Improving the R37 “Talbot” ballast hoppers (1)

Page created on 31/08/2024; updated on 03/09/2024.

Coupling of ballast hoppers with large side extension.

Observation

These wagons have a defect visible on the side view: the ends are more or less raised, due to their screw fixing on the central part. The correction of this problem is covered on the next page. For the moment, let’'s stay with something easier.

A load of ballast

The inside of the hoppers is detailed, with reinforcements and rivets; it’s a bit of a pity to hide this, but the planned load will be easily removable if needed.

Loading design

I want to make a load of ballast:

• as light as possible;
• removable;
• that doesn’t run the risk of scratching the inside of the hoppers;
• that looks as much like a real heap of ballast loaded from a chute as possible.

I’m going to use the gluing technique commonly used for ballasting tracks. I’m trying out two types of glue mix: good old vinyl wood glue on the one hand, and gesso — well, not exactly, it’s an acrylic gel sold under the Gerstaecker brand — on the other. In both cases, the dilution is approximately 50% glue and 50% household alcohol. Here are the results. When I applied the gel with a pipette (photo), it left large lumps, perhaps because I didn’t mix long enough, or because the product is a bit old.

Gerstaecker acrylic gel; Atelier Belle Époque grey ballast.

After drying, the “gesso” heap remains soft, and the lumps are almost invisible, but the grains are enveloped in a very thin plastic coating that rounds them off, making their appearance unlikely. With traditional glue, the consistency is very hard, but the appearance is more satisfactory.

First tests

The main difficulty I encountered was drying: the outer layer dries very quickly, while the inside remains damp. The surface peeled off and a few air bubbles formed, just like in baking bread! The result is a heap with unrealistic puffiness.

What I’ve learnt is that you need to make a heap that’s not too thick, and that it’s necessary to let it dry as slowly as possible.

Making a mould

I have four hoppers to equip, so a mould will ensure good repeatability of manufacture.

Making a load

Once this underlay has dried, the main heap is formed by pouring the ballast into the centre of the mould using a pipette transformed into a funnel: the top of the reservoir is cut off, as is the tube, leaving only its largest diameter, in this case around 4 mm. The smaller diameter, which has been tried, doesn’t allow the ballast grains to flow out.

As already mentioned, you need to leave to dry for a long time (at least 24 hours), at a moderate temperature. Next comes the removal from the mould.

Then it’s time for the finishing touches: scraping the sides to remove any grains that may have spilled over and could scratch the plastic of the hoppers. Sometimes too much is removed, and the white polystyrene base appears. If the gaps are small, you can apply a little grey paint (Humbrol acrylic slate grey No. 32 for example); otherwise, re-glue these areas, put the part back into the mould and reapply a little ballast.

Loading hoppers

For hoppers with a large side extension, an additional 3 mm layer of XPS is placed under the load to raise it. For others, this is not necessary. The weight increases from 78 g to around 94 g. This is slightly more than the NEM maximum, but this is not too much of a problem, as the axles rotate in brass bearings.

2 × 21 m³ large side extension hoppers.

With grazing light, you can see the relief better.

2 × 15 m³ small side extension hoppers.