That was a good day's modelling.
One important point to remember in this kit is the drawings are always orientated so the dynamo end is to the left. The floor web etch is annotated to this effect on its top surface, and I made a small felt pen mark on the underside to make it easier to spot while the current working is all upside down. It's important to keep an eye on where the dynamo end of the underframe is, although to all intents and purposes it is symmetrical until the sole bars are fitted.
This was the situation at close of play yesterday. The longitudinal girders had been formed, and with their help the three central crossmembers had been fitted.
In the cold light of day, I decided the crossmembers needed to be tidied up, so off they came and they were refitted with a bit more care!
After easing the slots over the bogie crossmembers, fitting the longitudinals became quite easy. Even without being soldered in place, it's quite staggering how much stiffness they impart to the underframe web.
Like much of the underframe, there's a fair amount of lamination involved in the crossmembers. Here are parts 6, the intermediate crossmembers where the fish belly truss angles up to the bogie mountings. I elected to laminate the various parts while the main etch was still held in its fret, for ease of handling in the main. The instructions say I should do this once the crossmembers are fitted to the floor web, which is perfectly doable, but a lot more fiddly than doing it this way. It also helped with cleaning things up, as I'm aiming to keep the soldering as clean as possible as I work. The crossmember etches here have six parts sweated in place each, as have the central crossmembers.
All the crossmembers are now in place. At this stage, I should have been fixing the angle sections (actually flat sections, but which make up the T-shape of the crossmember angles) but I left them off with good reason. Once all the soldering was tidied up, and things were checked for squareness, I formed and fitted the sole bars.
As you can imagine, the sole bars are nice long etches that have to be folded neatly to 90 degrees. My Hold & Fold isn't big enough to do this in one hit, and I currently don't have bending bars large enough to handle this size (guess what's been added to my ever-growing shopping list!), so I had to extemporise.
What you see above is a 24in steel ruler, a length of aluminium angle which has a nice square edge everywhere (I checked), and some clamps. You can make out the etch clamped in place. What I did was to gently bend the etch, working along its length using just bare thumbs, to an angle of roughly 10 degrees or so. It was surprisingly easy to do this. Once the bend had begun, I attacked it gently with the hide mallet, working from the centre, allowing the etch to bend a little further each pass, until the whole length was completed.
I suppose, inevitably, a slight curvature was formed along the length, but it wasn't enough that gently straightening with finger pressure couldn't solve it.
The sole bars are handed, in that one has a mounting lug for the dynamo bracket. This is why it's important to keep a note of which end is which on the floor as you build it.
Skipping ahead a little, I've soldered the sole bars in place. That sounded easy, didn't it? Well, it wasn't that hard.
The sole bars have shallow tabs at regular intervals along the entire length, with matching slots in the floor web. I tinned the tabs and slots, and carefully spot soldered an end, then a centre, then the other end, and then worked away at the other points. Working on an old glass kitchen cutting board, which is just long enough to lay the work flat as instructed, and using the longitudinals to stiffen the floor and keep it fairly flat while I worked, one side was fitted.
Here you can see the solder dabs coinciding with the slots and tabs. Once I'd finished this side, I turned the whole thing over, and worked along the upper edge, to seat the tabs properly. I was very aware that heat would cause buckling and stretch, so I worked as quickly as I could to get the solder to flow and make a joint without lingering.
I repeated the process on the other sole bar, then cleaned up the exterior faces with a fine file.
It's starting to come together very nicely now. Best Beloved commented that it was going together very much like the real thing did. Longitudinals are still not fixed in place, but the whole unit is now quite stiff and I feel confident in handling it without risk of damage. One reason for fitting the sole bars at this point was to aid with positioning the T-section detail on the crossmembers. Things still to do are the stiffeners on the longitudinals, but I think that's a job for another day.
, keep it up, cheers Rob
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