American freight trains-59 mph....German Freight Trains-80mph The FRA is FAXing US railroads over.

[Anonymous]

The best way to not a crash is to prevent one. CTC and real time dispatching systems using GPS to tell the tower where the trains are at all times means that passenger and freight CAN run together

[Anonymous]

Using CTC and Global Positioning Systems means that Passenger and Freight Can run Together
There was a lot of epermentation in the 60s but everytime the FRA shot them down. Railbuses and RDCs built in Europe cant run here because of the FRA.

[TH&B]

FRA ?
When was the last time a passenger train in the USA crashed and killed 100 people?
When was the last time a passenger train in Europe crashed and killed 100 people?
In Japan ?

[martin.knoepfel]

european freight trains are quite short, because the screw couplers do not allow for heavier trains. otherwise, you have to cut in additional locomotives (radio-controlled). unfortunately, the euro-coupler was never introduced although it works.

in britain, they run some freight trains (stone) at 100 mph, I guess, to avoid delaying passenger trains. the germans run some freight trains at this speed to on high-speed-corridors. the french have trains with refrigerator-cars (fruit and vegetables) for 90 oder 100mph.

[Hugh Jampton]

QUOTE: Originally posted by martin.knoepfel

european freight trains are quite short, because the screw couplers do not allow for heavier trains. otherwise, you have to cut in additional locomotives (radio-controlled). unfortunately, the euro-coupler was never introduced although it works.

in britain, they run some freight trains (stone) at 100 mph, I guess, to avoid delaying passenger trains. the germans run some freight trains at this speed to on high-speed-corridors. the french have trains with refrigerator-cars (fruit and vegetables) for 90 oder 100mph.

err,,, In Europe freight train length limited more by siding length than by the strength of the coupler.. According to Group Standards (GM/RT2102) screw couplers have an ultimate strength of 270,000lbs while the FRA says knuckle couplers have a strength of 400,000lbs. Yet train lengths in Europe are limited to750m (2460ft) while train lengths in North America can run upwards of 6000ft. plus. Plus.. most new freight wagons are fitted with knuckle couplers,, yet the train length remains the same. There are a couple of exceptions though.. The High Capacity Track Replacement Train is 846m (2775ft.) and can only be stabled in a limited number of places.

100mph Freight trains in Britain eh?? And stone yet?!?!?! Where is this exactly because I have never seen one.. As far as I know the fastest freight tains are the "Enterprise" intermodals that run on the East Coast Mainline at 75 mph, which also happens to be the top speed of any freight train running in Europe (where this 80mph figure came from in the title I'll never know).

[oltmannd]

QUOTE: Originally posted by trainfinder22

The best way to not a crash is to prevent one. CTC and real time dispatching systems using GPS to tell the tower where the trains are at all times means that passenger and freight CAN run together

There are plenty of other ways to cause crashes other than route conflict or exceeding movement authority

Trains can derail.
Cars can fail.
Train handling can cause derailments.

to name a few.

As long as there in no perfection in frt railroading, some sort of pass. car safety stds are needed.

[oltmannd]

QUOTE: Originally posted by 440cuin

FRA ?
When was the last time a passenger train in the USA crashed and killed 100 people?
When was the last time a passenger train in Europe crashed and killed 100 people?
In Japan ?

Chase MD would have killed over 100 had the FRA safety stds not been built into the cars.

...and this was on the safest piece of RR in the US w.r.t. signalling and track stucture.

Accidents happen. To not be prepared is negligence.

[Anonymous]

Very few freight cars in europe are capable to run at 80 mph. A few cars are allowed to run at 75... empty. And the heavy coal trains (about 6,000 tons) don't go faster than 50 mph.

Maybe an error when converting kilometers to miles.

[martin.knoepfel]

the 100mph stone trains were operated by foster yeoman.

when wisconsin central took over part of the british rail system, they were quite surprised thise was possible. I don't exactly remember were I read it, but it was most probably "trains".

[Hugh Jampton]

QUOTE: Originally posted by martin.knoepfel

the 100mph stone trains were operated by foster yeoman.

when wisconsin central took over part of the british rail system, they were quite surprised thise was possible. I don't exactly remember were I read it, but it was most probably "trains".

I think you're probably confusing mph with km/h. F-Y used class 59s, which had a max speed of 100 km/h (60mph) Although the last 5 were geared for 75mph (120km/h)
See http://www.thejunction.org.uk/cl59.html
It's an easy mistake to make,, who invented the bloody metric system anyway????

[Junctionfan]

Speaking of conjestion and the U.K. Clapham Junction supposedly runs 2500 trains a day.

[Hugh Jampton]

QUOTE: Originally posted by Junctionfan

Speaking of conjestion and the U.K. Clapham Junction supposedly runs 2500 trains a day.

Yeah,, it's about that,, currently around 2000 movements / day. But it's not congested,, there's 16 platforms at the station and several relief lines all serving 4 different routes,, and there can be upwards of 10 trains all on the move at the same time.. The signal box is manned by 6 people, and at rush hour it's a bit like controlled chaos...

[TH&B]

The heaviest trains in Europe generaly do not use the screw coupler, Foster Yeoman stone trains use knuckle couplers and so do the heaviest or trains in England. In Germany and Sweden use the Russian type semi-automatic coupler on the heaviest trains. I don't know much about this coupler, it is obviously stronger then the screw coupler but how does it compare to the knuckle ? does it have loose slack ?
One advantage to the screw coupler is that the lack can be adjusted, tightened or loosened. The disadvantage is that it has to be done manualy wich is labour intensive and dangerous to couple up etc. The TGV trains use the old screw coupler !

[Anonymous]

Look people, we have different standards than Europe. You'll probably never find any trains of great length in Europe like we have here in the northern americas. Their engines, although very powerful are also very lightweight. The AEM7's that we use on Amtrak, are 7000 hp, but weigh just 92 tons. They perform best when a consist is kept to less than 6-7 amfleet cars. When you start making the consist longer or adding in a couple of heritage or veiwliner cars, they take much longer to accelarate and hold at speed. Europe's axle lading is much lighter than ours', is why much of their freight equipment still has 2 axle cars, while we've had 4-6 axle cars for over a century. Not saying we can't have high speed freight service, but their has to be an extensive investment into it or it will be doomed from the start. By the way, you can't run 6 axle locomotives at high speed due to severe truck hunting. 4 axle loco's are best suited for the job.


Glenn
A R E A L RAILROADER...A TRUE AMERICAN!!!

[Junctionfan]

Like the P-42 with over 4400 hp. It is a very strong and fast GP like unit that would do a good job for intermodal trains.

[M636C]

With respect to Mark Hemphill's comments about truck hunting, today I saw, for the first time, a real example of truck hunting at speed. It was on a northbound Pacific National container train that we had followed up the western side of the Great Divide to the crest at Cullerin. As the train dropped down grade from the crest, it was drawing away from us as the car speedo indicated 120km/h (about 75mph)(20km/h faster than the road limit and 10km/h faster than the rail speed limit - although the car speedo might be fast). We drew level on the flatter sections, and the leading truck of RRAY 7036 (an articulated single level container wagon with two (end) 40' platforms and three 48' platforms) was oscillating fairly violently, enough for the container to be visibly moving laterally relative to that on the preceding wagon.

Twenty years ago I was involved in investigations into truck hunting, but this was the first example I'd seen (and in "the wild" too).

Peter

[CSSHEGEWISCH]

The American 3-piece freight car truck still exists because it's cheap and does what it was designed to do. It is NOT a high-speed design. 80 MPH freight in this country would require freight cars to be equipped with passenger trucks with their multiple suspension just to stay on the track.
As has been mentioned in other posts, there really isn't any economic demand for higher freight speeds than those we already have.

[Junctionfan]

I really would be more interested in seeing track improvement and reduction of crossings for bridges to allow the intermodals to go 70 like BNSF does out west, for a longer duration of time. If the trains could go 60-70mph for an extended period of time, than there would be few needs for crew changes and in-terminal waits.

[Overmod]

There's nothing about the inherent design of the American 'three-piece freight truck' that prevents high speed... it needs different and better damping. Look at the trucks on the MHCs, for example. Much of the "multiple suspension" requirement on passenger cars has to do with improving ride quality as perceived by the passengers, or implementing better carbody tilt or roll control; these are of far less importance on freight equipment. The equalization characteristics of three-piece trucks are inherently excellent; if I recall correctly, some of the early UP streamliners used Taylor-style trucks (which are essentially a glorified three-piece design).

There are ways to implement longitudinal damping (e.g. viscous coupling) between the bolster and carbody pivots, which will interrupt the kinds of resonance causing the yaw component of hunting (and which are not difficult to retrofit to existing designs of rolling stock). Torque struts and rods can be used from bolster to sideframes if desired, or across the ends of the truck between sideframes (with rubber bushings at each end) if more force attenuation is desired in any plane of truck action.

In the past, it's been desirable to use a longer truck wheelbase for stability, but this inherently causes greater wheel (and track) wear on curves. There have been designs for steerable freight bogies, but the cost and maintenance limitations on these (and the fact that most types don't 'fail safe' if their linkages fail or are bent) will clearly restrict their use in interchange service until a 'critical mass' of parts, service locations, know-how and general awareness has built up.

Braking becomes a much more critical factor than dynamic stability at speeds much above 60mph -- remember that kinetic energy roughly doubles between 60 and 80mph. Imho single-acting tread brakes don't cut it... and the logical alternative, cheek-plate disc braking, is expensive and somewhat difficult to apply to these trucks and, perhaps more importantly, traditional American chilled wheel profiles. (For example, applying the disc to the wheel both requires location points, which are stress raisers, and hides the wheel face behind the disc, which makes inspection for cracks and defects originating from those raisers difficult to detect) My opinion is that some form of multiple center-of-axle disc brake, similar in principle to that applied to passenger cars, may be the answer (with the caliper floating vertically, on a bracket close to the truck bolster, which helps absorb torque displacement of the sideframes on braking, and allows use of conventional carbody-mounted brake cylinders and reach rods) -- I've checked with the wheel shop adjacent to the Arkansas Railroad Museum and they see little objective difficulty in sourcing and servicing brake discs at the time wheelsets are renewed.

I might add (plug) that I've developed in principle a system to implement semi-ECP braking on standard interchange freight consists, using devices similar to FREDs that connect into the train line at intervals and use buff-and-draft sensors that fit between couplers. This was originally intended to make fast-acting PTC workable on long freight consists, but is perfectly suited for the high-speed service that PTC and PTS would make legal...

It might be desirable to put some additional castings or fittings on the trucks, for example to keep the sideframes from separating from the bolsters and wheel bearing casings after impacts or derailments. I believe that tension straps of modern materials could accompli***his easily (and be relatively easy safety retrofits to existing trucks, too, which expands the market and brings down effective marginal cost). But none of this stuff (while it *is* at least in part derived from rocket science) is particularly difficult, or requires expensive capitalization that only applies to boutique high-speed service. In my opinion, air resistance constitutes a logical economic upper bound to most freight service speed well below the critical speed of three-piece truck designs with proper detailing...

[TH&B]

Most freight is a bulk freight that realy doesn't need to move so fast. These "fast" European stone trains and coal trains and even mixed freights that run through passenger stations at 110km/h+ looks impresive. But the overall average speed for all European freight trains put together is as patheticly low as in North America. European freights are engineered to run fast mostly just to get out of the way of passenger trains.
They spend alot of time in the hole waiting for a window to move, some trains can only move at night and sit all day waiting. It is mostly bulk materials anyways and nobody is going to pay you for the extra speed, they may want it to go faster for free.. but it's not ecconomical. Imagine upgrading all US freight cars to operate at higher speeds just to get out of the way for Amtrak but not improving freight transit time ? Then you can foot the bill to the government or the rail shippers.

ps;- England alone may have a higher average speed because they have virtualy got rid of all loose car railwaying and operate almost exclusively limited unit type trains.

[Anonymous]

With respect to Mark Hemphill's comments about truck hunting, today I saw, for the first time, a real example of truck hunting at speed. It was on a northbound Pacific National container train that we had followed up the western side of the Great Divide to the crest at Cullerin. As the train dropped down grade from the crest, it was drawing away from us as the car speedo indicated 120km/h (about 75mph)(20km/h faster than the road limit and 10km/h faster than the rail speed limit - although the car speedo might be fast). We drew level on the flatter sections, and the leading truck of RRAY 7036 (an articulated single level container wagon with two (end) 40' platforms and three 48' platforms) was oscillating fairly violently, enough for the container to be visibly moving laterally relative to that on the preceding wagon.
Twenty years ago I was involved in investigations into truck hunting, but this was the first example I'd seen (and in "the wild" too).
Peter
-----------------------------------------------------------------------------------------------------------------------
On the subject of "truck hunting" I have been on Boxcars that were truck hunting and That was no fun. For some strange reason noty having to do with speed the trucks hunted then stopped then started again then stoped...Kinda like being in purgatory for 8 hours and could not get any sleep either. Stack Trains and Grainers that have a low center of gravity almost never hunt but Boxcars for whatever reason have a propesity to hunt..

[Overmod]

All it takes to induce hunting is the right oscillation frequency and either worn wheels or problems with the railhead profile... lubrication of the rail gauge face can also play a part. There is very little inherent damping in the pivot of a contemporary conventional truck, and modern lubricant methods for the pivot (remember those old Shell solid disk lubricant pucks from the '60s?) can reduce what little there is rather dramatically in the name of reducing absolute wear.

Every time I see trackwork on the NS Birmingham line, I'm dumbfounded that all the cars stay on the rails. let alone that truck hunting doesn't get induced regularly. There are spots in Douglasville, Georgia, for example, where rail of one weight has been reversed and welded back against rail of a different weight, without any attempt to grind or dress the difference in gauge profile. You can hear the trucks clash and work as they engage this, and while I did not observe overt truck hunting, you can see a certain amount of brinelling-like distortion in the gauge face up and down from the transition point...

I suspect that your observation about hunting is related much more to the relative loading of the truck springs -- the boxcars are almost by definition going to be empty; the stacks or grain cars loaded. I would think that an unloaded truck will hunt much more dramatically than one that's bearing substantial weight, since the on-center restoring force of the coned treads (and friction in the pivot) would be higher when loaded, but the polar moment of inertia and the flange impact forces from truck hunting motion would be essentially constant regardless of applied weight.

[M636C]

Some of our trucks have diagonal anti-lozenging struts, accompanied by rubber pads above the bearings to put some flexibility back. One grain train is completely equipped with these, and when empty it runs regularly at 110 km/h with no apparent problems.

The thing that struck me most about the hunting was the visibility of the axle movement, clearly driving the action, with the truck appearing to follow, rather than the truck appearing to rotate. It looked as if the bolster might not be moving, all the rotation being taken up in lozenging action in the sideframes. I wish I'd had a video camera along! If that was the case, all the work we did on pivots and sidebearers wouldn't affect that car!

Peter

[Overmod]

Peter -- Interesting!

For the benefit of our American readers who may think that lozenging relates to using Sucrets for a sore throat -- this refers to parallelogram skew (where the axle skews off normal and drives one sideframe back relative to the other and to the bolster, and this in turn skews the other axle in the truck). "Lozenge" is another word for the figure we call 'diamond' on this side of the pond, as in the diamond shape on a playing card.

I would be extremely worried to see this happening to the extent of visible carbody displacement -- it doesn't take much lateral thumping to disengage the axle from one or both sideframes, or to cause cocking or shock damage to the bearings -- in either case, you have a sudden derailment on the leading end of a car, which I would expect to have the kind of sudden and catastrophic effect that forward-end drifeshaft universal failure has in an automobile. I'd have reported this at the earliest possible opportunity (but then again, perhaps it's really not that unusual, or dangerous, in the real world. Of course, some NASA folks launched the Challenger knowing full well that the temperature was 20 degrees lower than the critical do-not-exceed temperature of the O-ring seals, so informed thinking may not be an adequate gauge of catastrophic event development...)

In my opinion, there would have to be something substantially wrong with the joints between the bolster and the sideframes to allow sufficient rotation there for this severe and self-sustaining degree of hunting action to persist. I would also speculate that allowing the oscillations to persist for any length of time would begin to 'hammer' these joints further and further open and loosen up the truck dramatically for lozenging.

Be interesting to see how sharp the critical resonance transitions for different types of manufactured three-piece trucks might be on different types of track subject to different construction and maintenance methods. It might easily be that only one or two mph may be the difference between relative stability and catastrophic resonant oscillation.

Are the struts you use primarily tension, compression, or both? Do they have rubber donuts or other elastomeric isolators at one or both ends?

[Anonymous]

QUOTE: Originally posted by Overmod

There's nothing about the inherent design of the American 'three-piece freight truck' that prevents high speed... it needs different and better damping. Look at the trucks on the MHCs, for example. Much of the "multiple suspension" requirement on passenger cars has to do with improving ride quality as perceived by the passengers, or implementing better carbody tilt or roll control; these are of far less importance on freight equipment. The equalization characteristics of three-piece trucks are inherently excellent; if I recall correctly, some of the early UP streamliners used Taylor-style trucks (which are essentially a glorified three-piece design).

There are ways to implement longitudinal damping (e.g. viscous coupling) between the bolster and carbody pivots, which will interrupt the kinds of resonance causing the yaw component of hunting (and which are not difficult to retrofit to existing designs of rolling stock). Torque struts and rods can be used from bolster to sideframes if desired, or across the ends of the truck between sideframes (with rubber bushings at each end) if more force attenuation is desired in any plane of truck action.

In the past, it's been desirable to use a longer truck wheelbase for stability, but this inherently causes greater wheel (and track) wear on curves. There have been designs for steerable freight bogies, but the cost and maintenance limitations on these (and the fact that most types don't 'fail safe' if their linkages fail or are bent) will clearly restrict their use in interchange service until a 'critical mass' of parts, service locations, know-how and general awareness has built up.

Braking becomes a much more critical factor than dynamic stability at speeds much above 60mph -- remember that kinetic energy roughly doubles between 60 and 80mph. Imho single-acting tread brakes don't cut it... and the logical alternative, cheek-plate disc braking, is expensive and somewhat difficult to apply to these trucks and, perhaps more importantly, traditional American chilled wheel profiles. (For example, applying the disc to the wheel both requires location points, which are stress raisers, and hides the wheel face behind the disc, which makes inspection for cracks and defects originating from those raisers difficult to detect) My opinion is that some form of multiple center-of-axle disc brake, similar in principle to that applied to passenger cars, may be the answer (with the caliper floating vertically, on a bracket close to the truck bolster, which helps absorb torque displacement of the sideframes on braking, and allows use of conventional carbody-mounted brake cylinders and reach rods) -- I've checked with the wheel shop adjacent to the Arkansas Railroad Museum and they see little objective difficulty in sourcing and servicing brake discs at the time wheelsets are renewed.

I might add (plug) that I've developed in principle a system to implement semi-ECP braking on standard interchange freight consists, using devices similar to FREDs that connect into the train line at intervals and use buff-and-draft sensors that fit between couplers. This was originally intended to make fast-acting PTC workable on long freight consists, but is perfectly suited for the high-speed service that PTC and PTS would make legal...

It might be desirable to put some additional castings or fittings on the trucks, for example to keep the sideframes from separating from the bolsters and wheel bearing casings after impacts or derailments. I believe that tension straps of modern materials could accompli***his easily (and be relatively easy safety retrofits to existing trucks, too, which expands the market and brings down effective marginal cost). But none of this stuff (while it *is* at least in part derived from rocket science) is particularly difficult, or requires expensive capitalization that only applies to boutique high-speed service. In my opinion, air resistance constitutes a logical economic upper bound to most freight service speed well below the critical speed of three-piece truck designs with proper detailing...

Overmod, I think you were the one who told be this some time back, but is it true that the single axle trucks naturally resist hunting? If I remember correctly, the problems with cars like the TTOX and TTFX Four Runner were with inflexibility through tight yard trackage, rail wear due to the 36' wheelbase ( I understand the TTOX's had some curving flexibility but not a true radial steering mechanism), and of course too light tare weight which could cause pull over on curves.

That being said, was it your conclusion that such single axle designs were actually better for high speed service? With larger wheels and journals to bear greater load weight (and adding a little more to the tare), an extended platform to handle 53' trailers, and radial steering, these cars could be apt for high speed intermodal.

[M636C]

Overmod,

The word "hammering" accurately describes the effect the axles appeared to be having on the truck, the leading end of the car, and the (possibly empty) 40' container on that platform. Thinking about it more, there probably was some bolster rotation taking place, but the whole process was being led by the axles visibly moving laterally. The amount of rotation would be fairly small, as would be the extent of lozenging required. The section of track where I observed the hunting, while straight, has relatively poor subgrade, and I've observed poor line and level there on occasions, despite the speed boards allowing 160km/h (100 mph) for passenger trains. The train stopped a few kilometres further north, (possibly because inspection and sinaling work was in progress) and I didn't see it again to see if the hunting continued.

The trucks with diagonal braces have rubber bushes at each locating point. I would expect that the rods are alternately in tension and compression. They are Chinese-made trucks but are generally similar to standard US trucks. They are used on container wagons as well as grain wagons, but there aren't many of that type.

I recall seeing fairly worrying oscillation on video records of a truck fitted with someone's idea of a "worn" profile we had expensively machined onto new wheels, but that was nowhere as fast (or rough) as the actual hunting I saw recently. Those experimental wheels were restored to standard profile fairly quickly.

There have been a number of freight trucks of rigid frame design used in Australia on 110 km/h vehicles, but the majority still use three piece designs (including a lot of second hand US "100 ton" trucks). The diagonal cross linkage was developed by a long time opponent of one particular rigid frame truck.

Peter

[Overmod]

FM, the classical definition I learned for 'hunting' many years ago was a coupled resultant of nosing (which is yaw) and rolling. I have since seen many people apply the term more to the observed yaw component and its effects, but it is helpful to recognize in some cases that 'pumping' from loading and unloading of the suspension can drive some of the oscillation.

The ForeRunner and its ilk do tend to be difficult to induce because their effective polar moment of inertia is enormous and their primary suspension is usually very closely constrained to keep the axles normal to the chassis; to the extent that the axle can yaw relative to the carbody, it's mostly 'shear' force taken by the springs, and that ain't usually much imho.

Now, you have a consequence with the longer rigid wheelbase, which is greater prospective wear (for a given equal axle loading) of the tread profile, greater incidence of flange contact on sharp curves, more possible racking on transitions or laterally uneven track, etc. There is no equalization between axles, so we're back in the 1820s again in that respect.

IN PRINCIPLE, I favor the 1950s idea of using separate wheels, able to turn at independent rates on the same axle, as was done on some of the lightweight passenger train designs, for single-container, four-wheel cars. I did some preliminary work on single-axle Talgo-style articulated container sets, but haven't pursued that approach lately. I recognize the implicit problems with bearings, lube, maintenance, suspension when the independent-wheel approach is used, but it does eliminate some of the problems that would otherwise require full proportional radial steering ... difficult with 36' wheelbase! -- to deal with.

M636C -- what's your opinion of magic wear rate, both theoretically and practically?

[Anonymous]

QUOTE: Originally posted by Overmod

FM, the classical definition I learned for 'hunting' many years ago was a coupled resultant of nosing (which is yaw) and rolling. I have since seen many people apply the term more to the observed yaw component and its effects, but it is helpful to recognize in some cases that 'pumping' from loading and unloading of the suspension can drive some of the oscillation.

The ForeRunner and its ilk do tend to be difficult to induce because their effective polar moment of inertia is enormous and their primary suspension is usually very closely constrained to keep the axles normal to the chassis; to the extent that the axle can yaw relative to the carbody, it's mostly 'shear' force taken by the springs, and that ain't usually much imho.

Now, you have a consequence with the longer rigid wheelbase, which is greater prospective wear (for a given equal axle loading) of the tread profile, greater incidence of flange contact on sharp curves, more possible racking on transitions or laterally uneven track, etc. There is no equalization between axles, so we're back in the 1820s again in that respect.

IN PRINCIPLE, I favor the 1950s idea of using separate wheels, able to turn at independent rates on the same axle, as was done on some of the lightweight passenger train designs, for single-container, four-wheel cars. I did some preliminary work on single-axle Talgo-style articulated container sets, but haven't pursued that approach lately. I recognize the implicit problems with bearings, lube, maintenance, suspension when the independent-wheel approach is used, but it does eliminate some of the problems that would otherwise require full proportional radial steering ... difficult with 36' wheelbase! -- to deal with.

When you refer to allowing wheels to turn independent of the opposite wheel on the same axle, is that by using a differential gear? I thought I read something about that in a TRAINS article awhile back, something to the effect that separate turning rates would cause more flange on rail contact, I'll have to dig back when I find time.

I may need to talk to you offline on this, but what is your opinion of a "half rigid" wheelbase wherein one end of the car is a true single axle truck and the other is connected to an articulated two axle truck? The only example I can think of is the Trough Train, where the end trucks were single axle. I think it may even be possible now to have a true articulation over a single axle truck, by using radial steering arms connected to each corresponding car body. This allows the articulated truck to turn freely with the curvature, and could be used in conjunction with the half rigid idea on both ends of a two platform car for a more ideal load factor for typical TOFC and single stack domestic container moves. Whether or not that would create more problems than it solves remains to be seen.

[Overmod]

All I mean is that each of the wheels has an independent bearing, and turns freely on it, rather than both wheels being rigidly mounted on an axle and constrained to rotate together. The book "New York Central and the Trains of the Future" by Geoffrey H Doughty has some illustrations of how this was done on the lightweight trains (a principal purpose being to allow very low aisle floor heights without walkovers). For freight, I would expect that each wheel's bearing housings would be in extended 'collars' outward from the wheel hub, to take the additional leverage on the bearings due to heavy lateral thrust. One potential benefit is that the truck-to-axle mountings no longer have a free-rotating requirement, meaning that the effective stiffness and compliance of the truck frames can be much better controlled. I proceeded on the assumption that the bearings could be effectively sealed 'for the life of the wheels' (which would be routinely Hegenscheidt-trued according to magic wear rate profiling, and perhaps tread-hard-coated, with the object being to have the wheels go to minimum legal diameter just as the bearings run out of 'life' -- about 500,000 miles, using Timken's stated bearing life from a few years ago, although of course YMMV.

I don't like single-axle trucks that aren't given drawbar guiding and steering, whether on one or both ends of a car. The 'easiest' way to deal with a two-wheel 'island' truck on one end of a set is to put the axle on some kind of steering carriage or lever arrangement linked to a drawbar pivot -- principle can be a la Talgo, for example -- so that the angle of steer is proportional to the drawbar displacement from 'straight ahead'. (How very typically HO model railroad!) Note that a similar arrangement, with the 'drawbar' being entirely between the two 'sideframes', can give you the equivalent of an articulated, steering four-wheel truck between adjacent units (I used a variation of this approach, with hydraulic equalizing (!), for a high-speed passenger design with easily field-switchable cars).

I think there are dramatically diminishing 'returns to scale' for attempts to put steering axles on articulated freight trainsets. Slightly revised -- and properly-maintained -- wheel profiles and independent rotation give you the benefits without the fancy levers ... or having to decide how you get them to position the axles, without forcing, relative to the carbody. (In my opinion, forcing two-axle-truck tracking via geometric levers is a very, very poor idea outside of computer simulations or drawing-board plans -- look what can happen in a derailment, for example).

Remember that radial steering is much more important on *driving* axles than it is on idlers, up to the point that very substantial weight is being applied to the wheel treads and railhead, above the deformation point for the metal under the martensitic layer. And at that weight point, I think track maintenance in general will begin to eat up more and more of the 'revenue' differential derived from bigger and heavier unit vehicles. High-speed track is a very, very different thing from heavyweight, slow-speed practice, imho.

You might look into a variant of Allan Cripe's pendulum-suspended two-wheel trucks between adjacent 45-foot carriages, if your axle loading in design can take it; this might give some interesting roll dynamics for stack operation of relatively light cargos. I've toyed with this but don't have any particular applications for it -- sorta like a railroad equivalent of Ettore Bugatti's 12,500rpm engine of WWII.

[M636C]

Overmod,

I'm not sure what you mean by "magic wear rate".

I have ridden in Spani***algo trains which have independent wheels at speeds up to 90 mph, although now they go much faster than that. The main impression was that more road shock came through than in a conventional car with trucks, but it was quite acceptable and I was surprised when I checked the speed against kilometre posts.

It shouldn't be a problem for freight cars.

I don't know if you know much about the experimental "Iron Highway", built for CSX by MK about ten years ago. It could best be described as a Talgo flat car set, with a single axle between each platform. There were trucks on each end car.

I was completely amazed to find this train, disassembled, in the Altona depot of Colin Rees Transport near Melbourne, Victoria, Australia (a long way from Boise!). I don't think they ever ran it, but two intermediate cars later appeared in a rail museum in Seymour, Victoria.

I bring this up because this appears to have been built with independent wheels, each carried by two standard roller bearings. This allowed a lower floor by locating the car articulation point lower since it didn't have to clear the axle.

The point of all this was that when I found the train, the first thing I found was the hundred or so two wheel trucks, which took a bit of identification. But the point I'm very slowly coming around to was that every "wheelset" had a light (1.5") torque tube connecting the two wheels side to side, bolted into the three bearing cap bolt holes.

This looks to me as though after initial tests with independent wheels, someone at MK (or MPI) decided they wanted wheels connected to eachother.

Apart from the above, I have seen the four wheel TTX cars in use on the RF&P, but most of the cars I saw had pedestal suspension. There were some cars fitted with a British design, with very long leaf springs, so called "taperlite" because the leaves had leaves with varying thickness. I would have thought that these would have very little steering capability.

Peter