Rolling brass roofs

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Jol Wilkinson
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Rolling brass roofs

Postby Jol Wilkinson » Wed Feb 28, 2018 1:30 pm

Following a discussion in a recent NEEAG monthly update, Richard McLachan has written a piece on how he came about rolling brass roofs and how he did it. I've attached it for reference.

Rolling and cutting brass roofs.docx
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Re6/6
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Re: Rolling brass roofs

Postby Re6/6 » Wed Feb 28, 2018 1:52 pm

Thanks you Jol. Most useful.
John

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David B
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Re: NEEAG February meeting

Postby David B » Wed Feb 28, 2018 2:09 pm

I cut my roof and other blanks from brass sheet with a steel rule and a sharp Stanley knife, scribing the brass repeatedly until there is a registration mark on the other side. I then bend back and forth along the line until it snaps and tidy up with a file. I do the cutting on a piece of wood because the knife digs in when it comes off the end of the brass. When bending along the line, it helps for longer rooves such as those for coaches if you can put the sheet in to some bending bars so that the edge is kept flat, but with smaller rooves, like those for vans, you can often just bend and snap them in your hands.

To roll the roof, I put the blank on a cutting mat and roll a metal rod, about 1/2" diameter, back and forth with firm downward pressure. This makes a single arc quite easily. If the cutting mat is too firm, put a thin layer of foam on top and roll on to that. With practise, you can roll edges more than the middle and create a double arc.

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Jol Wilkinson
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Re: NEEAG February meeting

Postby Jol Wilkinson » Wed Feb 28, 2018 2:28 pm

David B wrote:I cut my roof and other blanks from brass sheet with a steel rule and a sharp Stanley knife, scribing the brass repeatedly until there is a registration mark on the other side. I then bend back and forth along the line until it snaps and tidy up with a file. I do the cutting on a piece of wood because the knife digs in when it comes off the end of the brass. When bending along the line, it helps for longer rooves such as those for coaches if you can put the sheet in to some bending bars so that the edge is kept flat, but with smaller rooves, like those for vans, you can often just bend and snap them in your hands.

To roll the roof, I put the blank on a cutting mat and roll a metal rod, about 1/2" diameter, back and forth with firm downward pressure. This makes a single arc quite easily. If the cutting mat is too firm, put a thin layer of foam on top and roll on to that. With practise, you can roll edges more than the middle and create a double arc.


What thickness of brass do you use, David?

I think Richard said uses .5 or .6mm, which he considers gives a good approximation to the roof thickness, when we discussed the D&S NER carriages he is building for me.

John Palmer
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Re: Rolling brass roofs

Postby John Palmer » Wed Feb 28, 2018 2:32 pm

A very useful piece indeed. The information about piercing saw blades is particularly helpful.

As an alternative to a cutting mat with or without a layer of foam when using David B's technique I have obtained acceptable results with the use of a mouse mat.

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David B
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Re: NEEAG February meeting

Postby David B » Wed Feb 28, 2018 3:16 pm

Jol Wilkinson wrote:What thickness of brass do you use, David?

I think Richard said uses .5 or .6mm, which he considers gives a good approximation to the roof thickness, when we discussed the D&S NER carriages he is building for me.


The last bit I cut was 0.7mm for a wagon floor which was rather thicker than usual but what I had in stock. It was a while ago but I think I scored from both sides. Using a knife gives a nice straight edge.

DougN
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Re: Rolling brass roofs

Postby DougN » Thu Mar 01, 2018 1:34 am

Looks like I have a bit of a challenge coming up! :thumb I have a 10mm steel bar that I have rolled some things with previously. So I will give the coach roof a go. I may start with thinner brass then laminate on some plasticard around the edge to increase the thickness back up again!

Problem is this week the nights are booked and the next 2 weekends as well as every night next week! :cry: well there is some interesting things in there but no modelling.
Doug
Still not doing enough modelling

billbedford

Re: Rolling brass roofs

Postby billbedford » Thu Mar 01, 2018 10:22 am

The roof need to be cut from the sheet after it has been rolled. The reason for this is that it is impossible to get purchase from rollers on outer edge of the brass, so the outermost edge will always be a straight tangent to the curve the roller produces. This is not so much of a problem when making arc roofs, but it is nearly impossible to make cove roofs from a pre-cut blank.

Enigma
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Re: Rolling brass roofs

Postby Enigma » Thu Mar 01, 2018 12:26 pm

Just to add regarding cutting thin (say 20 thou) brass that I use an Olfa 'scrawker' cutter, lightly at first to create a mark then increasing pressure until the line appears on the other side. Bending along the line, as others say, then results in a clean break that can be tidied up with a file. Single radius van roofs can easily be rolled with a bar or tube of smaller diameter using something relatively soft as a base. i have often used my thigh for small roofs.

Daddyman
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Re: Rolling brass roofs

Postby Daddyman » Thu Jul 22, 2021 7:10 am

I've been doing a lot of roof-rolling recently, albeit with a rolling pin on a mouse mat (guidance on the advisability or otherwise of that welcome). I'm getting the same problem as Richard - the ends rolling more tightly than the middle - but I can't understand Richard's fix for this. These are his words:

As I progressed, the ends rolled a bit more tightly than the middle but this was corrected with some card from a cereal packet underneath the brass in the roller – about half of the width of the strip of brass, and the width of card trimmed to get a good cylindrical result. Different brass and different rolling machines will need different adjustment. I left a gap of maybe 1 inch in the resulting rolled piece of brass.


I can't work out from this where the card should go. I'm rolling a piece 21cm x 36mm, and I suspect the card should cover the full 36mm width, but not the full 21cm length; it should be 3-4cm shorter at each end. Would that be other people's understanding? I'm rolling 10 thou brass, by the way.

Thanks in advance.

davebradwell
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Re: Rolling brass roofs

Postby davebradwell » Thu Jul 22, 2021 10:45 am

I think I'd be asking myself why the ends are rolling more and might it be because you're pressing on the ends of the bar - like a rolling pin - and bending it? In this case, pressing on the centre should even things out, perhaps using a short piece of wood with a rolling action so you can apply pressure with 2 hands. Wonder also if mat is too short so edges are more compliant in which case perhaps try 2 similar mats end to end.

Usual problem with rolling is getting the bend right up to the edge.

DaveB

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David B
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Re: Rolling brass roofs

Postby David B » Thu Jul 22, 2021 11:06 am

I did a video on roofs, including a bit on rolling, for the EMGS a couple of months ago. It might help. Fixing the Roof. Rolling by hand is at 2.44 mins

I suggest the rolling pin may be too large a diameter. Try a smaller metal bar, perhaps 3/4" as I used in the video.

I went on to rollers after the hand rolling but decided to omit the bit about the ends rolling more than the middle because there are several factors involved. Mainly, it is because the pressure is greater at the ends because the rollers are flexing a little, a minuscule amount, in the middle. The longer the rollers, the greater the problem which, in the GW rollers, has been suggested that the rollers may be too thin. Putting card in the middle and leaving the ends 'unsupported' should help overcome the problem a bit. Likewise, when hand rolling, if the ends of the rolling bar are unsupported (as in the video) then that could help.

You are not alone with having this problem and in the end, it comes down to a bit of experimenting until you get the arrangement right.

Daddyman
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Re: Rolling brass roofs

Postby Daddyman » Thu Jul 22, 2021 6:04 pm

Many thanks, Dave and David.

Dave: I've been asking myself that! As David implies, I think it's just something that happens. I'm pressing on the middle of the bar. I can't believe that a rolling pin is flexing - or the 18mm brass tube I've also used. You might be right about the mats being softer at the edge - but then I get the same problem whatever I roll on - the carpet, newspapers, etc. Seems just to be a fact of life. I think putting a greeting card under the centre of the length is helping, but the roof has probably become work-hardened so I'm not seeing the effect too much. Time to cut out a fresh piece of brass I think and use the greeting card method from the start. I'll also try with the ends unsupported.

David: the radius with the rolling pin is fine. It's not there I'm having the problem - though I do mix the rolling pin and the 18mm tube (but I've been getting a kinked curve with the latter; the rolling pin then irons the kinks out).

Stephan.wintner
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Re: Rolling brass roofs

Postby Stephan.wintner » Fri Jul 23, 2021 5:45 am

The ends will tend to curl more, regardless of the roller, because of how the softer foam / rubber / mouse mat is behaving under the ends. In short, in the middle each mm of brass is pushing on 1 mm of foam, and it's neighboring mm of brass is pushing its own 1 mm of foam down. Near the edges , 1 mm of brass is pushing a larger volume of foam down, 4 and 5 mm perhaps, because it has no neighbor helping on one side. In a sense, this makes the foam "harder" at the edges, and hence the force is concentrated at the ends.

And yes, a strip of card or paper could focus the force in the middle and allow one to even it out. Positioning the edge of the mouse mat near the middle of the brass for a bit, shifting it back n forth, could also work.

If one was using a rolling mill, with metal rollers on both sides, with reasonable rigidity and low force, I'd expect a fairly consistent result - the edge effect would still be present, but lessened. If the forces get large, then the metal rollers will display a similar behavior. The author is using a rolling mill, but suggests he was using a bit of "grunt", so I'd expect a similar effect. Metals are elastic, after all.

Stephan

Daddyman
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Re: Rolling brass roofs

Postby Daddyman » Fri Jul 23, 2021 6:05 am

Thanks for that. I'll cut a fresh section of brass today, and cut a less long strip of something soft (maybe foamboard) to support only the middle of the workpiece and see how that goes. It hadn't occurred to me to use a shorter piece of foam; I'd tried the opposite (a shorter rod), but that's absolutely fatal to the workpiece, of course!

Anyone have any experience of these? Richard alludes to them in the article attached to the first post:
https://www.warco.co.uk/bending-rolls-r ... -inch.html

Stuart Firth
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Re: Rolling brass roofs

Postby Stuart Firth » Thu Aug 19, 2021 7:49 am

I have only ever rolled shortish roofs for vans, cab roofs etc. It is much easier to get a smooth shape without kinks if you anneal the metal on the hob first. Just hold a corner of it with some old pliers , and dangle it in the flame - you will see the colour change move across it, and when it's done it can be left to cool and then cleaned up with emery paper. After that it can be rolled very easily with metal tube or wooden dowel. It works quite well on your thigh, as if it were a cigar...

Daddyman
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Re: Rolling brass roofs

Postby Daddyman » Thu Aug 19, 2021 11:55 am

Stuart Firth wrote:I have only ever rolled shortish roofs for vans, cab roofs etc. It is much easier to get a smooth shape without kinks if you anneal the metal on the hob first. Just hold a corner of it with some old pliers , and dangle it in the flame - you will see the colour change move across it, and when it's done it can be left to cool and then cleaned up with emery paper. After that it can be rolled very easily with metal tube or wooden dowel. It works quite well on your thigh, as if it were a cigar...


Thanks, Stuart, but I try to avoid annealing at all costs as, once softened, the brass remains that way for life, meaning that any annealed part is susceptible to damage. There's a quite a lot of wresting still to do on a clerestory roof after the work of bending, and that wrestling would inevitably lead to distortion with an annealed roof. True, the roof could be bent back into shape again, but that becomes a never-ending job.

billbedford

Re: Rolling brass roofs

Postby billbedford » Fri Aug 20, 2021 7:25 am

Daddyman wrote:Thanks, Stuart, but I try to avoid annealing at all costs as, once softened, the brass remains that way for life, meaning that any annealed part is susceptible to damage.


This is rubbish. Brass work hardens, so if you anneal before attempting to bend your roof, by the time you've finished forming the metal it will be sufficiently hard not to distort with ordinary use. You can also harden brass by planishing with a hammer and stake, but it takes a good deal of skill not to make a mess of the roof profile while you work on it.

Daddyman
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Re: Rolling brass roofs

Postby Daddyman » Fri Aug 20, 2021 6:19 pm

billbedford wrote:
Daddyman wrote:Thanks, Stuart, but I try to avoid annealing at all costs as, once softened, the brass remains that way for life, meaning that any annealed part is susceptible to damage.


This is rubbish. Brass work hardens, so if you anneal before attempting to bend your roof, by the time you've finished forming the metal it will be sufficiently hard not to distort with ordinary use.


All evidence to the contrary.

billbedford

Re: Rolling brass roofs

Postby billbedford » Fri Aug 20, 2021 7:20 pm

I was trained as a silversmith. I know what annealing and work hardening does to non-ferrous metals.

splam32
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Re: Rolling brass roofs

Postby splam32 » Sat Aug 21, 2021 3:58 am

billbedford wrote:I was trained as a silversmith. I know what annealing and work hardening does to non-ferrous metals.

I agree, brass will also harden on its own over time, so needs annealing to allow you to shape and easily cut the brass, but later it will return to a more harder state.

Daddyman
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Re: Rolling brass roofs

Postby Daddyman » Sat Aug 21, 2021 6:18 am

billbedford wrote:I was trained as a silversmith. I know what annealing and work hardening does to non-ferrous metals.

I have the brass in front of me. It is still soft. It nudges out of true every time I so much as brush against it.

Stephan.wintner
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Re: Rolling brass roofs

Postby Stephan.wintner » Mon Aug 23, 2021 8:19 pm

Brass is sold in various hardnesses, achieved by the amount of work after the last annealing.

The time and temperature of the annealing, and the starting hardness, result in various hardnesses.

https://www.ampannealing.com/articles/4 ... icroscope/

When you annealed it - how hot, and for how long? If it was dead soft, then I'd imagine the cold work involved in forming the roof would still leave it quite soft. If it was annealed from say 3/4 to 1/2 hard or 1/4 hard, on the other hand...

(Some googling leads to any number of links where sport shooters reloading ammunition are getting quite excited about exactly that, except as applied to their cartridges.)

Stephan

Stuart Firth
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Re: Rolling brass roofs

Postby Stuart Firth » Thu Aug 26, 2021 2:54 pm

Yes I'm certain it hardens with both work and time. Rolling roofs and boilers, I've never ended up with anything that's too soft or distorts easily. Perhaps it does indeed depend on the temperature - I just let the colour change happen, as it if was turning to Nickel-silver or gunmetal, I certainly don't let it get red hot. And I've seen people say that to anneal you need to quench the metal. I always just let it cool. If I were rolling a more complex shape such as these carriage roofs - something that needs working on after shaping for instance, I would be tempted to leave it for a few weeks after forming it.

Daddyman
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Re: Rolling brass roofs

Postby Daddyman » Thu Aug 26, 2021 3:08 pm

Stephan.wintner wrote:Brass is sold in various hardnesses, achieved by the amount of work after the last annealing.

The time and temperature of the annealing, and the starting hardness, result in various hardnesses.

https://www.ampannealing.com/articles/4 ... icroscope/

When you annealed it - how hot, and for how long? If it was dead soft, then I'd imagine the cold work involved in forming the roof would still leave it quite soft. If it was annealed from say 3/4 to 1/2 hard or 1/4 hard, on the other hand...

(Some googling leads to any number of links where sport shooters reloading ammunition are getting quite excited about exactly that, except as applied to their cartridges.)

Stephan

Thanks, Stephan. I had the brass (from Eileen's) up to red/orange hot and quenched it immediately. It may be that I took it too far... Interestingly, some 10 thou given to me by Dave Bradwell is extremely hard and quickly goes back to hard even after being annealed to red/orange. And with the half-etched and full-thickness 15 thou N/S used in Judith Edge kits, I've often had to re-anneal as the work hardens quickly- something that Mike himself has recommended.


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