Another Zinc Pest Issue To Watch For...

You might be able to make that out of a piece of sheet or plate metal.

That would be a good 3D print candidate

I've been tempted to pick one of these up as I often see these at shows. I usually have other items that are on my list so usually pass to ensure I have enough funds for what I REALLY want. Good to know this is something I should look out for.

Thanks for the heads up during this zinc pest extravaganza on the forum! I checked my Bowser'd Corgi and thankfully all is well, but the dark color of your motor mount is curious. I'm wondering if maybe it was subject to an extreme weather environment? Good luck with your fabrication, I'm sure you'll get it running! Here is a pic of mine, note the mount is silver gray.  

Rich

Thanks guys.  For what I paid I certainly can’t complain about having to make a part...

I agree that 3D printing would be a great option, though I no longer have a CAD program on my computer and can’t draw it up.  If someone made a drawing and uploaded it to a 3D printing website, I would certainly buy the 3D printed part.

Rich, the lighting was bad when I took the photo.  In person mine looks like yours, just a little more crumbly.

Jake,

As long as you are going this far with the motor mount, you might want to think about installing a smaller motor with a fly wheel.  I suspect the trolley in working condition probably stops on a dime when the power gets chopped. The flywheel will definitely smooth out starts and stops.

Chris

LVHR

Since this is a DC motor drive (noticed the rectifier chip in the photo)...and I'm assuming the other truck has the center rail pick-up...it's too bad Northwest Short Line's O gauge Stanton Drive truck couldn't be used.  I know NWSL doesn't offer it (currently) with Hi-Rail wheels, but they might be persuaded to do so with a phone call.  And, they offer the O gauge truck in three wheel-base dimensions, which may not be compatible with the streetcar design. 

But the nice thing about the Stanton Drive is that the motor is within the truck block, leaving the interior completely free for detailing....something really nice for a streetcar!   And since the streetcar has only itself to motivate, the Stanton Drive would be plenty powerful.

Just a thought for a different approach. 

KD

I have a question concerning zinc warping and crumbling - the "zinc pest". Perhaps someone here who actually knows the metallurgy of the matter can respond.

So far as I know it is caused by foreign matter in the metal or die when cast; I have heard lead mentioned more than once as the common culprit. I have also heard the opinion - surely wrong - that zinc "always does this eventually". There are some really old stable zinc castings all over the world in all sorts of places.

My question, though, is actually this: can the "weather" - the environment, the temperature, the humidity, "the basement" - affect this warping and crumbling process? Not actually cause it, but accelerate it or make it worse?

This seems unlikely to me, given the ultimate cause. Anyone here (truly) know? 

As its easy to cut, grind, drill and mill, I believe that plate could be easily reproduced in aluminum.

D500 posted:

I have a question concerning zinc warping and crumbling - the "zinc pest". Perhaps someone here who actually knows the metallurgy of the matter can respond.

So far as I know it is caused by foreign matter in the metal or die when cast; I have heard lead mentioned more than once as the common culprit. I have also heard the opinion - surely wrong - that zinc "always does this eventually". There are some really old stable zinc castings all over the world in all sorts of places.

My question, though, is actually this: can the "weather" - the environment, the temperature, the humidity, "the basement" - affect this warping and crumbling process? Not actually cause it, but accelerate it or make it worse?

This seems unlikely to me, given the ultimate cause. Anyone here (truly) know? 

I would say that cold temps would affect the ductility.

High temps and or moisture would accelerate the migration of the zinc decay.  JMHO

D500 posted:

I have a question concerning zinc warping and crumbling - the "zinc pest". Perhaps someone here who actually knows the metallurgy of the matter can respond.

So far as I know it is caused by foreign matter in the metal or die when cast; I have heard lead mentioned more than once as the common culprit. I have also heard the opinion - surely wrong - that zinc "always does this eventually". There are some really old stable zinc castings all over the world in all sorts of places.

My question, though, is actually this: can the "weather" - the environment, the temperature, the humidity, "the basement" - affect this warping and crumbling process? Not actually cause it, but accelerate it or make it worse?

This seems unlikely to me, given the ultimate cause. Anyone here (truly) know? 

I did a little reading when this issue was mentioned here recently regarding another model.  According to an article I found, the environmental factors such as high humidity can accelerate the process, though any piece suffering it will eventually fail.  From what I understand, higher amounts of lead or other impurities (though I think lead is the main one) in the alloy cause the problem.  Castings that are 99%+ zinc don't have this issue.

dkdkrd posted:

Since this is a DC motor drive (noticed the rectifier chip in the photo)...and I'm assuming the other truck has the center rail pick-up...it's too bad Northwest Short Line's O gauge Stanton Drive truck couldn't be used.  I know NWSL doesn't offer it (currently) with Hi-Rail wheels, but they might be persuaded to do so with a phone call.  And, they offer the O gauge truck in three wheel-base dimensions, which may not be compatible with the streetcar design. 

But the nice thing about the Stanton Drive is that the motor is within the truck block, leaving the interior completely free for detailing....something really nice for a streetcar!   And since the streetcar has only itself to motivate, the Stanton Drive would be plenty powerful.

Just a thought for a different approach. 

KD

I wanted the  Bowser kit because it looked fairly robust.  The wheels are nowhere near scale and obviously it requires removing the existing interior seating piece to install.  I powered mine previously with a GHB international kit (motor integral to the truck, scale dimensions) that didn't hold up to the conditions I'm hoping to run it in.  Regular use on a public Christmas display requires fairly robust equipment, so I'm not so worried about detail as I am having it look good from a distance and run reliably.  I picked up the Corgi Detroit Street Railways PCC car awhile back, and have a second one as well.  They look great and are the only somewhat close to O scale Detroit cars I'm aware of, so I'd like to have a powered one for my collection.  I think I'm going to stick to my MTH trolley for my public display, but this should be nice for occasional running when I get it sorted out.

Dennis LaGrua posted:

As its easy to cut, grind, drill and mill, I believe that plate could be easily reproduced in aluminum.

I sent Bowser an email yesterday hoping they might have a spare casting left over from old production but they did not.  He did mention that aluminum would be a good material to use for it, and I have a piece picked out in our scrap pile at work that should work nicely.  I have to finish making the replacement whistle valve for one of our locomotives in the milling machine and then I'll hopefully be able to tinker with my project on my lunch break in the near future.

SantaFe158 posted:

I have to finish making the replacement whistle valve for one of our locomotives in the milling machine and then I'll hopefully be able to tinker with my project on my lunch break in the near future.

Once you get the machine set up, maybe it would be a good idea to make a few more and sell them to folks with bad ones.

D500 posted:

I have a question concerning zinc warping and crumbling - the "zinc pest". Perhaps someone here who actually knows the metallurgy of the matter can respond.

So far as I know it is caused by foreign matter in the metal or die when cast; I have heard lead mentioned more than once as the common culprit. I have also heard the opinion - surely wrong - that zinc "always does this eventually". There are some really old stable zinc castings all over the world in all sorts of places.

My question, though, is actually this: can the "weather" - the environment, the temperature, the humidity, "the basement" - affect this warping and crumbling process? Not actually cause it, but accelerate it or make it worse?

This seems unlikely to me, given the ultimate cause. Anyone here (truly) know? 

It is incorrect to think that "all" zinc castings will fail due to "zincpest".  This all has to do with solubility limits in the alloy etc.  A quick look on line will provide some general explanations.  All solids are represented by a crystal lattice structure.  This is the orientation of the atoms in the alloy with relation to each other.  There are several types of crystal lattice such as body centered cubic etc.  Materials science is a very interesting topic.  Here is some info that may hopefully help in an explanation although it is a very short and simple discussion.

It is correct that the presence of lead when the zinc alloy is poured is the problem.  It has been a problem since the 1920's and is still a problem today simply due to a lack of quality control.

Here is a little more info for the discussion. 

Off-Specification Alloy

All alloys may become contaminated or lose composition, but there is a greater chance with alloy made from secondary materials due to their narrower impurity margins.

Only an unscrupulous supplier would sell off spec. material and only a misguided die caster would purchase it. Not only will the material have inferior mechanical properties and be likely to fail in service, but it will also prove to be more difficult to cast thus resulting in higher scrap rates. Additionally drossing losses will be significantly higher.

By using such material, the die caster will probably finish with fewer castings per ton of metal purchased. Production will also take up more machine time, so that the "cheap" material costs him more in the long run.

The increased chance of part failure could cost him his reputation, his customer base and his market. Remember that product liability laws make a manufacturer responsible years after the parts have left his shop. Should a failed component be found to be out of specification for chemistry, then the manufacturer will be held at least partly responsible, even if the alloy composition had nothing to do with the failure.

How are off-spec. and secondary alloy associated?

Secondary zinc alloys, which are properly produced from carefully separated scrap material, are not inferior alloys. However, many secondary alloys, which are imported into North America, are often not produced with as much care as necessary.

Due to the impurities, which are generally found in scrap materials, it is significantly more difficult to produce in spec. alloy ingots from secondary materials than from SHG or recycled materials. Tin plating often used on electronic castings and pressed in leaded bronze bushings are just two examples of typical impurities. If too many impurities are allowed to enter the melt, the resulting alloy will be out of spec.

Particular attention must be paid to the very strict maximums which the spec. places on Lead (Pb), Cadmium (Cd) and Tin (Sn). The reason for this is not visible to the naked eye until it's too late. These three elements can cause intergranular corrosion in the Zamak and ZA alloys when any of these elements is present above the ASTM specification.

What is lntergranular Corrosion?

When a zinc alloy solidifies, the material's matrix forms microscopic grains. As the name implies, Intergranular Corrosion is corrosion which occurs at the boundaries between the grains.

Intergranular Corrosion can cause catastrophic failure in stressed applications. In fact, after only 90 days in a humidity cabinet at 203 F (95° C), zinc castings containing only marginally out of Spec. Pb, Cd or, Sn will lose most of their impact strength. Catastrophic failure caused by Intergranular Corrosion may occur very suddenly without any prior notice.

A low magnesium content in a zinc casting alloy can also promote the rate of intergranular corrosion when the levels of Pb, Cd and Sn are at or even near the maximums specified.

What happens when other alloy constituents are out of spec.?

While intergranular corrosion is certainly the most serious problem with off grade zinc alloy, out of spec. quantities of other elements such as aluminum, magnesium, and copper can also affect material performance.

Additionally out of spec. alloy not only affects the operations of the finished components, but it can also make a die caster very uncompetitive. Poor fluidity, high dross and poor surface finish are all attributes of "out of Spec. material".

However, in spec. material that only marginally meets the casting specification limits can also cause some variations in certain casting parameters such as fluidity. The ASTM specifications denote only the maximum tolerance permitted for use. Many alloyers will endeavor to hold these tolerances much tighter, especially in alloys produced from primary zinc, thus reducing variations in casting parameters.

After all, the true test of a material's cost is how many good components are produced out of a ton of metal. A 1% increase in production of "good" castings is worth much more than a 1% reduction in metal cost.

Time to get and keep the Lead out of our models.

Update on this...

I finally had a little time after work today to work on my replacement piece.  The milling machine is currently set up for a work related project, so I ended up just doing a rough job with our band saw and drill press.  It came out pretty well and should serve the purpose.

The plate is a piece of 3/16" steel with 1/16" shims between the top and bottom plates sandwiching the frame cross member.  I used longer screws with jam nuts on top to help keep things together since I didn't have quite as much material to bite into with the tap.

Finally a mechanism installed in my Corgi PCC body.  I've had this for a few years now and have been wanting a powered Detroit PCC car for our local events.  I'm looking forward to running it.

Jake, I'm curious which tourist line you work with. GV/HF right ? At the base ? Elsewhere ?

Adriatic posted:

Jake, I'm curious which tourist line you work with. GV/HF right ? At the base ? Elsewhere ?

I work in the roundhouse at Greenfield Village. I was a fireman in 2014 and I’ve been a fireman/engineer for the last three years.  At the moment I’m transitioning into a full time job as a locomotive mechanic.

  Thanks, that saved me some searching to verify my recollection.

  I've been much more active and have been considering braving a ride vs walking (shuffling) the Henry Ford Museum again.  It can't be a long mainline trip if I do and the Village seems about right . I just wanted to maybe be able to say hey while there is all. 

SantaFe158 posted:

D500 posted:

I have a question concerning zinc warping and crumbling - the "zinc pest". Perhaps someone here who actually knows the metallurgy of the matter can respond.

So far as I know it is caused by foreign matter in the metal or die when cast; I have heard lead mentioned more than once as the common culprit. I have also heard the opinion - surely wrong - that zinc "always does this eventually". There are some really old stable zinc castings all over the world in all sorts of places.

My question, though, is actually this: can the "weather" - the environment, the temperature, the humidity, "the basement" - affect this warping and crumbling process? Not actually cause it, but accelerate it or make it worse?

This seems unlikely to me, given the ultimate cause. Anyone here (truly) know? 

I did a little reading when this issue was mentioned here recently regarding another model.  According to an article I found, the environmental factors such as high humidity can accelerate the process, though any piece suffering it will eventually fail.  From what I understand, higher amounts of lead or other impurities (though I think lead is the main one) in the alloy cause the problem.  Castings that are 99%+ zinc don't have this issue.

OK - everyday, non-extreme environmental factors apparently can affect this process, and lead does seem to be the most common, but not only, cause of zinc casting failure, per the articles quoted above. I did not know this;

I presumed that the "weather" would not affect die-cast metal, beyond typical corrosion/oxidation, if the metal is prone to that in the first place.

Adriatic posted:

  Thanks, that saved me some searching to verify my recollection.

  I've been much more active and have been considering braving a ride vs walking (shuffling) the Henry Ford Museum again.  It can't be a long mainline trip if I do and the Village seems about right . I just wanted to maybe be able to say hey while there is all. 

Feel free to say hi if I'm at work that day.  This year I'll likely be mostly in the roundhouse with a day or two here and there on the locomotive.  The Village opens on April 14th this year, or the 13th if you're a member.

Our ride is about 2 miles long around the village with three station stops.  If you get on at the main station by the front gate and ride around to the third stop (Smiths Creek Depot), you'll be very close to the roundhouse and other railroad related things.

Jake, glad the fabrication worked out. With my experience using the Bowser motorized chassis, the single roller pickup is frustrating. Unless my track has recently been cleaned, the unit frequently stalls when traveling at scale (slower) speed. There isn’t much room on the motorized truck for a straight forward installation of a roller pickup, however, you seem to have a talent for fabrication 

Should you decide to tackle this flaw, please let me know how you did it, as a rarely run mine due to the stalling. It just looks bad running at fast speed.

Rich

  Thanks Jake. I know the grounds size well, I just haven't been in the Village for a long while. The stops make it even more likely too, I wasnt sure about a whole 2 miles. Walking that isnt as big a deal as vibrations may be. There is only one way to find out though. It'll be funny if I already know your face from around town too

Smoke Stack Lightnin posted:

Jake, glad the fabrication worked out. With my experience using the Bowser motorized chassis, the single roller pickup is frustrating. Unless my track has recently been cleaned, the unit frequently stalls when traveling at scale (slower) speed. There isn’t much room on the motorized truck for a straight forward installation of a roller pickup, however, you seem to have a talent for fabrication 

Should you decide to tackle this flaw, please let me know how you did it, as a rarely run mine due to the stalling. It just looks bad running at fast speed.

Rich

I’ll have to think about that.  I’m sure there’s a way to do something.  Perhaps a capacitor in the circuit would help?

Adriatic posted:

  Thanks Jake. I know the grounds size well, I just haven't been in the Village for a long while. The stops make it even more likely too, I wasnt sure about a whole 2 miles. Walking that isnt as big a deal as vibrations may be. There is only one way to find out though. It'll be funny if I already know your face from around town too

If you can handle the vibrations it’s definitely a good way to get to different points in the village.

Why is there not yet a "ZINC PEST" T-shirt? Big block letters. Maybe some small ones for kids - no, wait - definitely some small ones for kids, sold at train shows.

D500 posted:

Why is there not yet a "ZINC PEST" T-shirt? Big block letters. Maybe some small ones for kids - no, wait - definitely some small ones for kids, sold at train shows.

I wear a large unless they shrink a lot !    

(don't fret Jake, I'm actually usually pretty quiet and reserved unless you wind me up. ..and the "offswitch" works too)

A good sized cap. would help, the end result would be a momentum effect though. It would need to be a well balanced selection to be used without a control circuit of some type. 

  I don't know what the trucks underside looks like to hazard a guess as to what would work but I have ideas, and GRJ has posted some slick add on ideas for other trucks.   A shoe vs a roller might work too. And fyi, my single shoe pickup passenger cars seldom blink. That's roller stuff     I'm guessing with no load to tow, it can handle the tiny bit of shoe drag in stride.