Steam & Excursion > MU'd steam locomotives

Back in the day, (or now) when steam engines were double headed with other steamers, or with diesels, did any of the roads ever use MU lines to connect the main reservoirs? It seems odd that one air pump & MR was expected to do the work for the whole consist plus the train, when it would be so easy to hook them up MU style like they do today. I've been around several large steam engines, and never saw any MR hoses on either end, so it must not have been common practice if done at all.

ddg Wrote:
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> Back in the day, (or now) when steam engines were
> double headed with other steamers, or with
> diesels, did any of the roads ever use MU lines to
> connect the main reservoirs?

Back in the day: No

Now: Yes.

That's a pretty good explaination, and I have an understanding of air brake systems, but when I look at the old photo of the last days of AT&SF steam in New Mexico in the mid-50's, I have to wonder how much work the pump on that 2900 had to do to charge the train to start with, keep up with leakage, and to re-charge the train if it went in emergency. While the F-7's just pumped enough air to keep themselves happy. I had to assemble a circus train once at Valley Center, KS and the air supply tanks and brake reserviors on those cars sucked my air down so fast, it was all three units could to to finally get it all pumped up enough for an air test.

In addition,

What is now the MR line on Amtrak cars and Amtrak approved private cars used to be the signal line.

There were no hand held radios in the days of steam locomotives and the only way the conductor had of communicating with the engine crew, short of pulling the air, was with the signal (communication) line. Each car was equipped with a signal cord and the engine was equipped with a small, shrill whistle. A valve on the locomotive responded to the changes in air pressure in the signal line and caused the whistle to blow.

Per Rule 16 of the Uniform Code of Operating Rules, The conductor would use the the following signals to communicate with the engine.

(a) o o When standing - start.
(b) o o When running - stop at once.
(c) o o o When standing - back.
(d) o o o When running - stop at next station; where a train is required to flag stop between stations, it indicates stop at next flag stop for that train.
(e) o o o o When standing - apply or release air brakes.
(f) o o o o When running - reduce speed.
(g) o o o o o When standing - recall flagman.
(h) o o o o o When running - increase speed.
(j) o o o o o o When running - increase train heat.
(k) o o o o o o o When running - release sticking brake; look back for hand signal.
(l) ----------- (one very long) - Shut off train heat.
(m) o o - When running as prescribed by Rule 90.

Rule 90. The conductor of every passenger train must give communicating signal 16 (m) between one and three miles of every station at which it is to meet or wait for a train, clear a superior train, or to move through a siding or crossover when so instructed. The engineman must make running test of the brake as soon as practicable and then give whistle signal 14 (n) (- - o) in acknowledgement. Should the engineman fail to respond to signal 16 (m) as herein prescribed, action must be taken to stop the train before the station is reached.

In looking over my old 1952 rule book, given to me by a CPR engineer at Aylith Yard in Calgary in 1956, I am reminded what it meant to read and understand the rules. Everyone had a task to perform that required an intimate working knowledge of the Rule Book.

Most railroads also had whistle signals that the enginemen on the helper and road locomotive always used to communicate with each other. I'd have to look them up in my rule books but the meanings were: work steam (add power), shut off steam (drift) and cut in air brake valve. In doubleheading, the lead locomotive was always the helper and the trailing locomotive was the road locomotive. Cutting in the air brake on the road locomotive was only done in emergencies where the helper locomotive brakes became inoperative.

Now days, whichever locomotive is on the point has to have control of the air brakes on the train when doubleheading. In my original question, I was only asking about linking up the main res. lines on all the engines steam and/or diesel, for added MR capacity, to take some of the load off the lead engine's compressor. It wouldn't be any different than taking a modern consist today, and unhooking the MR lines behind the lead unit, and using just one compressor. Wouldn't make scense today, why did they do it back then?

The larger steam engines running today are all equipped with two air pumps. Both are running. They pump enough air to fill a pretty darn big train in short order. IIRC, the two pumps will give somewhere around 300 CFM at 120psi.
Not a lot of need for more air pump capacity.
Also, most steam today is pulling relatively short trains of 30 cars or less. Doesn't take long to pump up a train of that size.
If needed, the brakes on the so called "helper" diesel could easily be cut in on very short notice.
Mark D.

Also there is no provision to MU air on steam equipment that I am aware of unless there has been some modern day modification made. I can not recall any steam locomotive equipped with a MU2a or equilavent valve as standard air schedule equipment. The proper term would be doubleheading; MUing refers to controling a series of engines from one control point. From a safe operation point of view you would want the air controled from one point and that point by necessity would be the front most point avaiilable. As mentioned before; the only communications in that day(even late steam in most cases) were the various whistle signals(both train communications line and the road whistle) and in many cases there would be too long a delay in response. Andy

Ross Rowland installed an MU package on the C&O 614 shortly before its current retirement.
It did not allow a diesel to control the steam engine AFAIK, but it did/does allow control of the diesel from the steam engine.
But this is for running applications, and not for switching the air over.
Mark D.

Even though on Diesel locomotives the MR air is equalized through the MR hoses between units there is still a tendency for the lead unit compressor to load more than the trailing units.....Most units have a compressor sync circuit that trainlines through pin 22 (if memory serves me correctly) so that when the Detroit switch closes and the compressor loads on any unit in the consist they all start pumping......

765 and the UP steam program also have capibilty to MU and control trailing diesel locomotives. It's not tied into the steam locomotive's throttle or reverser, it much like a remote control. Just a box that sits near the brake stand and the engineer of the steamer and the engineer can adjust the throttle of the diesel to his liking.

In the few times I have seen this being used, the engineer would only use the diesel when first starting or to assist on heavy grades. The rest of the time the diesel was just along for the ride.

I actually have doubleheaded with a steamer in my career on AT&SF/BNSF. Several years ago, I ran a couple of 800 Class GE's behind AT&SF 3751 from Newton into KC. The engineer told me to let him take it out of town, then go to R-8 when we got over the MOPRR crossing. That we did, running 60 mph up the hill to Walton. After that, I was to use the DB to control train speed or to slow down. It worked pretty well, except when I needed to slow the train, he kept it stretched to the point it would not slow down like I wanted. Since my consist was trailing, I had no control over the train air brakes, just my independent. I had a ball, & had time to enjoy the ride. The RFE chose to ride 3751.

Focusing on the initial question, no the MR air lines were not used because a steamer did not have MR air lines. The train line and the signal line (previously mentioned) were it.

However, it was possible for the road locomotive to assist in charging/recharging the train line. Usually that was only done in the case that the helper locomotive's compressor was unable to sufficiently charge the train line. Also, on short runs the helper engine often headed the train but might not have air coupled. In that case, the road engine controlled the braking.

MarkD is correct, most modern North American steam locomotives were fitted with *two* air compressors (either Westinghouse A.B.Co. Cross-Compounds, or New York A.B.Co Duplexes), each of which had a displacement of 150 cfm, with actual Free Air Delivery (f.a.d.) of around 105 to 110 cfm. *Either one* of these two compressors can pump just about as much air as can be squeezed down the 1-1/4" trainline; the second compressor was there mainly as a backup, so that failure of an air pump would not leave a train stranded and plugging the section (because, as is noted several places in this thread, the vast majority of steam locomotives operated as single units).

Concerning how much air can be pushed down a pipe, the American Railway Association (A.R.A., ancestor of the A.A.R.) sponsored a series of tests, with the cooperation of both major air brake manufacturers, that proved, among a lot of other things, that the maximum practical, usable air flow through a 1-1/4" pipe was about 100 cfm. Anything above that was pretty much wasted effort because of the "damming" effect of "pipe friction", that is, the resistance caused by the friction between the air molecules and the walls of the pipe, which of course becomes progressively greater as the length of the train increases, and means effectively that, if you have more than 30 or 40 cars in the train, you could have a 10,000 cfm pump on the head end and still not get the caboose pressure up any quicker than if you had only the single cross-compund pump. So, there was not much point to putting a main reservoir equalizing pipe on a steam locomotive, because they didn't double-head very often; when they did, the helper usually only coupled up *after* the train had been pumped up with yard air, and in any case the air pumps on the helper would not be of any help to the ones on the road locomotive.

As a matter of interest, WABCO designed and tested air-operated controls for steam locomotives in the late 1940's, which could quite easily have been given MU capability, had there been any interest; however, they came too late in the day (along with improved steam exhaust nozzles, over-fire air jets, streamlined steam passages, etc.) to save the steam locomotive from the onslaught of the diesel.

The "MU control box" used on NKP 765, etc., was I think first used in the late 60's or early 70's on Clinchfield #1, so that #1's engineman could control the two F7B's used to help the little tenwheeler haul a 15 or 20-car consist.

If memory serves me correctly,1522 was equipped with an MU control box and MR lines through the tender and aux tank. On several trips the air pump on 1522 was not used,witht he air being charged with the trailing diesel.

tucker Wrote:
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> 765 and the UP steam program also have capibilty
> to MU and control trailing diesel locomotives.
> It's not tied into the steam locomotive's throttle
> or reverser, it much like a remote control. Just a
> box that sits near the brake stand and the
> engineer of the steamer and the engineer can
> adjust the throttle of the diesel to his liking.

Here's a picture of one I built for the SP&S 700. Many of today's operating large steamers now have them and probably no two of them are the same style. This one contains many parts from GEs and EMDs which were being parted out at Usk, Washington.

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I didn't know you could get a current readout through the MU cable.

filmteknik Wrote:
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> I didn't know you could get a current readout
> through the MU cable.

The MU cable has been modified specifically for use with the SP&S 700 and is marked with appropriate warnings forbidding standard MU usage.

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