quick to load

[Anonymous]

What is ment by the term "quick loading". Every one says EMD's are quick to load, yet some say GE's are "the real pullers"; sounds like a cotradiction of terms. Someone said GE's take miles to load. If so how can they be the "real pullers"? Being an obvious novice I equate loading to a dirt bike getting "on the pipe"(powerband) is this correct? how does this equate to a locomotive? please explain.

[Anonymous]

The short answer(I'm sure that the professional railroaders who post here can explain this better).
Remember,when talking about modern locomotives,your dealing with a Diesel ELECTRIC system. The Engine turns a generator(nowadays more likely an alternator)which generates current which then is used to power the electric traction motors powering the axles. But that's an oversimplification,as you have a complex electrical transmission system which regulates the power. This is complicated in a DC traction motor(which most commonly take the AC current from the alternator and rectify it to DC) and even more so in the newer AC traction motor units(which actually take AC,rectify to DC,then phase invert it back to AC). So an engines time to load refers to the interaction between the prime mover and electrical system.
Most industry sources that I've read support the idea that two cycle diesels(EMD 710,645,567 series)offer superior loading at low speeds than four cycle engines(EMD 265-H and all GE's).

[Anonymous]

I have always felt the turbo charger was the cause of the slow buildup of current in GEs. A GE has a true turbo charger, which means it is driven by exhaust gases and at low engine speed there is not much gas pressure. An EMD has a gear driven turbo at low gas pressure that disengages and works as a true turbo at higher exhaust gas pressures.

[wabash1]

in simple terms every time i get a notch on a emd unit it is instant response and loads amperage right then which keeps me moving at track speed easier but on a ge unit you get a notch and it takes up to 5 secs or more to get a response. at 50 mph you might go 1/4 mile before you start getting enough power to the rails to keep track speed with a ge. so you do things sooner than normal to compensate for this lag. on a emd if you need it just get it and keep going. as with most engineers i dont know why i dont get into the mechanics of them i can only tell you how many cylinders they have not displacement. we are into train handleing and moving freight. im not certified to work on them. thats someone elses job.

[Anonymous]

Is it correct to assume that how fast a locomotive loads is nothing more than how fast it's prime mover gains rpms? Is an EMD's quick loading attributed to its roots blower and a GE's not so quick loading attributed to turbo lag? How much maintainace does a roots blower require? Turbo mantainace?

[wabash1]

im not sure of why but i have seen a emd in the lead with a ge dash 9 trail unit and watch the engineer grab notches and the ge load quick like the emd and also the other way around a dash 9 lead with a sd 60 in the rear and it load slowly. thats why i came to a opinion that what ever the lead unit does loading and so on then all other units will do the same.

[Anonymous]

A high horsepower EMD does not have a roots blower. It has a turbo that is gear driven at low RPMs when there isn't nuch gas pressure. When the engine RPMs get higher and the exhaust pressure is higher the gear drive disengages and the turbo runs on gas pressure. This allows the EMD turbo to supply lots of air at all engine RPM ranges and I feel allows quicker buildup of power. I would expect the EMD turbo would have more failures because it is a more complicated machine. In fact I have had a number of EMD turbo failures and I cannot remember ever having a GE turbo fail. Then again I operated more EMDs than GEs. Also the number of failures I have seen over 28 years wasn't that high.

[Anonymous]

Hey ronald1...there is a difference alright, but of no consequence. Quick loading is paramount especially if road-switching operations are important. Making a 'drop' for instance demands that an engine with quick pick-up speed be in service. Starting a large train moving with the drone GE engines (junk!) is'nt that much of an issue, as you want a smooth start etc. anyway. But why in h*** do people think there needs to be a difference. Having a great pulling engine with quick loading is always compatible on good engines. Those engineers I know well are shocked at how poor performing the new DASH 9 etc. engines are especially on our 2.2% grade going to Wenatchee from Seattle-Everett! Long live the EMD's...Hommie

[Anonymous]

Thanks for the great info! Can you elaborate on the previos comment about EMD's and GE's loading in unison. Are units that are hooked together somehow regulated to load at the same pace(To prevent wheel slip or other problems)?

[Anonymous]

I don't think there is a differance. The observer is usually on the lead locomotive and his observations are based on that locomotive, it might feel like the GEs load quicker because the EMD you are on does. Old GEs didn't seem to be able to get the fuel mixture right before the turbo started relly pumping air, hense rolling clouds of black smoke and a lugging engine. The black smoke rolled no matter where they were in the consist.

[alangj]

Could it be the fact that two-cycle prime movers have twice as many power strokes per crankshaft revolution as four-cycle ones do (for an equal number of cylinders, of course)? It would seem like this could easily have enough of an effect on how readily they can accelerate themselves and the generator/alternator to the necessary speeds to achieve the needed output. Just a thought.

[Anonymous]

The differance between 2 cycle and 4 stroke could give better acceleration. But horsepower ratings between comperable sized diesel engines gives GEs equal or greater horsepower.

[wabash1]

if you have a ge 4000 hp unit and a emd 4000 hp unit how can you tell me the ge has greater horsepower?.

[Anonymous]

I believe I said that with comparable sized diesels GEs had equal or greater horsepower. In an effort to compare the 2 cycle EMD and the 4 stroke GE. So with half the power strokes the GE still gives similar power output.