K3s Progress 2014 to 2015
The outside cylinders continued
Following the 2014 exhibition work eventually got underway properly again in July. Perhaps retirement at the end of July speeded things up but it didn't feel like it at the time. Looking through the photographs shows that a lot of progress was made, to the extent that I have only taken this instalment as far as the end of February 2015. So the following describes the majority of the work on the outside cylinders and the primary machining of the smokeboxes . The final machining of the outside cylinders and the fabrication of the inside cylinders are for the next instalment.
The next parts needed to progress the cylinders are the passages between the valve chest and the cylinder . These would need to be split to go round the valve chest so the raw material was made in two halves and silver soldered together for machining.
The three holes are for the two location dowels and the bore centre
The part is mounted in the four jaw and bored to fit the valve chest.
After facing the part is remounted on a fixture and set up on the rotary table to be counterbored off centre with a radius at the base forming the cavity around the valve chest.
Milling operations complete the passageway, with a ball nose cutter to finish the internal corners.
The cylinder face is milled while still on the rotary table
The outside edge is then milled to radius
The sides are also milled to size and the part turned over to radius the outer edge with a corner rounding cutter
Machining complete on all eight steam passages
They were heated and split
A pair are in place on a cylinder but not fixed
Gresley designed cylinders had a cast in back cover so the next components to make were these. They are a simple turning exercise and have a spigot on the cylinder side to locate, with a thin flange on the outer face to make them appear flush with the cylinder back when dressed off.
Components are temporarily fixed using 10 ba studs. The parts are clamped together and tapping size holes drilled as necessary, tapped and the stud screwed in. This is normally sufficient to keep things together till silver soldered. Two of the back covers in place
Now at the point where the cylinder could have its first stage of silver soldering. All areas that would be better if they were not coated in solder were painted with correcting fluid (Tippex in this case)
The joints were then treated to a generous coating of flux, in this case HT5 because I fancied the operation might take some time.
Here's a cylinder set up on the hearth for the first stage
The silver soldered cylinders were cleaned up in a pickle of citric acid and because the soldering operation was difficult with areas that were not in direct sight it was essential to hydraulic pressure test to ensure there were no gaps in the joints. Figure 16 shows the hydraulic test set up. The arrow identifies the position of a leak to be rectified on the next heat up.
Cut outs were made in the cylinder end plates to make way for the exhaust passages from the ends of the valve chest to the already machined openings in the back plate. The sides of these were angled as required using the Dremel and files.
2mm brass sheet was machined to make a pair of side plates to neatly fit the valve chest flange.
After splitting these were shaped and bent to make the outer side walls of the passages.
Inner plates were made up similarly and fitted and stiffeners were made and fitted fitted as the prototype. The S shaped passage bases were labouriously cut, filed and bent to shape and clamped in position before inserting the 10 BA fixings.
An open cylinder end, masked, fluxed and ready to solder. Then on the hearth being silver soldered.
Once all the fronts were done the brackets for mounting the slidebars were needed so they could be silver soldered at the same heating as the backs. The cylinders were mounted vertically on the mill and two holes were drilled to locate the brackets.
The brackets were machined from phosphor bronze with two 10 BA tapped holes in the back Figure 25 shows all six complete with fixing holes for the top slidebar and for the side support ready to be fitted.
the components for the slidebar bracket a cylinder rear with the slidebar support assembled.
At this point I needed to start machining the partly built cylinders so the next parts to be fitted were in the correct positions. After careful measurement of the relationship between the cylinder and valve bores listed here
I made a setting tool that could be clamped to the cylinder to use to orientate them correctly for further machining and using the mandrel previously made for machining and testing the cylinders, they were set up on the rotary table.
Figures 29 and Figure 30 show how the setting tool was clamped to the cylinder and used with the dial gauge to ensure the bores were correctly positioned.
A reference face was machined to be used for future set ups.
At the same set up a 3/16" end mill was used to plunge mill the recesses for the lagging fixings around the inside of the end plates.
Brass inserts were made and drilled for tapping 10 BA and fixed, each secured by a 10 BA stud through the side.
The tops of the exhaust passages were fitted ready for the next silver soldering operation. Each passage was traced on to paper, cut out and glued to 2mm sheet brass, a process already used but not photographed for the floors of the passages. Care was taken to keep the gaps small as the silver solder would need to bridge these.
Next the seats for the cylinder drain cock flanges were drilled part depth and counter bored.
Pieces of bronze were machined to the correct radius for the cylinders and drilled for the cylinder drain passage and the drain cock fixing studs.
Cut into sets of 4 these were profiled in the milling machine to produce the flanges for the drains.
These were attached by the usual method.
The main steam inlets were bored next. As they enter with a considerable off set on the steam chest they were set up in the milling machine and bored with a centre cutting end mill.
The inlet flanges were made now and turned up from in bronze.
They were then screwed onto a mandrel and the boring head was used to create the matching profile to the steam chest.
To locate them on the steam chests a brass stud was screwed into the inlet and finally secured with a blind nut and a couple of 8 BA studs for security. Note also the brass bar fitted along the top of the cylinder for fixing the footplate angle.
The cylinder was then masked and fluxed ready for the final silver soldering operation.
After the soldering the cylinder looks a bit of a mess before being pickled.
Following the clean up the cylinders were hydraulically tested to 200psi to ensure they were mechanically sound.
The middle cylinders were now on the programme, and planning ahead it could be seen that the smokeboxes would be needed soon to help with making the smokebox saddle, which on the Gresley pony truck engines is integral with the middle cylinder. After searching for suitable steel tubing and discovering that I could get thick walled imperial cheaper than thinner walled metric, two pieces of 7 inch OD tube were obtained. These had 3/8" wall thickness so there was a lot of material to be removed to get the 9/32" wall thickness needed and I wasn't sure how long that would take on the Super 7, if indeed it could do the job anyway. Good friend Allan Bones came to my rescue with the offer of the use of his 6" Harrison. I last used one of these lathes when I was at school, where we had two brand new machines. Whilst Allan's machine has clearly been well used, it proved well capable of machining the smokeboxes to a high standard of finish and accuracy. The following photographs show the process of machining, taking a few afternoons over a three weeks period.
Machining the outside. Note Allan's extractor duct to get rid of the smoke from the cutting oil.
Starting the bore.
Smokebox outside finished.
Bored as far as the short tool can go. Deepening the bore with a longer tool.
Smokebox reversed to complete the bore. Bore completed.
One down and one to start.
Rather than show you a picture of an engine with the smokebox in place on my untidy bench, I thought this photograph, taken at the Main Line Rally at Gilling, was more interesting. The K3 is seen standing next to Geoff Moore's award winning 2-8-2 of LNER Class P1 No 2393. If my locos are just half as good as Geoff's mikado, I will be well pleased.
In the mean time work had started on the fabrication of the inside cylinders, a slightly different process than for the outside, but that's for the next instalment.