Would it make more sence to have railroad wheels that car turn indepent of each other instead of being fixed to a axel? That way trains would not have to sqeal around curves[:)]
But isn’t that what keeps them on the rails? If you mean like radial trucks on locomotives, in a way they do. They were designed for longer 6 axle engines so they could negotiate sharp curves. The only cars I see screetching are Light rail and Subway cars.
What he’s asking is why not have the wheels rotate on a fixed axle.
I think the answer is that arrangement would be harder/more expensive to construct and maintain. Also; it would have no effect on the squeal; that is the flange rubbing the inside of the rail.
I guess you would like to see independent suspension, and limited slip differentals on the truck assembely of freight cars. That would be something, but I honestly don’ t see a use for it. I would go about building radial trucks for the cars but, then again I don’t think the manufacters like TTX are going to want to spend the extra money for that, not when there are advances in locomotive technology. You would also have to build six axles trucks on cars too. That could get interesting.
If you have independently turning wheels you completely lose the self steering you presently have in the tapered wheels on a solid axle. Doing so would increase the amount of flange squeal, not reduce it.
It isn’t obvious when you look at a wheel set, but… the wheel running surfaces are slightly tapered. For all but the very sharpest curves, as the wheel set starts to ride outwards (but the flange isn’t touching the outer rail yet) the outer wheel will be riding on a slightly bigger diameter than the inner wheel – and this makes the whole wheel set want to turn in the same direction as the rails do.
If all goes well and the truck is free to swivel (but not too free) it will steer itself around the curve. Under some conditions (too many to go into here) the truck will start to swing back and forth; that’s called hunting, and is a pain in the …
But there’s no need for the wheels to be free to rotate independently – in fact, the truck steers better if they’re not.
The only real advantage for independently mounted wheels would be in single axle trucks, where the free wheeling characteristics can make up for the non-steering characteristic. Such a design would result in reduced tare weight since you’re eliminating much of the truck assembly of the standard four wheel truck, and a multi-unit freight car consisting of single axle design would have an immensely superior load factor and lower center of gravity at the expense of non-standardization (see Southern’s 1965 “100”)
futuremodal:
How does that Southern 100 work – are the axles guided in any way or do they self-steer within those 1-axle trucks using the wheel tread cone angle? Did anything ever become of it (it dates from 1965) or did they decide it was not worth the bother?
There were some early roller bearing that mounted between the wheel hub and the axle.
Don’t forget, that if you swivel the wheels, keeping the fixed axle the same length,
YOU CHANGE THE GAUGE
Take pencil and paper and draw it and you will see what I mean.
A raidal truck swivels the whole axle.
…Steering abilities of solid axle / wheels {with tapered running surface wheels}…must trump any exercise to allow wheels to freely rotate on the axles because of involved design, expense and maintenance necessary to do so. Railroad trackage and it’s gentle curvature must not be too severe for the solid axle / wheel arrangement.
Quite. There are a few (a VERY few) places where the curvature is so tight that there is slippage and appreciable forces on the flanges – but that’s really rare.
Keep in mind the fundamental railroading engineering rule: KISS. Keep It Simple, Stupid. Also Rule Zero of Engineering: if it ain’t broke, don’t fix it.[:D]
…And it doesn’t seem to be broke.
The Southern 100 and other single axle railcars had short enough wheelbases to allow the rigidity to negotiate curves, aided by the tapered design of railwheels. I think the 100 had only 25’ between the axles per unit. The problem with the 100 wasn’t the rigid wheelbase, rather they had problems with the pin couplings between the units. That and the non-standardization did it in.
The later single axle cars in the form of the TTOX spine cars had some radial “give” in their axles, but not true radial steering. This allowed them a wheelbase of 36’. The cars were recently pulled from service a few years ago, mainly due to their short platforms that could only handle trailers 48’ long and 65,000 lb max (and no containers), but also due to their light weight. This has been discussed on other threads, but I believe they were considered a derailment potential.
Speaking of TTOX, I was an advocate of remanufacturing the TTOX “Four Runner” cars (four TTOX cars connected by drawbars to form one unit) into a single axle/articulated hybrid with longer platforms, beefed up suspension, and larger wheels/journals. Thus, instead of an A+A - A+A - A+A - A+A design (if I am allowed to use locomotive wheel designation to describe rolling stock), you would have an A+B+A - A+B+A (with “B” designating a standard two axle articulated connection). By replacing the first and third drawbars/single axles with a standard articulated connection, and leaving the single axles on the coupler ends and the second drawbar connection, you partially alleviate the rigidity of the single axle wheelbases, which would allow you to lengthen the wheelbase
Track speeders(fairmont variety- woodings were different) have an sleved front axle to allow the wheels to turn indpendent when someone spins there car around. It is east to lock one wheel during a emergency stop which makes a flat spot and the axles are more prone to failer than regular solid axles.
The profile on the wheel is good for 98% of the curves a wheel will face in its life, the other should have flange oiler there anyway.
An Independent ‘wheel’ would require ‘location’ to mantain the proper guage under ALL circumstances, I would probably need bearing on both sides of the wheel (an inner and outer - the same as the wheels on your car. The simple shoe brakes of todays cars would have to be redesigned or changed to disk brakes whiich would begin to increase the complexity of the overall design.
The current truck designs are the results of over 150 years of continual engineering and economic development. Railroads have settled on todays truck configuration becaues it is cheap to build, cheap to maintain and above all it works.
I was hoping for higher speed passenger trains when going around curves with out have to bank the curves.
Talgo.
I’m not sure that the squealing is totally the flange against the rail. As you turn, the inside wheel is going a shorter distance than the outer wheel, and I’ve heard that the squeal is the torsion in the axle as one end is twisted farther than the other. Can anyone confrim/deny this?
Again, as posted earlier on this thread, the taper of the rolling surface compensates for this difference in nearly all situations.