Hi, I bought this engine today, and found that some of the wheels have chipped cast metal. I'm suspecting that this is zinc rot? Is there any way to save this engine?
Its a PFM/United Santa Fe 2-8-4...theyre pretty common as brass engines go.
I'm thinking the following...
1. buy a parts engine, switch the wheels for good ones, then sell it.
2. grind off the part thats chipped, use styrene to cover up the zince pest, and pray the rest of the wheel dosent just break off.
3. replace wheels with mantua 2-8-2 wheels...pray that they are somewhat interchangable.
What are your thoughts?
Charles
---------------------------------------------------------------------------------------------------------------
Modeling the PRR & NYC in HO
Youtube Channel: www.youtube.com/@trainman440
Instagram (where I share projects!): https://www.instagram.com/trainman440
Hi Charles. A few more details might help, but that's definitely zink rot, or pest. Repairing and sealing the wheels won't stop the nasty breakdown from worsening.
Mantua/ Tyco 2-8-2 drivers are 0.757 tall over the flanges. The 2 blind (flangeless) center drivers are 0.700 tall. The axles are 1/8", as most old American made HO are.
Depending on the brand loco you have there, where it's made, (SAE? Metric?) the screws from the Mantua may or may not interchange with the ones on your drivers there.
Let us know what locomotive you have there, brand, etc, and you'll probably get more helpful answers. Dan
Zinc 'pest' is the result of a metallurgical phase transformation at 'low temperature' that happens to coincide with the range of 'human environmental temperatures'. I think the best way to keep it from progressing or accelerating is to keep the locomotive consistently warm at all times, including when it is stored away out of sight.
Dp not mistake this for 'oxidation' or chemical reaction of some kind, and think 'grinding away affected areas' or priming/coating or dips will stop it. It is a change like that from pure white tin to gray tin.
My opinion, hopefully backstopped by experience of others here, is that you can ameliorate some of the effects of the lattice changes if you keep things 'religiously' warm going forward. Air-conditioned layout rooms and turning down thermostats to save energy in winter are NOT zamak-friendly. A penetrating self-curing liquid (perhaps cyanoacrylate?) can be allowed to 'wick' into the cracking to stabilize crumbling areas and to provide a non friable bonding surface for some sort of putty to restore contour or surface finish for painting. While I don't think you can reverse the existing phase changes (which have probably propagated in other areas of your model) you can treat any such area as if it were 'powder needing to be consolidated' after stripping original paint if desired to check underneath, and not worry that a process like oxidation or tooth decay will keep erupting under the fixes or new paint...
Southgate Let us know what locomotive you have there, brand, etc, and you'll probably get more helpful answers.
Let us know what locomotive you have there, brand, etc, and you'll probably get more helpful answers.
I shoot I'm sorry, forgot to add that. Its a PFM/United Santa Fe 2-8-4.
Overmod Dp not mistake this for 'oxidation' or chemical reaction of some kind, and think 'grinding away affected areas' or priming/coating or dips will stop it. It is a change like that from pure white tin to gray tin.
:(
Yea, that's what I thought. I added that option mostly to help with the appearance, knowing that eventually the entire wheel will break away.
Keeping the entire basement(a cool place to start off) really warm is unviable, I got parents(yes, Im a senior in High School) who love to use the heater as little as possible and we live in PA.
Thanks for the input!
You should be able to get suitable replacement drivers from Greenway.
This brass Mogul, belonging to a friend, had a severe case of zincpest in its drivers. I was able to get replacement drivers from Greenway (not inexpensive), and since it would be a pretty-much complete teardown, suggested that we also replace the open frame motor with a can-type, and at the same time, add a NWSL gearbox. Once all the mechanical work was done, I gave it a new paint job...
...and it not only runs a lot better, but looks better, too.
Wayne
There are signs of zinc rot in the adjacent driver's counterweight. Right now the damage is more or less cosmetic but if the spokes start to show signs and fail then there is a strong chance the wheel will cease to work right. Dr. Wayne's citation of Greenway for replacement wheels for brass engines is a good one. It would be nice but unlikely if there are Mantua or other cheaper commercial parts that would be drop in replacements, particularly given that in my experience even steam loco drivers of the nominal same size (that is, 73" or 80" drivers, whatever) is rarely the same from different sources and thus are often hard to mix (remembering also that the size of axle, the location of the openings for crank pins and the like, can also vary from make to make).
Good luck!
Dave Nelson
I should have mentioned that the Greenway drivers are specifically intended for brass locomotives, as the axles are 3mm in diameter, slightly less than the 1/8" diameter of the axles on most North American-made steam locomotives.I bought a set of Greenway drivers for a John English Pacific (my first steam locomotive, acquired, second-hand, in 1956) that I'm re-building. I'm also going to re-motor it and add a NWSL gearbox. On the advice of Dave (from NWSL), rather than create wheel bearings for the undersize 3mm axles, I'll ream-out the new drivers' to 1/8", then mount them on the Pacific's original 1/8" axles. For Charle's locomotive, the proper-size Greenway drivers should be a drop-in fit, without need of modification.
3mm is 0.118", and 1/8" is 0.125"
.
That difference of 0.007" does not sound like much, but when assembling press fit parts, it is HUGE.
Always be careful, and use a good micrometer or dial caliper to measure old parts before replacing.
-Kevin
Living the dream.
Thanks for the suggestions! I'll check out Greenway.
PS dumb question. When measuring driver diameter, its from the outer rim of the tire, right? We dont include the flanges into the measurement, nor do we meaure from the inner rim of the tire.
Thanks!
Zinc pest in a PFM/United brass import is very uncommon. I would be inclined to find another one(they made thousands of this model) and us it for parts. Greenway can work, but the mounting points for the side rods may be different and require different side rod screws/bolts. So there are some hurdles that might need to be overcome, along with fitting the original axle bearings, requartering and a new NWSL or Boo Rim gear box. (NWSL is closing in a couple months). A parts donor engine, IMHO, is your best/easiest option at this point. Mike
Silly NT's, I have Asperger's Syndrome
Thanks, yea I've never seen a United/PFM engine have zinc pest.
I checked Greenway, the wheels are $20 a piece! That's $80 for an engine I paid $127 for! I'd rather buy a parts engine, swap the wheels, then sell it off.
Thats what I would do, buy another one, swap the chassis out, then sell the rest. Someone will want it for the tender and boiler/cab assembly. Or keep the second one as a "rip track" locomotive awaiting repair at your engine house. Mike
Back in the 1950s and 60s (and perhaps into the 1970s) an amazing modeler named Bill Schopp would write almost monthly articles about modifying and using brass locomotives as parts supplies to make locomotives not otherwise available. He had the ability to solder at the same level of ability or better than the original brass manufacturers had. In a pinch he'd also use parts from die cast and even plastic locomotives but his favored material was brass, and I gather he had baskets full of junkers and parts.
I have this vague memory that he used the PFM/United ATSF Berkshire as raw material for some of these ... well they aren't exactly kitbashes but that captures the idea. He took advantage of the fact that on most big railroads there were clear family resemblences in cabs, tenders, boilers and smokebox fronts, as well as other details, so that any brass loco was in fact fodder for making something else. Now that there is some evidence that older brass can be had for reasonable prices (there is another recent thread on that topic) perhaps we will return to an era when the Bill Schopp.
I'll take a look at my old RMCs (the magazine index on this website being, as usual, nearly useless) to see if I can find it.
Trainman440 PS dumb question. When measuring driver diameter, its from the outer rim of the tire, right? We dont include the flanges into the measurement, nor do we meaure from the inner rim of the tire. Thanks! Charles
I've only encountered zinc pest in HO scale drivers twice. The first time was a set of 1950's Mantua Pacific wheels that came in a junk parts lot, and one of the wheel centers had expanded enough that it pushed through or around the insulator, creating a dead short.
The second time was on a Penn Line K4. One of the drivers was compeletely out of true, wobbling in and out of gauge. As a last resort, I thought maybe I could use a heat gun on low to carefully bend it back (a tip I learned from a friend who deals in a lot of brass & diecast loco parts as a fix for castings that are warped or bent), but the wheel center suddenly warped even further, with a few more chunks falling off.
This makes sense in retrospect: the casting was already grossly swollen; any further expansion from excessive heat wasn't going to do it any favors, especially given that the casting was internally fractured and had lost all integrity as a single part. All I did was exacerbate the expansion that leads to failure in the first place.
Lesson learned.
Nelson
Ex-Southern 385 Being Hoisted
What you all are calling zinc rot looks to be a form of electrolysis which is a common happening in damp areas that are exposed to an electric current. Zinc is the sacrificial metal used in the marine industry were electocis is present. Look it up on the web for more info.
All are correct in that you can not stop it and some locos are more susceptible to the degradation depending on the chemical formulation of the zinc alloy the frame is made from.
Early imports from S. Korean building Dong Jin (mostly Hallmark imports) were very prone to zinc pest. The ICRR 2-8-0, a beautiful little Connie had a horrible drive. Using the Tyco/Mantua motor and drivers that nearly always are now swollen with zinc pest issues. Thankfully not long after this, they switched to coined or cast brass driver centers vs diecast metal. Even today, we are seeing zinc pest in diecast trans made in the PRC, mostly in O gauge stuff in a couple different brands. I think the early Bachmann Spectrum GE 8-40C's were prone to issues with the diecast chassis. Mike the Aspie
Yea, this diecast wheel also expanded enough for the wheel to create a short when placed on the track.
Zinc pest also destroyed a Bachmann 2-8-0's frame, which is the first time I've seen that ever happen. Zinc pest really does occur in the places you least expect...sigh.
Thanks for all the input!
The only locomotive I have had with this disease is my Mantua 2-6-6-2. It has both the lead and trailing truck bracket effected.
In Wargaming we call this "Lead Rot", and there is nothing worse than seeing a beautifully painted Napoleanic Army rot away.
It must be avoidable through careful manufacture. Games-Workshop, Pegaso, Essex, Citadel, Reaper, and Marauder have never had issues that I know of.