drews trackside adventures shows a CN Locomotive in the middle of a train helping to push things along. Can a loco in the middle be MU’ed to the front?
Gary
Yes, if it is equipped with the proper radio equipment. They are called distributed power units, or DPUs.
As northwest says, yes. They are controlled from the lead unit, and the DPU in the middle, or on the end, as the train crest a hill or grade, can still supply power to push, while the lead unit can be in dynamic braking.
It's done by radio control.
From what I've read, in the days of steam, there was an engineer and fireman on each locomotive, and signals between locomotives was done with the whistle.
Mike.
My You Tube
Thanks for the replies. I had no idea this was done with Steam too. Much shorter trains albeit.
Before radio control, the helpers were manned whether diesel or steam.
While DPUs have eleminated most of the manned helpers they still exist.
Montana Rail Link uses manned mid-train helpers westbound out of Helena, Montana over Mullan Pass.
CSX uses manned mid-train helpers on the Sand Patch grade, when coupler forces require it. Otherwise they used manned pushers.
It is an economical question when to use run-through DPUs or to cut in manned units when the additional power is necessary only over a short distance.
NS uses manned pushers westbound out of Altoona, PA.
There might be more helper districts.Regards, Volker
Yes, if extra power is only needed for a few miles, but the rest of the run can easily be handled by the power at the front of the train, it doesn't make sense to drag the helpers along. Plus one helper set can assist multiple trains that ways. Easy to see at Horseshoe, you can watch a train being assisted up the hill, then the helpers come back running as a light engine move, then another train assisted up with the very same helpers pushing at the rear.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The DPU system allows up to 10 additional radio-controlled locomotives to be distributed with control signals for power and dynamic brake settings via dedicated radio frequencies. The DP units have their air brake systems set up so that brake pipe reductions affect them just as they do rail cars in the train. The system is highly automated and each DP unit to be added is entered by road number into the control display of the lead locomotive. In the DP units the same thing is done with the lead locomotive's road number and once the systems are properly set, the units are "linked" via radio frequency.
The greatest benefit of Distributed Power—and the reason for development of the original concept—is the reduction of drawgear draft forces, permitting the doubling in the size of trains without exceeding draw-gearstrength, through the use of mid- or rear-train locomotives.[2] There are also potential train handling benefits; over an undulating track profile, a skillful engineer can manipulate the relative power outputs (as well as dynamic and air brake applications) to minimize run-in and run-out of coupler slack throughout the train."[3]
Reduced draft forces along a train will reduce the lateral force between wheel and rail on curves, thus reducing fuel consumption and wear on various running-gear components as well as the potential for a 'stringline' derailment.
Another benefit is quicker application of standard air brakes. With all braking control at the front on a conventional train, it can take several seconds for brake-pipe pressure changes initiated by the engineer to propagate to the rear. Under radio-controlled distributed power operation, the brakes are set at remote locomotives simultaneously with the command initiated on the lead locomotive, providing a more uniform air brake response throughout the train.
trevorsmith3489 The DPU system allows up to 10 additional radio-controlled locomotives to be distributed with control signals for power and dynamic brake settings via dedicated radio frequencies. The DP units have their air brake systems set up so that brake pipe reductions affect them just as they do rail cars in the train. The system is highly automated and each DP unit to be added is entered by road number into the control display of the lead locomotive. In the DP units the same thing is done with the lead locomotive's road number and once the systems are properly set, the units are "linked" via radio frequency. The greatest benefit of Distributed Power—and the reason for development of the original concept—is the reduction of drawgear draft forces, permitting the doubling in the size of trains without exceeding draw-gearstrength, through the use of mid- or rear-train locomotives.[2] There are also potential train handling benefits; over an undulating track profile, a skillful engineer can manipulate the relative power outputs (as well as dynamic and air brake applications) to minimize run-in and run-out of coupler slack throughout the train."[3] Reduced draft forces along a train will reduce the lateral force between wheel and rail on curves, thus reducing fuel consumption and wear on various running-gear components as well as the potential for a 'stringline' derailment. Another benefit is quicker application of standard air brakes. With all braking control at the front on a conventional train, it can take several seconds for brake-pipe pressure changes initiated by the engineer to propagate to the rear. Under radio-controlled distributed power operation, the brakes are set at remote locomotives simultaneously with the command initiated on the lead locomotive, providing a more uniform air brake response throughout the train.
You can have 4 additional DP consists, in addition to the lead consist. The Remote Consist leader can have engines MU'ed to them, but there can be limits to how much power can be used on each individual consist.
The DP engine's air brakes are not normally set up like a box car. They operate the same as the lead's air brake. Otherwise they couldn't apply or release the automatic air brake. When the engineer on the lead consist makes a 10psi reduction, the remote consist(s) make the same 10psi reduction. The engine's independent bails off when the lead consist's independent is bailed off. There are situations that will cause the DP's brakes to cut out and go into "boxcar" mode. Until they can be reset or cut in, they then act just like a boxcar. They won't be able to apply or release the train brakes. Throttle and dynamic braking are the only thing that can be operated independently of the lead engine.
Jeff