Re: Why change from stub to point switches?

Hi,

There is about 10 feet of unspiked rail on a stub turnout - the stub.

This is about 20 feet or 7 yards of rail that needs to be moved to bend the iron.

For 30 pound rail, this is about 210 pounds. Not all the rail is moved the same distance so say about 1/2 the weight would be forced over - about 105 pounds.

Now the harp switch stand gives a leveraged gain of about 3 in 1 in moving the rail. So a 30 pound stub switch needs about 30 pounds of effort to bend the iron.

These numbers are not exact and many assumptions were made to keep it simple.

This means that a 30# rail stub requires about 30#s of effort.
For 85# rail, the effort requires about 85 pounds of effort to bend the iron by the switchman.
For 115# rail, the effort to throw is about 115# of effort.

I would guess that 60 # rail would be the most a single man could throw. When this was occurring (c1890), there were no electric switch machines.

A point switch has a point length of about 5 feet and is tapered on one end. The light weight end (tapered end) is moved farthest.

The physics and the electronic of the era pushed for the point switch for heavier rail.

AS one saying says, I can move the earth as long as a have a good fulcrum and a long enough lever.

Rotary switch stands replaced harp switch stands to gain mechanical leverage using gears for heavier rail.

History of technology (for me) is a fascinating study.

Doug vV