Author Topic: Am I Stark Staring Bonkers....probably?!  (Read 435 times)

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Offline John Candy

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Am I Stark Staring Bonkers....probably?!
« on: August 19, 2017, 07:22:12 PM »
I am considering how to produce carriage sides (up to approx. 88cm x 9cm) from either (or both) sheet brass/aluminium.

Current thoughts are to use a Warco mill and, with two vices to clamp the material to the table at its extremities, sliding the work piece through the vices as I work along the carriage side, which greatly exceeds the table length.

I know that, without CNC, this will be a slow and tedious process (but I don't feel that the cost of a CNC machine is justified) but does it otherwise sound a practical proposition, bearing in mind the light gauge of the sheet?

I anticipate the sheet will need a "backing" (in view of otherwise unsupported length and depth) to prevent bowing/distortion and am wondering what would be best options (not wishing to clog or damage the mill which would be only around 5mm dia. to produce correct corner profile on the windows).

Anyone tried milling brass or aluminium sheet 1mm or less?

First attempt will be to modify a pair of GRS "B set" coaches to GWR 57ft corridor stock by replacing the brass sides with new brass sides and that (if successful) would be followed by scratch-built GCR and LMS stock in aluminium and brass, with cast resin ends, etc.

John.
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Offline IanT

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #1 on: August 19, 2017, 09:07:48 PM »
Well I've not milled thin brass in the way you describe John but I have fly-cut and 'shaped' thin brass along its edges when it's clamped between two steel plates. Brass is quite grabby and I think you are going to have to hold/secure it near to the cut (rather than at the ends of the milling table. Otherwise I think you might get a bit of tear out or edge distortion but maybe not...

However, I think if I was trying this, I would probably make a pair of 6mm thick steel plates (120mm high x 50mm + window-mm wide) with a central cut-out for the opening/tool. The bottom plate would be secured accurately & aligned to the table (via T-nuts and NOT moved) and the top plate would be removable (in order to shift the material) but could be replaced (in alignment with the steel lower plate) by pins, preferably tapered ones. The sandwich would then be clamped tightly together by top-clamping. The actual table X/Y movement would be controlled by stops such that the cutter doesn't actually touch the steel clamps (5-10 thou clearance).

You'd need to accurately mark up the brass sides so you could index them across the table but you could work on just about any length doing it this way - even on a small mill. Thinking about it, I might also use the mill to cut a shallow channel (same height/width as the sides) in the bottom clamp once it's bolted down and aligned. Then you could fit the side into the milled channel, knowing it will be kept aligned when you slide it. The top plate could be made with a matching 'lips', so it still clamps the work securely and obviously you would still need to register the top and bottom plates together outside of the channel section.

I'm assuming that the 'openings' are mostly the same size, as you will need a clamp set for each different one. Sounds a lot of work but it's probably worth it if you are going to mass produce a lot of coach windows (e.g. even for just one coach...). If any holes need drilling, then the same clamp sets could also be used as a drilling/marking out jig - either drilling directly or tapping a pin-punch through to mark the hole position.

I'm pretty sure this would work but you can easily find out/experiment by clamping a short piece of the brass you intend to use between two steel plates and milling along the edge of the sandwich so formed. Whilst at it, you might also want to try milling an unsupported edge and one with a back-plate - to enable comparisons. With a smaller piece of work, a backing plate of some kind (aluminium perhaps) might have worked but each side would then have needed a full length sacrificial base and you still have the problems associated with getting the work set-up each time you move it - so I think the fixed clamp/jig is a better approach...

Anyway, that's my thoughts on the problem - but maybe others here have done something much simpler and been successful... 

Regards,

IanT
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Offline midnight miller

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #2 on: August 19, 2017, 10:09:30 PM »
hello All

Make a pattern , say three times full size . Rig a fence on the work table and use a pantograph miller .



                                                    John

Offline John Candy

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #3 on: August 20, 2017, 01:22:28 AM »
Ian,
Thank you for those useful suggestions which I shall study and get my head around.

John,
Unfortunately, I don't have a pantograph milling machine. If I did the pattern for a carriage side would be 8ft long at 3x scale size.

Regards,
John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline MikeWilliams

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #4 on: August 20, 2017, 08:43:46 AM »
If this is to represent flush-sided stock why the 1mm thickness (roughly a scale 1in)?  Could you use thicker and mill a recess around the windows from the back?

Or laser cut in steel or aluminium like Tim Kraay?

Or etch in bras with a join down the centre so its not too long?

Mike

Offline John Candy

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #5 on: August 20, 2017, 09:02:33 AM »
Mike,

Unfortunately, to have etched or laser cut requires CAD and I have never learnt that skill.
A quote from a leading etching co. suggests that the process would be uneconomical to produce just one set of carriage sides (which is all I need for the two types of GWR corridor coaches ... diagrams C67 and E148).

Roger Mc is obtaining estimates from a local engineering contact to see whether it is practical/affordable to have the sides CNC milled for the GCR coaches.

Regards,
John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline IanT

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #6 on: August 20, 2017, 10:19:16 AM »
Given the time and patience you've put into your other projects John - I think gaining the necessary skills to do a simple '2D' CAD drawing of a coach side would be a very good investment. I use TurboCAD DL which is not expensive if you buy a slightly older version (look on Amazon). There are some very good tutorials on YouTube which are worth doing as they will set good habits in place. The key thing to master is 'snaps' and once you  grasped these - it's very simple to do the kind of 2D drawing that a coach side would involve. You could then generate DXFs for laser cutting if you felt this was an affordable option (although the size of this project may be a problem cost wise).

As an aside - I've been playing with Fusion360 lately, a very modern parametric 3D CAD system but I have been wondering what I would actually use it for - as most of my needs are already met by TC and are not 3D or complex in nature. I can already generate DXF files for laser cutting if required.

Of course, if I wanted or needed to go 3D CNC or 3D Printing - then Fusion would be very useful. For Home use - the cost vs usefulness ratio (for me at least) still isn't attractive enough and although 3D printing may be more affordable, I have too many other unfinished things to worry about jumping into newer tech at the moment. But outsourcing small (laser cutting) jobs does appear more affordable these days...

Getting back to coach sides, in terms of actually cutting metal - however you do it - in essence each cut is a single X and matching Y cut - no complicated curves or profiles - the cutter providing the corner profile. Provided you can index the sides between each cutting area accurately, then nothing special is required - just repetition. So I think a 'low-tech' solution should be quite feasible and probably the cheapest - provided you don't cost in your time of course!   :-)

OK - coffee break (and rambling time) is over - lawns to cut.

Regards,

IanT           
Nothing's ever Easy - At least the first time around.

Offline MikeWilliams

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #7 on: August 20, 2017, 10:38:53 AM »
John,

I am sure there will be a laser cutting firm near you that would cut these.  They would also undoubtedly do the CAD work for you at a cost - worth asking.  Failing that, there are some on here able and willing to do it, including me.

Mike

Offline Spitfire2865

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #8 on: August 20, 2017, 07:31:39 PM »
Im pretty good ar 2D cad work. And my time is almost worthless!
-Trevor Young

Offline MikeWilliams

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #9 on: August 20, 2017, 08:04:10 PM »
John,

There's a great offer from Trevor and although he is far better than I am, I could also do it if you get stuck.  Just sketch out freehand what you need for the first sample side and send it.  These people should be able to cut it for you:  http://www.dmslaserprofiles.co.uk/  or they may suggest a smaller company nearby.

Failing that I can get it cut here and send/deliver to you.

The biggest problem I think you'll have is curving the sides.  It needs some long rollers (which I have) but the bend is very gentle and right down to the edge of the metal.  That applies whatever method you decide on to make them of course, unless you etch double thickness and include horizontal lines on the back of the inner sides.

Mike

Offline John Candy

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #10 on: August 20, 2017, 08:46:59 PM »
Trevor and Mike,

Thank you both for your generous offers.

I will copy the drawings/info I have on these GWR diagrams and check the dimensions tally with the GRS coaches , which should be the same size and profile... but with GRS and the Chinese manufacturers you never can be sure!

Will be in touch, it may take a few days to get it together.

Thanks again,
John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline MikeWilliams

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Re: Am I Stark Staring Bonkers....probably?!
« Reply #11 on: August 20, 2017, 09:13:45 PM »
John,

A final word for now.  I do suggest you contact your local people.  My local chaps have a laser which can cut aluminium but have no call for it, so never do it and the last time they tried got into all sorts of difficulty.  So, I suggest you find a fabrication firm who cut aluminium regularly - or use steel (or stainless) instead which everyone can cut because they do it all day long.

Mike