[dwb]

I have been wondering for some time why my two of my Parkside open wagons have changed shape. A 16 ton mineral wagon has distinct bulges in the center of each long side and a 5 plank wagon has "sprung" all five planks at one corner. Tonight it dawned on me what has probably happened.

I have weighted each wagon to about 50 grams using "liquid lead". I just poured it in and added a dilute PVA mix which then set holding it in place. Now I know we didn't have a particularly good summer but my layout is in the loft and it does get quite hot, sometimes 35 C up there. My guess is that the lead has expanded in the heat and that is what has caused the problem.

If I am correct, I think the cure will be to make an internal box to take the lead. The box would need some room around the edges for expansion but at least the wagon sides wouldn't be taking the strain.

What do you think?

David

 

[neil_s_wood]

David I think it equally probable that the plastic has become pliant with the heat. Different plastics have different melting points and it could well be that the plastic used by Parkside has a low melting point. The lead may have contributed to the situation by adding pressure to a pliant plastic but this couldn't happen without the plastic starting to melt. Have you insulated your roof?

I have to be very cautious with my Garage layout as I have a north (sun) facing window over looking my layout. This could melt plastic structures on the layout if I am not careful to keep the blinds closed.

 

[dwb]

QUOTE Have you insulated your roof?

I put in double sided bubble foil in late June and then moved the conservatory high / low thermometer up there as well. The highest temperature reached this summer was about 31 which seemed less unbearably hot than I remember from previous years.

I take your point about the plastics. None of the box vans with sealed roofs appear to be have been affected.

David

 

[34C]

I have seen a report suggesting that some PVA's have enough free acid in them, to slowly react with the lead. The resulting compound is less dense than the the lead, so there is expansion, and if it is confined the pressure can be significant, with the results described in the OP. A modeller on RMweb had a very fine brass loco model boiler ruptured in this way.

I have always preferred sheet lead (roofing or flashing) for rolling stock ballasting, and lumps ( fishing weights or old lead plumbing) for locos, in part because most of the time this comes for free. You get a good 20% or more weight in a given volume with solid as compared to fine shot. And it is very enjoyable belting it into shape with a hammer. Lightly secured with evostick, it is very easy to remove if that is ever necessary.

 

[7113]

I have had a similar problem in the past when the glue acidity attacked the plastic - I think that ended up in the bin.

Regards