A friend who has far more experience
than I do, suggested I check to see if the pony truck had enough swing to go round the
minimum curve of the track, which I believed was a 50 foot radius. So I went back to the
computer and laid out the lines,
rotating the truck through its present setting and found
that it was not enough and would only pass on a 60 foot without trying to spread the rails.
I had to re-set the blocks and springs which control the side thrust and now, at least
theoretically, it will go round a 40 foot radius. Hopefully this should do the trick. (Now
I discover the smallest radius is 75 feet!) The two pictures show the state of play at
the moment. The next job will have to be the springs and hangers before I can do the
coupling rods. Unfortunately, I haven't been able to get enough of the bronze strip
specified to complete four springs. But the cylinder castings arrived. They look very
nice but so they should for £179! This completes the castings apart from the brake handle
shaft; I'll fabricate that.
Before I can make the coupling rods, I need to make the axles at the same height and that
means making the springs. I'm doing the same as the original Romulus and an extra pair
for the extra axle.
As can be seen from the photo, there are a lot of individual bits to make. Some of the work,
repetitious. The hanger brackets have been fabricated as per the drawing and look rusty in
the photo. They have just come out of the pickle and this affects the colour of the silver
solder. The pickle which I use for steel, is a drain cleaner; spirits of salt. It's cheap
and has a base of hydrochloric acid. I dilute it about 2:1. Cleans the most stubborn of
stains including rust. The overall finish is a dull grey which wire brushes off to bright
steel ready for painting.
Out of all the lathe tools I possess, there are two which I could not now do without. The first is the quick-change tool post which lets me change tools in seconds. The other is the parting off tool. It's the sort that has tipped inserts. Both were expensive but worth every penny. To make the hanger straps I needed two rings 5/8" diameter with a 1/4" hole for each one; thus I needed 32 rings. This is where the parting off tool was at its best. Parting off speed was around 600RPM, with no lubrication on the EN1A. There was no binding and it was straight in. I wouldn't be without it. It's amazing the length of life of these tips. The only material it doesn't seem to like is phos.bronze.
The piece in the middle of each strap was done in the mill with a 5/8" cutter. Getting the length right was time consuming. The two rings are silver soldered in place as per the example in the foreground.
The bronze strips were cut to size and put through the roller to get the curve the correct
size, after the centre holes had been drilled. The bronze is surprisingly tough and could
not be bent by hand when slightly out of curve. Riveting in the block needed two clamps to
keep the lid on. Everything seems to be OK but I've only been able to make the rear springs
as the suppliers had run out of bronze.