Why stainless cars?

We've generally accepted that stainless cars for Amtrak and other carriers are good for durability. It comes at a cost of weight and price.

While SEPTA saw some Silverliner III last about fifty years, and the Amfleet approaching that, empirical evidence is coming out of other countries that cars can reach the same age in carbon steel and/or aluminum. The GO cigar cars and Horizon/comet cars are aluminum. The Brits have MkII and MkIII cars made of carbon steel. Recently we saw the Acela 2 is not stainless, either.

Has the stainless era ended? Is it better for long distance trains that are rarely updated?

Mr. Dunville, I think that in the case of the Acela 2, Amtrak is expecting to be back in the market for an Acela 3 in another 20 years, or well within the service expectancy of carbon steel. Should corrosion develop, it will be visible and can be addressed. This of course is different from that of Pullman-Standard and their unwise decision to offer, and the railroads like unwise, "sheathed" cars as part of the "postwar" re-equip initiative. Four roads coming to mind, NYC, RI, SP, and NH, all regretted that choice, when their cars all became "rotten apples".

Therefore, why spend the excess $$$ for a structure that will be obsolescent and those customers willing to pay "a buck a mile" will expect something new by then.

Just a dollars and cents decision; just as was that not to contour the Power Car's sheathing to conform with that of the Passenger Cars.

Agreed. The Acela Is will be retired before the similar, much older LRC coaches built from aluminum and carbon steel. There are still carbon steel Gallery cars running around. A high proportion of the original aluminum Comet Is are still in daily use.

I suspect Amtrak could have gotten four Horizons for every three Amfleet IIs; maybe five Horizons per three Viewliners*; probably two Horizons for every Superliner II. Wonder how many more Acela Expresses they could have purchased, had the cars simply been LRCs redesigned with a straight sill, but built with the original materials?

*whether you could make a sleeper from a Horizon is another matter.

mtuandrew wrote: ↑Mon Jun 15, 2020 10:09 am Wonder how many more Acela Expresses they could have purchased, had the cars simply been LRCs redesigned with a straight sill, but built with the original materials?

From what I understand, the Bombardier coach family is all a bit related. In other words, LRC, M7, and Acela coach all have somewhat similar architecture. This is railfan rumor - I have not seen the blueprints.

But I totally agree. Why we had to use stainless, or do anything but order a carbon copy of the LRC, is beyond me.

A well maintained car, with a superior shopping program, can last over half a century. DOVER HARBOR was out shopped in 1923, and was active in the Pullman fleet to 1965, then stored at Calumet until 1967, then in private service since. UP’s SELMA, born business car 100 the OVERLAND, has been in service over a century.

What we have learned from the streamline era:
- Cor-Ten steel is unsatisfactory for Railroad applications, especially in humid, salt air environments. SP and NH are proof enough.
- Mixing metals (particularly aluminum and steel) causes an electrolytic corrosion.
- Stainless (of that era) was not the greatest structural material ever.

My recommendations are four:
- In the slide rule era, engineers over designed things to be certain the margin of safety was assured. These days, we don’t do that. We should.
- The design life of railroad equipment was generally 40 years. Witness the ATSF Hi-level fleet, which served well over 40 years in daily service.
- Consult with the materials industry for products before designing.
- Design three carbody types: A standard height, a hi-level, and a HSR electric. Stick with them. ... Alternately, settle on existing designs.

John_Perkowski wrote:What we have learned from the streamline era:
- Cor-Ten steel isn’t unsatisfactory for Railroad applications, especially in humid, salt air environments. SP and NH are proof enough.

But don’t paint over it like ICG did!

John_Perkowski wrote:My recommendations are four:
- In the slide rule era, engineers over designed things to be certain the margin of safety was assured. These days, we don’t do that. We should.
- The design life of railroad equipment was generally 40 years. Witness the ATSF Hi-level fleet, which served well over 40 years in daily service.

For body-on-frame cars, that is entirely reasonable. You might even eke out 60-70 years in daily service with a frame-up rebuild or two, but that shouldn’t have to be the backbone of your fleet. (Looking at you, VIA.)

If you’re talking monocoque lightweights like Talgo, 20 years (with a stretch goal of 35) is more reasonable. It’s more than you can expect than a modern car anyway, and still gets you a long enough lead time to order new.

John_Perkowski wrote:- Design three carbody types: A standard height, a hi-level, and a HSR electric. Stick with them. ... Alternately, settle on existing designs.

Amtrak got in trouble with designing its own cars. Its most successful cars, on the other hand, were foisted upon the company in a “take it or leave it” situation. Take that for what it’s worth.

Stainless sheetmetal on carbon based alloy is the worse construction, often leading to rustout. The postwar Pullmans had this issues, as with all St. Louis stainless cars except Silverliner III and Arrow I.

Keep in mind most aluminum cars (MBTA 01500/01600/01700, Comet family, TTC cars) have steel subframes. BART pioneered aluminum monocoque design, in which the entire car is made of prefabricated aluminum panels assembled together.

John_Perkowski wrote: ↑Mon Jun 15, 2020 11:14 am What we have learned from the streamline era:
- Stainless (of that era) was not the greatest structural material ever.

Yet many Budds still remain (VIA for example, also many private charter cars and shortlines). The R32s and PATCO cars have been setting records for longevity for stainless equipment in heavy rail urban environments.

Easier to remove graffiti?

R36 Combine Coach wrote: ↑Mon Jun 15, 2020 5:04 pm

John_Perkowski wrote: ↑Mon Jun 15, 2020 11:14 am What we have learned from the streamline era:
- Stainless (of that era) was not the greatest structural material ever.

Yet many Budds still remain (VIA for example, also many private charter cars and shortlines). The R32s and PATCO cars have been setting records for longevity for stainless equipment in heavy rail urban environments.

Yeah and I'm not itching to completely dump stainless. I think it certainly has good applications. Long life, long distance, slower trains are one of them. The CP/Via fleet is strong as an ox. Perhaps if Amtrak had standardized on the ATSF and CB&Q stainless fleets as the two main fleets for the national system they could've had a more homogeneous fleet for parts commonality.

Subways are another good area for stainless as they are often underground and many big cities are near water, especially salt water. That said, I don't believe many subways are stainless outside of the Americas.

I'm not trying to roast Amtrak here, as stainless was clearly the best practice in 1971. But by 2001, when Acela 1 went into service, aluminum and composites were well-accepted in Europe and even here.

Tadman wrote: ↑Mon Jun 15, 2020 8:27 am We've generally accepted that stainless cars for Amtrak and other carriers are good for durability. It comes at a cost of weight and price.

While SEPTA saw some Silverliner III last about fifty years, and the Amfleet approaching that, empirical evidence is coming out of other countries that cars can reach the same age in carbon steel and/or aluminum. The GO cigar cars and Horizon/comet cars are aluminum. The Brits have MkII and MkIII cars made of carbon steel. Recently we saw the Acela 2 is not stainless, either.

Has the stainless era ended? Is it better for long distance trains that are rarely updated?

No. To the contrary, stainless steels are superior that Al alloys in almost all aspects except for weight:
1. Stainless steels are cheaper to produce than Al alloys.
2. Stainless steels can be twice as strong as commercially available Al alloys.
3. Stainless steels are more fire-resistent and crashworthy than Al alloys, bringing additional safety.
4. Stainless steels are more resilient to corrosion. They have a higher electrode potential of +0.2 V, while that of Al is -2.1 V. This indicates that the corrosion of stainless steels by water is inhibited by physics, specifically thermodynamics, while that of Al alloys is only preventable by kinetics. That's why Al-based railcars need to be painted (and repainted once several years, adding maintenance costs) while stainless railcars don't.

And in the past, there was an argument against the use of stainless steel, which is that it required spot welding, a process difficult to automate. The problem has been largely solved by the introduction of laser beam welding.

Axle load and the resulting wheel-rail impact is indeed an issue in some cases, and that's why today's high speed trains use exclusively aluminum for their bodies. But when it comes to conventional trains, be it commuter, intercity or long distance, I don't see a solid argument for replacing stainless steel with aluminum, especially considering that most tracks passenger trains operate on in the US are being constantly screwed by freights with an axle load not seen anywhere in Europe, making effect of the weight of passenger trains marginal to the maintenance costs of tracks.

The contrast between the European trend and American tradition just shows how path-dependent rail industry is. West Europe didn't embrace stainless steel railcars to the extent America did in the late 20th century.
Japan, however, is one of the few contries which make extensive use of both stainless and aluminum railcars, so its data provides a fair-ground for comparation. Statistics showed that at year 22, the whole-life cost of stainless steel railcars is lower than both carbon steel railcars and Al-based ones, being only one half of the latter: This may imply that even if Amtrak had made up its mind to refresh its conventional fleet every 20 years as someone mentioned above, stainless steel railcars would still be a better option.

phillyrube wrote: ↑Mon Jun 15, 2020 5:34 pm Easier to remove graffiti?

That was one of my first thoughts. When was the last time you saw graffiti on an Amtrak train? Probably almost never as paint doesn't stick to stainless steel very well. A quick trip through a high pressure car wash will remove it.

So the new ACELA II train-sets are not stainless steel. I wonder how long it will be before one gets tagged in Sunnyside. Yes, carbon steel is used a lot for trains in Europe. Looking at Videos from over there shows a lot of rolling "art gallery" trans.

Finally there's the longevity of stainless steel cars verse carbon steel. What ever Amtrak buys is going to have to last a long time as Amtrak doesn't have the budget of say SNCF or DB when it comes to renewing fleets. Something cheap in the short run might cost more in the long run.

hxa wrote: ↑Tue Jun 16, 2020 1:01 am The corrosion of stainless steels by water is inhibited by physics, specifically thermodynamics, while that of Al alloys is only preventable by kinetics. That's why Al-based railcars need to be painted (and repainted once several years, adding maintenance costs) while stainless railcars don't.

The PATH PA1/PA2/PA3 were painted aluminum, as are MBTA's 01500/01700. But the Comets are all bare
aluminum (other than window striping) and BART is unpainted. The BBD bilevels built in Thunder Bay since the 1970s are all painted.

Interesting topic.
My experience with stainless steel was largely around 35 years ago , whe n i did my apprenticeship as a welder in the food industry. stainless was hard work , it work hardened when cutting / drilling , and is a poor conductor of heat , meaning alot of twisting and heat deformation if welded without strong jigs , or heat spreading welding techniques. Stainless sheet was very challenging , you'd use the above techniques, left the clamps go , and the work would buckle and bend all over the place in the worst cases. its also a pain to try and buff / polish burnishes out of. in short a very specialised and expensive production technique.
It sounds like thing have improved with todays equipment. Though i note their were no facilities able to produce the viewliner bodies in the USA. CAF seems to be the holdout for stainless in Europe.
Corten steel has a bad reputation it doesn't deserve, probably because in its unpainted form it looks rusty. Yet The Ganz Mavag EMU's lasted 40 years in Wellington , NZ's,ferocious marine environment, where they spent much of winter covered in sea spray .
The latest technique in Europe/ Asia appears to be honey combed aluminium panels . you can have a 50 -100mm thick panel , with maybe 80 % of the strength of a solid panel , but 25 % of the material and weight of a solid panel . so your walls , floor and roof are made as strong as thinner solid Ali. I imagine the next step will be Carbon fiber , or even cellulose / plastic materials.

The welding aspect of this topic is interesting. If I recall, Budd made the stainless concept viable by inventing shot-welding. It sounds like another welding concept has been invented as well.

I know in aerospace and automotive (derived from aero) they have actually gone to some bonding/epoxy in place of traditional welds. While it's not a convincing substitute for railcars when framed as the way a Dodge is built, if it works for a 787 it might be viable for a railcar. Perhaps not as a complete substitute for welding but to reduce welding requirements?

I'm not an expert here at all.

And I do think the idea of keeping transit and slower trains as stainless has merit compared with higher/high speed trains.

Here's a good question: does a train of aluminum cars use appreciably less power or accelerate faster than a modern stainless train?

If anything more than spot welds, both stainless and aluminum require a lot of shielding gas (argon or similar); stainless in particular requires stress equalizing as Mr. Benton says. I think aluminum is more forgiving in terms of post-weld warping.

Both metals work-harden with fatigue. I’m not sure which one is more prone to cracks but I’ve specifically heard of stainless (especially early stainless) suffering fatigue cracks and resultant internal corrosion. Low-carbon steel can have fewer fatigue cracking issues and is easier to repair (again, heat warping.)

Re: corrosion, aluminum, stainless steel and Cor-Ten steel all block corrosion by forming a uniform, impenetrable oxide layer on the metal surface. An acid or salt solution will dissolve that barrier and cause water spots, fissures or full rust-through (see the ICG Highliners which trapped saltwater within Cor-Ten panels and suffered lots of rust issues.) Otherwise, they don’t require surface treatments as does carbon steel.

Tad: I bet you’ll find a lot of internal fittings and even some light structural features in trams are already attached via epoxy. Metal honeycomb or metal-skinned foam structural insulated panels are the wave of the future as far as I’m concerned, and would make a fine and lightweight body for an alternate-compliance train. They’re worlds lighter than the same strength panel made from steel.

The one huge advantage of aluminum over steel is forming & cutting. You don’t need the same strength of punch, press, form or cutting tool, which reduces cost precipitously. Doubly so if used with structural panels like I said earlier.