>
> > A similar, but unrelated subject: how can a train car turn corners without
> > skidding when the wheels and axle are a solid, single unit? (I know the
> > answer but I'm gonna make you sweat!!!!).
> >
>
> >
> > And, no, I have not figured out his solid axle comment yet. Either the
> > wheels are not connected to the axle, or maybe the inside wheel spin or the
> > outside wheel drags. Or, none of the above. I'll think about it for a
> > while when my headache goes away.
> >
> > Jay
As an old ex-railroad employee, I know this. A close inspection of a wheel-axle
unit will reveal that the wheels are tapered away from the inner rim, making the
inside diameter of the wheel larger than the outside diameter. When the train
enters a curve, centrifugal force
throws the mass to the outside of the curve, and the outside wheel rides on the
large diameter near the rim, while the wheel on the inside of the curve rides on
the smaller diameter on the outside edge of the wheel. This allows the wheel on
the inside of the curve to cover less distance for the same number of rotations
(or, in effect, travel slower than the solidly attached outside wheel)
This "differential" effect is far from perfect and each curve has to be
engineered properly and traveled at the proper speed. When speed is too high or
too low, the result is much grinding and squeaking with metal particles flying
(and sometimes sparks that can start fires!). Both rails and "tires" have to be
replaced often, when trains are forced by traffic to go around curves too slowly
and automatic "greasers" are often placed on such curves. ("The squeaky wheel
gets the grease" doesn't just apply to bearings!)
Ron Tebo
(Because of mis-spent youth as a railroad signal maintainer, telling you more
than you really wanted to know about this topic!)
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