Helper Locomotives

I've seen it in prototype operation and I've seen it on film where a locomotive will be put somewhere in the middle of a train to help move a
really heavy load such as a coal unit train. But can someone tell me how this actually works.
If the loco in the middle is actually pushing the cars in front of it, then it would take the slack out of the couplers of the locos that were pulling and they would no longer actually be pulling against anything.
Does the loco in the middle actually just keep the slack out of the coupler just in front of it and actually pull everything behind it or what. I can't seem to comprehend how this operation works. If this were the case, then it would appear that it would take a lot of skill on the part of the operator in the middle locomotive.
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On 8/9/2007 9:48 AM wa-kiki spake thus:

Couple things (and I'm guessing here, as I don't know for sure, but am pretty confident this is close to the truth): with a helper either at the end or middle of the train, I'm guessing the cars between the head end and the helper "float" to some extent, with pulling strain on the cars behind the head end, but with some (not all) cars pushed by the helper. In any case, the helpers still make their full contribution to moving the train along.
You're correct in guessing that it takes some skill to handle such a train, as it will behave much differently from a train with only head-end power.
So far as operators go, there are no operators in the helpers: they get operated simply as more MUs. (I'm not sure of the details, and am curious how exactly this works: how exactly are the signals communicated between locos? do helper locomotives get different signals from the head-end ones, to make them respond differently? anyone know for sure?)
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wrote:

    Back in the the Steam Era, MUs didn't exist. I do know the engineers had to co-ordinate things, usually by whistle blasts I believe. Could be wrong though. How else could they do this before modern communications systems.
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On Thu, 09 Aug 2007 10:15:54 -0700, David Nebenzahl
>So far as operators go, there are no operators in the helpers: they get

Ive you put the lead loco in throttle notch 5, the helper will go into 5 as well. Same for dynamic braking. Also if you draw off 15 lbs of air on the lead locomotive, the helper will also draw off 15 lbs.
Something I didn't mention in my other post, is that using either rear or mid-train helpers is also beneficial with the airbrake system, because the brakes come on faster and release faster than they do on a conventional setup where you have all locos on the head end...and most especially on a longer train, where it takes a while for a brake pipe reduction to become effective on the rear of a train (and more-so in cold weather).
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wa-kiki wrote:

Think of it in terms of two separate trains running _very_ close together. If the head loco pulls harder than the mid-train loco then it will begin to pull the mid-train loco as well as it's own train. If the mid-train loco begins to move more than it's share then it will begin to take up the slack and push the wagons ahead of itself. In each case the unloaded loco will have less work to do and will gain on the other.
One limitation of train length is the strength of the couplings and placing motive power at the middle of the train allows the train length to be doubled. Depending upon the stability of pushed wagons, the center loco might be placed somewhere between halfway along the train to 2/3rds along the train. At 2/3rds, the center loco would probably never by pulled by the head loco but would always be pushing in addition to pulling it's own section of train.
There was an article in MR some time in the 1980s in regard to a Canadian ore train (resin casting N scale hoppers) which described the operation with locos at the head, center and rear, the remote ones being radio control MUed from the front loco.
In model form our locos can't be pulled or pushed due to the worm gear drive normally fitted, so trying to recreate this sort of operation is likely to result in the wagons between the separate locos being 'stringlined' on curves. (pulled off the track)
Greg.P.
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wrote:

Greg we use 'manned' helpers on our club layout and it works fine as long as the helper engineman keeps an eye on the train to keep from being dragged by the head end where he could stringline the train on a curve or pushing too hard and popping cars out from the train ahead of him. We only use rear helpers and don't do mid train, since we have 'steel framed' cabooses we don't cut the power in ahead of he caboose. We use Digitrax DCC for control.
This is on 140 ft of uncompensated 2.5% grade with four 90 degree curves and one 180 degree curve.
See http://www.emraonline.ca/design/levels.shtml the portion described is from Edgewood on the lower level through Fire Valley to Monashee Summit on the upper level.
Have a look at the main page at http://www.emraonline.ca/ to see more of the layout including photo tours and a 'cab ride' in MOV format (about six minutes), the cab ride takes you down the helper grade.
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Mountain Goat wrote:

I run banked trains - train locos at the head, pusher(s) at the rear on 1:40 gradients and 22" radius hidden spiral. The banker locos have push only couplers and have higher gear reductions and smaller drivers (steam locos) The (model) train locos run slow due to the train load and the bankers run fast due to being "light" so they stay in balance. Perfect pickup is vital because if the train locos were to falter the train would "pop" as the coupler system has almost no slack. Analogue control and 3 crossovers in the spiral.
Greg.P.
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Greg, I would really like to see your layout. Do yu have a photopic (or similar) site? Shane
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scoot wrote:

Hi Shane, no I don't as the layout is still 90% without scenery and just now is standing on it's side surrounded in cartons awaiting the new house being built. (about Christmas-time if the council ever issues the consent)
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wrote:
>Greg we use 'manned' helpers on our club layout and it works fine as

I've always thought that modelling a DP/Radio train was the PERFECT use for dummy locomotives. Unfortunately hardly any manufacturer offers dummies any more, and I don't know why... There are some people who'd buy them for collection purposes if nothing else, simply because they are less than half the price of a powered unit.
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snipped-for-privacy@earthlink.net wrote in

Funny, I see all kinds of dummy locomotives around when I visit my LHS. Perhaps I simply pay more attention to those useless things...
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wrote:

The dummies you see are probably older Athearn units. I don't know of a single current manufacturer who is still offering dummy units of currently manufactured locomotives, except for Athearn's OLDER line of engines which are still being produced...and I'm not sure if they are still making new dummies of those...could be you're seeing what's been in stock for years, as a lot of people just don't want a dummy locomotive.
None of the newer line of Athearns are offered in dummies, nor are Atlas, Proto 2000, Kato, Broadway Limited, Tower 55, Precision Craft Models, etc.
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As stated above -- dummies of recent loco models are very rare. A fairly recent one I can think of though is the Genesis F units used in the Walthers Super Chief set. That included an AB powered set of Fs and a dummy AB set of Fs. The price of the dummy set wasn't less than half though. The powered set's MSRP was $255 and the dummy set was $200. If for some reason you had to have a dummy you might be able to scrounge around and find the components and put one together yourself. The cost and time to do that wouldn't be worth it and you might actually do it cheaper by yanking the drive from a powered unit.
J. Bright
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wrote:
>As stated above -- dummies of recent loco models are very rare. A fairly

That's my whole point...back in the "old" days you used to buy a powered Athearn unit for about 3 times the price of a dummy...case in point...I have an old SD40-2 powered for $26.50 US dollars (back about 14 years ago), and I also have a non-powered one that cost $10.50 (bought during same period of time).
I don't see why the manufacturers couldn't offer current locomotives with dummy options. Really on most model railroads, you don't need the pulling power of two or three locomotives in many cases, but you want the LOOK of two or three locomotives.
Running dummies would eliminate problems DDC MU's, gearing problems, etc. Also for anyone wanting to run distributed power trains (as we were discussing) you could have the look of DP without actually having powered units in the middle (or on the rear).
Considering that an average locomotive costs about 100 dollars these days, I don't see why they couldn't offer dummies for 50 dollars or less. I realize a lot of the cost of current locomotives are in the shells, detail parts and paint schemes, but considering that models with DCC and sound are about double the price of DC models, I'm sure that there'd be a substantial price difference between straight DC models and dummies.
It'd be a more cost effective way for one to increase their locomotive fleet. Also some people (such as myself) would probably buy dummies for display purposes, to put on shelves, or dioramas, where they didn't want to spend 100 or 200 bucks on a locomotive, but might be willing to spend 40 or 50 for a dummy model.
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I'd guess that with the increased demand for detail, the drive train is becoming a less & less expensive part of the entire model. I'm told that the difference in Bachmann vs. Spectrum locomotives is in the detail on the exterior, not in the mechanism.
dlm
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wa-kiki skriver:

You set the power on all engines from the loco in the front.
On rough terrain it is a demanding job for the operator to keep the train running smoothly.
(by the way try your question in alt.binaries.pictures.rail there are som "train-operators" writing there)
Klaus
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wrote:

Uh, my good friend, there is no operator in the midtrain units...they are operated by remote control, radio linked to the lead locomotive...
Likewise, in many cases when pushers are used, there are often no one operating them, but rather radio controlled too. Generally if a pusher will be on the train the whole trip it is radio controlled, but if it is only temporary (such as up a particular hill) then it will be manned and will be added and cut off as needed.
The way it works is that the pusher or mid-train helper pushes against the cars in front of it (and in the case of a mid-train unit) also pulls on the cars behind it...this reduces the drawbar effort of the locomotives in lead position...thereby allowing them to pull easier. Also when cresting hills and you have part of the train going back down hill, you still have power pulling the rest of the train up hill. As a general rule you are supposed to reduce throttle settings when cresting hills to reduce drawbar forces on the Knuckles and drawheads, or you could tear the train in half. Sometimes when you reduce the rear slows down and actually starts pulling the opposite direction increasing the possibility of "getting a knuckle" or ripping a drawhead out of the end a car (or engine). Using mid or rear train helpers helps reduce this possibility in many situations. Also, there are generally restrictions on how many powered axels can be online on the head end of a train, as well as how many axels of dynamic braking can be used. On the Norfolk Southern, just for an example, in most situations if using 6 axel locomotives, You can have up to 3 powered locos online, but only two of them with dynamic brakes operating. But, you have have or or two mid-train (or rear end) helpers operating with all axels online as well as dynamic brakes.
As a general rule, mid-train helpers will be 60% of the way back...so if you had a train with 100 cars, the mid-train unit would be behind the 60th car, with 40 cars trailing it. Of course in the real world, you'd not likely see a midtrain unit on a 100 car train, but rather 150 car train...unless the terrain was extremely demanding.
100 car (or less coal trains) usually have a radio-remote pusher on the rear, due to sheer weight of the loaded cars.
Norfolk Southern runs some coal trains with two locos on the head end and two on the rear. All four are under power on the loaded run, but when the cars are emptied, only the head end locomotive and the rear end locomotive are under power, the ones on the inside are shut down for fuel conservation and because they are unnecessary.
Back in the hey-day of Southern Railway (and early NS) they used a radio-receiver car that was fitted with MU cables and hoses. Southern could use ANY locomotive in their fleet as a mid-train helper (sometimes called a mid-train "slave") . Sometimes they'd have just one in the middle, sometimes more than one. The lead engine had to be equipped with Locotrol (the radio transmitter and control panel for the remote setup). The lead engine would transmit to the radio receiver car, and that car would relay instructions to the locomotives in the middle through the MU setup...which would make them respond as if they were up on the head end MU'd directly to the lead locomotive.
Nowadays, NS and other railroads have locomtoves that are especially equipped with the transmitter/receiver equipment, so as long as the lead locomotive and atleast one of the mid-train locomtives are equipped with "Distributed Power" equipment, you can run them as a "radio train" (or some call it a DP train).
Running a "radio train" is not the same as a regular train, as you have to be careful when cresting hills or you can tear a train apart as I've mentioned above.
Does this help you understand any better?
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On 8/10/2007 3:46 PM snipped-for-privacy@earthlink.net spake thus:

While we're on the subject, and since you actually seem to know how this stuff works, I'm curious: since the helpers are linked by radio to the cab, what kind of fail-safe mechanism is there if the communication link is lost? Does the train automatically go into emergency? coast to a safe stop? blink on some dispatcher's screen somewhere?
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On Fri, 10 Aug 2007 18:09:35 -0700, David Nebenzahl

That's a really good question, and YES you do lose communication with the helper units quite often. I had a train one night that I thought I was never going to get the rear-end helper to link up at all with the head end, but finally after stopping and resetting the system 3 times, it linked. You actually go through a check system before you depart to make sure you have radio communications. To be honest, they've never told me what happens if you lose communication permanently. I would imagine that after so many minutes the unit would probably go into isolation until communication was restored. But helper units are just like EOT's, they do go in and out a lot. EOT's sometimes go out and stay out, and the only way you can fix them is to stop and have someone reset it on the EOT itself (or in some cases replace the battery, if it's battery powered...or replace the whole EOT).
But just for the record, a train wouldn't go into emergency for a situation like that...just as it doesn't go into emergency if the engineer fails to reset the alerter in time...instead the locomotives would automatically draw off a full-service brake application which would bring the train to an easy stop. Going into emergency could cause jack-knifing. You only want to use emergency when there actually is one (i.e. car, truck, pedestrian fouling track, obvious signs of track damage ahead, large trees across track, etc.). And rules state you must also shoot the air from the EOT as well, since it takes awhile for the emergency application to reach the rear of the train...that way you have the application initiated from both ends travelling toward the middle, thus reducing the possibility of jack-knifing.
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It helps a lot, but I'm still not sure how the operator determines how much power the helper locomotive needs to do it's job efficiently. Can they tell how much tension is on the couplers and determine the power requirement from that?
And wow, I never even thought about the lead locomotives going down a grade while the helper is still pulling up the grade. This is much more complicated than I first realized.

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