G.E. "SKIRTS"

[Paul Milenkovic]

Overmod:

Are you thinking of the Amfleet "Pioneer III-style" air-spring truck?

One can never quite tell how a truck works without drawings, but as far as I can tell, the Pioneer III truck is a rigid, unequalized H-frame that connects inside axle bearings to a pivot point connection to the bolster. The truck frame pivots with respect to the bolster, but the bolster is constrained fore-and-aft but allowed up and down and side-to-side motion by these tie rods that connect the bolster to an angle iron attached to the car body. The bolster is connected vertically to the car body through two large air springs. The air springs have sideways give to substitute for swing hangers. The truck is unconventional in that there are no equalizers, no secondary springs, and no swing hangers.

I have ridden Amfleet cars as well as NEC Silverliner commuter MUs and thought they rode well, but I read somewhere that Amtrak thought them to be hard on the tracks, and the trucks they use on the Horizon cars are conventional equalizer, primary and secondary suspension, coil spring, and swing hanger trucks as what goes on the Superliner (the commuter Comet cars from which Horizon cars are derived have the Pioneer-III trucks).

[M636C]

Overmod,

Wow, give me a chance to look at all that! Off the top of my head, the "Um An" involved using body mounted motors and other techniques to uncouple the driving motor and gear masses from the wheels, a bit like the British APT which ended up with the BR Class 91 with its cardan shaft drive. Logically, if successful, the Um An would have influenced the DB 101, but right now I can't even tell whether that unit was Bombardier or Siemens!

Peter

[Overmod]

Apparently the term 'wing-type axle box' is not what American practice uses, but I don't know what is. And my attempts to find out have so far met with a Job-like lack of success.

Some of this may be useful in developing the truck article, so I provide links inline:

Here are some views of the Henschel/Adtranz/Bombardier FlexiFloat bogie:

https://www.getransportation.com/general/apps/specsheets/blue_tiger/3a7f.htm?SMSESSION=NO

where we give special attention to

https://www.getransportation.com/general/apps/specsheets/blue_tiger/3a7f-bo3.gif

which shows the component in question in a clear and detailed way (note the relationship between the lower spring-attach points and the axle centerline, and the very long secondary springing -- this appears to be a different design philosophy from the GE rollerblade truck suspension). I cannot find anything (in English or any language I can translate) that actually assigns a name to this piece.

An interesting revelation into this design comes from a software maker:

http://www.adams.com/anim_month/jan02_anim_month.htm

which shows some of the geometry involved -- and tacitly indicates that all the other dynamics of the suspension and guiding have been incorporated in the same Adams model from which the illustration was derived.

If you know the detailed history, and fate, of the Henschel "UmAn" project, please expound. I greatly enjoyed the shroud on locomotive 202 003-0, but have to conclude that the results were unsuccessful in some way; I still think the basic idea is a reasonable one, and shouldn't have compromised radial-steering.

There was a discussion of ABB-Henschel high-speed FlexiFloat trucks in the STECH '93 conference proceedings, but if there was a reference to the component name it escaped me...

By the way, what are your best references for 'state-of-the-art' in freight-truck yaw damping?

[Overmod]

Thanks. Those are interesting trucks.

If I remember correctly, at least some of the American predecessors were Taylor-style, with the circular bearing between the sideframe and the spring-plank attachment to the bogie. Had that been judged unnecessary by the time the Australian version was engineered?

Also: are you familiar with how the axlebox fits in the 'pedestals' in the truck frame -- I can't tell from the picture whether it is free to float laterally (although I presume it does) or whether there are fixed hornplates to take longitudinal brake force continuously or, if not, when braking effort (car moving in either direction) forces the axlebox side against the pedestal.

I assume (possibly incorrectly) that the general springing of these trucks followed American practice, and is in accord with Nystrom's experience over at Milwaukee. One conclusion Nystrom reached at that time was that high-speed springing was incompatible with both 'normal' track standards and with low-speed operation generally (e.g., the high spring rate for 'tuning' response with a lightweight car would be all wrong, particularly with respect to NVH [Nystrom didn't use that term], when operated at lower speeds). Which factors about these trucks were important in their relatively poor performance on 'local tracks'? (Note that I'm presuming it was NVH for sleeping passengers, not tracking, reflected energy, or other objective suspension issues.)

Ah, the invention of the air bolster spring! How many problems it solved for lightweight high-speed railcars -- in the vertical plane! (And how much fun it introduced in some of the other axes of motion... )

[M636C]

Overmod,

Try this

http://www.railpage.org.au/comrails/common/gm_001.html

Peter

[Overmod]

Peter, have you got a picture, or a good link to one, that shows these SAR trucks clearly?

[M636C]

The usual name for this arrangement is "wing-type axleboxes", at least in my part of the world. Looking at the axle housing casting without springs gives the appearance of "wings" either side. Another name I have heard is "Napoleon Hat", but this isn't widely used, although very descriptive.

The passenger trucks mentioned were a Pullman design and appeared about 1937 under the SP "Daylight" trains, on PS built Super Chief cars and on the big "Cities" UP Joint trains.

Copies of these trucks were built by the South Australian Railways, but the copies weren't quite as good on local track, and ended up under suburban diesel raicars rather than the sleeping cars they were built for.

A number of the 1940s SAR built steel coaches, used on steam special trains these days, use these trucks.

Peter

[Overmod]

Yes, these are housings for the primary springs. If you look here, for example, you can see a bit more clearly what's going on:

http://www.railpictures.net/viewphoto.php?id=37324

In a 'conventional' three-axle truck without drop equalizers, the springs between the axle bearings and the truck frame are up high. With this design, the effective point of action is down very close to the railhead; you see a similar design on some of the early Union Pacific streamlined-car trucks. Note also that the center of the coil-spring length is about on the centerline of the axle; I believe this helps with lateral motion accommodation in the same manner as the Henschel Flexi-Float.

[stantaras]

QUOTE: Originally posted by Overmod

Are you referring to the 'rollerblade' housings and springs?

Not sure if that is what they are .
These are shaped like a bell and are easily seen as they are on the outside of each wheel.The lower portion of the wheel touching the rail is visible at the bottom of these "bells'.
Thanks.

[Overmod]

Are you referring to the 'rollerblade' housings and springs?

[stantaras]

What is the function of the "skirts" or "boots" on the outside of the locomotives wheels?
I have noticed that G.M has no such equipment on their wheels.[?]