Matthew Mitchell wrote:And it's not like they get real rough service such as drilling strings of freight cars three shifts a day.
There's a huge difference between diesel engines optimized for road duty and engines optimized for rail/marine duty. In essence it comes down to big pistons moving slowly vs small pistons moving quickly. The latter is more reliable as not only are the bits moving slower there are fewer parts to move and way fewer combustion events, which is the fundamental unit of wear and tear in an internal combustion engine. Over the years engines from both EMD and GE have seen rising cylinder displacement and more power per cylinder. GE's EVO engine is their largest yet and had EMD's latest new engine design been built in the tradition of their previous ones and...actually worked, it would have been listed as the 1010 compared with their currently available 710.
Road use engines have a major requirement that rail use engines don't generally have and that's namely throttle response, which applies even with dealing with construction equipment or smaller marine craft where many of these engines are deployed. Smaller displacement engines have lower internal mass and thus can respond more quickly to power demands and as they run at double or triple the RPM of a traditional rail use diesel the higher rate of combustion events can also decrease the amount of time it takes the engine to get up to full load.
The problem is that internal combustion engines tend not to enjoy being run at high RPM for extended periods of time. Railroad locomotives don't have a red band starting at Run 6 and thrashing the engine is generally a much better alternative than stalling out on a grade. Rescuing dead push-pull trainsets day in, day out is going to tax a small switch engine trying to get up the ramp onto the Reading viaduct or making a quick move at an interlocking. A related issue are engines that can work well at constant speed (even full load), but not varying speed. This is what killed Fairbanks-Morse because their opposed piston diesels were designed for marine use where they could run weeks without a throttle change, not the constant changes seen in rail service. If the current CAT lineup includes engines designed for stationary and heavy marine use, I would not be surprised if constant speed changes will start getting to them.
Anyway, just some food for thought for the SEPTA's of the world just in case the next time one of their re-power locomotives craps out and Federal grants aren't around to replace them.
