7mm Richards P48 US Thread

[simond]

I’m puzzled by a diesel prime mover running rich.

You don’t throttle a diesel, you run it progressively weaker to reduce its power, so at full chat, it should be given *all* the fuel it can burn. If it isn’t burning it, that suggests too little (mass of) oxygen in the cylinder.

This suggests that the turbo boost pressure is low, the altitude is too high,(same thing), too much fuel, clogged/blocked air filters, or the oxygen content of the feed air is reduced. The first three are within the bounds of the designer‘s calculator, the last might be a bit difficult to estimate. Perhaps the airflow around the leading locos is sufficiently limited, and the combined consumption of the first few is enough to compromise the ones further down the train?

 

[mickoo]

It’s a lack of oxygen, the exhaust gasses deplete the oxygen for the following engines, bear in mind it’s not unknown for SP to have six or even eight engines on the point with speeds as low as 8-10 mph, sometimes lower; you need a lot of oxygen to keep those running clean.

I can’t find my reference but I’m sure SP helper crews were issued with portable oxygen sets on Donner, they certainly still are on Mullan to this day on MRL.

There are plenty of videos showing trailing engines at the head end, exiting a tunnel belching thick black smoke which quickly turns clean once clear of the portal in fresh air.

 

[mickoo]

Blossberg, aka, Mullan 2023.

Head end has three units on, two GE and one EMD, EMD's always burn rich in tunnels and because Mullan is manned helper territory they try to run all GE's up front, however, EMDs are really good on coal drags so they occasionally turn up on point.



Note smoke from tunnel portal just around the bend, caused mainly by this EMD at the head end. The exhaust is gradually clearing up in fresh air.



Moments later it has virtually fully cleared.



Mid train manned helpers, an all EMD consist, no exhaust as they're in dynamic braking mode as the majority of the train (ahead) is now downgrade. Coal trains are split roughly 70/30.



MRL really looks after it's engines and the intake filters are cleaned regularly to reduce rich burning, but even so this is the result of the smoke from the four EMD's. I believe the portable oxygen packs are full face to protect the eyes.

 

[mickoo]

Mike Danneman did a photo study of MRL at Helena, engine intake filter changing on a helper set.

Changing SD70ACe air filters by Mike Danneman, on Flickr

 

[richard carr]

Thanks Mick

That's all really helpful to know.

Richard

 

[mickoo]

No problems, as an aside, the Krauss Maffi hydraulics for SP and DRG also suffered terribly with engine breathing, not radiator cooling like EMD, SP over Donner and DRG over Moffat.

The car body trial units had intakes high up on the roof and both SP and DRG trialed extended vents/funnels to drag cooler air from below, later the ducts were placed inside (certainly on the DRG units and a grill along the floor was made, an easy spotting feature when they went to SP later.

Engine intake at high level above the tradesmen.



DRG scabbed intake funnel on the outside.



SP did something similar.



Finding good photos of these scabbed ducts is like finding unicorn poo, though the book mentioned below has a good selection as well as official reports and anecdotes to the issue.

Later DRG with internal duct and low level intake vents.



Later DRG under SP ownership.



In the end it was the hydraulic drive which was the Achilles heel, they simply couldn't cope with hour after hour at max torque on the heavy grades and high temps in tunnels; eventually they were all transferred to the flat lands away from mountain grades.

R J Zenks SP & The KM Hydraulics is a worthy read (if you can find a copy) I did manage to find one a few years back in mint condition and it cost a small fortune. There is a 2nd edition due this year 124916-SOUTHERN PACIFIC AND THE KM HYDRAULICS 2ND EDITION

Normal service is resumed

 

[AJC]

I know it isn't the American way, but the foregoing really does make a decent case for electrification. Or a base tunnel [tongue firmly in cheek].

Adam

 

[mickoo]

I know it isn't the American way, but the foregoing really does make a decent case for electrification. Or a base tunnel [tongue firmly in cheek].

Adam

A couple of Cascade tunnels were electrified, Stevens pass on the GN and St Pauls Pass on the MILW. The GN had 50-60 miles electrified through Stevens pass but the MILW had whole divisions electrified spanning several hundred miles (600 or there about).

Both were ripped out as life expended and new fans installed to cope with diesel fumes.

Donner never operated any fanned tunnels that I'm aware of but Stevens was and still is as is Moffat. Mullan was original force vented but they were removed in the 80's when the tunnel was enlarged to take high double stacks and widened to aid engine breathing.

Mullan fans were on the east side at the bottom of the grade so pushed air up the slope, incidentally, the same way as loaded trains; Stevens is flushed from the top and pushes the air down grade against trains coming up.

Mullan fans during dismantling.





Stevens was and still is capacity limited, it's around a 40 min cycle to fully vent the tunnel so the line is limited to a maximum of 24 trains per day but these days it's less.

Donner, tunnel motor territory, is slightly different, it has a lot more tunnels spread over a longer distance, but it also has a lot more snow sheds, even though one side is open or partially open to the scenery, they still generate a lot of heat at the top of the portal.

Donner now has a new 'base' tunnel which I think is naturally vented and the line used to have something like 40 tunnels on the route, though that might include snow sheds and they also double up numbers where the line divides and there are two tunnels through one outcrop.

 

[AJC]

Really interesting, Mick. I knew a little about the other systems, but I’m still surprised that fume related capacity restrictions haven’t resulted in the capital investment, either in effective ventilation or wires. As I said, it’s just not the American way (it’s as much a product of institutional cultures as anything else, no end of examples in the UK and elsewhere - the Western’s long-established ambivalence about timekeeping, a standing joke even on the modern railway, for example). Just a different way of doing things, that’s all.

Adam

 

[mickoo]

One final digression on tunnel cooling and only because it's DRG and they used tunnel motors, this is the Moffat tunnel ventilation control panel.

I'm trying to think of an excuse/workability to have something like this on my layout for the summit tunnel even if it's just an automated sequence of lights, ammeters and flow meters to simulate the train passing through off scene.

 

[timbowales]

That is one serious piece of kit
Tim T

 

[David Waite]

I remember reading about a steam locomotive that was working from a low to a high altitude area that was replaced
by a modern powerful diesel locomotive of equal power only to find that the diesel could not do the work of the steam locomotive, so a second diesel locomotive was supplied and were worked in tandem to pull the same load as the one steam locomotive did, the reason for this was the high altitude had less oxygen and so the efficiency of diesel engine was reduced. I desovered this problem myself with my 1969 ford Cortina I once owned it ran well in Melbourne at sea level but once up in the hills of The Great divide it ran poorly so I would adjust the carburettor mixture screw to suit which gave me power once again I then naturally readjusted it when I was back in Melbourne.
David.

 

[Stephen]

I remember reading about a steam locomotive that was working from a low to a high altitude area that was replaced
by a modern powerful diesel locomotive of equal power only to find that the diesel could not do the work of the steam locomotive, so a second diesel locomotive was supplied and were worked in tandem to pull the same load as the one steam locomotive did, the reason for this was the high altitude had less oxygen and so the efficiency of diesel engine was reduced. I desovered this problem myself with my 1969 ford Cortina I once owned it ran well in Melbourne at sea level but once up in the hills of The Great divide it ran poorly so I would adjust the carburettor mixture screw to suit which gave me power once again I then naturally readjusted it when I was back in Melbourne.
David.

Additionally the boiling point of water decreases at higher altitude, thus making it easier for steam locomotives to maintain pressure.

Cheers,

Stephen

 

[simond]

Additionally the boiling point of water decreases at higher altitude, thus making it easier for steam locomotives to maintain pressure.

Cheers,

Stephen

Er no. The boiling point of water in an open container will indeed reduce with lower pressure, and thus at higher altitude, but the temperature of the boiling point of water inside a closed boiler at say 160 psi will be the same at the top of Everest and at sea level.

it’ll not be a big difference, but the exhaust back pressure at altitude will be a little less, so a given loco should work marginally better at altitude than at sea level.

atb
Simon

 

[simond]

I remember reading about a steam locomotive that was working from a low to a high altitude area that was replaced
by a modern powerful diesel locomotive of equal power only to find that the diesel could not do the work of the steam locomotive, so a second diesel locomotive was supplied and were worked in tandem to pull the same load as the one steam locomotive did, the reason for this was the high altitude had less oxygen and so the efficiency of diesel engine was reduced. I desovered this problem myself with my 1969 ford Cortina I once owned it ran well in Melbourne at sea level but once up in the hills of The Great divide it ran poorly so I would adjust the carburettor mixture screw to suit which gave me power once again I then naturally readjusted it when I was back in Melbourne.
David.

if you get a chance to look at old piston aero engines, you’ll see that they typically had superchargers or turbochargers to ensure that the mass of air in the cylinder (which is the practical limit for the amount of fuel that can be burnt) is as constant as possible throughout the operating altitude range of the aircraft.

 

[Stephen]

Er no. The boiling point of water in an open container will indeed reduce with lower pressure, and thus at higher altitude, but the temperature of the boiling point of water inside a closed boiler at say 160 psi will be the same at the top of Everest and at sea level.

it’ll not be a big difference, but the exhaust back pressure at altitude will be a little less, so a given loco should work marginally better at altitude than at sea level.

atb
Simon

I stand corrected!

cheers,

Stephen

 

[richard carr]

Time to get back to some modelling.

The overland GP60 has been progressing, everything is now painted grey. I have been reprofiling the wheels and narrowing the trucks. I have also stripped the gearboxes and regreased them.





And then the truck gets put back together.



Narrowing the trucks is reasonably easy, the side frames screw to the bolster so all you need to do is drill new holes nearer the centre. You then have to shorten the axles. All very doable but it does take quite a while.






When are you are putting one back together remember to check which side frame goes where, they aren't all the same !

The speedo is now in the correct position on the front truck.

 

[richard carr]

The other thing JB and I have been working on is building the gradient on the layout. This is to take the mainline up and over the industrial area and turn back above part the existing fiddle yard for the S7 layout.



the gradient is 1 in 35, it looks steep, I suppose it is, but thats what we need to clear excess height boxcars !



Oh dear it looks like we are bit short !

OK for ordinary height boxcars



After a day of thinking about it the solution was fairly straight forward.

Lift the end up by 12mm with some plywood then fill in the gap with a bridge

 

[mickoo]

Most modern US main lines aim to keep to 2.2% (1:45) but Cajon pass track 3 is 3% (1:32) and used mainly for downgrades but can be used for upgrades of lighter trains, less than 8,000t I think I read somewhere.

Saluda (closed) was the steepest I think at 4.7% (1:21) and there are a few other main lines around 3.3% (1:30); BNSF 3.25% for Raton and Glorieta.

That's all for main line heavy tonnage, short line and branches can be much steeper and give the length of trains you'll run and motive power then you can easily (realistically) go steeper, BNSF branch from the Boeing facility in Everett is 5.6% (1:18) but they only shift light weigh aircraft parts (fuselages etc) up there.

Another trick is to have a ruling 1:35 then a short section of 1:30 or so to gain the height needed, railroad grades are rarely the same grade all the way up so some deviation is prototypical.

 

[Big Train James]

Oh dear it looks like we are bit short !

Unless the ramp is to be relocated elsewhere, I'm having a difficult time understanding why you need to clear trackage below in this particular position. There doesn't appear to be anywhere for the lower tracks to go, on either side of the bridge?

The gap does seem to have moved down a bay, as in later photos it is no longer under the outlet box.

Jim