Building the MÁV Class 327 steam locomotive model

Part #7

Mounting, testing

Before painting the loco models must be in a perfect mounted and running condition. After painting every correction results in destroying the paintwork. Some paints are less sensitive, others pile off after the smallest touch with a screwdriver. Do not give a chance to this! For this the model needs to be fully mounted, tested, dismounted, fixed and mounted again, until it looks and runs perfectly.

Already when designing the Class 327 I tried to consider its mounting and dismantling features, but as usual the result was not without flaws. The main reason for this was that the boiler - despite all design efforts - is not easy to pull over the motor. The extruding parts of the longboiler do not allow to move it horizontally to place. Thus it can only be pulled if the motor fixation is released. However, the motor should be fixed after this so, that its connection to the flywheel is already inside the boiler.

The cab with the firebox is also not easy to place. Its opening on the bottom is as wide as the gearbox itself. The gearbox screwheads, however, are wider. Thus the cab cab only be tilted to its place. After this the longboiler back end should be plugged into the shaped front opening of the cab.

The last step is to mount the wheels. This must happen as last action, as the third driver fits into the opening of the cab bottom. When the driver is in its place the cab can not be moved at all.

The second and third driver cranckpins are screwed. The first one also contains the eccetric crank, it is soldered in order to fix it against turning around. If the drivers are equipped with all connecting rods it is not necessary to take them apart, they can be mounted and removed from the frame together.

Isolation

As it was already evident in the design phase the electric isolation was an important issue. The Fleischmann wheels are isolated at the hub, they are from metal, all rods are electrically connected to the wheel and thus to the rails. The main rod and the eccentric link are isolated with small plexi inserts from the crosshead and the reverse link. This worked well but there were short circuits elsewhere. Sometimes the wheels touched the brake hangers. This could be eliminated by bending these small rods in a very exact position between the wheels. Sometimes the main rod touched the crosshead guide. As it turned out the crosshead was mounted a little bit higher than necessary. It was resoldered into the correct position. However, later one a short circuit killed a sound decoder, a rather expensive failure.

Weighting

During the model construction I was observing thoroughly where the center of gravity will be located. The cylinder block weighted the front side seriously, but the boiler add-ons were also on the front side, despite being lightened. The final situation was only revealed when the cab and the firebox was on place. Unfortunately the back end of the model was too light, the weight was mainly on the compensation beam, the rear driver did not even touch the rails. During the design phase a main goal was not to use the pony truck for support, thus the rear part of the model needed to be weighted down.

For this it was necessary to cast lead blocks that fit into the firebox. In addition a lead weight was also mounted below the roof of the cab. I hoped it will not make the model unstable. actually it did not do.

The patterns were made from wooden blocks, for the casting below the cab roof it was a piece of plexi glass. The mold was made from plaster. It was burnt out on the top of the oven.

The casting was performed in open air, with the usual technology. The lead was heated in a kitchen ladle and poured into the plaster mold. It was easy to remove the lead castings from the mold.

The lead weights were finished with a rough file. The weights on the side walls of the gearbox were also glued to place to make the mounting easier.

A more difficult task was to find a way to fix the weight that was placed below the cab roof. It was not possible to glue into the roof as in this case the firebox could not be placed inside the cab. The top of the firebox is just a few millimeters below the roof. Thus the lead weight was shaped to be removable. Inside the roof a crossbar was soldered and it was equipped with a threaded rod. The weight was drilled through, it was placed on this rod and secured with a nut.

Tracking

After mounting the model unpainted, rolling tests were done. Soon it was clear the biggest problem is the tracking, when the model negotiates curves. This problem was already visible in the design phase, in this picture you can see the placement of a 600mm (23.6") radius curve below the loco top view. This shows how the pony truck should move sideways. Unfortunately the ready-made model was even worse on the rail. The pony truck was equipped with a reverse spring and also contains lead weights, it derailed in the curves, and even more often on switches. There was no other solution as to give up the principle to keep the pony truck as a stand-alone component that is kept on the rails by its own weight. A springing wire was soldered in the distance holder above the pony truck and it holds down the truck. Of course this solution diminishes the tracking force of th elocomotive as a part of its weight comes now on the pony truck instead of the drivers.

Even this measure was not enough to ensure correct tacking, the sideways movement of the first driver axle needed to be increased. The tube bearing was shortened and the wheel plastic isolation ring was turned down to a minimal thickness. After this the loco can just negotiate the 22" rail radius, but clearly it needs a larger one for safe operation. Thus I have reconstructed my testbench, now there is a possibility to go around on 24.5" radius curves.

During the testing phase the model was disassembled and mounted again at least twenty times. Sometimes a small component broke, that was fixed again. The benefit of this practice was that I learned well how to take the model apart and how to assemble it. This knowledge is very useful at the final assembly, when the parts are already painted and wrong practizes might destroy the paint.

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