...interesting where the journey takes us sometimes. I had intended this week to build all the brake equipment between the frames (cylinders, plumbing, tanks etc..) I made a vacuum reservoir tank from telescoping tube as I don't have a lathe (no neeed for comment here Mr DLOS!) and it took a while to cut nice angular cylinders by hand. So I attached the assemblies to the frames and my immediate thought was that there would be a conflict between the tank and the bogie.
So I downed tools on the brake system and thought it'd be a better idea to build the bogie first. I have built a few pre grouping bogies recently and they all seem to be built along the same principals. I guess this loco had a fixed bogie and was effectively a 0-4-(2+2) arrangement. The bogie carries roughly half of the loco's weight so doesn't have any vertical springing between the chassis and bogie bolster. All the springing is in the bogie axleboxes and equalising beams, and there is just rotational and lateral movement at the chassis/bogie pivot. As I am going to have to make the second driving axle rigid to accommodate the patent Dunhill/Beeson/Smith drive mechanism, so the bogie will have to have some vertical springing or the driving wheels will lift off the rails on undulating track (I'm sure none of you have any of that, but just in case...)
So I have learned that buying a cast spring that is similar in size to the original brings inevitable re-designs to the eqalising beams (and almost every component on the bogie.) I decided to get Mickoo to etch the parts for the spring, together with the other components of the bogie, to test the hypothesis that it would be easier to fabricate individual springs from etched leaves than bugger about making a cast spring fit the rest. Well possibly maybe is the answer. I filed etching cusps off dozens of etched leaves, bevelled the edges, filed a taper on the ends and carefully bent them into a gentle curve.
The bogie chassis had phosphour bronze wire side control fitted.
The springs and equalising beams did take a while to make but do look better than a 'nearly' cast spring.
I had to assemble the bogie chassis on parallels blocks as the wheel axles were standard 3/8 tharg and the axles blocks accept 5/32 thargs. My mistake I forgot to get the axles machined. I think the finished bogies justify the effort.
Back to the GA and I noticed a plinth between the bottom of the chassis and the bogie bolster. I decided to make a pair, but a millimetre shorter so I can accommodate some vertical movement. Some experimentation with my dwindling stock of springs will be necessary! (Anyone know where to get very small numbers of smallish compression springs?)
Next week I go back to the brake system, via the couplers (if they ever turn up!)......