Zink Pest - When Die Cast Goes Wrong!

[murrayec]

Here is something we generally only see on those old Hornby clockwork loco wheels 'Zink Pest' This is the first time I've seen it on a more modern die cast model, a Bachmann Hong Kong made American thingy....

The chassis expanded to the point that the plastic body had no choice but to split and give more room for the expanding chassis.

https://en.wikipedia.org/wiki/Zinc_pest

Eoin

[warb]

Minor repairs and still running!!!!

[Broithe]

I remember a chap at 'work' making a full set of garden furniture from some scrap light alloy angle, of unknown origin, that he rescued from the skip.

He put a lot of work into it and it really did look the part - this was in the late 70's when stylish imported stuff had yet to arrive and the old-fashioned deck chair was still a common item.

After a few months outside in the damp summer weather, the whole lot just fell to pieces...

[murrayec]

15 minutes ago, Broithe said:

I remember a chap at 'work' making a full set of garden furniture from some scrap light alloy angle, of unknown origin, that he rescued from the skip.

He put a lot of work into it and it really did look the part - this was in the late 70's when stylish imported stuff had yet to arrive and the old-fashioned deck chair was still a common item.

After a few months outside in the damp summer weather, the whole lot just fell to pieces...

I made an aluminium side casing for a BSA motorbike restoration a long time ago, we made it from Coke & 7up cans cast into a home made oil sand mould in a metal bucket, using a styrene-foam master which burned out as the metal was poured in,  it worked but boy did we need a lot of cans! the casing has lasted for a long time....

Eoin

[Broithe]

At the same time, we made a particularly violent circuit breaker, which had its contacts supported by two half-drum castings, which were supposed to be made from LM6.

We had a foundry on site, but it was under pressure and so we had some castings made in Belgium.

These castings started failing regularly and we had to do something about it, so we had cores taken from failed castings and from known original castings that had not failed (yet) to see if there was any difference - there was - unfortunately, all the failed castings were the 'correct' LM6, and some of the intact ones were, but most of the intact ones were of some completely different alloy altogether - after some research, it was decided that the most likely candidate was an obscure alloy known as DTD 5008 B (I think), mostly used for the cylinder casings of radial aircraft engines, or some such exotic thing.

Neither supplier would admit that they had used it and further supplies were actually quite difficult to obtain, but we eventually managed to replace all the castings with the new 'wrong' ones and, as far as I know, no further failures (from that cause) occurred.

 

Edited November 1, 2019 by Broithe

[murrayec]

@Broithe

Now that's a big circuit breaker!

Eoin

[Broithe]

400kV air blast - a total monster - I wouldn't stand that close to it myself...

That's the breaker in the centre, with the three vertical cylinders on each half of each phase.

There was a rule that there would be nobody in the substation if there was lightning within a hundred miles - luckily, there were only two sites with them - Norwich and Indian Queens in Cornwall.

The central vertical chambers on the top were known as the 'silencer', but we still couldn't test them in the factory, within an enclosure with two-foot thick sleeper walls with a core of sand (for explosion dissipation) after 6pm - they could be heard some miles away...

We blew one up in Manchester on test and sprayed the Kelloggs factory next door - damaged quite a few cars...

We never had one come to bits in service, but the risk was always there.

[PorkyP]

I had a Hornby 9f that the chassis was disintegrating a bit, i think it's something to do with inclusions of some kind in the metal due to shoddy cheapo casting practices, or so I've heard..?    The recommended thing years ago for diy alloy castings was to use old pistons as I recall !

[Mayner]

There is an extensive thread on the subject on RM Web https://www.rmweb.co.uk/community/index.php?/topic/123769-zinc-pest-mazak-rot-the-affected-models-list/page/2/.

A high proportion of the afflicted models were introduced since 2000 and the list includes a number of the major manufacturers including Bachmann, Hornby & Heljan