OvermodI am not sure whether older pusher operations understood the concept of the 'node' as in modern DPU operations: that with power both pushing and pulling there will be a point within the train where coupler force (and hence draft-gear action) is effectively zero, and of course forces 'fore and aft' of that point will be proportionally reduced.
The Rio Grande did. Helper ops using swing helpers over Tennessee Pass are often cited for requiring exactly this sort of play between train weight and the distributed power. Videos show this was the case even in the days of steam, as articulated helpers were distributed in this manner. Diesels simply changed the form of the power, not its distrbtion. The peak of this practice is generally considered when done with the Tunnel Motors although I also saw the newer SP AC power working over it before it was...gone, except for the rails.
Mike Lehman
Urbana, IL
On Cajon pass all east bound Santa Fe trains have several helpers at the head end. But when they reach the ruling grade, which is the steepest part of the pass, the train stops and a couple of pushers which are waiting on a siding are added to the end of the train. They push the train up to the summit then they return by themselves back to the siding so they can push the next train. They are constantly busy because this is a very busy mainline. There is only one set of pushers but they only push just a couple of miles.
Overmod The situation gets a bit blurrier when ATSF and UP used steam locomotives, some of remarkably low top speed, to assist streamlined diesel trains up some of the severe grades in the West. While this had the effect of increasing speed somewhat over what the diesels themselves could have accomplished, I get the distinct impression that where a 2-10-2 is the power concerned the ability to get up the grade is more important than how fast the feat is accomplished.
The situation gets a bit blurrier when ATSF and UP used steam locomotives, some of remarkably low top speed, to assist streamlined diesel trains up some of the severe grades in the West. While this had the effect of increasing speed somewhat over what the diesels themselves could have accomplished, I get the distinct impression that where a 2-10-2 is the power concerned the ability to get up the grade is more important than how fast the feat is accomplished.
The grade over Raton Pass, for example, was compounded with very tight curves so increased speed wouldn't have been needed, or desired.
Ray
Overmod...with power both pushing and pulling there will be a point within the train where coupler force (and hence draft-gear action) is effectively zero, and of course forces 'fore and aft' of that point will be proportionally reduced....
That's to what I was referring in my previous post. I hadn't even considered that scenario until I actually saw it occurring.
Wayne
Something that hasn't been brought up yet (and is only of technical interest in modeling practice, I think) is that PRR, and perhaps other roads, made a clear distinction between two kinds of assist. One kind is when trains of a particular weight are given assistance to 'just' get them over a particular obstacle, probably at what becomes very low speed at the point of maximum resistance. The other kind is when speed is important, and the extra power allows negotiating the obstacle at higher peak speed and hence in shorter time... this of course being important for many passenger trains and for expedited fast freight.
This is where that odd-sounding term 'snapper' likely comes from; it's not just a quaint regionalism. You wouldn't put a pusher on the rear of a passenger train, and of course you wouldn't cut it into the middle of the consist; I suspect that even with long consists you're not concerned with pullaparts of various sorts. So it makes sense to put the snapper on the front, effectively turning the power on the point into the equivalent of a bigger locomotive.
The situation gets a bit blurrier when ATSF and UP used steam locomotives, some of remarkably low top speed, to assist streamlined diesel trains up some of the severe grades in the West. While this had the effect of increasing speed somewhat over what the diesels themselves could have accomplished, I get the distinct impression that where a 2-10-2 is the power concerned the ability to get up the grade is more important than how fast the feat is accomplished. So that would be a 'helper' rather than a 'snapper' in context.
I am not sure whether older pusher operations understood the concept of the 'node' as in modern DPU operations: that with power both pushing and pulling there will be a point within the train where coupler force (and hence draft-gear action) is effectively zero, and of course forces 'fore and aft' of that point will be proportionally reduced. Without the model equivalent of dynamometer car instrumentation measuring coupler forces, I can't say to what extent electrically powered locomotives would mirror what independent diesel-electrics, even coordinated by DPU commands, would produce as in-train forces.
Andy made a video about this a few years back. Helpers are becoming rare in the real world RCL and DPUs have replaced crews. There are some places where helpers and still needed first is the Blue Mountains in Oregon on the OSL Railroad UP who manages the line adds them at LaGrande and takes them off at Hinkle. Soldier Summit on the Rio Grande also uses them they go on at the appropriately named town of Helper and they are taken off in Provo. Also you see them in the Alleghenies on CSX railroads Sandpatch Grade also known as Blue Ridge and on NS' Horseshoe Curve. If you need to lug a heavy train over a mountain call a helper.
jacon12 wrote:Here in central Georgia, where the land is fairly flat I don't think I've ever seen a helper pusher. Many double and triple headers of course. I would imagine that as you get more up into the Appalachian Mountains it may be common.Thanks for the information.Jarrell
Jarrell...I have, just south of Atlanta. A 108 (give or take) car coal drag, and 3 or 4 locos pulling, 2 pushing.
Rotor
Jake: How often does the train go by? Elwood: So often you won't even notice ...
I've run long trains (over 60 cars) on my layout with a pusher on the rear end. Because of the shape and size of the room, and my trackplan, there are many curves (34" minimum on the mainline) and many grades (2.8% maximum), both up and down. With careful handling and attention to proper speeds, such trains can be run safely, even on my DC-powered layout. It's quite interesting to watch the point of neutral slack move throughout the length of the train as different parts of the train move uphill and downhill at the same time, all the while coiled around several curves in various directions.
It's important that locos, rolling stock, and track be in good condition and up to standards, but there's no reason why anyone shouldn't be able to duplicate this feat, with some care.
Steam trains used multIple crews and engines for operation. Early diesels used Radio Control. Today they have MU 'connections and R.F.
Model electric train simulation is tricky to push a string of 'empties' since everything is designed for 'pulling'. A 'dummy' engine being 'pulled' SIMULATES the prototype with far less problems.
If you are needing more power, do whar Santa Fe did... add a string of matched ABBA units. Yes, they and their crew sat on a siding until needed.
Even with matched engines, I'd put the fastest one on the point. (We play with TOY trains).
BCSJ wrote: markpierce wrote: Chuck said: " If either the road engine or the pusher stalls abruptly, the loco that's still running will simply spin its non-traction-tired drivers. That's the whole point of a train that neither locomotive can move alone. "Well, how did I as a guest operator once turn over almost an entire train twice in one day when the pusher stalled and the lead locomotive pulled the cars over to the inside of the curve? MarkThere was evidently too much power on the head end. When your helper stalls (or even if it gets throttled back), this kind of thing can happen. My point was that if the lead units will simply spin their wheels with that train without a helper, than adding a helper at the rear won't be any more of an 'anchor' for the train than just the train itself. But if the lead units can string line an unassisted train then running helpers becomes much more dangerous.I designed my curves, train lengths and MU head end power with this in mind. The result is I've not (knock on plywood) had this kind of a problem (yet).The live loads will also represent an especially tough case since the loads will raise the center of gravity of thes cars making them much more susceptible to super elevation problems.Regards,Charlie Comstock
markpierce wrote: Chuck said: " If either the road engine or the pusher stalls abruptly, the loco that's still running will simply spin its non-traction-tired drivers. That's the whole point of a train that neither locomotive can move alone. "Well, how did I as a guest operator once turn over almost an entire train twice in one day when the pusher stalled and the lead locomotive pulled the cars over to the inside of the curve? Mark
Chuck said: " If either the road engine or the pusher stalls abruptly, the loco that's still running will simply spin its non-traction-tired drivers. That's the whole point of a train that neither locomotive can move alone. "
Well, how did I as a guest operator once turn over almost an entire train twice in one day when the pusher stalled and the lead locomotive pulled the cars over to the inside of the curve?
Mark
There was evidently too much power on the head end. When your helper stalls (or even if it gets throttled back), this kind of thing can happen.
My point was that if the lead units will simply spin their wheels with that train without a helper, than adding a helper at the rear won't be any more of an 'anchor' for the train than just the train itself. But if the lead units can string line an unassisted train then running helpers becomes much more dangerous.
I designed my curves, train lengths and MU head end power with this in mind. The result is I've not (knock on plywood) had this kind of a problem (yet).
The live loads will also represent an especially tough case since the loads will raise the center of gravity of thes cars making them much more susceptible to super elevation problems.
Regards,
Charlie Comstock
Again, the theoretical. Helpers are added BEFORE the steep grade begins. Thus, the beginning grade is minimal and the power of the lead locomotive will be GREATER than that needed to pull the train at or near its starting point. I remain of the opinion that safe pusher-helper operation needs reliable and responsive equipment and control systems, as well as skilled operators. (I'm a quick student, and would welcome any open invitation to engineer a helper.)
markpierce wrote:Chuck said: " If either the road engine or the pusher stalls abruptly, the loco that's still running will simply spin its non-traction-tired drivers. That's the whole point of a train that neither locomotive can move alone. "Well, how did I as a guest operator once turn over almost an entire train twice in one day when the pusher stalled and the lead locomotive pulled the cars over to the inside of the curve? Mark
tgindy wrote:If there is a caboose in your train - as to the prototype...Pushing a metal caboose is much better for your health than pushing a wooden caboose.
If there is a caboose in your train - as to the prototype...
Pushing a metal caboose is much better for your health than pushing a wooden caboose.
Actually, it's the frame that's the important factor here: wooden frame goes behind the pusher, steel frame ahead of- or behind, depending on each road's particular practice. There were many wooden cabooses with steel underframes. I run steel-frame cabooses, but generally place them behind the pusher, as it adds an extra operational dimension.
A pusher waits, with its caboose, for another train to clear...
...then backs to the waiting coal drag...
Back in the 70's a couple long coal trains went through my neighborhood every day to service a power plant. They ALWAYS had helpers in the middle even though the line was pretty flat.Trains and locomotives did a show this mourning on the UP Cascade division. They'd pick up pushers in the last town before the grade and drop them in the first town after the grade. (I assume to wait for a return trip train to help going the other way)
Conemaugh Road & Traction circa 1956
BRAKIE wrote:Guys,You can add a pusher in the DC mode without any complications if both locomotives are close in speed...DCC is great but,there are many things we done long before DCC and of course the nay sayers of today.
Guys,You can add a pusher in the DC mode without any complications if both locomotives are close in speed...
DCC is great but,there are many things we done long before DCC and of course the nay sayers of today.
You got that right, Larry. I have run pushers and mid train helpers (steam and/or diesel) on my DC-powered layout many times, with no problems, including coal trains with "live" loads. As Chuck mentions, one loco shouldn't be able to move the train on its own: in other words, the helper is needed, not for appearance sake, but as tractive effort. The locos should have similar starting characteristics, and, like the prototype, speeds should be kept fairly low.
Helper service, to my mind, is the one area where DCC could be used to good advantage, although not by programming both (or all) locos to start and run the same. Rather, set each loco to more closely match what its prototype would offer in the way of speed, then assign an operator to each loco. See what you can learn about train handling instead of letting technology do the job.
Ahhhh.... You have found the quandry (or at least the main difficulty) of designing a helper grade!
To be "safe" the lead engines (no helpers) should spin their wheels when a train is too heavy WITHOUT the train stringlining. If this happens then even if a rear helper stalls and anchors the train to the track the lead power will not be able to stringline the train. This depends on a couple of things
Some people like helpers enough that they run what I refer to as "cosmetic" helpers - the helpers are there for appearance rather than because they're needed. This often is just asking for trouble.
Properly designed a helper district should be operable even by somewhat newbie crews without too much difficulty (probably not the place to put the guy who's having his first throttle time though...)
basementdweller wrote:I understood that once a pusher got to the top of the hill it would return to the bottom on the end of a decending train and provide additional dynamic braking.
Only true for diesels with dynamic brakes. You won't get much dynamic braking from a Y-6b, or from the 2-6-2T and (occasionally) B-B diesel-hydraulic that I've assigned to pusher duties. They get to run downgrade light - in their very own timetable-authorized slot(s).
Pusher service probably originated on the first railroad that had one steep grade and two locomotives - well before Herr Diesel was born.
Chuck (modeling Central Japan in September, 1964)
danmerkel wrote: SpaceMouse wrote:Going way out there on the speculative side of things.Could you not on a DCC layout, create a consist using the helper and the main locomotive, and synchronize them by running them unattached and adjusting speeds? Taking that a step further, couldn't you then form a different consist for each locomotive that uses the grade using the same helper so that every train was synchronized? But think about this... as the head engine hit the grade, it would slow down as the load of the cars going uphill increased. The engine at the rear, wouldn't. Conversely, when the head engine topped the hill, it would start to speed up as its load lightened; the rear engine wouldn't. So it would take coordination beyond just running two engines at the exact same speed.dlm
SpaceMouse wrote:Going way out there on the speculative side of things.Could you not on a DCC layout, create a consist using the helper and the main locomotive, and synchronize them by running them unattached and adjusting speeds? Taking that a step further, couldn't you then form a different consist for each locomotive that uses the grade using the same helper so that every train was synchronized?
But think about this... as the head engine hit the grade, it would slow down as the load of the cars going uphill increased. The engine at the rear, wouldn't. Conversely, when the head engine topped the hill, it would start to speed up as its load lightened; the rear engine wouldn't. So it would take coordination beyond just running two engines at the exact same speed.
dlm
I run a helper service in my
Bear Creek & South Jackson. I run the headend and helper engines with separate cabs to 1) avoid the problem mentioned above, and 2) because helper crew is a skill position (and a lot of fun). It definitely does take a bit of skill to shove an overweight train up the 2.8% grade between Mill Bend and Oakhill on my layout (and it was designed with that grade for that reason!)
One of the reasons I like to 'have the boyz over for an op session' is the interaction between the crews. The addition of a separate helper engineer increases the interaction (as well as making another head-ache for the DS to get the helpers back to the bottom of the hill!)
Cheers,
PigFarmer1 wrote: I know it's easy money, but try sitting for hours on end doing nothing and it's not all that much fun.
I know it's easy money, but try sitting for hours on end doing nothing and it's not all that much fun.
I can relate to that. In the submarine service that is what the majority of my day consits of, and it can tend to get quite old, sometimes we have to invent ways to entertain ourselves.
Why do helpers need to be manned nowadays since locomotives can be remotly controlled? Maybe I'm trying to compare apples to oranges, but I figure if you can cut in some extra power without haveing to pay an extra crew wouldn't the railroads try to go that route?
Jason
Modeling the Fort Worth & Denver of the early 1970's in N scale
To answer the other part of your question, helper crews may sit for 12 hours doing nothing. It depends on the helper district. On U.P.'s Powder River Sub. we have a set of helpers stationed at Shawnee Junction, Wyoming and more often than not those poor crews sit there for twelve hours doing absolutely nothing because the helpers are only used if needed and they're usually not needed. I know it's easy money, but try sitting for hours on end doing nothing and it's not all that much fun.
Back in S.P days helper crews working Donner were always busy because they were running 40+ trains a day and most of them required helpers. Those were the days.
markpierce wrote:Well, how did I as a guest operator once turn over almost an entire train twice in one day when the pusher stalled and the lead locomotive pulled the cars over to the inside of the curve? Mark
I lived near the Roseville yard on the SP during the 80s to DPUs and UP merger. The SP always called them helpers. Westbounds from Sparks usually had four 3,000 plus hp units on the front and up to a six unit helper set of 3,000 plus hp each about 2/3 back. Eastbound usually had four 3,000 plus unit on the front and a 3,000 plus hp unit pushing behind the caboose. In both directions dynamic braking was also provided by helpers.
One problem with this setup is when one or more units slip on a sharp curve as happened on the Sacramento river near Dunsmur.
On my own HO layout I had a long helper district where I used two powered units on the front and one powered helper pushing. I always watched coupler strain and the lower power of my helper keep things in order. I never had problems.
Rob
Chuck said: "Actually, Mark, the majority of my couplers are mounted on trucks - of the troublesome (From Thomas the Tank Engine) variety - 4-wheel freight cars."
I was aware of that, but I presumed the axles were several times further apart than the typical 5+/- foot wheel base of the typical truck.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
markpierce wrote: tomikawaTT wrote: .... As long as the pusher isn't pushing the road loco and/or the road loco isn't pulling the pusher, there shouldn't be any problems.Chuck (modeling Central Japan in September, 1964)Theoretically, and assuming all your cars like to be pushed uphill on your track. Chuck, I think I know you well enough to assume you don't have coupler-mounted trucks, least on your freight cars. Problems occur when one locomotive stops or starts unexpectedly and abruptly on a curve. These circumstances can't always be prevented. Go slow to minimize the potential disaster.Mark
tomikawaTT wrote: .... As long as the pusher isn't pushing the road loco and/or the road loco isn't pulling the pusher, there shouldn't be any problems.Chuck (modeling Central Japan in September, 1964)
.... As long as the pusher isn't pushing the road loco and/or the road loco isn't pulling the pusher, there shouldn't be any problems.
Theoretically, and assuming all your cars like to be pushed uphill on your track. Chuck, I think I know you well enough to assume you don't have coupler-mounted trucks, least on your freight cars.
Problems occur when one locomotive stops or starts unexpectedly and abruptly on a curve. These circumstances can't always be prevented. Go slow to minimize the potential disaster.
Actually, Mark, the majority of my couplers are mounted on trucks - of the troublesome (From Thomas the Tank Engine) variety - 4-wheel freight cars.
If either the road engine or the pusher stalls abruptly, the loco that's still running will simply spin its non-traction-tired drivers. That's the whole point of a train that neither locomotive can move alone. As for speed, maximum track speed on that grade is limited to 40kph (about 25mph) due to the curves and ongoing construction (modeled, not actual.)
I don't think my insistence on bulletproof track construction is any secret to Forum regulars...