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Will L
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Re: How to curve a brass coach roof

Postby Will L » Sat Feb 26, 2022 8:06 pm

Terry Bendall wrote:I have never tried to do this job but given that there are kits in the cupboard that need this type of roof it may happen some day. It seems to me that if there are insufficient formers.

Terry, like most sheet materials, brass sheet with a curve in one plain it is quite resistant to being curved in a second plane so you don't need too many formers, one each end will do at a pinch. The problems comes with the sides which aren't curved as David discovered, so they need to be supported by something to keep the edge strait. If the curve is over bent, then it tends to hold tight against a strait edge in the way, if its not bent enough you get the effect David described in his earlier post.

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Hardwicke
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Re: How to curve a brass coach roof

Postby Hardwicke » Thu Aug 03, 2023 9:12 pm

I'm just trawling through unread posts and saw this. As I'm going to be making a brass coach soon I'm looking at all info.
I was at Swanwick Junction (Midland Railway-Butterley) yesterday and looking at the sad remains of the only 48' suburban (as per the Ratio now Peço/Parkside rebranded) kit. Now if Peço sponsored it's rebuild ...
Anyway I was looking at what's left of it's roof and it has metal formers, screwed to wooden beams, with strips of wood screwed onto those. I'd say that making roofs like the prototype is far more accurate if a little more time consuming. They could then have a cover of say 5 thou plastikard. No more aluminium strips with all the compromises that entails, just as long as your formers are accurate. Clerestory, elliptical, arc, you could make them all. Strips of n/s and brass formers? I've forgotten the technical name for them but here's some Midland Clayton clerestory ones.
IMG20230528202440.jpg
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