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20/03/2016 8:28 am
Die cast cancer.
Not talking about paint rash here, though I'm betting it's related. More along the lines of what George reported with his poor 55 Pontiac. At first thought, you might think that if one has it, they all should. In part of my former life, I was a Die Maker and part of the trade was the care and feeding of injection molded plastic parts. In addition, I also spent some time in the metal pouring foundry of Pontiac Motors, where they cast heads and engine blocks, among other things. There are several things that effect the quality of molded and cast products, but only one that I can think of that would cause the eventual failure that George and others have experienced, and that is the mixture of the material. Not having witnessed the Chinese smelting and pouring I'm speculating a bit here, but I'd bet dollars to doughnuts I'm on the mark. The material for casting these cars is a mixture of various alloys. If the ratio of the alloy used was off, then all the cars would experience the same issues, pretty much to the same degree. So that means another explanation is needed.
If the mixture was made up, and then cast, all most all the castings would exhibit identical properties. That is leaving out those with other problems such as cold molds or short pours (more on that later). However if the mixture was made in batches large enough that allowed late pours to contain material in which the mixture did not meet specs due to settling out of the mixed materials the last castings would contain an improper alloy mixture, which could cause it to break down over time. In many casting operations, the bottom of the barrel, so to speak, is not used and poured out, either to be discarded or reused. My belief is the factories, in either cost saving mode, ignorance or perhaps indifference, used this last pour material, and hence the relatively small numbers of catastrophic issues, as compared to paint rash. It also explains why some models have literally self destructed, while others suffer less damage, but are still pretty bad, and others have no problems at all. As the pour came closer to the end, the resulting casts would have gotten progressively worse.
Another possibility is if smaller batches of material were used during casting (not as economical but in some ways better), the ratio of the mixture itself could have been off, effecting all the cars with that pour. Either a careless employee (most likely) or a mistake in the materials by the supplier (possible, but again, should have affected more cars). For this to be a cause, these mixtures would have to relatively small to explain why over all, the vast majority of cars aren't bad. We're talking mixtures for 20 to 50 cars at a time, maybe even less, which is not very cost effective. That's why I suspect the end pour issue explained above being the problem over this scenario.
Not that either of these two causes will make the owners of these crumbling models feel any better, which for them sucks, but it should give those of us who also own the same models hope that ours won't suffer the same fate.
BTW: the short pours and cold molds I mentioned refers to molds that weren't filled, hence only a partial car, or conditions where a cold mold caused the metal to harden too quickly, which in itself can cause a short pour, or irregularities of the surface of castings. Over heated molds can cause issues too, but more along the lines of the material taking too long to set up, which would create distorted models when removed from the mold. In any of these cases, the end product would be noticeably bad and discarded or recycled.
20/03/2016 8:50 am
This is the most worth while reading about diecast cancer - Thank you .....
Finally some meat and potatoes article
20/03/2016 11:29 am
THANK YOU Thomas for a most informative perspective on the die-cast cancer.
And I second your comment in hoping that others will not have cars that will suffer the "rot decaying" that my FM '55 Pontiac's are enduring.
I'm going to guess many can relate to what I'm going to say, is that we all have cars in our respective collections, that for whatever reasons they are personal favorites. It might be the color combination, or the year and make, or they like because it brings back memories of a real one they may have owned.
In the case of those FM Pontiac's it is because I love the model year and the awesome color combinations. So to have those two cars fall victim to the cancer, makes it that much tougher a pill to swallow.
I love all my cars, don't get me wrong, but there are just some that are more special than others. In my collection, and I'm sure it's this way in others collections too, there are some cars that if the rot cancer were to affect them, it wouldn't be as hard a blow.
Thanks again Thomas for your great comments.
George Schire
Oakdale, Minnesota
20/03/2016 11:43 am
George that top down Burgandy Horch was amoung my top 10 favorite models I own
So I feel your pain and agony!!! It's since been replaced and so far so good!! Thrilled my second one didnt fall apart!! My DM 1969 RS Camaro with the door that fell apart didn't bother me much. The model was bought second hand for about $50 and it was never a favorite nor a particularly well done model. Sold that as is don't miss it at all. And last my 66 Corvette.... Miss it never replaced it but DM refunded my purchase price! So broke even there!! All in all aside from some rash my cars are doing well As a whole and the majority are still pristine!!!
20/03/2016 12:42 pm
Thomas....your analysis is correct. For 34 years I worked for a company that did a lot of diecast molding using Zamac 3 (I think that is the correct name) and recall many discussions regarding quality problems with our diecast parts. The questions always were was the process correct and or was there a problem with the zinc mixture?
20/03/2016 1:19 pm
HMM i have all of the Horchs top up and down
Have not looked at them since i packed them up in 1999 think i need to find them all and inspect
20/03/2016 2:11 pm
OUCH hope they're ok but am regretful to say that most probably one or more WILL have diecast cancer
Do you have the Top UP LE Black/Silver Horch? I do and its nice but has paint rash on some panels. It did even when I first bought it so....
20/03/2016 2:16 pm
thanks for some more insight! BUT as mentioned die-cast rot/cancer/degradation is not the norm or all that common. If you count ALL scales I have over 330 models and to date only THREE have been affected but this condition and all were 1:24th. Of 1:24th scale i have about 270+ models so that's ONLY a tad over 1 % affected a very small percentage! (THANK GOD)! George has about the same size collection and if I am correct to date he has had 4 cars with diecast cancer. 2 1955 Pontiacs, a 1959 Impala and a 1960 Thunderbird, so for him it's about 1.5% (one POINT five % not 15) of cars have this issue, still a low percentage luckily! 
20/03/2016 4:40 pm
@ Phil and all here...bottom line is this guys, though it hurts us when our little collectibles get the rot cancer and to a lesser degree some paint rash, it's important to keep it in perspective in the scheme of things in life.
For over 25 years these cars have brought me such a tremendous amount of joy, and we all know that nothing in life is without some minor setbacks along the way. So, with close to 300 cars and having only 4 (so far) with the cancer, I'd hardly call it the end of the world.
I will just continue to watch my cars, pay attention to others comments with regard to theirs and we can all share in the woes together.
Always remember guys, if every morning we see the sun come up in the east, all is really okay with the world.
George Schire
Oakdale, Minnesota
20/03/2016 8:01 pm
I agree Totally George!!!!!
20/03/2016 10:26 pm
Thank you
Thomas, a very valuable contribution to the ongoing discussion
21/03/2016 3:58 am
Great info. Makes sense.
John Merritt
South Lyon, Michigan - USA
21/03/2016 7:13 pm
Yes i do have that one i am scared of what i may find have to take the car in for pollution test tomorrow and than off to doctor and than i wont be able to move very well for a few days after him so i will in time find and inspect the cars