GWR Four Wheel Coaches

M

Mikemill

Western Thunderer
A model of a GWR 4-wheel coach is one on the to do list. The coach body is made from styrene sheet of various thicknesses, the inside layer is 2mm thick to form a ridged base, then 3mm vertical tapered spacers are fixed with solvent to this layer, to allow for the tumblehome and create pockets for the glazing. The 0.5mm panel layer is fixed to the outside layer, the droplights and the bolection mouldings are then fixed to the door and windows openings, followed by fixing the outside layer to the inside. Finally, the sides are fixed to the floor and the ends slot into the overhang of the panel layer. The roof is formed over a styrene framework that plugs into the body and is removable to allow access to the interior. After painting the glazing is dropped into place.

Mike


P1000567B.jpg P1000568A.jpg
 
geoff_nicholls

geoff_nicholls

Western Thunderer
That looks very nice indeed. I do like those bolections. I tried to produce something similar myself, a few years ago. A 5 comp 3rd, brake 3rd and 4 comp composite, in laser cut rowmark. I was hoping they would be patterns for one piece resin cast bodies. But forming the tumblehome in rowmark defeated me.
 
adrian

adrian

Flying Squad
Mikemill said:
The coach body is made from styrene sheet of various thicknesses
Click to expand...
That is really impressive - the layers really add a superb depth to the body. Are the layers hand cut (given the consistency - hard to believe) or computer cut, silhouette, laser or router cut?
 
AndyB

AndyB

Western Thunderer
Very impressive, Mike.
I assume, for the 'lacy' bits, you start near the centre and work outwards from there in order to keep the area being cut as stiff as possible?
Do you not get any distortion when cutting the second side of a narrow bead?
Can you tell / show how you hold the sheet down, and about the cutter type & speed?

Thanks,
Andy
 
M

Mikemill

Western Thunderer
Andy

I hold the sheet to be cut in a jig made of MDF as in pic, then work from the top row of panels along the length then down to the next row, if you make the start point the bottom of the panel the cutter is always working against solid material. I use a 2mm cutter running at 3000rpm and 4in per min.

Mike
DSC_0007.JPG
 
M

Mikemill

Western Thunderer
Dave

Yes it's a brake third, I am planning on building a first, second composite as well.

I would like to build some clerestories but in G3 they are over 30in long and take up a lot of room.

Mike
 
Dave Bowden

Dave Bowden

Western Thunderer
Could I ask what the prototype your using, with the measurements over the headstocks & wheel base. I have copies of the GW Coach Lots & Wagons.

If you wish I will be able to provide details.

Dave
 
paratom

paratom

Western Thunderer
Very impressive Mike, I'm amazed that the cnc machine can handle the very narrow sections without distortion. I have a small cnc mill but have only ever used it to cut nickel silver and brass. I suppose you could do these coaches in the same material if you wanted to. I also have a laser cutter and have thought about using Romark to make coache sides and ends. The ducket must have been really tricky to put together. On a 51L Midland Railway brake van kit I was putting together I decided to 3D print the ducket rather than try and solder it together. It came out fine using clear resin which was then painted leaving the glass sections unpainted. In the end I decided to not let myself be defeated and used the etch one but what a bugger to solder and put together.
 
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M

Mikemill

Western Thunderer
The tumblehome is not a problem I used 1/8 square section styrene with the curve cut from half way fixed to the inner layer vertically between the compartments, then fix the two layers at the base first when dry fix the top half of the outside layer, this will follow the curve of the spacers to form the tumblehome.

The joy of using styrene is it sticks together instantly with solvent so you can form shapes very quickly

Mike
 
paratom

paratom

Western Thunderer
Mikemill said:
The tumblehome is not a problem I used 1/8 square section styrene with the curve cut from half way fixed to the inner layer vertically between the compartments, then fix the two layers at the base first when dry fix the top half of the outside layer, this will follow the curve of the spacers to form the tumblehome.

The joy of using styrene is it sticks together instantly with solvent so you can form shapes very quickly

Mike
Click to expand...
Sorry I meant ducket not tumblehome.
 
M

Mikemill

Western Thunderer
The ducket is formed over a framework, the two sides with the window opening and ribs to hold the sides to the correct width. Using 1mm styrene the outside can be curved using your fingers, I fix the middle first, let that dry then the curves, once set the panel moulding is applied, again styrene is pleasant to work with.
 
paratom

paratom

Western Thunderer
Do you use Lemonene or Mekpak to glue your parts together? A friend of mine builds very good architectural models using Lemonene and finds it gives him a bit more time to make sure the pieces he is sticking together are in the right position. It is also less aggressive than Mekpak which is helpful when glueing very thin parts which can almost melt away when using the other stuff. I imagine you can vary the spin speed on your cnc miller otherwise you could end up melting the plastic caused by friction.
 
M

Mikemill

Western Thunderer
I use Mekpak to fuse styrene together, cutting styrene on the mill is a question of speed and feed rate like all materials they have different requirements. When I started to use styrene, I did get build up on the tool, but with experimentation I found a new cutter to be half the answer.

Mike
 
Dave Bowden

Dave Bowden

Western Thunderer
Hi Mike
Here's the details on the build and steam Htg dates I told you about. There were 10 built on that Lot no. 978

942 Built 8/01, Htg 1/03.
949 " " "
950 " 9/01 9/01
951 " 10/01 11/01
952 " " "
953 " " 8/02
954 " " "
955 " 9/01 9/01
956 " 11/01 8/02
957 " 9/01 9/01

There were only 3 fitted with steam Htg from new, 950,955 & 957. The rest were done later.

Dave
 
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