MTH HO K4 - Mixed feelings?

Folks:

It's unfair of me to say this. I don't own it, nor will I, given its $400 list price. Still, based only on the review in the July MR my feelings are indeed 'mixed', to say the least. And you know, most of these aren't unique problems, just rather extreme examples of what I consider common features of modern HO steam.

  1. What happened with its speed? Indeed, what happened with the 12v HO standard? MTH says it runs 70 @ 12v, MR says 13 SMPH...what happened? Anybody else there got this machine yet? Did somebody calculate wrong? Not so much overthinking here, really, but perhaps a little too much voltage drop through diodes? Too much electronic complication?

  1. Power pickup through tender, automagically switching to engine when required? Why not just pick up through the lokey all the time and eliminate the committee of vigilance? There's a triumph of overthinking for you.

  2. 10 car pulling capacity? Seems a little low on the level. My MDC 2-6-0 can probably do better than that. Traction tires really aren't an elegant solution...I hope there's a way to add weight.

  1. Puffing smoke...nice for a show, and the puffing feature is ingenious, but you know, the Reynolds number just isn't right on any smoke unit I've ever seen. Perhaps if it were ejected at 87 times the real velocity? :) Perhaps they could use hydrogen-based smoke ? :D

  2. Yellow LED -- almost rather have a jewel. They just don't look like a headlight. Headlights look yellowish but not like an LED...

That's all. I'm not saying it's a bad engine, just that I'd like to see more opinions. Care to comment?

Cordially yours: Gerard P.

Reply to
pawlowsk002
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In addition to the things you mentioned something does not look quite right about it. Its a really nice looking model but the space above the trailing truck looks very empty. In the pictures I've seen of K4's it looks like the frame or something takes up more space under there. Can't say I'm right for sure, maybe is just the pictures don't show the space well. I have not seen a straight on side view of other K4s by BLI or Bachmann so I can compare it to those either. I don't model the PRR but K4s are beautiful locomotives. Bruce

Reply to
Bruce Favinger

Bruce, you are correct, the frame and ashpan occupy that space on a real K-4.

Mark.

Reply to
mark_newton

snipped-for-privacy@gannon.edu wrote: [...]

[...]

Um, from my study of photos and articles, I'd say that 10 heavyweight cars was close to the limit for the real K4. It could haul more if it had to, maybe, but it no doubt struggled. The K4 was built for speed, not drag loads.

Then there is the question of protoypical train lengths. In HO, a K4 plus 10 cars would be 9 to 10 ft long - a pretty good size in that scale. In real life, it would be about 900ft long - the length of three football fields! Too long: railroad companies didn't want their customers to have to walk too far. Keep in mind that these trains originated and terminated in stub terminals, and were loaded from the end. The NYC's 20th Century was assigned five to seven cars through most of its history, if photos show typical consists. The PRR's Broadway Limited (hauled by K4s in its heyday) appears to have been the same length. During WW2, trains were of course much longer - and slower, too.

Many model railroaders seem to have an exaggerated idea of how much a steam loco could pull. OTOH, hard data on actual train consists is surprisingly hard to find. I have a Classic Trains article on three name trains: nowhere in it is there any data on actual consists.

BTW, 10 cars would be about the limit for a 2-6-0 on a typically hilly branchline.

HTH

Reply to
Wolf Kirchmeir

Is there a way to calculate required tractive effort? For example, how much TE is necessary to pull a give weight up a 3% grade? Passenger trains would normally be shorter in length to minimize weight as freight can wait whereas people can get owly being delayed even a few minutes.

Cheers, John

Reply to
John Fraser

Wolf:

Hmm. Starting tractive effort for a given train has to be equal to or greater than the static friction in its bearings, right?

Using:

K4 TE -~44 000 pounds. Heavyweight car - ~170 000 pounds Coeff. of static friction (est.) .036 (.16 bronze/steel * 8"journal dia/36" wheel dia) (Disregarding rolling resistance (small) and number of journals (not considered in classical static friction mechanics)

Weight of train = 44 000 / .036 Number of cars = Weight of train / 170 000 = 7.2

So a K4 could start a 7 car train...probably too conservative since I didn't allow for slight slack or sand, but it appears you are right.

And, hmm, if the MDC 2-6-0 weighs 80 tons (seems right) and has 3/4 of that on drivers (probably a bit low), using the 25% formula to calculate tractive effort for a 2-cylinder engine, I get 80*2000*.75*.25 = 30 000 pounds, so I guess the K4 can't start much more of a train...but it can surely go faster. Sparta No.

9 would certainly be full-steaming long before it got the DeLorean up to 88.

I'd still wonder if a model that ran light at realistic speeds with that small a pulling power would be able to maintain realistic speeds at its maximum load. That K4's engineer might have needed sand and profanity to start a 10 car train but once it was going he should have been able to maintain 70 or so on the level, given the steam locomotive's torque and power curves.

Cordially yours: Gerard P.

Reply to
pawlowsk002

Reply to
Bruce Favinger

Pretty close. Wayner's "Passenger Train Consists" includes the actual consist of PRR #29 as it arrived at Alliance, OH on 11/13/41: PRR 5147 - 4-6-2 PRR 5248 - Baggage-mail PRR 6051 - Baggage-express City of Fort Wayne - 18 Roomettes Harbor Point - 2 DBR/Buffet/Lounge PRR 4512 - Diner Imperial Crest - 4/4/2 Hamilton County - 13 DBR Metropolitan View - 2 MR/1 DBR/Buffet/Lounge/Obs Geezer

Reply to
Geezer

John:

Sure: the Davis formula, valid for level track, and working best for speeds to about 5 to 40 mph, and good enough for a general idea at higher ones:

R=1.3W + 29n + 0.045WV + 0.0005AV^2

where R is the train resistance in pounds per car, W is the weight per car in tons, V is the speed in miles per hour, n is the total number of axles, A is the cross sectional area in square feet, and V^2 represents the square of the speed.

For grade resistance, take the Davis resistance and add

20 lb resistance per ton of car weight per grade percentage point. Curve resistance is roughly equal to an 0.04% grade per degree of curvature.

These last two figures were found here:

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I also found here that the starting resistance (above freezing) of a solid-bearing equipped train is about 25 lb/ton. From this, I find that a K4, with TE 44 000 pounds, could start 44 000 / 25, or 1760 tons ... 20 heavyweight cars, a very considerable train. In winter, it could start 15.

This would imply that the MTH K4 has about half the TE that it should...and oddly enough, the review shows its TE as being about half the average for HO locos! Interesting that they should emulate the prototype in this way...

Cordially yours: Gerard P.

Reply to
pawlowsk002

I wrote the Davis formula:

Using this (somewhat inaccurately) with: Speed 70 MPH Weight 85 tons per HW car Axles, 6 per HW car Cross-section area about 200 sq ft per HW car

I get:

R = 1.3*85 + 29*6 +.045*85*70 + .0005*200*70^2 R = 111 + 174 + 268 + 490 = 1043 pounds per car. Grades: Add 20 lb / ton / percentage

1% grade adds 20*85=1700 pounds...total R, 2743 lb/car

Using a boiler horsepower of 3000 (a bit high? The M1 had 4000, but I can't seem to find K4 HP figures just now) for the K4, at 70 MPH:

TE = (3000 HP * 550 (ft*lb)/(s*HP)) /(70 MPH * 1.47 (ft/s)/MPH) TE = 16000 lb

Cars on level track = 16000/1100 = 14 on 1% grade = 16000/2800 = 6

Ah...I just noticed that Bowser had some figures on their site...apparently the K4 was designed to pull 11 cars when hand-fired, and uprated to 16 cars with a stoker, at an average speed of 65-75 MPH...not too far off the calculations, really. Now I feel like a chump for going through them all. :)

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Cordially yours: Gerard P.

Reply to
pawlowsk002

My questions is, "Why *another* K4?"

Its like another F7A.

-- Cheers

Roger T.

Home of the Great Eastern Railway

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Reply to
Roger T.

Rog:

To be fair it's been like this since early in the hobby. I have a magazine from 1935 where letter writers were griping about the ubiquity of K4 Pacifics and NYC J3 Hudsons.

Cordially yours: Gerard P.

Reply to
pawlowsk002

Because eveyone who models PRR steam can always use another K4. Bruce

Reply to
Bruce Favinger

represent the frame and ash pan over the truck?M There are a number of pictures on the BLI site. While the angle of the shot doesn't really tell to me there is not much daylight under there. See this picture;

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It seems all the latest steam engine have detail in that area that should be improved. As was guessed the reason is sharp curves. I personally would buy the BLI simple because of the havoc MTH caused the sound decoder industry.

Reply to
Jon Miller

So if the model could get 2 or 3 cars up a 3% grade it's doing better than the prototype. Why do modelers have such a tough time understanding what an engine can pull.

Reply to
Jon Miller

"Jon Miller"

We need models that can pull better than the prototype because our models have to haul trains that are generally steeper than those commonly (Commonly, yes commonly) seen on the prototype. A 1% or 2% grade is very common on a model railway but they were considered very steep on the prototype. Therefore, our models need to pull up a 1% or 2% grade than the prototype could pull up a 0.5% or 0.25% or less grade.

One more time, notice I used the "commonly"? We don't need people now pointing out that so and so railway pulled trains up two, three or even four percent grades. That's NOT common. The vast majority of grades were and are less than 1%, a "gentle" grade for modellers.

-- Cheers

Roger T.

Home of the Great Eastern Railway

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Reply to
Roger T.

Oh. I thought it was some folks liked that hunchback Belpaire look.

Reply to
Steve Caple

Yeah, me. I love it. Probably because the God's Wonderful Railway adopted the Belpaire firebox.

But that doesn't mean I'll buy another K4. One is enough. I don't model the PRR, so the K4 has to be a, er, um, guest, maybe.

HTH

Reply to
Wolf Kirchmeir

snipped-for-privacy@gannon.edu wrote: [...]

I doubt it, since a heavyweight car with six axles is equivalent to

1-1/2 four-axle freight cars. Thus, about 14 cars in summer, about 10 cars in winter. On the level.

Well, more like 2/3rds I think.

Anyhow, data provided by other posters shows that most of the time, the trains the K4 hauled had about 10 cars.

But I guess a little extra weight --> tractive effort for BLI's version wouldn't hurt.

HTH

Reply to
Wolf Kirchmeir

My understanding of haulage power of a steam locomotive was based on the formular of starting & constant tractive effort, wieghted against boiler pressure, for the main gradient on the assigned line. Now that may be a very simple way of putting it, but that was the way that it applied on steam that I worked on in Australia.

This meant that a locomotive's load was arrived at for its respective speed at maximum load on maximum grade, rated at 85% boiler pressure.

EG: A train travelling from A to E, over the section had C & D as the maximum grade had the load applied at that section. From the starting station or, at any point along the way, the loco had to be able to lift the load with a boiler pressure of 80% of maximum BP

Thus, an 245psi eniine was rated at 220psi for its starting & continual load.

On the issue of the MTH model, & for that matter, I agree with those who talk about realistic loads vses what the modellor expects. We have a new manufacturer/ distributer here for OZ models, & with the new garratt models coming out, there was a push from several modellors to want to have the loco pull 60 wagons.

I reality whilst these loco's in real life were powerful, the only time they could have hauled that amount of loading in bogie vehicles was out in the back blocks of the country side where they never ran anyway.

To run any train with any locomotive realistically, one needs to really look at how they operated in the real world. I can not imagine that even the big boys or y6b's could haul the loads of modern diesel traction, yet, to many modellors that is what they often want. It would seem they are caught up in the visualisation of the big trains of today, & trying to equate that back to the old days.

snipped-for-privacy@gann>

Reply to
a6et

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