I practised a bit on pieces of scrap with my new TIG welder, so that I was confident enough to start the difficult work of welding the tender tank. Stainless steel is not an easy material to weld, since the seams shrink quite considerably, warping the plates. However, thanks to the "tab and hole" jigsaw construction, I was able to tack weld the pieces together without any significant warping, and after that I used the "backstep" technique to minimize distortion. The welds on the tank side are here already ground smooth, and they will eventually be covered with a row of rivets. (I have a rather clever way of doing fake rivet heads, but I'll leave that for another time... ;-)

"Backstepping" is welding short segments like this:

This "locks" the joint in place at the start of each new bead. Thanks to this technique, I could weld the pretty complicated coal bunker with little distortion. This photo shows the result - and I've done absolutely nothing after welding, there's no slag to be chipped away, the welds are nice and clean as soon as they're done. TIG welding is a wonderful invention!

Many of the welds are "autogenous", i.e. no filler material is used, the plates are just fused together with the TIG torch. This gives the best looking result, but it is not always possible - some parts must be welded with filler, due to their angle or poor accessibility, so all welds do not look as good as this one...

Here's the rear of the tender, with the lid for the water tank.

Opening the lid, you can see the construction of the hinge - it's just a piece of 2 mm stainless rod, and three tabs on the lid. The rod is welded to the tank with two short beads. This gives a bit of springiness, enabling the clasp welded to the inside of the lid to catch onto a "bump" welded to the inside of the oval rim. The big round hole in the middle is for keeping a funnel in place, on the full-size tenders, the entire area was open, of course...

One of the tabs - it is welded to the lid only, and rotates on the rod. Note also how I've prevented the tab from sliding off the rod - a short pulse from the TIG torch "balled" the end of the rod.

Here is a photo of the special buffers in the coupling between loco and tender.

The buffers press against corresponding plates on the rear end of the loco.

Here's how I made the rounded rear corners of the tender tank - I cut 90° pieces of stainless steel tubing, and tacked them to the plates before doing the "backstep"...

Inside the tank, there's a brass "floater" that is connected to the tender's water gauge. The floater is just a watertight, soft-soldered box made of thin brass.

Here's the pointer that shows the water level in the tank. The axle comes through an O-ring gland that prevents leakage, but still lets the axle rotate easily.

'til next time...