One of the many things that I love about having a lathe, is the fact that it makes it so much easier to get a consistent result while tackling some of the more tedious tasks in railway modelling.
A task that I have aways found tedious*, is cutting/filing crank pin bushes to length so that they allow some play in the coupling rod and don’t bind or unscrew themselves when running in reverse.

*Mainly because although I can follow a line with a saw without too much difficulty, I really struggle to file surfaces at 90 degrees to the edge.
To get around this on the 8F, I turned up a little Arbor from some mild steel bar (more recycled toner cartridge rod). I threaded the end 10ba and using a 10ba nut, I was able to fit the tapped bush on the end then lock it with the nut and quickly and consistently remove 0.9mm from each one.

I have spent the last week or so fixing a number of mistakes that I made back when I didn’t know any better. For example, I realised when trying to fit the wheels that I had assembled the Premier coupling rods as a pair rather than handed, so one side only fit inside out. At the back of the workbench, I found an old pin punch. I popped it in the lathe and turned a small spigot on the end, to allow me to carefully pop out the rivets and swap the sections of rod around.

Once corrected I was happy to find that the rods ran smoothly in both directions without any sign of binding.

(As an aside I do like the built in motor restraint which is a nice bit of design work.)

The next bit of corrective action took most of a day to sort out. I had previously bent and fitted the two steam pipe sections that fit between the grease separator and the exhaust steam injector. These are made from 3.1mm copper rod which takes a bit of working to shape. Fast forward a few years and the grease separator casting had come adrift from its mounting pad and I hadn’t actually secured the front section of pipe. It was just pressed into the front flange of the grease separator casting. Without paying much attention I soldered the grease separator casting back in place and moved on to more of the motion parts.

While working on these I thought that it might be wise to fit the wheels and check that the Premier coupling rods matched the MOK wheel base and that I had a smooth-running chassis. It was at this point that I realised that the route of the steam pipe prevented the rear axle from moving through its full travel once the motor was fitted – The rear axle sat a good millimetre higher than the front axles. So, I removed the pipe (and the castings at either end) adjusted them and refitted to find that the pipe now hit the tyre on the rear wheel.

At this point I stopped refitting the castings and just kept adjusting the pipe bends. I did much of this with the aid of my vice, a thick-walled steel tube filled with lead and a white rubber mallet. I also made use of the “Markits” BA nut spinner set for making the tight tweaks to the very end bends after finding that the 8BA size just fit over the copper rod. I spent a couple of hours on Christmas Eve and around six hours yesterday before I finally got it to fit in place and clear both rear wheel and allow full vertical movement of the gearbox.

In reality once I come to set the ride height, the vertical movement of the gearbox may be less of an issue but better safe than sorry.

It was kindly pointed out that there is in fact a second spring that sits in the same place behind the pony truck but it isn’t shown fully on the plan view of the GA. If you look very closely at the plan view you can see just a small section of it that has been cut away to show other detail. But once you know what you are looking at, you can see it clearly on the side view.

Like most things making a second one was easier than the first because I revised the order of operations and I didn’t part it off from the main stock until after I had wound the ‘spring’ wire around it giving me a hand to hold whilst winding.

I also turned all the centre section down to the largest diameter which is that of the plates at either end of the spring, then I used a hexagonal collet block to mill the two nuts using a 2mm end mill and then finally turning the other sections to final size then using a round file to shape the curved sections at each end.

Once the cosmetic spring was added it looked like this. It only needed the finest touch with a file to remove the parting nub to make it fit between the frames.

For a mad moment I did consider remaking the first one but then sanity prevailed and I decided to put the first one to the back where it won’t be seen at all and put the second better (in my view) one at the front where not much of it will be seen either.

Although progress has been slow since my last post, I haven’t been entirely idle.
First, I fitted the brake cylinder that Adrian made for me some time ago for which I am very grateful.

Then for some reason which I can’t recall I was looking at the GA of the pony truck in the Wild Swan book and realised that detailed as the MOK Pony Truck is it’s missing the side control spring.

I scanned the GA, imported it into Fusion and having scaled it, I then drew up the spring and it’s mounting.

From there it was easy to create a dimensioned drawing to allow me to attempt to make one.

I debated whether to make it in one piece and then wind wire around it to represent the spring or to make it in two pieces and thread the centre section 4ba (3.6mm) which is the nearest sized die that I have to the 3.5mm that I had worked out from the drawing. I decided to have a go at making the one-piece version first. If that didn’t look good enough, I would have another go.

There was a slight discrepancy between the GA and the actual width of my pony truck so I ended up turning a couple of thin spacers to fill the gap but it worked out okay in the end.

As you can see, it actually sits largely out of sight (when viewed from the front) but I enjoyed making it, and I know it’s there.