Building the MÁV Class 327 steam locomotive model

Part #1

The Tender

It might sound strange but the building of the Class 327 model started with the tender. That time I made several freight car models thus building the loco tender was a natural step forwards. In addition the design of the loco model was slower than expected and I did not want to start building a loco model before the design issues for all details are settled. There is a good chance some parts will not fit or they need to get rebuilt. The tender design was quickly ready.

The Trucks

These tender trucks are not similar to any other car truck, they were built from scratch. Typically they show many rivets and other small parts like springs, supports and bearing parts.

The side panels of the trucks contain many rivtes, these were made by drilling holes using the CNC drill machine and soldering brass wire into these holes. The rivets are not all alike, there are smaller ones which were made from 0.4mm wires and bigger ones from 0.5mm wire. The "rivets" on the bearing blocks were made by etching.

The arrangement of the rivet holes was programmed and the CNC machine drilled the holes of the list into a 0.6mm thick nickel silver sheet. The same procedure was used for the front and backside sheets that also contain many rivets in the prototype. The parts were cut out with a piercing saw and filed to shape. This was a hard job to fit the top line shape above the wheels.

The wires were soldered from the back side thus the excess solder did not show up on the visible side. First the thin wires were soldered and filed to a lower height, after this the thick ones, as these were filed to a higher extrusion. The rivet wires on the center part were not soldered this time as their back side fits to the thick bridge that connects both side sheets.

The bridge was cut from a thick, 1.0mm nickel silver sheet. This bridge contains the hole for the truck kingpin and supports the tender body. To solder the framesides together an aluminium distance holder was turned in the lathe, this kept the frame structure in place for soldering. After fixing the frame and the bridge the center rivet holes were drilled again and the rivet wires here intrude into the bridge material giving a mechanical enforecement to the soldered frame.

The front truck can swivel in all directions, a small diameter distance holder is mounted on its kingpin allowing all movements. The rear truck, however, can only perform a nodding movement, it must be rigid in sideways direction. Here a disk is pulled on the kingpin that supports the frame rib on both sides. This dick is soldered to the truck bridge.

The last item soldered on the truck bridge is the support for current collectors. This is a small two side PCB block, the lower copper surface soldered to the bridge. On the top side a 0.3mm diameter nickel silver wire is soldered. The wires contain a loop that increases its flexibility. They touch the top side of the tender wheels. A thin isolated flexible wire conducts the current from the trucks into the tender box where the DCC decoder is mounted.

The Tender Frame

The tender frame is built on a simple, 1.0mm thick nickel silver sheet. It is 2-2mm narrower on both sides than the tender superstucture, as it clears the place for the tender box internal braces. The sheet contains holes for the kingpins, couplers and current wires. The pin for the locomotive drawbar was made later, when the loco itself was ready, as this determined the drawbar height which must be equal on the loco and the tender.

The buffer beam was soldered to the end of the sheet together with the reinforcement triangles. The frame C-profiles are from 3.0x1.0mm brass. They are longer than the base sheet, they protrude forwards and they are covered by the tender box. The crosswise braces are also soldered on the base sheet.

The buffers are springing. Their body is conical, it was made by turning from brass. In the internal part they are equipped with an M2 thread thus they can be screwed into the buffer beam.

The model of the brake cylinder and air tank are frame fittings. They were turned from brass. Brass pins are soldered into their body that keep them fixed on the base plate. The brake rod is also shown, but its lever ends at the frame profile. The brake rig is not modeled below the tender bottom and trucks.

The Tender Box

The tender superstructure is an open bottom box. Its sides are sodlered together and it can be fixed with screws to the frame. The side walls show many rivets, arranged in vertical, horizontal and slanted rows. As they are dense it was not possible to emboss them, the tender walls were made by etching. They are from 0.4mm nickel silver. It was not possible to etch the walls ready as etching through 0.4mm material, i.e. 0.2mm from both sides would have etched away the rivet rows. Thus only the surface was etched and the wall shape was cut out with piercing saw and filed to size.

Along the bottom edge of the sidewalls a thick nickel silver sheet was soldered, other sheets crosswise at the front and rear walls. These accommodate the threaded holes which serve to fix the tender box to the frame base.

The front of the tender box is more detailed. It has a bottom plate, two toolboxes on both sides. The riveted front wall above the boxes was also made by etching. Inside the box there is a slanted top sheet that separated the water tank from the coal area on the prototype. Its front part is slanted, that helped the coal to slip towards the fireman. A 0.5mm diameter brass wire was soldered to the top edge of the tender box. The prototype shows a similar edge.

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