At its most basic and concise, yes, but it is worth noting why the choices are limited: Dave, in posing his question, asked about plastics. Plastics are largely rejectible due to: 1. Weight - you gotta have weight on driving wheels to get pulling power, and plastics are too light. 2. Electrical conductivity - with split frames being common, having metal being both for weight and electrical conductivity is efficient. And the overall drivers of cost: coppers and aluminums are expensive materials. Coppers are going to corrode, aluminums will, as well, unless anodized. Brasses (copper & zinc alloys) are about ideal as far as properties go, including long durability, but the high copper content makes it fairly expensive. Steels - low-end steels, although not inherently super expensive as materials go (although more expensive than zincs), are more expensive to machine, due to their being generally harder and stronger. And they tend to rust. You can go with alloy/stainless steels. but the nickel & chromium run their costs up.
Plastic frames with separate weights have been used successfully for many years. Life-Like did it and with a minimum of wiring. Modelers just don't like it because it seems "cheap". Zamac is still cheaper than using single metals that are heavy enough. Doug
That may or may not be true depending on ones impressions. As I have said before, it is their fault for a lack of quality control with the manufacturer. And to just turn a blind eye and deaf ear to someone that has been a loyal customer for many years just shows they are basically incompetent when it comes to providing a quality product and taking care of customer issues. If they cannot control their subcontractors, then it is their problem! Ignoring the issue is the same as doing it on purpose!
I pretty much knew the answer when I asked, but wanted to point out that we are crying about the Zamac issue, but there isn't really a good option. Actually, plastic WOULD be an option.......a lot of older locos have plastic frames. They fixed the conductivity by simply wiring everything......it's becoming more common for manufacturers to wire their locos.........Atlas is now using wired trucks, and BLI locos are almost entirely wired. If you are going to wire, you don't need a conductive frame. The old locos solved the weight issue by putting metal weights inside the shell.........not very elegant, but functional. I'm not sure what the weights were.......possibly Zamac, but if the weights self destruct, there are all kinds of things you can use for weight, and at least you still have a functional (but light) loco. A lot of my cars have a steel weight in them....the cost isn't that much because it's just a piece of flat stock cut to length. I remember reading an article a number of years ago........it was about the future in model railroading. One of the things mentioned was that it was possible (but costly) to actually make the chassis as a battery. Apparenty there were working prototypes, but again, the cost was prohibitive. But you could get about an hour on a charge and you could bury a wireless charger on the layout, and recharge simply by parking the loco on top of it......just like refueling a real loco. And you could have wireless remote. I haven't seen any more about the technology, so either the cost was too prohibitive, or possibly the company doing the research went under......who knows. But it did point out that there are other things out there.
Is brass cost prohibitive. It is heavy, could be milled easily. Can be soldered to and the milling scraps easily recyclable and brass is conductive.
I know but that could be addressed and other makers have gone back to that in an effort to mitigate current interruptions in DCC locos. And actually, the Life-Like diesels don't have hardwired trucks. They have contacts and on the E units, there is only one short wire to the top motor brush and the two relatively short wires to the headlight. Milling for DCC would be easier because you could just remove the weights and mill them instead of having to handle the whole chassis. That is if you had a non-DCC ready loco. Plastic frame locos could be made DCC ready. Everybody just seem to be married to the split frame. It could all be worked out. Doug
I’ve often thought about the beauty of such an arrangement: 1.No wiring of the track at all. Except to send power to the charger. 2. No block wiring, no polarity switching for reversing loops, wyes, etc. 3. No jacking around with juicing frogs, etc. 4. Traction tires everywhere. Would probably relieve some need for locomotive weight, as the batteries wouldn’t achieve the same mass as solid metal. You could save some cost of the system by foregoing wireless charging & wireless control, and charging through the track: Make ONE “power block” with plastic rail joiners, and do your charging there in that block. If you want multiple charging locations, make the section longer, or spread a few charging blocks around a yard. You’d just have to leave a pair or two of wheels without traction tires to have a charging path. Leaving a few wheels without traction tires would be the conventional DCC signal path through the rails, as well. Just a few thoughts.
Copper is awful to work at the best of times and it's quite expensive. Maybe you were thinking of brass ?? Aluminium is quite light so locos would probably be slippery on their feet, it can be die cast though. Steel rusts quickly ..... (Stainless steels doesn't rust but can be hard to machine) .... both are fairly impractical to use for casting for N scale products. If I suddenly found my tunnel motors had failing frames I'd machine replacement frames from brass. (I really have thought about this). It's probably not economical for even large manufacturers like Kato to CNC machine loco chassis this way due to the length of time to make the finished parts. I would even guess a chassis would require mostly CNC milling followed by more metal removal in a CNC EDM (electrostatic discharge machine) to make the square corners that are needed in these small parts. Plastic is pretty good , just look at Life-Like E's and PA's with plastic chassis , we aren't typing page after page about them failing. The mould for casting the parts is 10 of thousands of dollars though. Plastic chassis do have the added complexity of needing a zamac weight for ballast to be made and fitted. It's rather ironic that when zamac is used purely for ballast then it doesn't seem to fail. I've also considered polyurethane as a plastic substitute ..... in fact for a small number of parts it is probably my number two choice after brass. A decent mould / die still has to be made and that isn't dirt cheap either. BJB Enterprises makes some great polyurethanes that can substitute for resin if you know what you want and don't intend to modify parts after they are made. Polyurethane is a sort of rubber ..............
When it come to weight, and N scale locomotives are all about weight to get pulling power, zamak is the best game in town...as long as it is treated and done right. 308 did a great breakdown of why other metals won't work. Even plastic chassis, which could melt and/or warp due to the motor heat if an engine was run long enough, still needs weight added to make the engine pull. A quick search of the internet says that brass is 30-80% more expensive than zamak. Here's more info from my trip down this rabbit hole: Brass weighs 8.4 grams per cubic centimeter, whereas Zinc ore weighs 3.4 grams per cubic centimeter. With the addition of other materials you can expect a Brass product to weigh around double that of an identical product made from zamak. Stainless is about 20% heavier than zamak but is much less conductive than zamak. The cost of stainless steel can be the biggest determinant for many industries. Because stainless steel is made from Choronuim, it costs more to manufacture (about 45% higher than zamak). Another drawback of stainless steel is that it’s not as easy to work with as other metals, and you’ll need special tools to machine them. Zamak can be electroplated, powder coated, wet painted, and chromatic-conversion coated. zamak cannot be left un-finished, as it will corrode quickly due to environmental factors. If used outside, Zamak-based products will deteriorate in a matter of weeks or months, as factors such as extreme temperature change, UV exposure after rain, frost, and chemical or salt composition in the air will attack the finish and cause the plating to flake off, exposing the vulnerable Zamak base metal beneath. Zinc alloys are found to be stronger than carbon steels, particularly in shear strength, and have non-magnetic properties (important when combined with motors).
Nice breakdown, Jeff. I see brass was mentioned briefly. Could it not be cast into a frame shape and, if so, is cost the only prohibiting factor? Also, anyone know what type of metal was used in the first run(s) of the Atlas N scale VO-1000? The ones with the weird, super-shiny finish? Is that just zamac with a different finish?
Ironically, among the locos I've more frequently seen damaged by zinc pest are Life-Like's plastic-frame GP18 and GP38. The weight slabs swell up and crumble and the effect is just the same as if the whole frame was metal. From what I understand, brass oxidizes with a thick non-conductive oxide layer that would negate the current-carrying advantages of a metal frame. It'd have to be a nickel silver alloy like track (which despite having silver in the name is basically brass with nickel added), and I'm sure the bean counters and/or people who have to actually work with the stuff have a reason to have avoided that even though it's the standard for track.
Brass can be cast with lost wax process to pretty accurate sizes ....... I forgot to mention that. In live steam modelling probably the best detail parts are brass lost wax castings. Brass does tarnish or oxidise making electrical contacts fail but brass is an excellent material to electroplate. Instead of making the whole thing nickel silver, a brass lost wax casting could be nickel silver plated. I also found a video on BJB's FD70 polyurethane ...... it's only 6.5 minutes long ,,, the second half is quite worth it.
^^^^^^Never mind, he already answered it.\/ \/ \/ \/ \/ The wires in the LL plastic frame E-units and SD-units do not move.. On the F-units and the plastic frame FA-2s, they pivot with the trucks. The constant flexing causes the soldered joint to come undone after many hours of operation. The current collection system that LL used for the plastic frame E-units and SDs was the best. The tabs on the trucks made contact with stationary phosphor bronze strips. non flexing wires went to the motor. This made it far simpler to install a decoder; you simply unsoldered the wires from the stationary bronze strips or motor terminals and wired in the decoder. The SD units did not have the pulling power that I might have liked as there is only so much room for weight in a road-switcher configured locomotive. The plastic E-units had great pulling power, despite having idler axles, as there is far more room for weight in a cab diesel.
Yes, I forgot to mention the LL F units were still made the old way with wires but, in spite of their quiet and powerful running characteristics, their appearance is a major detriment to being used for scale modeling. I have three but they cost me very little and I just run them every once-in-a-while just to see them run. Doug
At the end of the day...I just think we are all a bunch of 'Grumpy Old Men'... If we ain't complaining about something everyone else wants to know if we are OK ! For some reason I think it's part of the rules for being a Model Railroader...
