Re: Porter 1203 TE

These numbers are a little misleading.

Due to the extensive radiator modifications done by USG in the early days, this locomotive is thought to be closer to 80 tons than the nominal 75 tons builder's design weight.

The gross horsepower should be 660. The generator output horsepower is typically used on larger engines, so it will be 600 after losses, air compressor and radiator fan is considered. It is unknown what the mountain elevation (despite the turbo) and engine condition may limit horsepower.

There are actually three different TE figures to consider:

The first is starting tractive effort. This is the point the wheels will slip, and varies from 20% to 30% of weight on drivers depending on conditions. For this era diesel or steam it is generally considered to be 25% (or a factor of 4 in steam terms). The 1203 should have up to 40,000# starting TE (160,000 x .25)

The second figure is continuous TE. This represents the power that the engine can develop without burning up the electrical system. I suspect that the 19,200# figure might be the continuos TE suggesting a minimum continuous speed of about 9.6 MPH at full throttle. Where did this figure come from?

The third figure is the TE at the speed you intend to operate at. Assuming that the 1203 must maintain a schedule of 10 MPH the TE would be about 18,480#, assuming full horsepower.

These are all theoretical figures and subject to the actual conditions and experience. Realize that a good portion of its TE will be used to move its own 80 tons up the hill. The extra weight on drivers isn't really an advantage here.