Wednesday, May 25, 2016

Chimney Turnig

Ever since I first held the model of Skarloey in my hands the chimney has looked wrong. Mostly I think it's that the band around the upper part stands to proud and is too far down. After my success turning buffers and spectacle plates I thought I'd see if I could produce a replacement. Unfortunately thinks didn't go quite to plan this time.

From a drawing of the prototype I worked out all the main measurements and set to work reducing a piece of 6mm diameter brass rod. The first stage was to reduce it down to 4.6mm which is the diameter of the cap, I then reduced most of it down to 3.25mm which is the diameter of the band around the chimney.

I then fitted the top slide to allow me to turn the taper for the cap; I went for a taper of 45 degrees which seemed to match up with the drawing. With the two parts now joined by the taper I cut into the body of the chimney slightly (0.2mm) to produce the top edge of the band, and then turned the rest down by 0.2mm leaving a 1mm wide band. I then worked out where the base of the chimney should be, made a witness mark, and then turned the rest down to 2mm to act as a locating pin.

Next I parted the chimney off from the rest of the bar leaving a few millimetres above the chimney cap, before turning the part around and remounting it with the locating pin in the 3 jaw chuck. I then faced off the top of the cap until I almost met the edge of the taper, I then faced off just the edge leaving a raised section in the middle. The final step was to then drill out the centre of the chimney. I started with a 1.5mm hole but it didn't look big enough so I changed to a 1.8mm drill which is where things started to go wrong.

One of my pet hates on models is chimneys where the central hole is only a millimetre or so deep so I made sure the hole was nice and deep. Unfortunately I forgot that the mounting pin was 2mm wide and my drill was 1.8mm and when it got deep enough the chimney snapped leaving me with the locating pin in the chuck. Worse was to come though when I went to open the chunk only to snap one of the tommy bars.

Fortunately the tommy bar is still useable, if a little short, and in retrospect a number of things were wrong with the chimney. Not only was it too short (I wrongly measured the drawing) but the 45 degree cap looked silly. So I set to turning a second chimney following the same stages which produced something that looks a lot better.

Initially I was happy with this one, but on reflection, and after looking at some photos not just the drawing, it's still not right. I'm happier with the height and the angle of the taper for the cap, but the band is too high up the chimney (there should be more straight section above it before the taper), so I'll have to have another go at some point. I'm still calling it a success though, as it's by far the most complex thing I've turned yet and it's all good practice.

Monday, May 16, 2016


My work-life balance seems to be all over the place at the moment, and even when I'm at home modelling has ended up fairly low down the list of priorities, but I did find some time this weekend for a little bit of modelling, including a balance pipe!

Due to the chassis block the pipe had to be made in two pieces that put up against the chassis but once it's all painted I think it will do the job. I also added the small pipe from the saddle tank into the drivers side of the cab. This isn't on the prototype now, but is clear on old, pre-preservation photos. No idea what it does but I thought it was worth adding.

Not sure what detail will be next, although I'm still trying to figure out if there is any pipework across the boiler in front of the dome during the early years of the loco. None of the photos I've found are particularly helpful.