by Noel Weaver
BlockLine_4111 wrote:Let me see if this makes sense.Let's put it this way, diesel engine = horsepower
4 axle - 2 stroke locos (e.g. EMD) are good for expedient mainline service.
6 axle - 4 stroke locos (e.g. Alco, GE) are good for 'drags', lugging of hefty tonnage.
Question - where do the following fit into the scheme?
4 axle - 4 stroke locos
6 axle - 2 stoke locos
Are both equally suited (or thereabout) for secondary and mainline manifests?
Traction motors = tractive effort
Diesel engine puts out 3000 HP, on a six motor engine there is less HP per
axle and more motors to soak up the same amount of electricity. On a
four motor engine there are two fewer motors to use the same amount of
power. Thus a four motor unit of 3000 HP or more is the best power for
a realtively fast intermodal train over a railroad line that is basically built
for speed and does not have severe grades. Six motor engines generally
do a better job where tractive effort is very important and speed is more
of a secondary nature.
Another example, two 4000 HP, six motor locomotives (GE or EMD) will
generally handle a good size through freight train at 50 MPH most of the
way west or east between Selkirk and Buffalo. These same two units will
also handle an intermodal train but will have difficulty maintaining the 60
MPH van train speed.
The result is that either another six motor unit is added or they will use
three four axle units. It does not always end up actually being done this
way as sometimes they just do not have available power in the above
combinations.
Actually, during my Conrail days, three or four B-40-8's were probably the best power for the vans, they each packed 4000 HP into four traction motors and would go "like the wind".
Noel Weaver
