Getting the body dry assembled showed me how the motor gearbox has to fit, so it has been back to the chassis. I discovered that the holes in the cylinder front and rear etches are smaller than the size of the cast parts that fit therein. No surprise of course, but like an idiot I didn't check and open them out before soldering the etches in place. Not an issue for those parts that fit outside the frames, but for the whitemetal castings that form the middle cylinder slidebar assembly and valve chest cover it's a bit of an issue that may require me to file down the locating lugs on the castings.
The slidebar/crosshead assembly has taken time to get right, but time well spent I think. It took about 3 hours of careful filing and polishing to get the excellent lost wax castings sliding nicely together. The time taken was mainly me not wanting to rush it and taking a only little off at a time before trying again. I did have one issue: the distance between the square hole on the cylinder plate and the centre of the hole for the piston rod is not quite the same as the distance from the lug on the slidebar assembly to the piston rod. I had to open out the hole for the piston road gland and file the lug down.
If I have read the instructions correctly - and I did misread them once already - DJH supplies a 1/8" 10BA cheesehead screw to hold the con rod in the crosshead, but the cross head is 1/4" thick. I countersunk the rear of the crosshead and substituted a 1/4" countersunk screw, which will help with clearance to the leading wheels.
Here are the crossheads, con rods and piston glands.
DJH notes that the inside rear of the slidebars need filing to give clearance for the con rod. To get an idea how much would be needed I set about fitting the wheels and coupling rods in place first. The leading and trailing wheels use 12BA screws, but I replaced the Slaters ones with countersunk steel screws loctited in place. DJH supplies a set of reduced height crankpin bushes to fit on the leading axle. DJH also supplies a special crankpin for the centre axle which requires the wheel to be tapped M2. I had a slight problem with the thread on one of teh crankpins being bent slightly, but hand on heart I cannot say that it wasn't me being ham fisted when trying to clean up the thread on the pin with an M2 die. For some reason I just couldn't get the die to start and resorted to using a steel M2 nut a few times until I could run the nut on and half by hand. The crankpin can be seen in the following photo.
It was very pleasant to find that with the coupling rods on the chassis rolled freely first time without any binding.
I was concerned about fitting the slidebars to the cylinders. With the crosshead captive in the bars, the whitemetal piston gland casting has to be in place as the slidebars are soldered in place. I was concerned how to do this without melting the whitemetal and getting the alignment correct. In the end it was far far easier than I could have wished for. The slidebars are actually held in place by the motion brackets, both of which are formed from two etches, one of which represents a piece of metallic origami.
I used a piece of 1mm wire to align the eccentric pivot rod holes and soldered to the frames.
The slidebars and gland were placed in position in the cylinder etch and then the pre-tinned slidebars soldered to the motion bracket. Finally the slidebar locating lug was quickly soldered to the inside of the cylinders, the alignment of the gland checked so that the crossheads still run freely in the bars and then soldered in place from the inside of the cylinders. There isn't much clearance between the con rod and the bars, but not much is good enough!
So next is the remaining cylinder furniture and brake gear, then off to the paint shop.