Sunday, 15 February 2015

Bogie Bodge

I received my first test set of blank FR carriage bogie etches a while back and this week I got around to doing something with them.

The first stage is to sacrifice one of the etches and use it as a template for various structural details such as the axle boxes and suspension which I add on with styrene.

It is a little tricky as I use superglue to fix it to the brass and it is the most unforgiving of solvents.

This then becomes the master from which I create a rubber mould.

After leaving the rubber to set for a day I was able to start casting the first copies.

4 are required for a pair of bogies and they all turned out satisfactory at the first time of asking.

Next go back to the brass bogie frame, solder in the 'top hat' bearings and fold up the frame so it looks like this.

Then the castings, which have been cleared of flash and the holes for the axle boxes reamed out, can be pressed into place and glued on. It's so simple!

I've made it sound as if it all went perfectly, and in a way it did, but very early on in the process, right from the moment I offered up the first styrene axle box to the brass frame I began to suspect we hadn't got the size / shape of the etch quite right.

On its own the outline of the etch looks right enough but as the details went on it became clear that they should have been made taller with more frame above the axle boxes.

Then when I placed one of the bogies side by side with the Dundas Vale of Rheidol bogie which we have been using up until now it became crystal clear that they need to be taller and the stretcher where the bogie is bolted onto the carriage is much too low for it to be a like-for-like replacement.

So I think we're going to have to go back and get the etch redrawn and go for a MkII design.

I'm not in any way upset about this. All design is a process of trial and error and I take inspiration from the memory of our late friend Stefco who I'm sure would have thought noting of tweaking and trying again to get things right.

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