Rockies climb throttle position question
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Siegmund
Lead Service Attendant
Most likely yes, if there is no traffic ahead of you to slow you down: a quick back of the envelope calculation suggests that with ~8000 HP pulling 2 engines and 10 cars up a 2% grade with 10-degree curves, you would max out at around 35 mph.
In the F40PH days, I was on a CZ/Desert Wind/Pioneer that briefly got delayed by traffic and slowed down to walking speed. While we theoretically had the power to maintain 25 mph or a bit better, if we had been GOING that fast, we weren't able to accelerate well enough to achieve that speed, and wound up creeping along at ~10mph for a while and overheating the engines; we stopped somewhere high up in the tunnel district, before Rollinsville, and sat for about an hour, then tried again and proceeded without incident.
In the F40PH days, I was on a CZ/Desert Wind/Pioneer that briefly got delayed by traffic and slowed down to walking speed. While we theoretically had the power to maintain 25 mph or a bit better, if we had been GOING that fast, we weren't able to accelerate well enough to achieve that speed, and wound up creeping along at ~10mph for a while and overheating the engines; we stopped somewhere high up in the tunnel district, before Rollinsville, and sat for about an hour, then tried again and proceeded without incident.
Thanks for the info. I appreciate it. Two other questions, if you don't mind. How loud would it be in the engine room or the cab when under full power? Also, I know that they use 2 units, as one is needed for hotel power. Does one locomotive provide the electricity and the other for motive power, or do they share it? Thanks again.
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Not really on topic for the California Zephyr, but I rode in the lead locomotive (an FP7A) of the eastbound CP Canadian on the steep grade east of Field, BC in 1977. I do not recall that the noise in the cab was excessive. The locomotives seemed to handle the grade very well.
Siegmund
Lead Service Attendant
One unit can do both (and does on shorter trains: the Portland and Seattle sections of the Empire Builder get one unit each). A quirk of the P42s is that the generator is limited to a lower RPM when supplying hotel power (it has to produce exactly 60Hz electricity, not just run flat out) - such that each unit can either produce up to 4200hp for propulsion only, or up to 3500hp divided between hotel and propulsion - so if you have more than one unit, you usually want one unit providing all the hotel power.
On a train like the CZ climbing out of Denver you would probably have one unit putting all 4200 into the rails, the other putting a few hundred into the hotel load and 3000 or 3200 into the rails.
I don't have any specific numbers re the sound. Loud enough I wouldn't care to be in it. The soundproofing in the cab has to meet OSHA limits, which are going to be somewhere around 85dB.
I got to do the same thing in ~’83 in an FP-9. Such an awesome experience for someone in 6th grade. I’ll agree, it was loud when they actually had to use full power. I really wish this was an option today.
Update: We went up the hill rather slowly. At Grandby I saw the engineer walking around and he said that one of the locomotives was down and that he had been running full power. That was pretty impressive when you think that they were pulling a 2% grade and supplying hotel power at the same time.
That locomotive had a Roots blown 2 stroke that could howl. Beautiful sound.
I'm curious why the engines overheated. At 10 MPH they weren't in run 8, but even if they were, I don't see why it would matter. I would think that, to the prime movers, only throttle position matters and not speed. 74 MPH in the 8th notch should be the same as 15 MPH at the same setting to the engine. In addition, wouldn't the cooling systems keep the temps where they should be?
I'm not disputing what you said - I'm sure you know what you're talking about. I'm just interested in the reasons behind it. Thanks.
ehbowen
Engineer
It may not have been the prime mover which overheated. The electrical drive system also is prone to heating up, especially when run at high power and slow speeds. I have an F3 manual from the bad old days with an ammeter chart showing the limits of what the traction motors could take. The system is different now, but I-squared-R is still the same.
I see what you mean. He said "engines," which is what threw me off. I think with AC motors it wouldn't be a problem, but I bet these have DC. ACs can pretty much take whatever you throw at them.
Siegmund
Lead Service Attendant
At a distance of 30 years it's hard to provide too many details --- when I said "engine" I meant those-things-at-the-front-of-the-train in general, not specifically any one component. I would assume it was traction motors overheating. As ehbowen mentioned, at low speeds the limit is on current, not horsepower. For 70s/80s era freight units, there was a minimum speed, between 10 and 15 mph, below which you couldn't continuously use full power even if the wheels weren't slipping. In a passenger-geared unit that limit might have been even higher, around 20.
Come to think of it, that may well have been the cause of the problem: we may well have been following a freight train that was maxed out at 10mph in notch 8, and forced to follow it slower than we wanted to.
I have no memory of whether we overtook a freight at the top of the pass or not.
F40PHs were DC, as was just about everything else at that time.
Come to think of it, that may well have been the cause of the problem: we may well have been following a freight train that was maxed out at 10mph in notch 8, and forced to follow it slower than we wanted to.
I have no memory of whether we overtook a freight at the top of the pass or not.
F40PHs were DC, as was just about everything else at that time.
I see what you mean. I read Al Krug's famous HP vs. TE essay and I'm not sure that they can get down to 10 MPH in run 8, but pretty close, I guess. They would sound pretty awesome in that mode.
I didn't know that about the '70s and '80s units not being about to run at full power even with no wheel slip, but it does make sense. Glad to see the AC motors of today. I will attach Al's PDF in case anyone is interested and doesn't have it.
I didn't know that about the '70s and '80s units not being about to run at full power even with no wheel slip, but it does make sense. Glad to see the AC motors of today. I will attach Al's PDF in case anyone is interested and doesn't have it.
