Load of wire crowns
for bogie flat wagon

Original page created on 01/09/2021; updated on 16/05/2024.

Preliminary study

This load concerns crowns of steel wire, known as machine wire (is it the actual name in English?), which can weigh up to 2.4 tonnes. This wire is used, among other things, for the manufacture of… wire (yes!), but also mesh and iron for reinforced concrete, etc. See this link provided by Mathieu on the Loco-Revue forum.

On the actual R90 wagons, you can see most of the time the crowns arranged in two layers. The first layer has fifteen crowns, the second seven. The latter are loaded in the centre of the wagon, which surprises me a little. I would have rather placed them above the bogies, but there must be a good reason. If you count correctly, 22 crowns of 2.4 t equal 52.8 t: this almost reaches the maximum 55 t C-load for a Res 90 flat wagon.

Photo Patrick Sambourg (excerpt) on wagons-europe.net.

Dimensions of a crown

Crowns come in a variety of sizes. From the link above, here are the dimensions we’e interested in.

Dimension (mm)	Actual	1:87
Maximum length	2 000	23.0
External diameter	1 300	14.9
Internal diameter	800	9.2
Wire diameter	6 to 16	0.07 to 0.18

In practice, the wire chosen will be oversized, as will the internal diameter, so as to lighten each crown while respecting its external diameter.

The winding will be done on an 7/16” (11.1 mm) core (Evergreen tube), in three layers. Why three? Because it is neither too much nor too little… The wire used is galvanized wire ⌀ 0.3 mm, easy to find in DIY stores. The current best price is €4.60 to €4.70 per 50 m. If you want to make a large quantity, you can find it much cheaper, sold by the kilogram: it comes to €0.44 per 50 m, ten times cheaper than in DIY stores!

Note that brass wire is paradoxically cheaper than iron wire. But it will be more difficult to obtain the correct colour rendering!

What length of wire for a reel?

For the sake of the future crown’s solidity, the first layer will be made with contiguous (or almost contiguous) turns. Taking into account the expansion factor, I calculate a space of 0.4 mm (not 0.3) per turn, over a length of 23 mm, which gives us about sixty turns.. The other layers will have looser turns, say half as many, or 30 turns per layer. This makes a total of 120 turns. If I take an average diameter of 12.5 mm, so a circumference of 39 mm, this gives a wire length of 4.7 m. To make 22 reels, we need about 100 m, so two DIY coils.

How much will a reel weigh?

According to the seller, 1 kg, or 1000 g, corresponds to 1825 m of wire; a 4.7 m reel will therefore weigh 1000 : 1825 × 4.7 = 2.6 g. It will be seen that the reels made will be closer to 3 g, which implies a slightly longer length of thread.

Making

The winding mandrel

The mandrel is made with the means at hand. Apart from the dimensions of the core, the rest depends on availability. As already mentioned, the core is made of Evergreen tube ⌀ 11 × 25. For the axle, I used an M8 screw and two large washers. The difference in diameter between this screw and the tube (inner ⌀ 9,7) is compensated by a layer of 0.7   thick cardboard. This does not need to be accurate.

Preparation of the winding

Once the parts have been assembled, the core and the inner faces of the flanges are coated with grease.

Then a plastic film, cut from a packaging bag, is rolled up and taped to the core. Note: the tape is on the outside, not stuck to the core!

The ⌀ 0.3 wire is clamped between the screw head and the washer. The assembly is tightened moderately.

I am currently out of wire, after six attempts. This is just for demonstration purposes.

Winding

The assembly is fixed in the chuck of my screwdriver. Winding can begin, at very slow speed, then a little faster if you feel comfortable. If the wire overlaps, you can always go back by reversing the direction of rotation. Advice: don’t over-tension the wire during winding; stop and release the tension from time to time to loosen the turns and possibly tidy them up properly.

The following picture shows another mandrel used before, unnecessarily complicated… The first layer, with almost contiguous turns, is finished.

Once this layer is done, I coat the reel with CA glue on three or four generatrices of the cylinder, then I wind a layer of scotch tape. This way, the turns of the next layer will not tend to insert themselves in the first one, and they can be spaced a little (saving wire and weight…).

Once the second layer is finished, likewise, glue with CA glue, insisting on the edges, as this conditions the good holding of the reel, and a layer of scotch tape.

Third and last layer, like the second. Here, I only put glue on one line which will be placed at the bottom to be invisible. Although, when the glue is dry, you can’t see it too much.

Next, the mandrel is removed, and the core is “de-moulded”. Thanks to the plastic layer and the grease, and also to the fact that I don’t tighten the turns too much, I haven’t had any difficulties to slide the reel out of the core, on the five copies made with this method.

Finishing

Cutting the ends of the wire. Sometimes they have to be glued back on if they “bounce”. The inner plastic film remaining inside the reel is removed with a pair of tweezers.

When the turns are spaced out, they show the shiny tape. I will apply a veil of matte varnish once all the coils have been made.

Note: the coils obtained have a diameter of about 13.5 mm (for 14 mm, which is not bad), and a mass of about 3 g. The load of 22 coils will therefore have an approximate mass of 66 g. The HJ wagon weighs 82 g when empty, for a NEM recommendation of 92 to 120 g. With the load, the mass will rise to 148 g, which is 28 g more than the standard. However, this is still acceptable.

Ligatures

Ligatures are the ties that hold each reel together. From the photos, it looks like there are four per coil. Out of laziness, I only put three. But no, I’l put four after all.

I use fine EZ-Line thread. Advantages: it is elastic, so it will hold well without being too tight; it is thin, black (other colours exist) and therefore discreet; and it is very well glued with CA glue.

So the thread is slipped inside the reel, then a simple knot is made over it. To avoid sticking to the reel, a small piece of tape is inserted.

Click on the picture to see the reel more closely.

The thread is held slightly taut by spring clips.

A drop of CA glue is applied to the knot. After setting, the ends are cut off.

Then the thread is slid parallel to the axis to make the knot disappear inside, and positioned at the desired location.

Note: the mandrel is only present to prevent the spool from rolling…

Once the three four ligatures are made, the piece of tape is of course removed.

Result :

Note: the lashing ropes for fixing the reels to the wagon will be made of “coarse” EZ-Line wire, as already done for the PAM pipes.

Let’s speed up the manufacturing process a bit

Ejecting the core

To facilitate the ejection of the winding core, I made a simple tool: in a random block of wood, I drilled a ⌀ 12 through hole (just a little larger than the core), followed by a ⌀ 14 counterbore (just a little larger than the reel), to a depth of about 2 mm.

I place the reel into the tool. Using a socket wrench bit, I gently tap the core, which is ejected without damaging the reel.

Twenty-two crowns!

With patience, and a brand new thread (it shows!), I finally get the 22 coils I needed. The ligatures are not yet in place.

Ageing tests of the galvanized wire

As you can see on the previous picture, there is a big difference in appearance between the wire I bought several years ago, which has oxidized, and the new one, which is very shiny. The real crowns have an intermediate appearance. On the advice of members of the Loco-Revue Forum, I have experimented with some treatments.

Note: as the crowns have been generously bonded with CA glue, the treatment will not be able to penetrate the bonded areas, nor under the layers of adhesive tape, and therefore the appearance may not be perfect. That’s why I’m going to do two series of tests, first on new degreased wire, then on these already made crowns.

The different treatments are indicated on the pictures. I am using an ABE burnisher supposedly for arcap; 14% household vinegar, undiluted; 23% hydrochloric acid, either diluted to one part HCl to four parts water, or pure.

Test on bare degreased wires

Test on already made crowns

The observation above is confirmed on already made crowns, with a more visible effect.

The yellowish aspect of the acid-treated wire is striking, and is not the intended purpose! As for the burnisher, it gives a very dark appearance, increased here by the fact that the lower layers not touched are clearly visible.

In conclusion, if you want to age the galvanized wire, you should do it before making the crowns. The burnisher seems to me to be the least bad treatment, but perhaps with some dilution to get a less marked effect.