Tapered tread, conical wheels, are supposed to reduce flange wear and wear of une inside of curvede rails. i beleve most "cylindricle" wheels stilll have a very slight taper. The North Shore for example,
daveklepperTapered-tread, "conical" wheels are supposed to reduce flange wear and wear of the inside of curved rails. i believe most "cylindrical" wheels stilll have a very slight taper. The North Shore for example...
Remember that the issue involved here is not curve guiding, or radial steering, it is the hunting produced by oscillating 'miscorrection' of true wheelset following whether on straight track or curved. Note also that there is an implied 'mating taper' on the inside railhead that assists the coned wheels in staying centered in the nominal gauge.
For the cylindrical tread profiles (which do in fact have a very shallow 'centering' taper) it is assumed that the root profile of the tread, or in fact actual flange-area contact, will be necessary either for lateral force displacement or curving force accommodation. Unsurprisingly, for true LGV, we're talking about minimum designed curve radii on the order of 12 miles, with spiraling taking account all the way down to lock in the position derivatives. We're also probably talking about profoundly damped truck rotation or actual alignment control to make the cylindrical flanges effective, whereas at lower speeds the dynamics work as Wickens indicated to 'self-steer' the frame and thereby allow very low pivot and side-bearing friction -- something VERY desirable for interchange cars that may go an extended time between receiving maintenance of those areas. (As an interesting aside, there is a long history of 'independent wheels' on wheelsets being "innovated", including the original Talgo and Train X systems and at least one patent dividing a three-piece truck wheelset so the halves independently rotate. Guiding on these is vastly inferior to solid axles (again as Wickens somewhat surprisingly concluded) and it will pay you to comprehend why.
Now, the more interesting question -- and the one of most relevance to this thread -- is where the high-speed design benefits begin to outweigh the coned-tread ones. In my opinion (which should not be relied on) this may be well below the 125mph peak speed in the PRIIA spec that will likely define Amtrak service outside the NEC for the foreseeable future.... but it might not be even for 110mph peak. I also suspect that the (enormous) number of miles this equipment would run on freight-optimized track and geometry, where there are fairly obvious disadvantages to high-speed wheeltread profiles, might be significant.
Perhaps this is the thread to raise the question, ewhat should be done about wheel profiles on the modern ubiquitous low-floor "trams," streetcars," light-rail" cars ior whatever you wish to call them. All strikingly modern in appearance and passenger and operator amenities, but mechanivcally simply the old "two-rooms-and-a-bath" design multiplied. In other words, a bunch of four-wheel fixed-truck cars linked together by body sections suspended between them. With the multiplied forces on flanges and rail edges and screech on curves without flange oilers (as compared with cars with swivaling trucks). Any opinions on the optimum wheel profile?
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