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BL28 MU'ed with X44 pass down the Outer Circle. |
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As one is aware, MU is short for Multiple Unit Operation, where two or more locomotives are
controlled from the one cab by the one driver. The loco can be made to be Lead/master loco,
slave loco, or lead loco but not powering itself. Yes this is s simplification of a complex
System.
Model Railways simply couple them together and run, with the locos sharing the current and voltage. For DCC operation you can "consist" them together to do the same thing. At DVR we have always wanted to try MU. There have been many attempts by many different people, and there are no standards set even now. Real locos have plenty of space for all the control equipment, DVR's haven't the space. But with the advent of PLC's, computer control chip etc. more could be done. What is presented below is a summary of some attempts. It is not a definitive description or intended to be a technical resource. One item common to most of these locos is the air system, which allows for MU. Whenever you double head a loco, you have to bypass the slave's brake handle. This is because the lead loco has control of the brakes. So while double heading, the second driver can only power and reverse, but cannot brake. This works into MU system quite OK as a separate system. NT78 - 8792 8792 and NT78 have a limited MU capability. 8792 is always the master loco with NT78 always a slave. Special connections are required along with a physical lever to physically throw the r reverser on Nt78. In operation NT78 provides power as 8792 powered up. But to reverse the 8792 driver has to switch both locos physically (8792 first, then NT78). This system has been around shortly after NT78 was built. No other locos are compatible. PERM - E1103 This system is more of a slug arrangement with the PERM powering the E1103, bypassing E1103's batteries and controls. This was done only a few years ago and has been well used by it's owner. No other locos are compatible. TAITS The privately owned Taits has it's own system, including braking. Each unit can be run with another, and driven either direction. It allows for many a combination The system is closer to that of a model railway, as the Taits motors are permanent magnet motors with batteries. But it works very well. A Harris motor car is being built by another member, Paul Gillard which will be compatible. X44,900,Y121, 700, BL28 OF the systems, this one is the most complex and most expensive, and widely used. It relies on a servo and controller unit out of a ventilation unit. The servo is connected to the throttle, and the controller acts as the throttle. Through a relay and electrical module, the locos can be MU'ed. A basic 4 position switch has the following settings: MASTER, SLAVE, DEAD MASTER, OFF. Dead Master is like taking the lead loco off line yet still controlling the powered units behind. Since every loco fitted with this system also has a remote reversing system (heavy duty relay or home built contacter), One can stop and reverse with no trouble. You can also turn on/off the field switch to ensure the loco will not move even with the throttle moved. There is also a kill switch which just shuts every engine down, and the same thing happens if you pull the MU cable off a loco while in use. There is no ties to the Air system at present. Like any rough standard there is a description of what each pin does on the MU cable. This allows others to built a MU system compatible yet different to the originals. At the moment only X44 has it as a duel control option. All the rest have this system full time. Added to this the Overland Set has the MU cables running through the carriages, allowing us to "XPT" or do a "Bacchus Marsh". There is talk of a plug in controller to allow control in a steam loco ( aka Westcoast) or in another carriage. When we evolve the system some more I am sure We will let others know of the standards, for really it is still "under test". One wouldn't want to start buying equipment now and find we 'moved the goalposts' with new developments. So, stay tuned for more info. For those who are thinking of taking up this system, when your loco is at a stage where you are ready,(ie bogies, frame bodywork, most wiring, and control panel ready to be done) would be the time to contact us to work these things out. |
