I was reading a paper on multiple unit controls for steam locomotives on Martyn Bane's website and found this

"The concept progressed from there to a single driver controlling a number of locomotives with Wabco engineers during the 1940’s having been said to have designed and patented pneumatic and electropneumatic control systems specifically for the multiple unit operation of steam locomotives."

Can anyone clarify this "having said to have designed"?

On another site, another reference to this elusive system..."Attempts at implementing this kind of system were made by Wabco engineers in the1940’s. They designed and patented pneumatic and electro-pneumatic control systems for the multiple unit operations under a single driver (a pneumatic system is a system moved or worked by air pressure)"

What attempts?

From the ever unreliable Wikipedia.."In the early years of this technology, Wabco also had—for a relatively brief period—a competing system called 'RMU' (Remote Multiple Uniter) which was installed on a few North American railroads. However this system did not prevail and soon went out of production."

Who, what and where? Is this simply a internet meme?

http://www.martynbane.co.uk/modernsteam/jmullaney/multipleunitcapability.pdf

Bruce, I don't have any details, but I seem to recall that these efforts were related to WABCO's development of the anti-slip controls applied to the Pennsylvania Q-2 4-4-6-4's. These locomotives had pneumatically controlled butterly valves in the steam lines to the front and rear cylinders. The controls were supposed to automatically throttle the steam to the front or rear cylinders if wheel slip was detected on the front or rear set of drivers. I've read that this system wasn't entirely successful, but it does show that WABCO was working on applying automatic controls to steam locomotives. It wouldn't have been a huge jump from these controls to complete MU control (exclusive of firing the boiler).

A patent search may turn up some more info.

Hugh
I vaguely remember reading that a engineer "assistance system" was applied to the T1 that some felt resulted in a significantly lessened control over wheel slippage as well as the Q2 having been tested by the N&W was found to be unbalanced with the greater share of steam being supplied to the front set of drivers. This could be what you are referring to (?) It almost sounds as if the clock ran out on this application and a patent search would prove interesting and I know from other examples that steam controls that were later refined and patented were never applied in an actual test bed. I wonder if this is the case with Wabco's R.U.U..I should have added that I found reference to a Wabco Remote Unit Uniter that sounds an awful lot like this lost technology thats buried somewhere..I'll keep searching. It certainly sounds like the forebear of the MU system.
Bruce

U.S. Patent 2,440,124 - C. K. Steins - PRR - Wheel Slip Prevention Mechanism - April 20, 1948

PCook
Is this the Remote Unit Uniter or an application that's similar? From reading the abstract this device appears to be confined in application to duplex drives or two engines on a single frame versus two entirely separate units..This seems to be very similar in principle but does not seem to fit other the other sources as to it's purpose. Thanks for the Patent #.
Bruce

Bruce,

The patent PCook posted is the system applied to the Q2's. Here's a link to it at google patents:

http://www.google.com/patents?id=alBYAA ... &q&f=false

The problem with Duplex locomotives was that one set of drivers could start slipping, but the engineer's throttle controlled the steam to both sets of cylinders. This system was an attempt to automatically arrest wheel slip if only one of the two sets of drivers started slipping.

I believe the gizmo on the T1's was a pneumatic servo for the throttle, much like a power reverse. I can imagine if it were like a power reverse, it would slow the engineer's ability to quickly shut off the throttle which would NOT be helpful if you were trying to arrest wheel slip.

Dave Stephenson undoubtedly knows much about both these systems; hopefully he'll chime in.

The British did have a mechanical method of controlling a steam loco from a passenger cab car. It wasn't practical for long trains because of lost motion and slack action in the linkage between carriages. A fireman was still needed on the engine. Maybe this method could be used for pairs of locomotives.

The pair of GWR 0-4-2T's which played the part of the main engine in the film "Titfield Thunderbolt" have that remote control feature so they can be run from an "auto coach" with a driver position. That probably explains the extra apparatus seen seen on the backhead.

Steve

I gave a bit of thought to this yesterday, while stuck in traffic; good 'think time'. As stated previously, the economics were against the idea of a diesel leading steam in MU; once diesels gained acceptance in road service, steam was on the way out. Also, the technology for an unattended steam locomotive was in its infancy, although the posts regarding the N&W 4-8-0 showed that automated firing and water tending was possible.

Throttle control, with steam trailing a diesel, may not be all that complicated, if you are willing to accept only eight throttle positions. The Alco 539 switchers and RS-1s had a throttle operator, sometimes called a 'grasshopper motor', mounted below the governor. Three air cylinders, through a series of levers and rollers, operated the governor. A larger version of this could open and close the throttle, in sync with the A, B, C, D, solenoids that a Woodward has.

Cutoff is another story, though. I've never really run steam, just a few light engine and switching moves, but I have fired a fair amount, and know that you start with the reverser in the corner and then hook up as your speed increases. Unfortunately, as I recall, hooking up is sometimes done with reductions in throttle, so using another grasshopper motor, in concert with an F unit or GP-9's four steps of transition, may not work. I think this is a seat of the pants thing that an engineer has to be on the locomotive to control.

I believe the Army 2-8-0 with rotary valve gear may have solved the cutoff problem, but again economics were against any sort of MU development here. Why put any money into automated controls on a piece of obsolete and labor intensive equipment, due to be replaced in the near future?

Fun to think about, though-