Bringing heavy trains safely down Donner Pass grades using Cab Forward

[_o_OOOO_oo-Kanawha]

One of the standard scenarios that comes with the Southern Pacific Cab Forward demands you to bring a heavy train safely down the grade in the snow.
The scenario fails and aborts when your train runs away or exceeds line speed a few times too many.

How does one bring a train safely down? What is the ideal speed?

My practice thus far is setting 6-8 PSI brake cylinder pressure when commencing the descent and then lapping the brakes and applying 20-40 % throttle and 20-30% cutoff to keep the speed around 12-14 MpH. Because of the short level stretches, I do not release the brakes at all, just apply more throttle to prevent the train from stopping due to that continous braking. When descending again, I reduce power so the train maintains an even 12-14 MpH again.

Would such practice exhaust the brakes in real trains? Do they need to stop on level track at certain intervals to let the wheels cool down and recharge the reservoirs on each car?

I read in the documentation Tori provided for the COARW that it was C&O practice to set a certain amount of air on the cars during the whole of the descent of the Alleghanies, which is much less steep than Donner Pass.
So that's were I got this information I am using right now and it seems to work. I now dare to let the train accellerate to 20-22 MpH and can maintain that speed by manupulating the throttle on a subsequent run of the scenario.

What was Southern Pacifics practice during the steam era? Braking under power is a waste of energy afterall and all that brake shoe wear leads to increased maintenance.



Was air set on the cars using these so called retainer valves or was the main brakestand used by the engineer?

[_o_OOOO_oo-Kanawha]

Yes, but is "pumping" the brakes safe practice with a 4000 ton train going down a long >2% grade using exhaustible air brakes of crude design?
I suppose those steam era box cars and reefers had single release triple valves only. So once the brakes were released, the car's reservoir had to be filled completely before the next brake application could be made. With a long train and leaks along the trainpipe that should take some time and all the while gravity pulls ....

Anyway, while releasing the brakes in this particular scenario the train quickly exceeds the speed limit and goes into emergency because the scenario aborts.
So I'd rather set this small amount of air on the cars and sort of "pull" the train down the grade.

Where Cab Forwards also used as pushers and did they stay on the train once it got over the top? There is that covered turntable near the summit for a purpose, though I haven't tried to turn a Cab Forward there yet. Were pushers connected to the train line and braked from the road engine? Or were they bailed off and relied on the engineer working the independent brake? Was it SP's practice to cut out the caboose and put it back behind the pusher? If the conductor needed to put the train into emergency by dumping the air, the caboose had to be connected to the trainline, and hence the pusher also.

Interestingly, you meet several opposing reefer blocks using just two GP9 pulling about the same amount of cars. I don't know yet wether open hatches denote empty cars.

[philmoberg]

... So I'd rather set this small amount of air on the cars and sort of "pull" the train down the grade. ...

I knew some old-timers who did this, but it got tricky if the grade wasn't uniform. It helped to have your brakemen clubbing the handbrakes, but this practice largely died-out when steel freight cars began showing up in large numbers. My great grandfather, who was not quite senior enough to become a conductor, at that point, was not sad to see it go.

More often, what they would do - especially on the heavy grades out West - is set retainers at intervals, for example, every fifth car. The retainer would maintain a minimum brake brake reduction (IIRC you had a choice of a 5 of 10 pound reduction on the retainer valve) even when the train line was pumped back up to the full 60 pounds, which was the normal train line pressure for freight in those days. This would help the engineer maintain a more uniform speed while descending a heavy grade. Based on what those who did it have told me, they kept their speed down to somewhere between 20 and 25 mph, depending on what the special instructions for the division required. Obviously, they would have to stop at the bottom of the grade and re-set all the retainers before pumping up the train and proceeding. The closest approximation you and come to retainers is to open the coupling view and set the hand brakes on a few cars

Ice bunker reefers would run with hatches open for a couple of reasons, an obvious one being that they were recently empty, and needed to dry out to prevent mold and mildew developing inside. They might also run with hatches open if they were being used as insulated boxcars for produce, such as bananas, which didn't/shouldn't need to be refrigerated. I remember reefers running with their hatches partially open in the Spring and Fall, but I don't know what they were carrying.

Different railroads had different rules abut whether a caboose would run ahead of or behind a rear end helper. All of the crews I've talked to over the years greatly preferred to be behind the helper, in case of a wreck. I don't know what SP's approach was. Typically - I don't know of an exception in U.S. practice - helpers were cut off at the top of the helper grade, which was not necessarily the summit of the route. In cases in which the caboose was ahead of the helper, the conductor would usually cut off the helper on the fly. The helper's air would be dumped the moment the hoses parted so that it wouldn't be hit by the train it was just pushing when the slack stretched.

[_o_OOOO_oo-Kanawha]

Thanks, Phil, for your elaborate answer.

Slack action, haven't thought about that yet. Pulling a train down a grade against its brakes will probably stretch the train. And since Donner Pass grades are quite uneven in our route, slack will run in and out with all consequences.

I think there is sufficient evidence that being a steam locomotive engineer in those days was a very skillful profession and not without excitement and even danger. You really needed to know the road and your steed very well to make it safely and on time over the Pass in adverse winter conditions.

We can only hope that continuous improvement of RSC's game engine, physics, route and rolling stock will once allow us to feel ourselves real locomotive engineers instead of just players in a train game.
I welcome the Cab Forward to my collection and with an updated Donner Pass in the near future look forward to some exciting new scenarios.
I hope the Cab Forward inspires RSC to bring more key US steam locomotives to our rosters. ATSF, PRR, SP and UP have many desirable engines to add to our fleet.

[XDriver]

I said this elsewhere about running steam down grades. Use your reverser in the opposite direction when going down hill. Play with your percentages on the throttle the reverser and you will get the feel for it. You can find a sweet spot on some grades where you won't even be using the brakes at all. Keep in mine this also consumes fuel so keep an eye on your water and coal/fuel levels while descending.

[Kali]

IRL you'd probably be safe from overheating if you keep down to 20-25mph, although the upper is apparently getting dangerous.

[_o_OOOO_oo-Kanawha]

I said this elsewhere about running steam down grades. Use your reverser in the opposite direction when going down hill. Play with your percentages on the throttle the reverser and you will get the feel for it. You can find a sweet spot on some grades where you won't even be using the brakes at all. Keep in mine this also consumes fuel so keep an eye on your water and coal/fuel levels while descending.

?? Like in braking on the engine of your car when going down a grade ??

Was this prototype practice with US steam locomotives, or merely possible in our simulator (game)?

There was once was a steam locomotive 'engine' brake named after a German engineer Riggenbach. Here the cylinders acted as compressors using special valves, retarding the train going down steep inclines. Water/oil mixture needed to be sprayed into the cylinders to cool the casting and lubricate the liners, pistons and valves. So there probably was white exhaust come out of the smokestack.

[SteelRoad]

I said this elsewhere about running steam down grades. Use your reverser in the opposite direction when going down hill. Play with your percentages on the throttle the reverser and you will get the feel for it. You can find a sweet spot on some grades where you won't even be using the brakes at all. Keep in mine this also consumes fuel so keep an eye on your water and coal/fuel levels while descending.

This is what I figured out earlier. For the 2.5% downgrades I usually kept them near a 50% Reverser/35% Throttle setting IIRC, but I'm probably off on the numbers a little.

[philmoberg]

... Pulling a train down a grade against its brakes will probably stretch the train. And since Donner Pass grades are quite uneven in our route, slack will run in and out with all consequences. ...

That's true, but since you would be pulling at a fairly low speed against a brake application that would otherwise slow the train, you'd end up with more control over the slack than might first be apparent. Still, as you rightly noted, this was a very dangerous business if you weren't alert and careful about it. To think that they were doing this under the Sixteen Hour Law, and a normal extra turn might take all of sixteen hours in all extremes of temperature and humidity, is a real testimony to their strength and fortitude. When I was a kid, the railroads were often criticised for education by osmosis, but when you look at this sort of railroading, the only effective way to learn it was to see it done, day after day, under every conceivable circumstance. My hat's off to them.

[arizonachris]

downhill, I usually kept throttle at about 30%, reverser at zero. self lapping brakes. if i needed to, full train brakes as well as the independents. but usually on B-SB, self lapping did quite nice. OK, full service once in a while. Never emergency.

[_o_OOOO_oo-Kanawha]

Obviously different players use different methods of descending grades driving steam locomotives.

"Retarding by steam" using reverse throttle sort of makes sense to me, but due to the laws of thermodynamics generates lots of backpressure and heat as the superheated steam entering the cylinders is compressed further. It should make for really powerful and loud exhaust, hence perhaps the "blast splitter" over the Cab Forward's smokestack?

Zero reverser should not allow any steam to enter the cylinders, and IMO is therefore the same as pushing down the accellerator pedal of your car with the gears in neutral, i.e. useless. And dangerous in a steam locomotive as the cylinders aren't lubricated while there is stil heat generated by the compression of air. I even think it is not possible to move the engine at all until the opening of the cylinder cocks or by the use of some snort of snorting valve. Must look into that Riggenbach power braking system to make sense of this.

I will try all mentioned methods to satisfy my curiosity, but will probably stick with Phil's explanation and methods as these comply with the few operating rules I have read on this subject.

I hope I am not boring you all my persistent inquiries into practices long gone and forgotten, it only makes driving trains more realistic for me to stick to prototype practice as far as the sim allows.

But which of these is prototypical to Southern Pacific using Cab Forwards on Donner Pass I still don't know? I'll go try and find employee timetables or rulebooks online since I don't own any books on SP and Donner Pass or Cab Forwards.

[Kali]

In the UK it wasn't generally accepted good practice to stick a steam engine in the wrong gear, although I've noticed shunter drivers ( switchers ) would sometimes use it to slow down the last few mph quickly. Our steam-era heavy freights generally didn't have continuous brakes at all - you stopped at the top of the hill & applied all the handbrakes, and that was it other than the brakevan.

I don't know if US engines had pressure release valves on the cylinders - some of ours did so that you didn't blow the end of the cylinder off if it tried to compress water.

[philmoberg]

... "Retarding by steam" using reverse throttle sort of makes sense to me, but due to the laws of thermodynamics generates lots of backpressure and heat as the superheated steam entering the cylinders is compressed further. ...

I'd offer you a couple of comments on this. In essence, Riggenbach's system worked effectively for two reasons: 1.) the train weights involved were relatively small, and 2.) he developed this for locomotives using the rack system he also invented, and being rack locomotives, there was no tendency to slip under load as there is, to a greater or lesser extent, for all types of locomotives operating on adhesion alone. These are the reasons his system was not widely adopted. BTW, if you ever have a chance to visit Luzern, go to the Verkershaus and see one of these with the cylinders sectioned: it's a remarkable testament to the extent they were stretching their technology in those days.

Under the sorts of train weights prevailing in North America, this system would be impractical because of the relatively small cylinder displacement compared to the mass being restrained. Assuming the locomotive didn't slip, and the train's velocity was slow enough, you could probably get away with it. The green eyeshade types might grumble that the additional wear and tear on the locomotive was not worth it, compared to having to change out a bunch of brake shoes; but that, in theory, at least, would be the worst of it. The problems start to happen if your locomotive slips: this applies some fairly extreme dynamic loads on the cylinders, rods and crankpins more-or-less immediately, and the consequences can be serious. Apart form the damage to the rails, both from engine burn and hammering, you'd run the real risk of breaking a crankpin or a rod. The best case consequence of such an occurrence is that you would end up with an immobilised train blocking the main, which would then require a great deal of time and effort to clear. More likely, you'd end up with at least some of the train in the ditch, requiring an even greater effort to clean it up. For example, the story is told of one of a Pennsy T-1 that broke a side rod just just behind the forward crankpin: the rod then swung backwards and began slapping madly, slicing off chunks of the cab - and leaving the engineer literally within an inch of his life - until it sliced off the brake stand, dumping the air and throwing the locomotive off the rails.

Railroaders, being a cautious bunch, didn't need to crunch the numbers to conclude that the potential benefit wasn't worth the potential cost, and chose to stick with the aggravation of clubbing brakewheels and setting retainers. This began to change with the advent of the early DC electrics using regenerative braking, and subsequently, diesels with dynamic braking. In those cases, the only thing that would slip would be already-rotating masses, which could be brought under control much more quickly and easily. Subsequent improvements in locomotive power and braking have made it possible to handle heavier and faster trains in such conditions. The dangers of mountain railroading are different these days, but require no less attention and respect than those that earlier generations faced.

[_o_OOOO_oo-Kanawha]

Railroaders, being a cautious bunch, didn't need to crunch the numbers to conclude that the potential benefit wasn't worth the potential cost, and chose to stick with the aggravation of clubbing brakewheels and setting retainers. This began to change with the advent of the early DC electrics using regenerative braking, and subsequently, diesels with dynamic braking. In those cases, the only thing that would slip would be already-rotating masses, which could be brought under control much more quickly and easily. Subsequent improvements in locomotive power and braking have made it possible to handle heavier and faster trains in such conditions. The dangers of mountain railroading are different these days, but require no less attention and respect than those that earlier generations faced.

Thanks again, Phil, for your elaboration.

I conclude therefor that Tori's excerpts from her COARW operating manauls are correct. Steam train crews either set handbrakes or retaining valves at the top of the grade on a certain number of cars depending on grade, weather and season and either coasted or "pulled" the train downhill against the brakes. At the bottom the trains stood still for sufficient time to fill the reserviors, turn up the retainers, let the wheels cool and have all trucks visually inspected for sticking brakes, cracked wheels etc.

Passenger cars don't have retaining valves right? US heavyweight passenger trains could easily reach 1200 tons and more during the steam era.

Were Cab Forwards also used on passenger trains over Donner Pass or did SP put GS4's up front?

[philmoberg]

... Passenger cars don't have retaining valves right? US heavyweight passenger trains could easily reach 1200 tons and more during the steam era.

Were Cab Forwards also used on passenger trains over Donner Pass or did SP put GS4's up front?

Tori's information squares with everything I've heard, as well as what I've read from various special instructions in a range of employee's timetables.

Now that you mention it, I don't remember seeing retainers on any of the old passenger cars I worked with, but then the line I worked on was was relatively flat. Passenger trains typically ran with 90 pounds in the train line (as opposed to 60 for freight equipment), and since there were far fewer cars in a passenger train, the brakes tended to be more responsive. The rule-of-thumb was that it took one second per car for the brakes to be fully applied, which would be less than half a minute for a 25-car limited, as opposed to a minute and a half for a 90-car freight. There was a similar savings in slack action, and once tightlock couplers became common, passenger train slack was again significantly reduced. If push came to shove, the handbrakes in the vestibules could be wound up, but nobody I knew could wind a handbrake tighter than a 90 pound application. One of my fellow trainmen learned this lesson the hard way when he wound up a couple of handbrakes after the engine crew had cut off for the end of the day: they simply let the air dump when they cut off for the last time, and we couldn't budge the handbrakes until the next morning, when they pumped the train line up again.

I've seen at least a couple of pictures of Cab Forwards on passenger movements over Donner, one of which appeared to be a mail and express train. I would have to believe that, at least with respect to the longer and slower passenger movements, this was more the rule than the exception: GS-4s weren't drag engines, by any means.