Brass for 7mm tank loco, Thickness?

[Porkscratching]

Probably a schoolboy question, what gauge or thickness of brass sheet, in mm, do you suggest for scratch building the basic structure of a simple tank loco ?

I realise a variety of gauges of metal would finally come into play here, but I'm just needing a start on the basic "shell" of the project, I've perused some of the astonishingly good builds within the forum which have been very informative and inspirational to say the least, ......still you've got to start somewhere!  Cheers gents...

[micknich2003]

I personally would use Nickel Silver sheet. Most 7mm etched kits are 15tho sheet, but 10tho in many cases will suffice.

 

[Porkscratching]

Less than half a millimeter then !

The nickel silver would be somewhat harder to work than brass I'd think..I'm wanting a fairly easy intro as it is a first attempt,  (I've done a fair bit of fabricating in real life, mainly with steel and arc welding tho !!! )

I realise there's lots of different solders at various melting points too....I can see the point of not wanting to melt what you've already done when adding bits!..would the basic structure be joined with a plumber's type solder and flux ?  I'd assume the multi core electrical stuff wouldn't quite do, but ??

[polybear]

I think the usual would be either 188 or 145 degree, with a separate flux (probably 145 degree, since with the mass of the basic structure acting as a heat sink there's less chance of melting those joints when adding smaller detail).

HTH

Brian.

[uax6]

Tinplate solders well as well.....

 

Andy G

[Porkscratching]

I hadn't thought of that, the heat sink effect, good point ! 

There's boat loads of sheet brass available on evilbay for not a lot of money, which is all good....tbh going with my real life tendency to 'over engineer' , I'd be tempted to go for at least a 0.5 mm sheet (  ie circa 20 thou in old money )

Tin is a nice idea, I like the old fashioned-ness of that !  The snag there, I imagine, is where to get some nice sturdy tin ? I'd think the modern biscuit tins are a bit flimsy !

[uax6]

4d modelshop sell sheets ..... http://modelshop.co.uk/Shop?term=tinplate

 

 

Andy G

[Michael Edge]

0.015" is thick enough with brass or n/s, I mostly use 0.012" and 0.010" shim steel though. 0.010" is best where the edge of the plate has to be visible - e.g. footplate edges.

[Porkscratching]

Cheers gents, I'm assuming once the thinner gauge stuff is together it's reasonably rigid, what's the situation with distortion and heat?

Possibly not relevant but as a welder it occurred to me !

[Lissadell]

I think that the commonest material for 7mm scale chassis is nickel silver.

 

I’ve mainly worked with 0.55mm(22 thou) but other manufacturers use 0.7mm (28 thou)

 

Nickel silver is very nice to work with, but even the standard half hard variety is quite tough to saw and drill.

 

I maybe wouldn’t go thinner though - you might be asking too much of the chassis in 7mm if you do.

 

Regarding the bodywork, my own efforts and many others I’ve come across, use 0.5mm (18thou) material.  Most commonly brass, but n/silver is a very worthwhile alternative.

I guess you could try out 0.45mm (15thou) sheet - it will certainly be easier to cut and file.  But personally I wouldn’t use anything thinner than that.

 

Why not?  well one reason is soldering.  The metal will heat up very quickly and spread over a wide area - whilst you’re waiting for the solder to run/reach temperature, you might be entertained by thin metal starting to curl, twist and generally protest!!

 

Another reason is handling the model and vulnerability to dents - very easy to get this damage, not very easy to deal with it.

 

Adrian

[Guest Lyonesse]

1 hour ago, Michael Edge said:

0.015" is thick enough with brass or n/s, I mostly use 0.012" and 0.010" shim steel though. 0.010" is best where the edge of the plate has to be visible - e.g. footplate edges.

Michael,

 

Where do you get your shim steel, and do you run into any problems using steel sheet instead of the more usual N/S?

[Porkscratching]

1 hour ago, Lissadell said:

I think that the commonest material for 7mm scale chassis is nickel silver.

 

I’ve mainly worked with 0.55mm(22 thou) but other manufacturers use 0.7mm (28 thou)

 

Nickel silver is very nice to work with, but even the standard half hard variety is quite tough to saw and drill.

 

I maybe wouldn’t go thinner though - you might be asking too much of the chassis in 7mm if you do.

 

Regarding the bodywork, my own efforts and many others I’ve come across, use 0.5mm (18thou) material.  Most commonly brass, but n/silver is a very worthwhile alternative.

I guess you could try out 0.45mm (15thou) sheet - it will certainly be easier to cut and file.  But personally I wouldn’t use anything thinner than that.

 

Why not?  well one reason is soldering.  The metal will heat up very quickly and spread over a wide area - whilst you’re waiting for the solder to run/reach temperature, you might be entertained by thin metal starting to curl, twist and generally protest!!

 

Another reason is handling the model and vulnerability to dents - very easy to get this damage, not very easy to deal with it.

 

Adrian

That all tends to go along with my gut feeling and what I do when making full size things!

I'll probably go with the circa 0.5 mil brass to begin with, bearing in mind I've never built a metal loco before, and ease of construction would be nice!

Also distortion would be a most annoying factor with ultra thin material, obviously I've encountered distortion many times with welding ops.

I'd be creating the 'body shell' first and worry about chassis later, (again probably erring on the side of hefty for that too)

Thanks for all the input thus far...

[RLWP]

1 minute ago, Porkscratching said:

That all tends to go along with my gut feeling and what I do when making full size things!

I'll probably go with the circa 0.5 mil brass to begin with, bearing in mind I've never built a metal loco before, and ease of construction would be nice!

Also distortion would be a most annoying factor with ultra thin material, obviously I've encountered distortion many times with welding ops.

I'd be creating the 'body shell' first and worry about chassis later, (again probably erring on the side of hefty for that too)

Thanks for all the input thus far...

 

I think you'll give up pretty quickly

 

The thin nickel silver will cut with a reasonable pair of domestic scissors and is more resistant to accidental bends and dents. It doesn't tarnish quite so quickly too, so cleaning for soldering is easier.

 

Sawing 0.5mm will become a chore pretty quickly, and is going to make bends tricky - not to mention the consumption of sawblades. Most of the available brass seems to be pretty soft and grabs blades, if you must use brass search out half hard sheet

 

You won't get massive heat distortion with solder, welding is a much more intrusive process! And thinner materials don't need so much heat

 

I'd suggest you have a rethink

 

Richard

[Porkscratching]

As I say, I've never done this before, so all this is good info!

I guess coming from fabricating stuff in the "12 ins to the foot" scale, half a millimeter sounds tiny, and very flimsy, but in 7mm scale I guess it's equivalent to armour plate!

The sheet I've been perusing on evilbay....some has called itself 'half hard' as you mentioned, I take it this is the stuff I want?  CZ 108 seems to be a 'spec' that's bandied about, I'm assuming this is a copper/zinc formula or percentage ??

The model I envisage btw has very few bends involved, really just the roof, other than that just flat sheet fabricating...the boiler I'd try and source a piece of tube, if I can find the right diameter

Edited July 8, 2019 by Porkscratching

[RLWP]

3 minutes ago, Porkscratching said:

As I say, I've never done this before, so all this is good info!

I guess coming from fabricating stuff in the "12 ins to the foot" scale, half a millimeter sounds tiny, and very flimsy, but in 7mm scale I guess it's equivalent to armour plate!

The sheet I've been perusing on evilbay....some has called itself 'half hard' as you mentioned, I take it this is the stuff I want?  CZ 108 seems to be a 'spec' that's bandied about, I'm assuming this is a copper/zinc formula or percentage ??

 

I started out like you thinking brass was the right stuff, until I used some NS. It's much easier to get good results with the nickel silver

 

The spec for CZ 108 is available in all kinds of places: https://www.smithmetal.com/pdf/copper-brass-bronze/brass-alloys/cz108.pdf

 

It has good cold working properties suggesting it's going to be good for making pressings

 

You really need to be using a range of different thicknesses for different things. Here, for instance:

 

 

This is a modified Brian Madge 009 kit. The new 'frames' are 0.010" as is the cab. The cab then has an embossed wrapper made from 0.005" glued on

 

Thin sheet is surprisingly strong yet easy to work with

Richard

[Lissadell]

The half hard nickel silver sheet spec (my earlier reply) is, I believe, NS/CW409J/HH

 

0.55mm nominal can be between 0.53 and 0.57mm

 

0.7mm ( the stuff you don’t want to tackle with hand tools!)  is within an accepted band of 0.68 - 0.72mm

 

A little guillotine and some multi tool (bend and roll) like the mini ones Warco do, wouldn’t go amiss.........

 

However, as the previous writer hints, maybe you’re letting yourself in for a lot of hard work scratchbuilding!

 

I can’t help thinking a bit of time spent learning just the rudiments of CAD could generate a few etches quickly.  You could then use your time productively in assembling something from the parts you’ve drawn.

 

If you’re tidy (and thinking small) it’s surprising what you can squeeze onto an A4 sheet - that won’t cost the earth to tool up and print etches from.  

 

You could even do a combination of scratchbuilt simple parts  and home drawn, etched, more awkward parts.

 

Dunno if that makes sense?

 

Adrian

[Porkscratching]

Thanks for the pics, gives me an idea of the thinner gauge..

...Ooh Cad, I'm afraid I'm an old bloke who does mainly 19th century engineering, with a minimal smattering of modern tech..!

I've got a reasonable selection of tooling, bending I'd probably do in the big vice with some nice smooth angle as guides, tho the thing I'm planning doesn't have much bending required, simple flat planes.

Having searched my stash of metal all I have in brass ( just to get a feel) comes out at circa 1mm according to messers Moore & Wright, though some of this may be useful for a solid footplate, chassis rails, buffer beams etc..

I would probably transfer my 'drawing' to the metal ( flat pieces anyway) with the old photocopy glued on to the plate trick, mark and cut around it..

[RLWP]

Right - only as the loco is symmetrical you want to cut two bits at the same time:

 

This is the new frames for Cadfan being cut:

 

 

This is a stack of the original frame, a bit of scrap brass, the two new frames, then another bit of scrap. All are soldered together - the original frame to the scrap completely, the rest of the stack by solder tacks at the end. When the cutting is complete, the stack comes apart

If you solder two bits of 1mm plate together to get a symmetrical loco, that's 2mm you will be working with. Ideal for heavy duty drilling and filing but otherwise rather an overkill

Keep that bit of 1mm for the footplate

 

Richard

[Porkscratching]

Cheers! ...Good idea stack cutting the frames ( tho I wont be doing a chassis until I've got a cab, boiler, footplate assembly together)  and as the cab/tank sides are identical, the same deal with them...

Yes, I did rather fancy that nice lump of brass for the footplate as you say !

( I've got a few more pieces the same in my odds and sods dept. too )

[RLWP]

In case it isn't obvious, I wanted the frames to be thin because the etch they replace was also thin. So there are two strips of NS.

 

That's too thin to saw (but easy to shear even with domestic scissors if well chosen), so I used a couple of bits of sacrificial brass on the outsides. That brings the stack up closer to 1mm which is easy to cut with a piercing saw. Tack soldering and using bits of scrap makes a lot of things easier

 

Richard

Edited July 8, 2019 by RLWP

[Michael Edge]

8 hours ago, Lyonesse said:

Michael,

 

Where do you get your shim steel, and do you run into any problems using steel sheet instead of the more usual N/S?

I get it from Mitchell Fox in Leeds. It's not difficult to saw and straight cuts can be made by scribing and cracking. Solder with phosphoric acid as flux, this is the basis of rustproofer for steel. The soldered joints do need quite a lot of cleaning out but the big advantage of this material is that it's easy to keep flat. It presses out very cleanly when forming rivets as well.