Testbenches

While a model is being built it is necessary to test its running qualities.When it is in front of us ready-made, painted and lettered, it is too late to discover its wobbling or poor running qualities. Earlier I tested the models on sectional rails plugged together on my desktop. This is enough to find out if the model runs at all. For more detailed tests a longer track is needed. First I used a loop made of sectional rails on the floor. This is very uncomfortable, however, to watch a model lying on the floor. For the models the floor is not a safe place anyways. So I have designed a testbench.

The first Testbench

The first testbench was designed to run along the dining room walls. The module length is 900mm (~3') determined by the flex rails available. These rails are made from steel, a small Italian manufacturer offered them for the US market. I purchased them in Germany, much cheaper than the usual sectional tracks. I also bought sectional pieces from this cheap rail. As the rails are stored in the rather dry room no corrosion has been observed in the last 10 years. It is true, the steel rails get dirty faster than the nickel silver ones. But far not as fast as the brass rails.

The rails start on the workdesk, go along the wall of the dining room, turn with a soft curve at the wall end and climb up on the top of the heating radiator. At the end, of course, a stop guard is mounted to avoid trains roll off the testbench.

Originally I planned a dual track system with loop on each end, this would let the trains to run continuously around. But the construction problems and space requirements of the loops did not allow to build this structure. Now the trains can run along the 7 meters (23') long layout and they reverse back the whole length. Interestingly no train derailed ever, not even while reversing. The rail connections are far from perfect, at some section ends there are some 1-1.5mm gaps between the rails. These let the trains to give nice clicking noise but no derailment. The curve shows a 585mm (22.5") radius, this makes it possible to operate even brass steam locos without difficulties. The module width is 150mm (6"), the supports are cut from 25x50mm (1x2") construction wood. The bottom part is wider than the top to fix the modules well at the walls. The top surface is cut from wooden panels. They are fixed to the legs by M5 screws with angles made from aluminium sheets. The layout is not static, it can be mounted in a half an hour. It is possible to disassemble in 20 minutes - putting the usual furniture back into place included.

The flex rails are fixed on the wooden surface by tiny screws and fixing plates. They have rail joiners on the ends but these are not fixed to any rail as it could break down during mounting and storing. For a secure current supply there are 10 pole flat cables mounted on the surface top and 2-2 poles are connected to the rails by soldering on every module. The flat cables are equipped with IDC connectors which allow an easy connecting and deconnecting.

The second Testbench

The main problem with the first testbench was that it was not possible to let run the trains continuously. This is, however, necessary for running in the locos. Thus I have constucted another testbench, an oval one. Sometimes we use the old layout, but the new one gives more joy.

When designing the new testbench the first task was to find out how to construct a 22' radius oval without buying a 50' wide panel. Some experimenting with the CAD program resulted in an interesting solution. The 90 degree curves can be mounted on a surface made from a 820x250mm (32x10") panel, easy to buy as bookshelf material. Only the corners need to be cut off under 45 degree. The sizes shown on the drawing are very important and refer to the usual 22" sectional rail. When using other rails, more common in Europe the plate dimensions must change as well.

The second testbench has no legs (not yet), it can be placed on the top of the dining table. The 22" (559mm) radius is enough to operate brass steamer models. The layout is in both dimensions larger than the table but this makes no troubles. The new table is longer and here the module joints are not any more outside of the table surface. To clean the screws on the bottom the layout will be put on distance holder pieces. It is also possible for the future to construct legs and then the dining table is not necessary for the operation. The modules are connected with aluminium plates on the bottom side. I use rail joiners here too.

Instead of a simple oval track I designed a layout with more difficult sections to test the running qualities of the models. The straight line of the first testbench was not really demanding. Here a switch and a counter curve are also included. In the first version this was a real S-curve but several steam models could not negotiate that really demanding part. Thus I added a short straight rail between the curves to ease the tracking of steamer models.

The switch area of the second testbench minipic

The switch goes to a siding where the supply can be cut by a small switch. This is the place to store locomotives. I plan another switch in the opposite direction also with a switch. This will allow to do some simple switching movements.

On this layout the rails are not fixed by screws or nails but with a double face tape. This fixes the rails very strongly, the first attempts to remove rails from the surface (when incorrectly fixed) resulted in by destroying the rails.

The only way to remove rails from the surface is when we cut the double face tape into two using a sharp knife and after removind the rail it is possible to scrap away the tape from the surface and the rail bottom separately.

This close picture also shows I did not succeed to mount the rail ends exatly in line with the panel edge. On some connections there is again a 1mm gap. Usually this does not make troubles, not even in the curves except if the rail ends are not lined up horizontally or vertically.

The switch came from the German manufacturer Tillig. This version has a 11 degree angle at the frog and 15 degree at the switch end. This construction allows a rather soft curve, its radius is as large as 700mm (28"). Thus the brass locos can negotiate the switch easily. I did not want to build a remote control facility on the testbench but I constructed a manual setting equipment. This picture shows the bellcrank that moves the points. Its interesting form was dictated by the nearby hole which serves for the panel fixation to the support. The crank must clear this screwhead. The spring that fixes the points in the end positions is not mounted here, at the switch, but incorporated in the handle.

This is the manual switch setting handle. The U-shape steel wire is the spring which keeps the points in the end position. When the second switch will be constructed it will be operated with the same handle too. Both switches must be either straight or curve at the same time anyways.

This is the frog of the Tillig Elite switch. These switches are sold as kits. In a plastic bag you get all components, the ties, the rails cut and grinded to shape. With some experience it is possible to assemble a switch in 20 minutes. The only tool is needed a plier to bend the rails around the frog. As you see in this picture the Tillig switch has no traditional frog, but the rails are cut and bent similarly to the prototype switches. It is up to the owner to decide if he wants an insulfrog solution or isolate bothrails and feed them by an electric switch that connects the supply according to the switch state.

I have isolated the rails. The consequence was that the locomotives made a short circuit always when crossing the frog with one wheel and having contact with the other one. As the short circuit was a short time one, made no problems with the traditional analog operation. With DCC it became worse. The DCC controller has a very efficient overcurrent sensor that stopped the operation even at the shortest time short circuit.

Because of these difficulties using DCC I decided to modify the frog. I made a new frog from nickel silver. This was glued with two thin isolator sheets between the edges of the rails. This remains unpowered, but due to its tiny size makes no problem during the operation.

The other parts of the tast layout are made from Atlas Code 83 sectional tracks. The Atlas ties are very fine structures, especially the nail imitations. I destroyed several of them when handling harshly. Here a power connection is soldered to the rail.

This is the connection of a Tillig Elite rail and an Atlas Code 83 rail. The Tillig rails have nicer, narrower rail profiles but the ties are rather strong and the tie distance is a bit too close. The Atlas rail profiles are wider but the ties are nicer.

This is the old Code 100 steel rail. You can see it is also possible to solder wires to steel rails. You need a rather agressive flux and a powerful soldering iron. The flux residues, however, must be cleaned very thoroughly after soldering. When they remain on the steel surface it starts to corrode very soon.

Second Testbench upgrade

Shortly after finishing the testbench a need for an upgrade arised. First the "station" was extended by a siding to store unused locos. With this a new switch was added and the siding was electrically separated from the main track. The next big upgrade was to add two short sections where the first one allowed to return the second rail of the "station" to the main line. This way it was possible to let running locos and trains continuously using the second rail and thus the curved path of the switches. As a last improvement the left side half circle was extended by a second rail. This way it is now possible to operate two trains in parallel using DCC.

In addition all tracks were placed on a new rail base. This is constructed from two layers of 2.0mm cork plates. The upper layer is 42.0mm (1.65") wide, the lower one is 46mm (1.8") wide. This way it will be possible later to add ballast. The two track left side of the circle was fully newly costructed. the old Code 83 Atlas rails were removed from the old baseplate and a new, wider baseplate was cut that can accommodate the double track. The new, larger radius track was made from Tillig-Elite flex rails, using the new rail bender tool.

This picture shows the doube switch on the right side. The switch set mechanics was extended to move both switches at the same time. Either both switches are set straight or both are curved. This follows the usual handling of the "station".

This double switch structure is on the left side. Similarly to the other side the switches are both either straight or both curved. The moving wire does not go parallel to the rails. The reason for this is that I did not want to place the operation lever to the plate edge.

A closeup photo of the left side mechanical setup. The lever with the set spring (the U-form steel wire) is a simpler construction than the right side one, but it works similarly reliable. The moving wires are connected to the lever with a brass sleeve equipped with a setscrew. This allows to tune the exact wire length.

The far side switch can not be operated by mechanical setting as it is on a different layout section. Thus an Atlas switch magnet was mounted there, this moves the points of the Tillig-Elite switch points. These, however, are rather rigid, the plastic lever of the Atlas component could not press them towards the rails. This part was therefore replaced by a similar lever made from nickel-silver, as pointed at by the red arrow.

The new sections have no rail joiners. These joiners were problem items anyways: when touching some rigid during the mounting they could lift off the rails from the sleepers. Especially sensitive are the fine Atlas rails.

The new rail ends are now soldered to PCB strips. The exact rail distance must be kept due to the missing joiners. The distance between the rail centerlines is 60.5mm (2.4", this is the standard distance for Tillig-Elite tracks.

Reconstruction of the second Testbench

The second Testbench served well for long time. However, the Class 327 Loco model design did not allow to negotiate 22" radius track. Thus I designed new, curved sections.

The left side track contains 22" radius curved rails on the inner track, the outer one has 24.4" radius, which is well negotiated by the Class 327 loco models. The other part on the right side that contains a single, 22" radius track was impossible to upgrade. Thus I made a decision to change the double track modules from the left side to the right side. For the left side new modules have been constructed. Here the inner track has the 24.4" radius, the outer one is constructed with 26.8" radius. These are Tillig flexible rails, using the rail bending tool. This way the whole testbench has grown by 4.8" wider and 2.4" longer. Fortunately, the support beams were long enough to handle the new size.

The new, double track on the right side gave the opportunity to add a switch to the end of the S-curve. To operate both remote switches a wired control connection was installed.

This way it was necessary to reconstruct not only the curved sections but the whole far part of the layout. Thus the old track was removed and new cork base was cut and glued on the baseplate. The tracks were made from Tillig Elite flexible rails. On the far side a "real" S-curve was laid down, but still maintaining a minimal radius of 27.5".

The new switch needed a remote controlled switch machine. I had no Tillig switch machine at home, so I quickly constructed a hand made switch machine. The coils are wound from 0.2mm copper wire, the iron core is cut from old transformer core iron sheets. The magnets operate the switch using a lever, similar to the hand-operated switch lever. The spring inside the lever keeps the point to the rail.

The switches are operated from the "station" section of the layout. Here on can find two electric switches, the current is fed by flat cables installed on the curved sections.

The testbench has no more rail joiners. The rail ends are all soldered to a fixation screwed to the baseplate. As most sections have dual tracks it is not an easy job to arrange the rail ends exactly enough. To make this task less difficult I made a jig from nickel silver sheet that arranges the rails in exact distance.

The more difficult leveling of the sections when assembling the layout makes the setup more than one hour. During the first runs it is often necessary to fine tune the rail connections on the places where locos derail. To dismantle the layout needs usually half an hour. The flat sections piled up do not need much space on a shelf.

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