This message contains some info regarding Diesel motors, then moves into a little coverage of Diesel electric locomotives. Nothing very technical, mostly just some "did you know" kind of stuff.
Originally, the message was a reply to a thread in the mike holt forum ["reliability" thread], in which I was tossing things back and forth with Mr. Bennie Palmer.
He and I commonly throw topics back and forth that are outside the scope of the thread's topic [I'm sure you agree Bennie].
Anyhow, I copied and pasted it to this forum because I am sure you guys will want to see it.
I really intended to make the reply simple and brief, but one thing led to another [like usual], so it ended up being long.
Take a look at it and let me know if you want me to elaborate this topic further, just for an FYI type topic.
At least, it should be of some interest to you.
The first part might be hard to follow, as it is the intended reply to Mr. Palmer. It picks up after that.
Hope you enjoy!!
My first year in Diesel Mechanics [High School Elective] was where I first seen one of the motor generator sets like the ones you mentioned.
They were Military surplus items donated to our school for us to use for lab work.
A group would be assigned to each one, the exercises were to dismantle the prime mover, identify the parts, measure, and then reassemble the motor.
If the motor fired up and did not blow a rod bearing, the group would pass.
We had 2 types of prime movers [Diesel motors for those wondering] that were used on these sets: DD 671 [Detroit Diesel straight 6 cylinder block, 71 CID per cylinder - or 426 Cu In] and DD 8V92 [Detroit Diesel V8 block, 92 CID per cylinder - or 736 Cu. In.].
Both motors were, of course, 2 stroke with 4 exhaust valves per cylinder [I am almost positive there was 4 valves, but I could be mistakenly thinking of DDA motors for the Locomotives].
I am positive that they both had Superchargers [Blowers] and Turbochargers.
These were so cool to work with as compared to gasoline motors - except the major weight differences!
I am glad to have taken that class, as it has been quite helpful to know this stuff - even if only for non-serious reasons.
It was the senior, or Advanced Automotive class' optional field when I was a High School Senior.
The class began that year, so that rather makes it special to me in a way.
Oh, there was one other little motor that I believe came out of a tractor.
It was, like the others a Detroit Diesel, but was only a 4 cylinder, 71 CID, blown and turbocharged 2 stroker V block [4V71],
or was it 4V92?
Gosh, seems like only yesterday - too bad my memory does not feel the same.
Thanks for bringing up the Diesel Mechanics!
Feels good to run that stuff through my mind once again.
FYI: Most modern Diesel-Electric Locomotives used here [North America] since 1983 are manufactured by General Electric [GE], and General Motors' Electro-Motive Division [EMD] - now known as General Motors' Diesel Division [GMDD] is now 2nd.
Before 1983, EMD was the top seller of Diesel-Electric Locomotives in North America.
EMD was the company that introduced the famous F7 Locomotives [along with the E3, and the entire early F classes of F3 and FTs]. These were the Locomotives that changed railroading history from Steam to Diesel.
Major changes in the Locomotives' technology have taken place since I first learned the way one operates.
Back then [circa 1977], the "Hottest" EMD Locomotive around was the SD40-2. Almost every railroad had an extensive fleet of these "Fast 40's".
These units used the common 645 motor that was almost a standard issue from 1966 to 1984.
The exact block design was 16V645, with a 45-degree V block. These were 2 strokers with 4 exhaust valves per cylinder.
Aspiration was done with Superchargers [AKA Blowers] and many also included Turbochargers [to assist with the high-end output].
Horsepower for these 10,320 CID motors was 3,000.
As with many of the legacy Diesel-Electric Locomotives of this era, the traction motors were big bulky DC motors.
The SD models, having 6 axles, would of course have 6 traction motors per Locomotive, whereas the GP and most F models had 4 axles, totaling 4 traction motors.
All these later model loco's used 3 Phase AC Alternators, which were coupled to the prime movers, for traction motor power.
Needless to say, the change from DC generators reduced generator brush maintenance costs and time, but early Diode Trios had their share of hassles until perfected.
The SD40-2 was one of the first EMD Locos to incorporate Microprocessors with the controlling functions. This was EMD's lead to the future and everyone loved the response of the Fast 40's.
Meanwhile, General Electric's most common Locomotives were U30-B, U30-C and C30-7.
GE's locomotives used a variety of Diesel motors manufactured by Caterpillar, Cummins and Cooper-Bessimer. Most blocks were In-line [straight], with either 8, 12 or 16 cylinders. 12 cylinder blocks were the most common.
GE preferred to use, and still does use, 4 stroke Diesels. These do not produce as many pollutants, as their 2 stroke companions do, but the sacrifice is a lag in brake tractive effort [many Engineers complain that they are "dogs" when it comes to needing quick and available power].
The slang term for GE locomotives typically used is "U-Boat" and you can tell a U-Boat a mile away, just by it's sound. Very thumpy "chugging", as where the typical EMD would be a "whistle".
Dynamic brakes whine about the same on both brands when you listen to them descending a long grade [like a 2.2% grade].
The basic designs of U-Boats would be classified by some to be "Tunnel Motors". This means that the Radiators are located at the rear end of the unit [called the Long Hood], with the fresh air intake being at the level of the walkway approximately 8 feet above the ground, and the convected-exhausted air is blown away at the top portion of the rear hood.
This was a design issue requirement for at least 2 major railroads - Southern Pacific [SP/SSW] and Rio Grande [D&RGW] in which they posed EMD with, in order to come up with a solution.
The problem was; these railroads had very long tunnels on moderate grades, given that when a train was stopped inside a tunnel, then was cleared to proceed once again, they were overheating because the tunnel recirculated the hot exhausted air from the radiators back through again and again.
This left many stranded trains stuck in tunnels.
The solution by EMD was to incorporate a "Tunnel Motor" technique to augment certain classes of SD40-2 and SD45-2 prototypes. These became the very easily recognized SD40T-2 and SD45T-2 models.
The tunnel motor design kept the hot air from being recirculated back downwards easier than in other EMD designs.
FYI - The radiators are located in the last section of the locomotive.
EMDs have typically 3 top mounted fans for radiator cooling at the rear.
Located in the center of the hood, just beyond the cab, is the Dynamic Brake resistor array's grid.
6 axle units have 2 Dynamic Brake fans located above the intake grills, where 4 axle units have only 1 fan.
Since the increased usage, reliability and lower overall costs of VLSI technology [Microprocessors, or just simply "Chips"], they have become the primary systems' control techniques for both major manufacturers [EMD and GE].
This, along with the use of AC traction motors and 4 stroke prime movers, has resulted in a fantastic technological breakthrough.
The EMD model SD90MAC is one of high mention. This Locomotive can deliver upto 6,000 Horsepower using a relatively small prime mover, the GM 16V265H model engine [16 cylinder V block, 265 CID per cylinder - total of 4,240 Cu. In.].
It utilizes AC traction motors, plus 32 bit CPUs.
This is a major output HP increase, with decreased fuel consumption, as compared to the 3,000 HP, SD40-2, which used the common 16V645 engine.
Here we have 6,000 HP delivered from a 4,240 Cubic Inch prime mover, whereas the SD40-2 delivered 3,000 HP from a 10,320 Cubic Inch prime mover.
GM and GE have taken the issue of head - end power on Passenger type fleets to a better approach.
Head-end power means that the Passenger cars receive their electric power form the Locomotive [If you have ridden Amtrak in the last 20 years, you probably have wondered how the cars got their AC power for lights and Air Conditioning].
Prior to the release of EMD's F59 PHI, or GE's P-42 /P40-8 [known as "dash 8's"], the most commonly used Passenger Locomotive for Local and Road service was the infamous EMD F40PH - a 4 axle, 3,000 HP 16V710 based 2 stroker locomotive, which was supercharged and turbocharged.
It was the preferred workhorse for Diesel-electric passenger use.
This locomotive had two separate AC alternators connected to the 16V710 prime mover.
One was for the traction motors [called the primary unit], the other was a 600 KVA 480 VAC 3 phase 4 wire Wye connected alternator, which was used to power the passenger cars [called the auxiliary unit].
Since both alternators were directly coupled to the prime mover, this locomotive's diesel engine was always running at high speed [around 720 RPMs, which sounds slow here, but when standing next to an F40PH, it sounds like 10,000 RPMs!].
Load variations were controlled by use of a pneumatic actuated governor, so when the locomotive had to deliver high power to the traction motors, the engine speed would remain at a near constant 720 RPMs for the 60 Hz AC output to be steady from the auxiliary, or head-end power alternator.
Furthermore, the governor suppressed excessive prime mover speed when the train was stopped at a station, or in a block [sidings, and such].
The newer F59PHI and GE's P42's + Dash 8's use a separate diesel motor for the head end power, which allows the prime mover to idle down at station stops, or in sidings.
Sure hope this is interesting to you guys! I love to talk about trains!!
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!