MU Operating

[Anonymous]

What are "tying down," "cutting the motor out," and what is the difference between them, for us dieselsemi-literates.

Thanks,
Daniel

[oubliette]

QUOTE: Originally posted by edblysard

Heres another odd way to put nice flat spots on a locomotives wheels.

There are so many causes for flats on wheelsets. We also over here in the UK regularly see locomotives or wagons with flats on the wheels caused by various factors. The most common cause is to drag a wagon or loco with the handbrake still applied to it. I have seen a wagon with flats so severe it had to have a wheelset swap.....not the best wagon to break down in the middle of no where as its cargo was potentially deadly. This was caused by a handbrake being left on the wagon.

Another cause is to drag another loco having left the straight air brake on in the trailing loco. In reality this should be spotted as it should be difficult to get the train moving but if you have so much head end power you can drag a loco for miles and create massive flats. This should all be checked for by the driver before he moves off but in reality these things get overlooked.

It can also happen if dragging a loco as a swinger, i.e. not piped up, so basically the leading loco is dragging a dead loco. Again if the trailing loco's straight air brake is left on this could cause flats or if the air has not been bled off the trailing loco by using the dagger valve to release the brakes from the bogies, (trucks). A swinger is not permitted on the mainline so something like this would only happen around depots or yards.

Dragging brakes caused by faulty distributors or overcharge problems can be a cause of wheel flats or hot axle boxes. I recently saw a 100mph sleeper car come in that was stopped on the mainline as it set off a hot axle box detector. The cause was dragging brakes iniated by a faulty disributor.

Flats can also be caused by to heavy a brake application causing the locomotive to slide with the wheels locked up. There is a distinct mark on the tread when this happens and this is all picked up on the 48 hour exams. If very bad the loco is booked for tyre turning on the wheel lathe to skim of the damage and correct the profile.

If a flat is so bad the locomotive/wagon or unit has to be put on a skate to get it back to a repair depot.

Going back to the original context of the thread MU working. Its quite amusing sometimes when loco's are in multiple and they operate at slighlty different biting/braking points. In theory anything done from the front loco should replicate down the trailing loco's if in multiple. So if power is applied to the front loco the second takes power and if the first brakes, so does the second. Some loco's may for various reasons load up or take power slower or quicker than others. So the lead loco may intially be putting all the power down to the rail whilst the second loco thinks about it before getting its act together. So the first loco is screaming to the second loco "keep up with me." On the other hand the trailing loco may pick up power faster than the first one and keep nudging the back end of the leading loco saying "faster, faster."

Most of the loco's here are fitted with shackles and not buckeye (knuckle) couplings and the stress on the coupling can be severe with the train lurching or banging if the shackle is not wound up tightly.

A dead loco does not provide any air to the train brakes so any air built up in the operating loco's has to blow up the brakes in the dead loco, taking longer to build air. A loco that may not be in multiple but running will provide air to the train brakes. Dragging dead loco's in a train is only really used for positioning moves and also if there is enough brake force within the consist to stop the whole train. Here in the UK we are only allowed to have 5 loco's together on a mainline, whether they be dead whilst being towed or all on line in multiple.

Cheers

Rory

[Anonymous]

[^] Thank you all for your replies. I think I'm beginning to understand something of the operation of a locomotive and a lash-up. For those of you who work in or on locomotives, I envy you, but I'm sure that sometimes, the job has got to be a hassle. I wish I could make friends with a crew that would let me have a cab-ride, but around here, that's not going to happen, unless the local switching crew happens to do it. I don't get a chance to meet any of them, because when they're operating, I'm as far away as I can get so as to not interfere with their operations or distract them, but close enough that I can watch them work. [sigh]

I love the technical details and the comprehensiveness of all of the replies and I'm glad I asked the question. However, it now occurs to me that there are a couple more questions that arise out of this thread.

1) If a diesel-electric locomotive is DIT, do the motors on the trucks generate any electricity (I'm presuming that's the way that dynamic brakes operate, but being a non-engineer, I'm probably wrong.) and if so, where does that juice go, or are the motors electrically isolated so that no current flow can occur?

2) If a diesel-electric locomotive is DIT somewhere back in the middle or the end of the train, are the brake lines connected to the cars on either end, so that in the event of a braking situation, the locomotive will also brake.

Please bear in mind that I'm really not that well educated on locomotive operations. It took me years to realize that steam locomotives use two steam chambers per cylinder so there is a constant application of steam on one side of the piston at all times. When it comes to diesels, I'm even less educated. Hence, the original question.

[bow] [D)]

[oubliette]

QUOTE: Originally posted by Mark W. Hemphill
Traction motor leads connected backwards. This happens too, but normally it's discovered the first time the locomotive is moved under power in the engine terminal. It may also not show up as a wheel slip. If it does it for very long the wheelset will develop an outside flange.

Usually a simple test is done and this is called a rotation test. Basically all the traction motors are isolated apart from one. Power is applied and the wheel should turn in the direction of the reverser (power handle) indicated in the cab. Each motor in turn is tested whilst all the others are isolated. If a wheel spins in the opposite direction then the cables have been put back wrong. Normally when disconnecting them we tape one lead and the same with the socket it came from so there are no confusions when putting back together.

Cheers

Rory

[jchnhtfd]

As Mark said a few posts back, one of the nastiest tings to happen to diesels in MU is to have a motor bearing seized somewhere back in the consists... slid flats, false flanges, and truly spectacular pile ups. A brief review of the DOT web site for wreck investigations shows a bunch of them in the early diesel days. Not so common any more -- both better pinions and better alarms.

For Joe -- if a locomotive is dead in tow or isolated, the traction motors will develope no electricity, as they are disconnected. To generate electricity, as in dynamic braking, they have to have some current supplied by the prime mover (oddly enough) so that they can then generate a lot more -- I know it sounds like something from nothing, but the lot more current is what slows the train down.

[Anonymous]

QUOTE: Originally posted by jchnhtfd

For Joe -- if a locomotive is dead in tow or isolated, the traction motors will develope no electricity, as they are disconnected. To generate electricity, as in dynamic braking, they have to have some current supplied by the prime mover (oddly enough) so that they can then generate a lot more -- I know it sounds like something from nothing, but the lot more current is what slows the train down.

In other words, the prime mover's generator must act as an exciter for the field coils of the motors so that the motors act as dynamic brakes, right? This was what was required on my second ship - the diesels (four 1000HP Caterpillars) provided power to four 1100HP electric motors, with one diesel providing excitation.

[tree68]

I recall reading somewhere not too long ago that the NYC once discovered that they occasionally had wheels slipping in MU ops, to the tune of over 90 or 100 mph. That was before wheelslip control got sophisticated (and probably one reason that it did).

[edblysard]

Hi Daniel,
Tieing down the locomotives,

Tieing down is slang for applying the hand brake, either on a car, cut of cars, or a locomotive.

Cutting the motors away.

Motor is another slang term, means a diesel electric locomotive, most likely came from the first electric locomotives, which used electric motors, the term motorman came from the same place.

Instead of using the term locomotive, or engines, its easier just to call them motors.

Cutting them away means detaching them from the train.

Normaly, whan a crew delivers a train to a yard, they close the rear angle **** on the last locomotive, pull the pin(lift the cut lever) and pull up a few car lengths, then tie a hand brake or two to the cut of cars.

By leaving the angle **** on the cars open, the air brakes go into emergency on the standing cut, holding them in place along with the hand brakes.

Joekc6nix, yes, they generate a current, all electric motors, even when running under power create a back emf, back electric magnetic field.
By setting the isolation switch to isolate, and turning the generator field off, any current is sent to ground.

Ed[:D]

[wabash1]

Bristolian the engine will recieve its signal from the cable pluged in it, this tells the unit which way to go from the end the signal comes from. the headlight switch only tells it which unit gets its headlight on. it has no other function than that. I have left the headlight switches in the wrong position on perpose as i didnt care if i had a light on the rear unit anyways. the only time i need light on the rear unit is when i detach from the train.

trainjunky as ed has said tying down is slang for putting the hand brakes on and securing the train or consist. and as far as cutting the motors out. this means cutting traction motors out. to do this you must isolate the unit and depending on which type of engine you have you can cut out 1 motor at a time or on older emd it was a pair of motors. this happens when you keep tripping the ground relay . in which either there is a dead short or a flash over from one motor to the next. Now when you cut out a motor it reduces its tonnage rating by 10% per motor . if its a six axel unit rated for 5,000 tons with one motor cut out now its good for 4500 tons and it will have no dynamic brakes. when you cut out motors you lose dynamic braking on that unit.

Joekc6 if the unit is in the consist back in the train yes the air hoses haft to be coupled this is the only way the rest of the train gets air for its brakes. there is a valve under the engineers seat that bypasses the engine controls and sets it up like a box car. the main resivior will hold 20lbs of air only and from this air this is what operates the brakes. they will apply with a reduction of the brake pipe only and there is no way to bail them.

[Jackflash]

Ed, if that ever happens again about draging locomotives behind a cut
of cars with out air on the cars get on the controling unit and set the
automatic brake handle in suppersion and bail off the brakes, you can
pull these engines around all day and the allerter wont come on, if the
cars have air on them put the brake handle in handle off and cut out
the brake pipe,, in both cases make sure the independent is released
and cut in.
ALSO...no there is NOT a switch or control on a trailing unit to tell it which
way to go with respect to the controling engine , this little bit of magic is
done in the jumper cable between units AND the foward and reverse wires
at the back end of each engine (the wires are crossed in the jumper cable
and crossed again at the back of the unit) The headlight switch does just
that...control the headlight and nothing more
By the way, on distributed power locomotives (mid-train helpers and un-maned
engines on the rear of trains) there IS a switch that must be set to tell that
engine which way to go with respect to the leading controlling locomotive.
jackflash

[Anonymous]

Thanks to everyone who participated. I did learn more about mu operation. What about the helper units in mid train or the end of the train (pushers). How are they controled? Most cars just have a brake line connection. So how are the units controlled from the front unit to the end???

[kenneo]

QUOTE: Originally posted by Jackflash


this little bit of magic is
done in the jumper cable between units AND the foward and reverse wires
at the back end of each engine (the wires are crossed in the jumper cable
and crossed again at the back of the unit)

And that is how you change the polarity

[hogger42]

QUOTE: Originally posted by nancy

Thanks to everyone who participated. I did learn more about mu operation. What about the helper units in mid train or the end of the train (pushers). How are they controled? Most cars just have a brake line connection. So how are the units controlled from the front unit to the end???

Nancy

In a nutshell, The remotes are controlled by radio signals from the lead unit.

[Anonymous]

Probably doesn't have anything to do with it, but I remember back in the 60s on the B&O a Geep and 5 Fs on a frt train where the lead and 2nd unit died. Quietest ride that crew had into Cinci since the engine came out of Blue Island.... John.

[Anonymous]

Thank you hogger42.

[Anonymous]

Have seen lots of pictures in TRAINS showing steam locomotives having diesels as "backup power". My question is... can a steam locomotive operate a diesel unit in MU mode... or do both locomotives need engineers and fresh batteries for their radios?

Thanks,
Erik

[ValleyX]

Hey Wabash, you'd better study your NS-1 a little closer, that independent isn't to be operating on more than three units if any one of those units is a six axle unit. I'd look the rule up for you but it's upstairs in my grip!
With kindest regards,

[wabash1]

ValleyX

I have rechecked my statement and stand beside it if you find the page in which you say i must cut out the engine brakes then let me know. respectfully I welcome your response. and your opinion.

[tree68]

QUOTE: Originally posted by erikthered

Have seen lots of pictures in TRAINS showing steam locomotives having diesels as "backup power". My question is... can a steam locomotive operate a diesel unit in MU mode... or do both locomotives need engineers and fresh batteries for their radios?

Thanks,
Erik

To the best of my knowledge, both units need engineers these days. On the other hand, the Clinchfield's excursion steam loco was really too small to handle the trains they wanted to run, so they painted a B unit to match the passenger consist, then installed controls for the diesel in the cab of the steam loco. I almost think I saw that loco somewhere not long ago, and the controller was still mounted in the cab.

[ValleyX]

My apologies to you, Wabash, actually, it's in-tow or dead units but since you can only use up to 24 conventional axles under power or 32 on a grain train, we find ourselves in this dilemma frequently. Again, my apologies. As I did yesterday.

[M636C]

Guys,

The discussion made me think of remote control, and the Harris Locotrol system that I've seen in use. That system could just have the remote units working as if they were normal MU locomotives, but to allow operation over steep grades, a second miniature control stand was fitted on top of the control stand in the lead unit, so if you were passing through a long dip in the track, you could have the lead units under power but the trailing units still in dynamics to stop the train bunching at the bottom of the hill, and the reverse over a ridge where the lead units were in dynamic but the trail units were still pushing up the hill.

There have been a couple of really nasty derailments in Queensland with electric coal trains where the lead units stopped but for whatever reason (radio failure due to terrain blocking the signal in one case) the rear units kept pushing until all the cars between the two sets of power (more than 80) were concertina'ed and sitting at right angles to the track.

In Western Australia, BHP would often run trains in two equal sections with remote units in the centre. I watched one day as the second half came up and stopped next to the front half on an adjacent track. When I got my photos back, I realised that the units on the second half had steel plates covering the windows to protect the glass from damage from fine ore being blown off the wagons ahead of the remote units. I then thought, how could the yard crew drive with these plates still in place and realised that the train was being driven from the lead units on the stopped first part of the train on the adjacent track. It was still under remote control, it just wasn't coupled up any more!

Peter

[kenneo]

QUOTE: Originally posted by tree68

QUOTE: Originally posted by erikthered

Have seen lots of pictures in TRAINS showing steam locomotives having diesels as "backup power". My question is... can a steam locomotive operate a diesel unit in MU mode... or do both locomotives need engineers and fresh batteries for their radios?

Thanks,
Erik

To the best of my knowledge, both units need engineers these days. On the other hand, the Clinchfield's excursion steam loco was really too small to handle the trains they wanted to run, so they painted a B unit to match the passenger consist, then installed controls for the diesel in the cab of the steam loco. I almost think I saw that loco somewhere not long ago, and the controller was still mounted in the cab.

The 4449 has this arrangement and I think the SPS 700 does also. Would not suprise me if the two UP steamers also have been fitted with an AAR control stand.

[tree68]

If I remember right, Clinchfield's was mainly just a rotary switch mounted on the front bulkhead of the cab, above the window. Of course, it's a small engine. The more modern engines would have a little more space.

Thanks for the update, Eric.