That's true..so what's changed besides a bit more horsepower? 30 years ago some railroads like coal hauler Chessie and mountain road Western Pacific preferred the four motor units over their six motor cousins. In fact WP never rostered a six motor.
Today freight trains are generally shorter than they were 30 years ago..With today's emphasis on FASTER, more frequent, scheduled service one could argue a four motor locomotive is better suited.
High horsepower 4 axles are notoriously slippery - the wheel slip and spin without going anywhere, before the full horsepower is used. There's also a limit on the amount of weight you can put on the drivers, which limits the size of a 4 axle. Santa Fe's GP60M's pretty much maxed out what a 4 axle can practically weigh. The only way SF could add the wide cabs was to sacrifice fuel.
6 axles spread the weight over more drivers, which means they can weigh more. Alot of which is fuel. A modern ES44 or SD70 holds 5000 or more gallons of fuel, compared with about 3000 in most 4 axles. That give them greater range. Weight, among other things, give them more tractive effort. Here's an example from the tonnage graph for my sub division:
GP40-2: 3000 tonsSD40-2: 4600 tons
That may not seem like a big difference, but 1600 tons is 16 loaded cars, or 30 to 35 empty ones.
The REAL reason 4 axles where prefered was that they were easier on the track at speed. Current steerable truck technology, eliminates this advantage.
And from a crew standpoint, 6 axles ride better. Riding a GP60 or B40 is like riding an out of balance washing machine.
Nick
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
Ulrich wrote: That's true..so what's changed besides a bit more horsepower? 30 years ago some railroads like coal hauler Chessie and mountain road Western Pacific preferred the four motor units over their six motor cousins. In fact WP never rostered a six motor. Today freight trains are generally shorter than they were 30 years ago..With today's emphasis on FASTER, more frequent, scheduled service one could argue a four motor locomotive is better suited.
Well trains might be shorter than 30 years ago(not sure about that one) but they are MUCH heaver that they were 30 years ago. That is a great argument for six axles. One other thing that has not been metioned is flexablity, a six axle can pull a van train tonight, then a grain train the next day, and a coal train the following day. A four axle can not do that.
An "expensive model collector"
Our community is FREE to join. To participate you must either login or register for an account.