Have You Ever Wondered... How The MPC Engineered Fast Angle Wheels Worked...

[ADCX Rob]

And how they relate to 12" to the foot scale operation?  Very prototypical!

[lionelsoni]

It's actually much more complicated than that:  https://en.wikipedia.org/wiki/Hunting_oscillation

The wheelset's rate of turn is proportional to its across-track distance, and the across-track velocity is proportional to the turn angle.  The solution of the differential equations of these two relationships is an undamped sinusoid, called "hunting," in which, rather than running in a smooth path between the rails, the wheelset continuously travels back and forth in the clearance between flanges and rails that Stevenson added a half-inch to from his original 4'8 gauge.  It is usually not severe enough to be noticed.  I was once able to observe it through the chinks in the floor of a converted flatcar on a tourist railroad.  I have also seen it at the rear truck of model cabooses with "fast angle" wheels.

The video is also misleading in showing the rail cant as matching the wheel conicity.  The usual rail cant is 1/40, while the conicity of a new wheel is twice that, or 1/20.  Wheel treads typically wear faster close to the flange; so the (approximate) conicity decreases to zero with age, at which point the wheel is condemned.  The conicity therefore approximately matches the rail cant at midlife; and wear is distributed between the corners of the railhead.

Some railroads, BART for example, use cylindrical wheels.  

[Expat1]

[quote user="lionelsoni"]

It's actually much more complicated than that:  https://en.wikipedia.org/wiki/Hunting_oscillation

The wheelset's rate of turn is proportional to its across-track distance, and the across-track velocity is proportional to the turn angle.  The solution of the differential equations of these two relationships is an undamped sinusoid, called "hunting," in which, rather than running in a smooth path between the rails, the wheelset continuously travels back and forth in the clearance between flanges and rails that Stevenson added a half-inch to from his original 4'8 gauge.  It is usually not severe enough to be noticed.  I was once able to observe it through the chinks in the floor of a converted flatcar on a tourist railroad.  I have also seen it at the rear truck of model cabooses with "fast angle" wheels.

The video is also misleading in showing the rail cant as matching the wheel conicity.  The usual rail cant is 1/40, while the conicity of a new wheel is twice that, or 1/20.  Wheel treads typically wear faster close to the flange; so the (approximate) conicity decreases to zero with age, at which point the wheel is condemned.  The conicity therefore approximately matches the rail cant at midlife; and wear is distributed between the corners of the railhead.

Some railroads, BART for example, use cylindrical wheels.  

 

I don't think it matters much on small wheels.  The old London, Brighton and South Coast Railway in England ran with straight treads on the real thing in the 19th century.  I've built some O gauge live steam toy trains with straight treads and they run fine on tubular track. 

[KRM]

All I can say is I don't care much how they work but they fixed my set of Lionel Conventional Classics 6-27767 Santa Fe blue stripe Passenger cars from derailing in wide curves. I tried removing the axles and replacing them with Post war ones,,,nope same derail in the turns. So I decided to replace the axle and wheel sets with modern Fast Angle 9050-54s and BOOM PERFECT operation. Before swapping out the axle and wheel sets these cars were JUNK!!! BTW I had to re-wire them all to. The stock wires were stiff and tied in too tight and all pulled off the pick-ups.

Shame when you have to re-engineer something brand new fron a supplier.

 But I am sold on Fast Angle wheel sets.