Exploding chassis

[DesertHound]

Some poor chap handed his heljan drs 47 into the shop for repair - the chassis had swollen and cracked the end of the body. Normal route for this is a replacement chassis from Heljan but howes (the uk dealers) are nil stock. So it was shortened and the body repaired - best to avoid buying any of these!

BUT it was nowhere near as bad as this chap on rmweb...

http://www.rmweb.co.uk/community/index.php?/topic/73731-heljan-47-chassis-expansion-can-anyone-beat-my-model/

At least this is one thing we dont seem to suffer from as yet.

Russ

That's bonkers Russ!

[Mr Sprue]

"MAZAK" = UK brand name for a zinc-based alloy more commonly known as Zamak!  i.e. Zinc, aluminium, magnesium, and copper.

For what it's worth Zamac (Z2) is the only metal that has similar density to human bone and is used for the construction of crash test dummies, if Zamak had expansion properties do you really think it would be used for these expensive tests?

[DesertHound]

Dave

You're familiar with Poole chassis I know. What are your thoughts on those, keeping their shape over time?

I'd echo elmo's earlier post that they are okay, but I have a few that I have my suspicions over. I'm not necessarily talking expansion, just some form of deformity. This could have been during manufacture mind, and not the result of later changes to the cast.

I can't remember if we concluded they were mazak too.

Cheers

Dan

[Newportnobby]

Presumably muzak loses the aluminium and has uranium in it?

[Dr Al]

How old are these crumbling Atlas chassis, just to out things into some kind of context?

Pretty old - of the order 30 years, though I don't know when the problems with them started manifesting themselves to owners - that's a bit before my involvement with N!

But similar aged Farish is still solid as a rock, so I'd be fairly confident in their longevity.

Cheers,
Alan

[Dr Al]

I can't remember if we concluded they were mazak too.

They are Mazak - well, that's what was said and shown in the factory tour in Model Rail video 2 when they showed the ingots being melted down to cast the blocks.

Cheers,
Alan

[DELETED]

"MAZAK" = UK brand name for a zinc-based alloy more commonly known as Zamak!  i.e. Zinc, aluminium, magnesium, and copper.

For what it's worth Zamac (Z2) is the only metal that has similar density to human bone and is used for the construction of crash test dummies, if Zamak had expansion properties do you really think it would be used for these expensive tests?

What an awful analogy! Use is poles part at either end of the spectrum.

[DesertHound]

How old are these crumbling Atlas chassis, just to out things into some kind of context?

Pretty old - of the order 30 years, though I don't know when the problems with them started manifesting themselves to owners - that's a bit before my involvement with N!

But similar aged Farish is still solid as a rock, so I'd be fairly confident in their longevity.

Cheers,
Alan

I'll go with that. I don't think we'll suddenly have an explosion (pardon the pun) of Farish chassis crumbling. The oldest ones see to have stood the test of time.

[NinOz]

Mazak rot hasn't afflicted any Farish or Dapol models to date (and hopefully never will).

The occasional the Peco Jubilee can suffer from bulging tender drive (on a minor scale though, usually fixable). Some fairly ancient Rivarossi motors can suffer from something similar in the motor magnets which seizes up the whole motor to a write off. I believe some early Atlas models can suffer from crumbling chassis blocks.

Both my Peco Jubilees went with the bulging cracked tender bodies.  Similar aged and older Farish stored along side show no signs of any dimensional instability.
Early Farish do seem a different metal than the corroding Pecos based on cutting and filing over the years.

[Luke Piewalker]

It seems to be down to impurities in the Zinc (possibly lead, google 'Zinc Pest').
I guess they either need to keep a better eye on their suppliers, or find out if they are doing something in the smelting which is causing the trouble.

[DesertHound]

I have one or two Farish diesel chassis (not more than that) which seem to have "blistered".  By that I mean they have a bulge, a bit like a cist (sorry for the analogy) and I can only think that's down to an impurity.

Anyone with expert knowledge care to comment? Dave?

Dan

[msr]

It is the Rivarossi SNCF 231 'Chapelon' that is perhaps the worst sufferer of Mazac decay. The expansion of the motor block cracks the tender body. Here is a classic example:
http://www.ebay.co.uk/itm/N-GAUGE-FRENCH-RIVAROSSI-LOCO-SPARES-REPAIR-2-6-4-15-/201257564696?pt=UK_Trains_Railway_Models&hash=item2edbe2ba18&nma=true&si=a7Dfu%252FOWEvRmZL0vobClKtHJ7mk%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

However, not all Chapelons suffer this effect. I have one which looks really good and runs very well, the equal to the Peco Jubilee from the same stable from about the same periof.

If you really want a good, reliable, Chapelon then save up for a Fulgurex one!

Mike

[Mr Sprue]

"MAZAK" = UK brand name for a zinc-based alloy more commonly known as Zamak!  i.e. Zinc, aluminium, magnesium, and copper.

For what it's worth Zamac (Z2) is the only metal that has similar density to human bone and is used for the construction of crash test dummies, if Zamak had expansion properties do you really think it would be used for these expensive tests?

What an awful analogy! Use is poles part at either end of the spectrum.

I can appreciate that your comment is probably based on electronic physics, but before the debate continues lets first use the correct name for the metal which is Zamak. The probable answer to this thread is not something scientifically elaberate, but as Luke Piewalker has already stated  most likley to be zinc pest.

So to make things clear and simple those who have a collection of early models with zinc alloy chassis, storing them in an environment with high humidity runs a great risk of damage, but it doesn't stop there either! Sudden temperature changes could also start the process, so if you store your prize collection in the loft it's not a good idea.

As a precaution it would be prudent to examine your cherished oldies periodically, check the alloy chassis for pitting or blistering, its worth knowing that zink pest affected some batches of models probably upto around 2005.

Last of all lets not forget that Zinc is also used as a sacrificial anode to protect submerged metals below the water line on boats!

[Mr Sprue]

I have one or two Farish diesel chassis (not more than that) which seem to have "blistered".  By that I mean they have a bulge, a bit like a cist (sorry for the analogy) and I can only think that's down to an impurity.

Anyone with expert knowledge care to comment? Dave?

Dan

Dan damp or humid conditions friend!

[javlinfaw7]

This form of corrosion also affects 1950's Dinky Diecasts