Why and What is a Run Eight Control

Tommy posted:

It is unclear to me why eight "steps" seem to have been standardized in locomotive control.

Well, "standard" in diesel electric units, since about 1939 anyway.

As we know heavy trucks may have many variations in gearing.

Remember that highway vehicles are pretty much "direct drive", with the prime mover directly connected, through a clutch, to the transmission and drive axles.

 What exactly happens with each step?

First, a diesel electric locomotive is essentially a "mini-powerplant" on wheels, i.e. the prime mover ONLY drives an electric generator, and the various throttle positions/steps ONLY control electrical energy from the generator to the traction motors, by way of various load control circuits.

May steps be skipped?

Yes.

With what consequences?

None.

Does every step have to be entered?

No.

I note there have been comments about "wiping" the controller. Are all engine controls alike in this manner?

Not really, as all the load controlling circuitry is doing is sending electrical information to the prime mover electro-hydraulic governor, which controls the prime mover speed (newer units now use electronic fuel injection). The specific seven engine RPM settings are generally based around NOT having the engine operate in "critical vibration" speeds for optimum smoothness.

Thanks.

It is unclear to me why eight "steps" seem to have been standardized in locomotive control ...

The Woodward governors that were used on EMD 567 and 645 engines for decades have four solenoids that act on a triangular plate, which works against hydraulic pressure and flyweights to establish a governed engine speed. These are known as the A-B-C-D solenoids and they need only four dedicated wires (plus ground) to establish eight engine speeds, plus engine shutdown. It's a "digital" control, in a sense: each of four valves is either energized or not. This system allows locomotives to be operated in multiple unit consists with one control. Locomotives don't need a continuously variable throttle control like a truck, but they do need the MU capability for general service.

The electro-hydraulic governor controls engine speeds in eight steps. A load regulator works off the engine governor to balance the electrical load according to the governed engine speeds. When engine RPM and electrical load stabilize, each step of engine speed produces a fixed horsepower output.

I've seen old GE U28C locomotives that had 16-notch throttle controllers but I believe there were only eight steps of MU control.

I think some early EMD switchers with no MU option had straight mechanical linkage from the throttle to the engine governor.

Thanks for both replies!

IIRC Baldwin diesels had a different system which allowed a much greater range in controlling engine speed. Unfortunately, it was very complicated and didn't stand up to long term wear and tear, and wouldn't work with other builder's diesels.

wjstix posted:

IIRC Baldwin diesels had a different system which allowed a much greater range in controlling engine speed. Unfortunately, it was very complicated and didn't stand up to long term wear and tear, and wouldn't work with other builder's diesels.

I have seen photos of both New York Central and PRR true diesel doubleheaders (two crews operating two different MUed sets of different manufacturer's diesels) because of this reason. The doubleheader always had a Baldwin set of power and usually an all-EMD, all-ALCO or a mixed bag of EMD and Alco units. This defeated one of the major selling points of diesel-electric motive power, ie, the ability to control an entire locomotive consist with one crew. I believe at least some FM units lacked MU control altogether. I know the C-Liners on the LIRR did not have MU controls. I have seen pics of true diesel doubleheaders involving LIRR FMs on the heavy east end weekend runs to Montauk.

Ace posted:

I think some early EMD switchers with no MU option had straight mechanical linkage from the throttle to the engine governor.

I ran some NW2 and SW9 engines that were built without m-u capability and had the can-style control stand.  As you pointed out, Ace, they lacked any notches on the throttle.  Would you agree that it was an air pressure throttle, though, instead of a mechanical linkage?  Later EMD switchers with the small cash register control stand (after about 1956) had 8 notches, whether or not they were equipped with m-u control.  We had some of them, too, SW1200m's.

The WABCO air pressure throttle used on Baldwin, and a small number of Fairbanks-Morse, road diesels did not have eight distinct notches with clicks.  However, the Engineer could gently relax tension at any position in which he had the throttle, and it would stop at that position as soon as it moved slightly toward IDLE, creating a "soft notch".

Number 90 posted:

Ace posted:

I think some early EMD switchers with no MU option had straight mechanical linkage from the throttle to the engine governor.

I ran some NW2 and SW9 engines that were built without m-u capability and had the can-style control stand.  As you pointed out, Ace, they lacked any notches on the throttle.  Would you agree that it was an air pressure throttle, though, instead of a mechanical linkage?

The early EMD switchers, that I had to work on, without an electro-hydraulic governor, did indeed have a mechanical linkage that ran from the throttle to the mechanical governor. The engine speed was infinitely variable with no notches.

 Later EMD switchers with the small cash register control stand (after about 1956) had 8 notches, whether or not they were equipped with m-u control.  We had some of them, too, SW1200m's.

Hot Water posted:

Number 90 posted:

Ace posted:

I think some early EMD switchers with no MU option had straight mechanical linkage from the throttle to the engine governor.

I ran some NW2 and SW9 engines that were built without m-u capability and had the can-style control stand.  As you pointed out, Ace, they lacked any notches on the throttle.  Would you agree that it was an air pressure throttle, though, instead of a mechanical linkage?

The early EMD switchers, that I had to work on, without an electro-hydraulic governor, did indeed have a mechanical linkage that ran from the throttle to the mechanical governor. The engine speed was infinitely variable with no notches.

 Later EMD switchers with the small cash register control stand (after about 1956) had 8 notches, whether or not they were equipped with m-u control.  We had some of them, too, SW1200m's.

 

That settles it.  I concede. 

Railroads could buy engines with M.U. capability or not as they wished. Many early diesels were bought for one specific job, like running on a branchline hauling a few cars where it assumed the engine would just work there by itself til it was retired...so the railroads might not order it to have M.U. connections.

wjstix posted:

Railroads could buy engines with M.U. capability or not as they wished. Many early diesels were bought for one specific job, like running on a branchline hauling a few cars where it assumed the engine would just work there by itself til it was retired...so the railroads might not order it to have M.U. connections.

That's not quit true for EMD road locomotives, as "Multiple Unit Control" was basic. The switcher type of units, did indeed have "MU Control" as an extra cost option. I don't know how GE or ALCO handled their MU Control.

Some of the EMD BL2 locomotives were built without MU (1947 - 1949) but had it added later. Perhaps that was a transition point after which MU became a standard feature. The BL locos "evolved" into the more functional GP series.

https://en.wikipedia.org/wiki/EMD_BL2