Challenging Commissions

I do like a challenge!

I find the repetitive stuff in building model railway items the hardest just from a motivational point of view. I guess I get bored easily and need to be challenged to keep me interested.

This one was certainly a challenge! In more ways than one as it turned out.

The commission was to make an model of an original Spooner bogie to 16mm scale. The first challenge was converting ancient blue prints that didn’t tell you all the information into a modern CAD model.  Only heavily modified descendants of the original Spooner bogie exist so looking at them only helped with clues rather than providing something that could be copied. At the very least they have been modified to include brake gear which wasn’t even an optional extra on the original. There have been changes to the suspension as well over the years.

I use SolidWorks for my CAD so a full solid model was created in the CAD comprising of many individual components then put together in an assembly drawing to see if it all fitted together.

Now here’s a thing. When drawing a pen and ink blue print you can draw a line any length you like and write a dimension on it and no one says a thing. (well, the bloke on the shop floor might call you names but then he’ll just build it how he’s always built it.)  3D CAD wants the dimensions , wants them to be right and gets cross with you if they are not. Often it refuses to go any further until you do get them right, or at least work out a lie that its happy with.

Now the thing with the Spooner Bogie is that it has a spherical centre and then a secondary suspension arrangement that takes some of the weight off the centre with a sort of spring in a cartridge arrangement which bears on castings on the inside of the frames.

Sorting the design out was the first challenge, then it was on to making it. Many of the parts were to be 3D printed on my new 3D printer.  Learning to use that was the second challenge as this was the first real job to be done on it. It was quite a steep learning curve with more than one false start whilst the boundaries of what is possible were tested.

My printer is a Formlabs Form 2, a proper production machine rather than a hobby machine, and probably the closest you can get to a desktop printer at the moment.

Its still not straightforward with the prints having to be cleaned and then cured but it us developed to the point where its a process in which you don’t have to touch the resin or the wash.  Its still messy with uncured resin and buckets of Propanol swilling about.

Eventually the process produced a load of printed parts to which then had to be added metallic parts and then the whole thing assembled. Trying to turn and thread 14BA suspension bolts generated some poor language!

Also practical assembly resulted in some mods and some reprints.

 

Eventually it all went together. It was then painted and weathered and a bit of display track made for it.

Just a quick note on weathering. It’s weathered to show up the details and to mimic the way it catches the light. I was asked if I was going to paint it black just as I finished it. I was not impressed!  On the other hand if I had painted it gloss black I could have missed half the details off as they wouldn’t be seen.

Anyway, here are two pictures of the finished item. You decide if it came out alright

 

 

 

One thought on “Challenging Commissions

  1. Brilliant recall seeing the original version at Trent valley and it looked impressive there BUT as u state in your blog we have to settle on one scale and mine is now 7mm on 16.5 although going thru Harbour stn and seeing the slaters 16mm quarry hunslet nearly cost me several hundred pounds and a static model ! anyway looking forward to the wagon kits idc and finding the money for the l and b loco at xmas pleae do keep up the very good work both as a modeller and as a f.r. notable will see u over the agm weekend cheers Richard pyatt

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