Mixing steam and diesel in pusher service

Model Railroader Prototype information for the modeler
1

A key aspect of CPR mountain division modelling is emulating a pusher service.

We designed in and built a fairly complex pusher storage track at the base of our steepest grade together with return mainline crossovers and a “back door” access to our engine yard and parallel connection to our main freight yard. While these connections are not necessarily prototypical as built they do compress a number of features that would have to exist in the prototype in some fashion.

I just acquired a copy of Lavallee’s book Canadian Pacific Steam Locomotives and, to my surprise, it includes pictures of diesel locomotives and steam locomotives consisted in pusher service. This could be fun to include in our modelled operations. It seems that book has achieved collector status and I am now looking for the companion diesel volume.

But, my question is, how common was this? I can see for the occasional emergency situation but how about as a routine operation during our lengthy transition era out here.

Given that diesel and steam operate quite differently, I would guess only very skilled engineers could drive these mixed consists, particularly the steam engineer. The engineers would need high levels of confidence in each other especially on these very dangerous grades (so dangerous, particularly downgrade, we still have fatals even with the most modern train control technology available). Modelling pusher service is pretty much the pinnacle of model railroading in this area and for all eras.

One really fun aspect of modelling CPR mountain division pushers is you get to buy a lot of extra locomotives for no particular reason, and some really big ones that. They just weren’t needed to haul any trains, just push (most often pulling in the steam era although pushing from the back was also done). CPR built several unique 0-6-6-0 (Rapido, are you there?) just for pushing over the Big Hill and the Rogers Pass, both in the early days before the long tunnels were

2

May depend on what you mean exactly. If you’re talking about a diesel engine and a steam engine being assigned to work together for weeks or months as essentially one ‘pusher’ to help trains over a grade at a particular location, I would think that was extremely rare. If you mean just a diesel powered train having a steam engine helper added at some point, or a steam powered train having a diesel engine added, that would be fairly common.

It did happen that to get enough horsepower that a diesel and steam engine would be assigned to pull a train for it’s run, but that negated a chief benefit of diesels - that multiple diesels could be controlled by one engineer, where a steam engine and a diesel (or two steam engines) would each require a separate crew.

3

There were plenty of examples of mixed steam and diesel power on consists, and even steam and diesel together in helper consists. Remember that any two locomotives (or more) can be incorporated in real-world consists and not ‘fight’ each other – would that the model world were a bit more consistently like this! – but just as different diesels load at different rates and have different speed-related restrictions, steam develops torque ‘worse’ at very low speed compared to diesel, but can sometimes work effectively while the diesel is still in short-term traction motor restriction, and of course has what may be a steeply rising characteristic up to the effective horsepower peak.

Crews experienced enough to run these types of motive power will probably understand how to run them efficiently ‘together’ (and in any case keeping the locomotive ‘just off slipping’ is a perfectly adequate technique to maximize dbhp and efficiency together). Expect the diesel to do the lion’s share of the work up to its amperage restriction in near-instantaneous loading, with the steam engine probably kept in relatively wasteful long cutoff up to what may be the speed of low-end TM restriction, probably about 10-12mph for road gearing.

4

Technically speaking you cannot “consist” diesels and steam locomotives together at all - the diesel set and every individual steam locomotive would have its own crew. Steam locomotives can’t control diesels or each other, so when double- or triple-heading trains with steam locomotives, each engine had it’s own crew. A diesel or set of diesels can definitely take the place of a steam locomotive and double-head with a steamer… just the diesel and steam engine both are operating independently with separate crews, and those crews have to manually keep them operating together.

5

Technically speaking, the power ‘consist’ is the makeup of locomotives pulling a given train, not whether or not they are in MU.

6

There will always be two camps in the model world, I guess. Those who think any locos consisted must run in perfect lockstep across the entire speed range, and those of us who realize people ran locos together long before DCC and a super precise setup is not required. However, the nice thing about some sort of command control be it DCC or something prior to that, is that you can run helper operations with full crews very easily. There, it might be more fun if the locos were widely different - then it will take skill and coordination between the two (or more) engineers driving their locomotives. Add open hoppers with live loads and now there’s more at stake than just derailing a car…

Modern era of course there are mid train helpers that are remotely controlled, so there’s that, but in my modelered era, if another set of diesels coupled on the back, or a steam loco was used, with diesels up front, there was always another crew involved.

I’m looking for pictures to see if I can see any evidence of diesels and steam locos used together to push trains on my railroad. Steam locos were heavily used as pushers on diesel powered trains, as they lived out their last years in such service. Certainly would be interesting to see both coupled on the back of a train shoving.

–Randy

7

I often run trains with multiple locos, either all on the head-end or with some pulling and others pushing, along with locos interspaced within the train, and, in the time before I backdated my layout to the late '30s-era, this included both steam and diesels…of course, much simpler that the real-life steam/diesel combinations, as all of mine run only on electricity.

My layout, DC-powered, has lots of grades and curves (many occurring at the same places), and most trains operate with more than one locomotive. If a train requires multiple locomotives to move it efficiently, I have found that almost all locomotives, steam or diesel, will get along pretty-well as far as speeds are concerned.

The two locos shown below did illustrate somewhat of an exception, though…

The 34 is a modified brass locomotive, with a good-quality can motor, while the 37 is a modified offering from IHC, also with a can motor, but of lesser quality.
When starting, the 34 responds well to the handheld DC throttle, and begins to pull the not-yet-active 37, along with a few of the trailing cars, until the applied voltage is sufficient to get participation from the 37. From that point on, the two locomotives run very well together, each contributing to keeping things rolling, which is especially important when they get to the aforementioned grades. I eventually replaced the 37’s motor with a better-quality one, and they now start in unison.

Before I backdated my layout to the late '30s-era, I often ran trains in excess of 70 cars, using steam and/or diesels, in various combinations, with some all on the head-end, or split front and rear, and even dispersed throughout the train.

In all cases, as long as the train actually needed that amount of motive power, the locomotives got along just fine speed-wise.

8

In my neck of the woods I’ve seen quite a few instances where steam helpers were added to diesel trains and vice-versa. B&O’s Sandpatch and PRR’s Horseshoe curve are two that come to mind immediately.

PRR_Bennington by Edmund, on Flickr

When I emulate it on my layout I simply assign one throttle to the diesels and another to the helper.

PRR_T-E7_sm by Edmund, on Flickr

Cheers, Ed

9

Just the information I was looking for. On the CPR the helpers were called pushers regardless of where they were inserted into the train. They were inserted on level track. That would eliminate the problem of getting the train moving with the widely differing traction force effects.

I have noticed that different model locomotives generally pull well together when loaded. The odd back and forth hunting you get due to different gearing and motor characteristics shows up worst under light load on level track.

I particularly appreciate the separate operator aspect of these pusher operations available under DCC control. The slight disagreement (semantics again) about whether a consist also has to be MU (arguably yes for Diesel, at least after MU control was introduced, but of course never possible with steam) combined with the connection made to the difference between DCC consisting and DC consisting (a rather neat parallel I thought) resulted in a serendipitous thought applicable to our layout. As for prototype mixed steam and diesel we could, once DCC is in operation, use a separate operator to run the pusher service. Thanks v much for that unasked for idea.

While we currently enjoy 100% DC block controlled operations we have wired so that DCC can be inserted easily, for one booster. If we add a second booster we will need to also rewire the return bus* by disconnecting at appropriate bus bar(s) to create a separate power district for each booster. A direct return wire will then connect the separated bus bar to the applicable booster. As I now understand how DCC and DC power delivery methods differ. I think.

*our DC uses “common rail” but double isolated so the return wire “rail” is actually a series of 16 gauge bus wires cross connected only at bus bars. The rail itself is not common anywhere outside a block.

10

Widely differing traction force didn’t matter. Picture a tug-of-war with, say, ten hefty brutes on each team. Along comes a skinny, wet behind the ears kid and joins in. Bingo, that’s all that’s needed for a win.

There were a times when some of the New York Central passenger trains needed help out of the station at West Albany hill. The station switcher, an 0-8-0 as I recall, would be coupled to the rear of the train for assistance. Yes, most roads did not use pushers on the rear of passenger trains but the NYC did, at least in this limited capacity.

That helper was cut off “on-the-fly” as the train continued west.

The Clinchfield had a small steam locomotive (#1 a 4-6-0) used for excursions. They mounted an EMD control stand in the cab that was “wired” to a trailing B unit for added tractive effort. Not exactly MU but almost there.

Regards, Ed

11

Maybe I should be doing this on my layout. I have never used pushers. [:'(]

Rich

12

Exhibiting at train shows, using my Digitrax DT501 throttle, I double head my Proto 2000, 2-10-2 with my Bachmann EM-1, 2-8-8-4 one on 35 steps, the other on 52 steps to give a scale 25 mph, though I should add this is on a mainly flat track. (I should also add my diesels are “consisted”.)
So, I should be able to use one as a pusher though I’m not sure I would as I’d like to be able to keep a close eye on both locomotives. Knowing my luck, I’d end up with a large derailment.

You’re quite right Wayne, though I’m not sure I actually have that much trust in my local MRs to be able to concentrate without having the BIG OOPs, as already mentioned.
Cheers, the Bear.[:)]

13

I’m normally in single power mode on my layout, but two years ago I applied my PCM Y6-b to the rear of a string of 19 H2a hoppers trailing a Class A. I didn’t consist them digitally, but played with the two handy encoder knobs on my DT400 throttle until they worked in concert, and there were no derailments. It was kinda fun, working both locos separately, and so easy to do with the DT400.

I have yet to consist two locos…ever. I think I’m with Wayne on this; it’s more fun, and more prototypical, to have to manage two diverse engines at either end of a long string of coal hoppers going around curves, on a grade.

14

Of course things have gotten a tad more sophisticated since then. UP844 has had full MU (of trailing power) for many years; it was instrumental in the notorious ‘driver flatting’ episode a few years ago.

2926 has one:

http://www.nmslrhs.org/Sidebar/NewsLetters/Library/Vol-XVI-No-4.pdf

765 has one:

https://c2.staticflickr.com/8/7121/8165222301_62e63172d0_b.jpg

There is a wealth of material on remote-operating multiple steam locomotives from a common cab in conjunction with the later years of the ICC ‘fling’ with mandated ATC between 1930 and 1928. Much of the technical detail of one of the better systems survives, essentially buildable, in the Sprague files at the NYPL. Full control of throttle and cutoff is needed for proper ATS, let alone managed speed control.

The ACE3000 proposal was designed to be operated in MU from a leading diesel … not that it would work well in practice, but all the theoretical work was done. There are many developed systems for controlling external-combustion engines of various kinds ‘in servo’ with 8-notch MU leading. Even in states like Ohio that specifically disallow power boilers above a certain size (200 boiler horsepower there) you would only need one man, not two, on a trailing steam unit o

15

As mentioned above, using steam and diesel together was common place on the B&O.

In fact, the B&O quickly realized diesels made better helpers, so early ABBA sets of FA’s and EMD F3’s and F7’s were assigned as helpers on Sand Patch, Cranberry and other grades.

Cranberry grade required helpers in both directions, ABBA diesels did not need to be turned. and only required one crew, as opposed to the two 2-8-8-0’s they replaced.

Yet, most of the trains they were helping were still steam powered.

This practice lasted until the switch to diesels was complete.

Also the WESTERN MARYLAND, I have a series of photos, showing a mix of 5 Consolidations and 4 ALCO RS units moving about 100 hoppers out of one of their mine branches. The trackage and curves did not allow bigger power.

That is one locomotive for every 11 cars. The locos were split up into lead, mid train and pushers, with no regard for the position of steam vs diesel.

Like Dr Wayne, I run DC and have no trouble using steam and diesel together, or using a mix of different steam wheel arrangements and brands of locos.

Example, my Proto 2-8-8-2’s run perfectly with my Spectrum 2-6-6-2’s. Nearly all my trains require more than one loco.

Sheldon

16

I’ve done it on a few occasions but — you’ve really got to be on your game.

If the lead power stalls and your pushers keep pushing you really will need that crying emoji. Similarly, if the pushers are coupled to the last car and stall while the head-end keeps pulling, well — [banghead]

Still, it does add an interesting aspect to operations. Just keep an eye on things while you’re at the throttle.

Cheers, Ed