50Hz vs. 60Hz

[Sridhar Ayengar]

Chuck Guzis wrote:
>> The same way train wheels work.  Train wheels are of slightly 
>> smaller diameter to the outside edge than they are on the inside 
>> edge.  Makes the train sit between the rails rather than on them.  
>> Along the same lines, the capstan sits in the middle of the belt 
>> instead of on both outer edges.
> 
> I'd always been given to understand that the reason for the taper in 
> train wheel profiles is to facilitate travel on curves; i.e. the 
> wheels on the inside edge of a curve travel on the smaller diameter 
> of the taper and the ones on the outside, the larger.  Saves a lot of 
> flange-banging.

It's more than that.  If the wheels are profiled to the reverse of the 
common configuration, the stress on the system is enough to derail the 
train, even with flanges in place.  The flanges do help keep the train 
on the track on curves (they act sort of like a bump stop at the end of 
the wheel's "play"), but their primary purpose is to help guide the 
wheel through the points at switches.

The profile of the wheels is one of the main reasons why railroad ties 
(or sleepers, if you're on the other side of the pond...) are necessary. 
  When a train passes a section of track, it exerts a large amount of 
force pushing the rails away from each other, because the train is 
sitting between the rails instead of on them.

Next time you're near some worn, straight track, check out the wear 
pattern.  You'll find that the inside of the rails is slightly more worn 
than the outside.  It's very subtle, but you can see it.

Peace...  Sridhar