Punto di regolazione automatica

Overhead line – February 2015

We have come to the difficult side of model railway, the work that has always challenged the modelers… the overhead line!
Its creation and installation is complex, uncomfortable and delicate. Especially when there are big risks, such as, making it operate at all!
And this is the ultimate goal. Our O.L.S. will be tensioned and operational.
But let’s take a step back and see what it takes to complete this work; we have already published two videos concerning the making of MEC type frame steel portals (watch videos). In fact, the station will be equipped with 7 portals, as well as a fair number of Mannesman standard poles. The tension of the wires has already been tested with some success here; its application over considerable lengths is left to be seen, but we are quite confident.

The construction of an operational O.L.S. inevitably results in distance calculations, exact poles, portals and tensioning devices positioning. It also means designing a diagram inspired by reality, foreseeing section breaks, calculating the number of steady arm brackets for each cantilever and taking polygonation into account. It is therefore necessary to send the drawing of the tracks to the CAD and trace the individual wires lines on this. The resulting intertwining is more of a trail to follow than a real project. During the execution phase, the forces exerted on the wires, on the steady arms, on the tensioners and much more must be taken into account. It will therefore be probable that there will be some adaptation of the position and number of poles, as well as the number of brackets per pole.

Station O.L.S. diagram
Station O.L.S. diagram

After making the frame steel portals, for whose construction technique please refer to the videos, we will drill the holes for inserting the posts and provisionally position them.
The project includes 7 portals installed at 40 cm from each other.

We need to check the distance of the cantilevers from the track bed, ensure the correct geometries and and that they are held securely, by tightening the nuts under the board. The base plinths are made of resin cast in a silicone mold.

MEC portals installation
MEC portals installation

Catenary welding will take place on site. To make the work easier, it is better to start welding from the first track and gradually go down to the fourth track. We should prepare the necessary poles for the assembly of the first catenary section. this is the one that goes from the right tunnel to the left entrance (looking from the side of the 4th track side) of the station, to the first automatic tensioning device installed on portal n ° 2 (from left to right, always looking from the 4th track side).
We have the photoetched plates, brass profiles and insulators required. Thye are going to use an M29B pole, composed of 3 sections, whose diameter in scale is, respectively, 3, 2.5 and 1.5 mm by approximation and usesthe availables tubes on the market.
We weld the 3 sections, weld the spiked safety band and drill the hole for the registration tube on the pole. We then insert the swivel bracket and the registration tube, weld both to the pole and then weld the cantilever dropper hook clips.

1st track poles
1st track poles

We then weld the dropper to the brackets. We also make cantilever parts. This consists of 7 parts:
  1) steady arm bracket support eye clamps
  2) catenary wire support clamp
  3) upper insulator pin
  4) steady arm bracket
  5) registration arm insulator
  6) registration arm support
  7) registration arms
Details 1), 2), 6) are photoengraved, detail 4) is obtained from a 1.0 x 1.0 mm brass profile, on which we drill a 0.3 mm hole for fixing of the registration arm parts. We shape the steady arm bracket and insert it into its eye clamps. All parts are then welded onto the registration tube. We then insert the insulator and the steady arms and fix it to the steady arm bracket. We weld the pin 3) to the support 2) and insert the insulator.

Cantilever detail
Cantilever detail

We prepare all the poles needed for the first section of the catenary. These are both M29B and M26 type, , the latterwith 2.5, 2 and 1.5 mm section diameters. We paint everything with acrylic silver and apply a strong weathering on the upper part with AMMO MIG products, specific for static modeling. In our opinion results are very good.

1st track poles
1st track poles

Finally we make some decals reproducing the pole markings. This is done using transparent decals paper for ink-jet, coated after printing with opaque transparent varnish, this will give a decent end product.

Poles marking decals
Poles marking decals

The application of these “homemade” decals on the M26 pole is certainly not easy, final effect is remarkable, as seen on photographs. The details are virtually invisible to the naked eye!

Poles marking decals
Poles marking decals

Even if it doesn’t affect the section of catenary we are going to install, we decide to try the assembly of a double registration tube M29B pole. This type of installation is not uncommon on Italian railway networks; it is currently used to distribute the load of the catenary cables over very long registration tubes. Given the width to be covered and the forces involved, much greater when compared to the real ones, the double registration tube is just what we need. And while we’re at it, we can use the pole to install an automatic tensioning device.

Double registration tube M29B pole
Double registration tube M29B pole

Before starting the catenary welding, installing everything that would be difficult afterwards is mandatory. There is not much left, apart from platform lighting, for which we use AKA Models lamp posts. These are made of brass, except for the resin ceiling light and the diffuser.

AKA Models station lamp posts
AKA Models station lamp posts
Lamp posts installation
Lamp posts installation

The distance between the lamp posts varies from a minimum of 16/17 meters to a maximum of 20. We choose a metric scale measurement and place them at 20 cm from each other where possible. We’ll need 20. The LEDs real colour is different from that in the picture, it is much whiter, while the light diffusion is optimal.

Lamp posts installation
Lamp posts installation

And we have reached the crucial moment, the first catenary section assembly . We remind you that this will be tensioned between two points, as in real life.
We use 0.2mm phosphor bronze wire, which has incredible resistance to tension (normally used for guitar strings) and is very easy to solder. We then stretch the contact wire from the fixed point inside the tunnel to the automatic tensioning device, for the operation of this please refer to this videos. We then pretension and weld the contact wire to the steady arms.

Automatic tensioning system
Automatic tensioning system

Next we then weld the catenary wire with much more slack than the contact wire, this prevents it from arching, once the two are connected by means of the droppers. Finally we weld the droppers. As you can see from the image, the contact wire is almost unaffected by the pantograph thrust, despite its diameter being very small, only 0.05 mm larger in scale than the real one.

The subtlety of the work is very evident.
But we are only at the first step and there is a long way to go. We will have to check if our calculations are correct for the rest. We noe prepare to weld the catenary on the first station track.

Catenary  and contact wires tensioned
Catenary and contact wires tensioned
Catenary detail
Catenary detail

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