In the quest for lightness - people overlook how mass and gravity work in holding a railroad together.
Never too old to have a happy childhood!
Further regarding Hybrid Composite Beams ("HCB"):
There's an article in the current Railway Track & Structures (April 2018) in the "TTCI R&D" department (pgs. 12 - 14), summarized as "Revenue service test results are presented for hybrid composite beam spans". It has some interesting graphics of mid-span "displacement" (deflection) and "Average bending strain peaks" for both BNSF and CP trains. This link should take you to that issue, then flip through to those pages:
https://issuu.com/railwaytrackstructures/docs/rts_0418digital/1?e=5257055/60378867
There's also a pretty good article on Norfolk Southern's new Portageville, NY arch bridge - 963 ft. long, x 235 ft. high - "Norfolk Southern's ARCH Spans Many Challenges" - on pags. 22 - 24 and 26.
- PDN.
http://bgr.com/2018/02/08/super-wood-densification-building-material/
Well here comes wood boxcars again
Murphy SidingI don't know why no one has mentioned titanium. Surely that would be lighter.
Not light on the pocketbook, though! And pyrophoric as hell in accidents -- fountains of sparks.
Hell, we could mention columbium, zirconium, vanadium, molybdenum and all the other fun things admixed with titanium to make interesting things. They are expensive too...
Subway cars were made from steel for both strength and fire resistance after some horrendous telescoping and break-apart collisions, and fires underground. Going to carbon fiber would seem to reintroduce those risks and thus be a step backward, it seems to me.
tree68 D.Carleton Heading in that direction: https://www.enr.com/articles/43731-chinese-firm-makes-prototype-for-first-carbon-fiber-railway-car The linked article says they are subway cars. I wonder how carbon fiber will do against US crashworthyness testing for mainline passenger cars. Recall that Chevy Corvettes are/were noted for disintegrating in collisions. Maybe Balt can speak to how carbon fiber does in race cars.
D.Carleton Heading in that direction: https://www.enr.com/articles/43731-chinese-firm-makes-prototype-for-first-carbon-fiber-railway-car
Heading in that direction: https://www.enr.com/articles/43731-chinese-firm-makes-prototype-for-first-carbon-fiber-railway-car
The linked article says they are subway cars. I wonder how carbon fiber will do against US crashworthyness testing for mainline passenger cars.
Recall that Chevy Corvettes are/were noted for disintegrating in collisions.
Maybe Balt can speak to how carbon fiber does in race cars.
When carbon fiber part are subjected to the stresses they were designed to encounter they are exceedingly strong. When subjected to stresses they weren't designed for they will shatter like glass and leave exceeding sharp shards that can cut tires down in a instant. Additionaly carbon fiber parts either work or fail catastrophically - there is no inbetween.
I don't know why no one has mention titanium. Surely that would be lighter.
Thanks to Chris / CopCarSS for my avatar.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Editor Emeritus, This Week at Amtrak
Balt,
That is why more research is required. For every discovery there is a caveat.
Research should be unending.
Norm
Norm48327Overmod, You are several steps ahead of me. In my career in aircraft maintenance I had to familiarize myself with rivets and the technology that accompanied them from the days aluminum became the prevaling choice of the manufacturers. Composites are a recent development and I have not kept up with them. OTOH, I do recognize that carbon fiber can be stronger than steel in some applications. I have a friend who made a pair of wheel pants for a Cessna 140 from carbon fiber. He stood atop one of them in a demonstration of the strength of the material and even jumped on them a few times. The other Cessna 140 owners were horrified when he did that. I think what his demonstration emphasised was that when used properly there can be strength of a material that was not previously recognized. He could have made a fool of himself but he did the proper research ahead of time. New discoveries of the simplest things are made every day. Think back to the days of the stone arch bridge and a few other discoveries. Some may have been incidental but others were discovered through research. While it may take some time for railroads to get the message that technology may benefit them in the long run I do understand their position. Sans some discoveries of the past fifty years we would still be communicating through snail mail. and waiting a long time for a reply.
You are several steps ahead of me. In my career in aircraft maintenance I had to familiarize myself with rivets and the technology that accompanied them from the days aluminum became the prevaling choice of the manufacturers. Composites are a recent development and I have not kept up with them. OTOH, I do recognize that carbon fiber can be stronger than steel in some applications.
I have a friend who made a pair of wheel pants for a Cessna 140 from carbon fiber. He stood atop one of them in a demonstration of the strength of the material and even jumped on them a few times. The other Cessna 140 owners were horrified when he did that.
I think what his demonstration emphasised was that when used properly there can be strength of a material that was not previously recognized. He could have made a fool of himself but he did the proper research ahead of time. New discoveries of the simplest things are made every day. Think back to the days of the stone arch bridge and a few other discoveries. Some may have been incidental but others were discovered through research.
While it may take some time for railroads to get the message that technology may benefit them in the long run I do understand their position.
Sans some discoveries of the past fifty years we would still be communicating through snail mail. and waiting a long time for a reply.
From a racing view point, where carbon fiber construction now dominates the professional levels of the sport (except NASCAR). The carbon fiber parts are exceptionally strong when confronting the stresses that they were designed for; however, they are exceedingly fragile when subjected to stresses they had not been designed for. In the real world you don't know what all you don't know and thus you can't design parts for all potential eventualities.
Overmod,
Not all designs are suitable for every location--but the Thomas Viaduct has been holding up for more than 180 years--if you want to talk longevity.
Johnny
cx500 Another aspect to look at is repairability should a defect appear or a wayward truck/train/barge cause damage to the beam.
All of my experience in handling damaged structural fiber-reinforced composites has been to replace them. It is theoretically possible to fix delamination (including blisters) with adhesive or resin injection followed by pressure autoclaving, but it can be difficult, probably for many instances of bridge construction in situ, to do appropriate NDT to establish that the fibers are still oriented and intact after the delamination event(s). I don't think specialized 'portable' or mobile repair equipment for these is easily available yet... if ever.
There is a hidden issue inherent in most of these structures: they have a large relative factor of safety even with some types of damage (the structure distorts in ways that load the very strong fibers appropriately) but can progress from apparent serviceability to severe brittle failure with very little advance warning even to embedded condition gages and other monitoring methods. So even 'smart bridges' may be prone to more surprises than their instrumentation engineers were expecting.
An interesting design idea. I wonder if it can be scaled up to longer spans. And the other question in my mind is the actual lifespan. Will it match the 90+ years I have seen on some concrete spans? Steel spans much older are all over the rail network and often replacement is driven mostly by weight restrictions inherent in the original design. Another aspect to look at is repairability should a defect appear or a wayward truck/train/barge cause damage to the beam.
An amusing issue here is how Hillman managed to get trademark protection for the acronym/initialism "HCB" for these things. Shades of "we'll call it 'Pull' for me and 'man' for you"!
A nifty idea, much like engineered-composite ties. Some similar economic concerns.
I have not seen anyone try to patent self-healing composites for HCB bridges, but it seems so obvious an improvement that someone (perhaps Hillman) surely has it close to marketability by now.
I believe there is a medium-span bridge of carbon-fiber material under test as the TTCI test track in Pueblo, Colorado. I recall seeing an article on it in Railway Track & Structures a couple years ago, and it seemed to be doing OK at that point.
It's called a "Hybrid Composite Beam", or HCB. Here's a link to the article, dated January 2013:
http://www.rtands.com/index.php/track-structure/bridge-retaining-walls/ttcis-wins-asce-award-for-hcb-span-research-collaborates-with-csu-pueblo-on-new-degree-program.html
Of course, the weight savings mentioed in the article is of trivial importance for a railroad bridge; the corrosion advantage is more significant.
IslandManElsewhere on this forum there is a topic about steel becoming brittle at low temperatures. Some steel alloys do not become brittle even at extremely low temperatures: http://www.totalmateria.com/page.aspx?ID=CheckArticle&LN=EN&site=kts&NM=48
I suggest you read up on the characteristics of successful modern rail steels, then go back, re-read the reference you provided, and tell me why you think it supports the idea of very-low-temperature rails.
Other uses of steel, yes. Not so much railroad rails. (But I'll grant you this: better than the performance of carbon-fiber composite rails or likely boron nitride rails at those temperatures...)
Another problem with composites is how expensive they are overall. We have composite springs on all our trucks at my bosses company along with other parts for weight savings. However when they get damaged they cost 3 times what a steel one does to replace. Body panels if one of our hoods gets destroyed that is a minimum 25K to replace in the body shop however some of our O/O's have Peterbilt 389 glider kits with aluminum hoods on them. They can get a panel put in for less than 6 grand.
cx500 Steel is comparatively cheap, easily repairable, performs adequately in all temperatures and withstands the shocks and vibrations of railroad service. Most other materials had fairly significant downsides in one or more of the above. The railroads do experiment, and now aluminum bathtub gons are generally replacing the steel versions in coal and sulphur service. The initial aluminum cars had problems and various design details needed to be changed to yield a reasonable lifespan. I don't however know if their life will be as long as the steel cars, some of which are now approaching 50 years.
Steel is comparatively cheap, easily repairable, performs adequately in all temperatures and withstands the shocks and vibrations of railroad service. Most other materials had fairly significant downsides in one or more of the above. The railroads do experiment, and now aluminum bathtub gons are generally replacing the steel versions in coal and sulphur service. The initial aluminum cars had problems and various design details needed to be changed to yield a reasonable lifespan. I don't however know if their life will be as long as the steel cars, some of which are now approaching 50 years.
Steel is also a material under continuous development, extending its range of uses. For corrosive environments steel rail with a zinc coating (e.g. Zinoco) can be used.
Elsewhere on this forum there is a topic about steel becoming brittle at low temperatures. Some steel alloys do not become brittle even at extremely low temperatures:
http://www.totalmateria.com/page.aspx?ID=CheckArticle&LN=EN&site=kts&NM=48
The lowest temperature found in any regularly inhabited part of the planet is about -65 C in eastern Siberia so it should be possible to produce rails resistant to anything, anywhere, the elements can throw at them.
OvermodThe fiberglass sides conducted the sound of the clanking shackles too well.
Kinda like those mobile homes
Um, NO! (the damned stuff burns..and rather easily at that)
https://drive.google.com/file/d/0B-ZSNsX3Ho0bNGJkMTkyYmUtNDMwYy00YmE1LWI5MzAtNDRjODE5ODQ0Y2I2/view?hl=en
Leave the real world railroading to the professionals. The amateurs, with their expert opinions, already caused the mess called PTC.
Overmod Deggesty Are you sure that there was no cartel that took the cars and refused to let their advantage be known? The fiberglass sides conducted the sound of the clanking shackles too well.
Deggesty Are you sure that there was no cartel that took the cars and refused to let their advantage be known?
The fiberglass sides conducted the sound of the clanking shackles too well.
DeggestyAre you sure that there was no cartel that took the cars and refused to let their advantage be known?
Guys ... when did fiberglass composite get lighter than properly-designed aluminum? In sailplanes, proper composite can be massively heavier; other advantages compensate for the 'higher tare weight'.
The big problem here is that none of the armchair designers seem to recognize how brittle carbon-fiber composites are. ESPECIALLY in RCF-inducing conditions comparable to head-hardened rail! Furthermore, damage to most stranded composites is progressive, irreversible, probably invisible, and difficult or impossible to detect with inexpensive or intuitive-to-interpret NDT equipment. Bicycle or aircraft parts are not subject to some of the extreme transient loading in railroad service.
There are some comparable arguments historically for other 'lightweight' substitutions, the late-'30s and early-'40s flirtation with alloy boiler steels being a particularly painful one.
I'm saving discussion of some of the use of very light materials like lithium aluminide or carbon-carbon composite until April rolls around.
Their capacity was too large for cart-els, Johnny!I also believe that FRP was tried as shielding on auto-rack cars and as covers for coil steel cars. More things that you no longer see around, after the railroads went back to steel.
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
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